# Show and tell on a... Monday? Milestone: carbon lugs.



## Drew Diller (Jan 4, 2010)

Via sweating out the aftermath of many failures, and with the help of many people, I'm now able to do this kinda bladder inflation molded bizniss, rough cut and unpolished as it may be at the moment:









Don't know how many times I failed to produce this sort of result. No idea.

Once I get a proper 3 axis CNC mill, I should be able to prototype these very cost effectively. Now to work out more of the bugs.


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## TrailMaker (Sep 16, 2007)

Damn dude!

About time you got off your duff and got some of these made!

I'm UTTERLY TOTALLY KIDDING of course. You are a testament to dogged determination, if nothing else. I somehow knew you would figure it out eventually, and I am sure you will keep figuring it out for a long time to come as you refine your process. If anyone else has been thinking about doing this, you better be mentally tough enough to keep your head down and your eye on the prize. It's a LOOOONG climb!

Mucho kudos, Amigo!


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## Eric Malcolm (Dec 18, 2011)

Great to get that milestone. Tick off another box. Keep going.

I know that this is a lug, but my traditional heritage would have me wanting to sort of make the sockets 'pointy'. Its early days to ask this question, but can that be done from a lug like this? Carbon Tubes bonded in, instead of filler as you would use with steel. I just like the art work....

Eric


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## Drew Diller (Jan 4, 2010)

TrailMaker - I know you kid, but there's some truth to it even if unintentional. Fell on my ass a bunch!

Eric - I follow what you mean, and I think those frames are timeless. The answer is yes it could be done - diamond edged hole saw and careful manual cleanup. I want to have lots of less ambitious trials done before I take a stab at that style.


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## TigWorld (Feb 8, 2010)

That's looking great. Any more pics of the molds and bladders?


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## Drew Diller (Jan 4, 2010)

TigWorld said:


> That's looking great. Any more pics of the molds and bladders?


Some attached. In order:

1) A "2D" or lay-flat bladder.
2) Wet sanding after polyester sealing the milled area of the MDF.
3) Put on an epoxy topcoat for a bit of shine, it's not evenly applied as would be had with a proper clearcoat. EDIT - I was SUPER pleased to see the mallard plumage effect after polishing and epoxy coat. I think the iridescent effects of UD fiber is way more interesting to look at in person than twill fiber patterns.

I'm not actually using this part as I damaged the mold in use, wanted to just get a reasonable idea how a part might turn out once I learn more about the foibles of high pressure mold design.

For starters, not going to use MDF. I bent some Uni-Strut reinforcement and dimpled the crap out of the exterior of the mold.

I think one reason that this topic is not better documented the way metal working is pretty well documented is maybe because it is dangerous if disrespected. I think I remember calculating _after_ damaging the mold that there was a near half-ton parting force between the mold halves at a "mere" 25 psi.


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## Testmule (Jul 27, 2013)

Nicely done!

I have another CF frame planned for this spring or summer, along with some ideas of my own. Will share when I am under way.

And by the way, its alway a little sweeter when it works after many failures.


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## Drew Diller (Jan 4, 2010)

Hah, definitely. Can't appreciate the good without the bad. Now that I've had some time to stop being pleased with myself, I gave the part a thorough inspection and judged a whole BUNCH of reasons on why it's not ready for prime time. That stuff is really difficult to photograph with the equipment I have.


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## ktm520 (Apr 21, 2004)

Room temp cure?


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## compositepro (Jun 21, 2007)

drew

i was trying to figure out if the radius finished edges were a feature but now i ve seen the tool it makes sense obviously its a front triangle not just a head lug but same system is used

I have attached a picture to flikr for ya drew this is how we mold a head tube with bearing seats and everything to size

i will try to crop down another image to show you the overwrap and bonded joint area where the tubes get glued to the lugs


__
https://flic.kr/p/14034619351

one of the reasons i dont really show and tell with bladders is that pressure is dangerous and you get some guys trying to hit 200psi because they heard somewhere thats what company A does it at and then they heat it up to 90 degrees
well it goes without saying someone will say i saw it on the internet


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## Drew Diller (Jan 4, 2010)

compositepro said:


> one of the reasons i dont really show and tell with bladders is that pressure is dangerous and you get some guys trying to hit 200psi because they heard somewhere thats what company A does it at and then they heat it up to 90 degrees
> well it goes without saying someone will say i saw it on the internet


Yeah, that's kinda what I'm driving at. The super high pressure is so whatever small voids you leave during even careful layup, the air bubbles will *dissolve*, right?

Well - you also need, like, a full size truck to squish those mold pieces together.

And all I drive are sedans 

Which kinda bums me out - I was initially so bummed out about how little doco there was on the net about this stuff, and I see it might be for a legitimate reason. My hatred for censorship and my appreciation for safety are butting heads here.

ktm520: the raw material was a prepreg that accepts 180 F to 240 F, I used 200.


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## compositepro (Jun 21, 2007)

Drew Diller said:


> Yeah, that's kinda what I'm driving at. The super high pressure is so whatever small voids you leave during even careful layup, the air bubbles will *dissolve*, right?
> 
> Well - you also need, like, a full size truck to squish those mold pieces together.
> 
> ...


Well high psi isn't a prerequisite I know we have solved problems for factories where too high a pressure was assumed to be beneficial frames were light on resin and delaminating even demoulding them

Using a bladder and incorrect pressure you can trap and lock off air in the laminate it wont escape or boil off any volatiles(older resin systems) as it would in an autoclave

Do you know about your resin cure cycle through to its tg at some point it will have a lower cp (more fluid) this usually happens before gel though not always hence you can time the bladder pressure to ramp at certain points this means you can run less psi throughout the process

Don't rule out sticking a vacuum line in their just as a further experiment


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## Drew Diller (Jan 4, 2010)

compositepro said:


> Well high psi isn't a prerequisite I know we have solved problems for factories where too high a pressure was assumed to be beneficial frames were light on resin and delaminating even demoulding them
> 
> Using a bladder and incorrect pressure you can trap and lock off air in the laminate it wont escape or boil off any volatiles(older resin systems) as it would in an autoclave
> 
> ...


I have some rather detailed docs on the prepreg resin I'm using, unfortunately I don't have a heating system (yet) that can go into the sort of detail described.

Also, what you're saying is consistent with what I saw during my first pressurization test with this mold (which failed), the resin viscosity at time of demold was very thin, sort of like snot. I had to laugh at myself after the fact, I wasn't using a thermocouple or anything, just a few reference plies that I checked on intermittently - yeah well, MDF is wood and glue and therefore has a stupidly low thermal conductivity, I basically interrupted the first molding's attempt when the resin was pre-gel state.

So yeah. Thermocouples. Duh.

I've been kicking a few other ideas around in my head to possibly increase the safety factor. Nothing definite yet, and at the moment more focused on getting a halfway decent mill running. With this mold, the machining costs alone... if I were to make say just 20 prototypes in house, I'd break even _super fast_ on a mill heavy enough for high speed non-metals machining.


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## ktm520 (Apr 21, 2004)

Interesting that the MDF mold will withstand elevated cures.


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## Drew Diller (Jan 4, 2010)

ktm520 said:


> Interesting that the MDF mold will withstand elevated cures.


Forgot that detail: it didn't. The parting faces of the mold were not touching and as such I can't use this cured part (among other reasons).

There was 2-3mm of curl away from plane on each face at the edges.


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## TigWorld (Feb 8, 2010)

Love what you're doing. Keep up the good work.

If you're not going to use mdf then what next? Big lumps of alu are not cheap. For that head-tube area a mold could be made out of sectioned pipe, mitered, welded and flanged. Miter all the pipes, weld them together, cut in half, weld on flanges so you can bolt back together, bolt back together and then bore in from each open end to your desired dimensions.


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## Drew Diller (Jan 4, 2010)

TigWorld said:


> Love what you're doing. Keep up the good work.
> 
> If you're not going to use mdf then what next?


Either a frangible mold design, or something else I haven't even tested yet and people who I mention it to thinks I'm crazy (but my dad doesn't, and he's a nutcase about plastics).

Jury's out on that subject.


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## TrailMaker (Sep 16, 2007)

How'bout cement?


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## Drew Diller (Jan 4, 2010)

TrailMaker said:


> How'bout cement?


Like the Corian variety? Yeah, possibly. I caught a handful of molds composed of that.


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## bme107 (Jul 23, 2008)

TrailMaker said:


> How'bout cement?


Mortar or concrete found in a ready mix bag at your home center ranges from 3000-5000psi compressive strength. Plenty to resist the parting pressure but you'd need to bind the halves with some A36 (or better) steel shapes and high-strength bolting. Unistrut is not the answer as you found.
You might need some sort of interior metal sleeving as I'm not sure you'd get repeatable results out of the mortar alone. I think the sharp corners and creases would break free because they are thin and brittle.


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## Drew Diller (Jan 4, 2010)

bme107 said:


> Unistrut is not the answer as you found.


Indeed so. I've been kicking around ideas on a poor man's hydraulic press. Fight air pressure with air pressure, contained in some ridiculous steel frame.

Again, one thing at a time - I lack a way to prototype the molds cheaply, working on that.


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## compositepro (Jun 21, 2007)

Drew Diller said:


> Indeed so. I've been kicking around ideas on a poor man's hydraulic press. Fight air pressure with air pressure, contained in some ridiculous steel frame.
> 
> Again, one thing at a time - I lack a way to prototype the molds cheaply, working on that.


Look at cider press 4 posts with a dental screw you will be surprised how many companies use a screw press


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## bme107 (Jul 23, 2008)

Drew Diller said:


> Indeed so. I've been kicking around ideas on a poor man's hydraulic press. Fight air pressure with air pressure, contained in some ridiculous steel frame.
> 
> Again, one thing at a time - I lack a way to prototype the molds cheaply, working on that.


Hydraulic or a "brake press" would work for one axis. Still need to confine the other 2.
If you found a way to standardize the size of the mold, say 12x12x12, you could invest once in a solid "mold holder box" made out of steel plate and shapes.


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## Drew Diller (Jan 4, 2010)

bme107 said:


> Hydraulic or a "brake press" would work for one axis. Still need to confine the other 2.
> If you found a way to standardize the size of the mold, say 12x12x12, you could invest once in a solid "mold holder box" made out of steel plate and shapes.


Agreed on both counts - a square foot buys me a lot of real estate.


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## bme107 (Jul 23, 2008)

You could build a cubic foot holder and always block some of the interior off with solid blanks if the part/mold didn't require that volume.
Size of the BB/DT/ST/CS lug would govern but drop outs would need far less space.


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## Ene (May 8, 2014)

bme107 said:


> Mortar or concrete found in a ready mix bag at your home center ranges from 3000-5000psi compressive strength. Plenty to resist the parting pressure but you'd need to bind the halves with some A36 (or better) steel shapes and high-strength bolting. Unistrut is not the answer as you found.
> You might need some sort of interior metal sleeving as I'm not sure you'd get repeatable results out of the mortar alone. I think the sharp corners and creases would break free because they are thin and brittle.


Would it not be possible to make the mold in fiberglas and the concrete as support?

And great work Drew!


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## bme107 (Jul 23, 2008)

Ene said:


> Would it not be possible to make the mold in fiberglas and the concrete as support?


Mortar and concrete are really only good in compression. Tension strength is roughly 10% of compression. They could be the outer supporting material but they'd either need to be reinforced with rebar or their mass (size) increased to the point that their self-weight would hold the 2 halves of the mold together. It'd be a much more efficient use of materials if they were confined by something with better tensile strength to clamp the mold halves together.


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## Steve Ash (Jun 19, 2014)

Hi Drew!
I'm very fascinated by what you are able to do. 
I am trying to find the way to build my own bladders. 
Can you help me? 
I was thinking to a system like spry or liquid latex to be sprayed or brush into the mold. 
I am using latex tubes but I have also to put the silicone intensifiers in the joint areas such as head or seat tubes and bottom bracket. 
What's your opinion?


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## Drew Diller (Jan 4, 2010)

Hey man, I'm going to answer your question, I have to draw a picture so it'll be a little bit.


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## Drew Diller (Jan 4, 2010)

Steve Ash said:


> Hi Drew!
> I'm very fascinated by what you are able to do.
> I am trying to find the way to build my own bladders.
> Can you help me?
> ...


You already have the right idea, but the keyword "the" mold, singular, is where you're wrong in practice. I had the same idea, I was wrong too.

Mold*s*. You need two patterns. Reason being, you can't line the entire female mold with a gel that will become a semi-solid, and expect it to be a useful bladder. The exterior of the resulting bladder is going to be covered in fiber, which will then be a few millimeters too voluminous to fit in the mold.

Further, my opinion is that you need a temporarily solid agent inside the bladder, or at least a very thick / stiff bladder with a touch of air pressure in it during fiber layup.

I tried "lay flat" silicone bladders that mimicked what I saw with welded seam polyethylene film bladders. Three standoffs (or a perfectly level surface to start with), a shallow basin to allow unvulcanized silicone to pool in, wait about an hour for first layer to vulcanize part way, then add a parchment paper pattern that represents your air chamber, followed by a second layer of silicone. Despite the first layer already being partially vulcanized, the two layers will adhere very well to each other.

You get something like this.

There are some drawbacks to this simple approach.

First, you waste some expensive resin depending on how intricate your basin is - if it's a big square like I did, you'll waste quite a few dollars worth. If it closely matches the air chamber pattern, that'd be less wasteful.

Second, the seam of the two layers means that the air chamber has to double over itself along the seam when inflated against a female mold cavity.

Like this, the X marks represent cross linking between the two silicone layers, on the right is a cross section of the lay flat bladder with no air pressure, on the left is with air pressure.









What happened with the bladder used in the part pictured earlier in this thread is that it withstood pressure for many hours, but the neck eventually burst in the way I just outlined.

SO...

So that means "3D" bladders are the correct choice, because they don't introduce little stress risers or tiny areas where a stretchy material has to stretch way too much. My rule of thumb for silicone rubber is no more than doubling the undisturbed length, anywhere. 1.5x would be better.

Essentially the challenge with making 3D bladders is gravity and viscosity. You want unvulcanized viscosity that isn't so thick that you get a lumpy bladder, but when using a resin that thin, it's just going to spill off a male pattern or make a big pool inside a female pattern.

The answer is to spin the pattern gently during vulcanization. Got a translucent gallon of milk handy that is mostly gone? Turn it end over end and watch the milk coat the interior surface, right. What if that wasn't milk, and was rather some liquid slowly solidifying? That is "rotocasting" in a nutshell.

Here's a proof of concept I made with a Gatorade bottle, I chose that shape because of its complex features (which didn't turn out well at the bottom, I just wanted to know) and lack of similarity to a bike part, as in, I wouldn't get attached to it.










Thing is, you don't *need* a female pattern to rotocast. You could use a male pattern. You'll just lose a little bit of resin onto the floor, you'll have to experiment with proper rotation speed and amount of liquid applied to the outside of a male pattern to minimize waste.

Important caveat: latex won't work well inside a female pattern. It has to evaporate the solvents that are keeping it in liquid form. Silicone, on the other hand, is a thermoset, doesn't need to breathe, so it can usefully vulcanize inside a closed environment.

A male pattern with a bladder painted on slowly would be handy in the sense that you already have a firm core around which to apply manual pressure when doing the fiber layup over the bladder. You just need to figure out how to get that core out later, in order to remove the bladder at the end. There are a few options for this, I have not settled on one.

My first rotocaster that I built with lumber, some bike parts, a miter gear, and a $6 freezer ice auger from Poland (lol) ended up dismantled because it was a piece of sh!t. I'm going go design version 2 so that the two rotating planes will have independently adjustable speeds.

This help at all? I feel like I've given options and no concrete answers, which is useful or totally useless depending...

EDIT - one other note on latex vs silicone... if you use too much material, latex will be slow to cure because it needs to be thin for each layer of the stuff (you'll need several or many to build up thickness), pretty much like working with latex paint. If you glob it on, you'll get an uncured squishy glob that resembles a zit that is ready to pop. If you use too much silicone inside a female mold, remember that it is a thermoset, and too much mass means exothermic acceleration, which means you'll get a thick blob of silicone somewhere, and the heft of it will mess up the rest of the casting. Learned both of those the hard way.


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## Drew Diller (Jan 4, 2010)

Cripes, man.

Almost two years since I updated this thread.

What the @#$* is up with that?!

Answer: *struggle and repetition like you suggested*. In the last year, I'd been having big big troubles with my sustainable molding concept. I finally have worked out the majority of the bugs. Unseen behind this shiny (unpolished, btw) lug are two Cub Foods bags of crappy, half infused, hole filled, bladder collapsed, seam showing bunch of rejects.

Each failure was a learned thing. I learned SO much, most of it written down, some of it in my new muscle memories.

The biggest thing I ran into with the use of prototyping wax as a mold material is the drastic deformation shown when subjected to heat. ...Even a little bit of heat created a lot of warping.

I had to switch to Resin Infusion of some kind. Room temp, yo.

It just happens to be much, MUCH more difficult to achieve a good result than working with prepreg carbon. The fiber is much more prickly when dry and unbound by anything.

I was becoming paranoid that, after failing to make the prototype *bicycle frame* I'd hoped for by December, I was feeling that maybe I wouldn't so much as make ANY good infused parts in all of 2014 and 2015 combined.

With just a shred of time to spare, I proved myself wrong.

In other words, I did a LOT of the "do it again" practice. I now feel strong. Part failures are so much easier to react to objectively now.


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## JohnnyMagic (Dec 7, 2014)

There are "casting resins" that are used in the auto and aviation industry that OUT PERFORM even cnc's AL molds.
AL has a nasty habit of thermal expansion. Can be quite a bit.

I can't believe more people in the bike and guitar industry don't use the stuff???

For making lugs, I ALWAYS use mandrels (solid) with the female molds.
As you are finding; wet lay-up and bladder molding don't get along too well.
Sure it CAN be done, but why?

Waxed and PVA coated hardwood mandrels are used by mold makers for dozens if not hundreds of parts.

Round stock AL also works well for mandrel material. (can't do complex radii) 

You can still remove consistent radius "tubes" from the mold.
That gives you accurate ID along with OD. You end up with (some) flange from pressing the female halves together.

But, carry on any way that works for you.

Resin Services/Reklin Plastics is a good source for commercial grade casting resins.
You can get room temp cure, or high heat stuff.
They have other material added for strength and desired use.

It is used for complex plastic castings as well cause some parts can't be machined.

Nice looking lugs!

JM


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## JohnnyMagic (Dec 7, 2014)

http://www.resinservices.com/custom.asp?CustomID=14


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## Drew Diller (Jan 4, 2010)

JohnnyMagic said:


> As you are finding; wet lay-up and bladder molding don't get along too well.
> Sure it CAN be done, but why?


Well, I'm doing dry layup, but it's still very unfriendly compared to prepreg.

I'll attempt to answer why, the big thing is I started with bamboo bikes and realized pretty quickly that jigging up some rare, expensive bamboo only to mess up a wrap-over type reinforcement because of some vacuum problem... is a bunch of crap.

I needed Separation Of Concerns in more ways than one. I didn't want to subject the bamboo to extreme heat (outside of the bamboo hardening process itself), I instead wanted to do secondary bonding.

I have an odd background with injection molding of plastic, so I decided to see how much the skills transferred. A fair amount. I will probably end up with a hybrid approach of part internal mandrel, part bladder inside a female mold pair, because as you said, known ID and OD.

I also want to be all What You See Is What You Get regarding customer previews, and female molds with their defined outer surface and everything, they really push a bunch of my hot buttons.


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## Drew Diller (Jan 4, 2010)

I've never before achieved two-in-a-row with some of my conditions validity checks removed - for instance, no dry pressure two hour run to try and exhaust the bladders before wasting any epoxy. Just infused "blind".

They're within a few grams of each other. Using flash on my camera revealed some places where I had flow media too close to the surface (the red fibers). You can also see white tracer material where tiny surface air bubbles remain. The idea is to not know the tracer is even there, but this is pretty close to good enough. (But it is not good enough, just... feelin' good)









It's an odd bit of tech. It doesn't work unless conditions are all Goldilocks just right. And when that balance is achieved, it looks as though it will work every time.

I'm pretty happy that I can now get a part to cure overnight at room temp. Get all the air machines shut off and unplugged before sleep, wake up the next morning with a snazzy lug in hand. I can live with that, yeah.

Happy new year! I am friggin' PUMPED!


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## Daniel Thomas (Aug 1, 2015)

I'm amazed that you managed to make this complex shape as a single part!


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## Eric Malcolm (Dec 18, 2011)

Drew

You mention having started with Bamboo bikes. The purpose of the lug making is to create a Bamboo tubed/carbon lugged frame? Where are you intending to go with this project?

I'm curious, but impressed with the tenacity of this project. It looks very good and a credit so far.

Eric


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## Drew Diller (Jan 4, 2010)

Eric Malcolm said:


> Drew
> 
> You mention having started with Bamboo bikes. The purpose of the lug making is to create a Bamboo tubed/carbon lugged frame? Where are you intending to go with this project?
> 
> ...


Thank you for the encouragement! I was hoping to impress, this niche has been kicking my ass for too long.

Improving my bamboo frame building craft was the original goal. I wanted the bamboo to undergo particular heating phases that did not jive at all with prepreg carbon requirements. Maybe if I was Boo and had access to the highest quality bamboo on the planet, then it'd be a different story. But I can only get what I can get in the lower 48.

Once I started getting closer to high quality carbon, the thought crept in "I could use this for a lot more than bamboo bikes", so the motivations morphed.

The bamboo stuff isn't going away. It's just that I've figured out potential bamboo bike customers don't need to be sold on the idea, they either love it or are repulsed by it... so, it will no longer be the sole game in town. I'm very interested in suspension and gearbox stuff, and bringing the cost of the latter down to Mere Mortal levels.


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## Drew Diller (Jan 4, 2010)

Ever watch a baby deer slip around while learning to walk? Like holding themselves up reliably is more of a parlor trick than anything else.

That's how developing my understanding of composite processing has felt. Accomplish something, think you're cool, try to repeat the process and it gut punches you and takes your lunch and steals your girlfriend.

I often remind myself I no longer have a commute and to STFU and get back into the kitchen, so to speak. Hard knocks in the shop, yeah so what, SHUT UP and do it again. Shut up and repeat. Repeat. Think you're cool? SHUT UP, DO IT AGAIN, AGAIN, AGAIN. Ari Vatanen didn't learn to shift in a day.

I've hit seven infusion processes in a row, with repeatability that is finally on the cusp of journeyman / semi pro area. I'm making molds four times faster than when I started learning how to do milling. What has felt like massive turbo lag for a long time now feels like it is starting to spool. Habits and muscle memory are coming along, while the daily bumps and hiccups are becoming fewer and fewer.

All this hard work is starting to bear fruit. Feels good man. Feels good.

Resin content is somewhere in the 41% to 43% range (still honing the math stuff). If I really want to compete with the big boys weight wise, I need to hit 38%, which... isn't going to happen soon. I'm prioritizing bullish toughness over light weight. I tend to break stuff, which is really dumb because I barely push a buck seventy even while stuffing my face with pizza constantly.

So, it's time to take this tech and make my seventh frame / first one like this approach. It's time to implement. Gonna make a thing that's like a Zerode G1, even though it's going to be a pedal watt sucking monster. My mission is to liberate the rear axle of any barnacles. No more derailleurs for this guy. The cheapest most available way to go forward with that is to suck up the efficiency penalty and cobble and Alfine into the beer belly of a weird looking bike frame.


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## Eric Malcolm (Dec 18, 2011)

So....You're finally going to make THAT bike!!!!


Cool.

Eric


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## Drew Diller (Jan 4, 2010)

HELL YES

I've been wanting this since I first trashed a rear derailleur on the first mountain bike I bought with my own money. I worked at a bike shop when I was 15 and learned that I was a terrible mechanic, they fired me in a month. Was just enough to afford a Schwinn Moab 3, which I used as an escape mechanism. And not very far into its life, I had a suddenly lame bike out in the woods.

And now it's 2016. The bicycle market is NOT flooded with gearbox bikes, and that *really pisses me off* so I'm gonna do anything I can to change it.


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## Drew Diller (Jan 4, 2010)

View from a "side B" mold that has a featureless parting face. The carbon surface has some flaws evidently created by the CNC's chassis wobble, which isn't helped by the primitive NC code that I generated.

Worse than that is the flaw at right where the edges are sharp. That sort of part feature will reliably kill inflation bladders *after* the epoxy curing is done. An unceremonious death. I need to improve my technique here.








Here is a shot of the interior when things go well. I can see your underwear! About halfway up, that's where the mold parting face would be. Note that you cannot see a hint of it. I used to have such trouble with the result of _this is supposed to be a closed shell piece, and all I've done is conjured an unnecessarily complex way to make two disjointed half shells_. Not anymore!

Note from the white particles that I need to bolster my shop cleanliness. Those are just particles I missed when cleaning the bladder prior to layup.


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## bluechair84 (Sep 30, 2008)

Mega impressed here!
I'm currently working on a carbon garage project as well. I'm not at the stage of experimenting with carbon yet - this week I've gotten most of a main triangle mandrel made. I'm just polishing it up this weekend to start making a female mould from it. 
It's been interesting reading your posts on the mould. My plan is two female halves in fibreglass and I'm expecting a bladder pressure of about 14psi. Have you got any advice on mould building or some reading I can do before I begin this venture?
Cheers


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## Drew Diller (Jan 4, 2010)

bluechair84 said:


> Mega impressed here!
> I'm currently working on a carbon garage project as well. I'm not at the stage of experimenting with carbon yet - this week I've gotten most of a main triangle mandrel made. I'm just polishing it up this weekend to start making a female mould from it.
> It's been interesting reading your posts on the mould. My plan is two female halves in fibreglass and I'm expecting a bladder pressure of about 14psi. Have you got any advice on mould building or some reading I can do before I begin this venture?
> Cheers


Regarding mold pressure: I'm using a bit more than 14 psi (but still a lot less pressure than in a road bike tire), but I've been told that it is possible to do closed molding with just 14 psi. After all, if it is possible to do open shell vacuum bagging with a natural limit of a touch over 14 psi, then it follows that you could feasibly do it with a bladder.

It's just, I had trouble getting it to work. I tend to use a little too much temporary tack adhesive. One or two little puffs covers a surprising surface area. If the plies are stuck together too firmly, they won't want to slide along each other during compaction. If the plies are not stuck together at all, it's absurdly difficult to get the preform into the mold... like bathing a cat, or trying to put an angry baby squid into a jar.

Also on mold pressure: check your math regarding clamping forces. Get an idea of the surface area of the empty parting face of one mold, get it in square inches and multiply that by what your psi is. You'll probably be like _what the heck, that much force?!_from that little pressure, yikes.

These are good clamps. Note the compression rating. I use a backing plate to avoid killing my molds, and I fasten each clamp in an iterative way... like when you put a wheel onto a car, you don't just tighten one lug nut fully and immediately.

Regarding making the molds, I am coming at this from a machinist perspective, which is possible when you have a CNC handy. Whereas you are taking an inverted copy of a male plug. I don't have any useful advice on what specific tooling epoxies to use, just some general advice about surface tension. Eddy currents happen the world's rivers and they happen here too. Walls, hard transitions, pockets - expect some possible crappy mold results in those zones first. I've read that some tooling epoxies are "no shrink", but everything shrinks a little bit.

Locating pins for the A and B sides should be placed as far apart as you can without damaging the trueness of the dowels. It's weird but if you crack open one side of the mold only, and try to lift fully from there, you'll be bending the @#$* out of either the dowel or the dowel hole at the other end. You have to _scoot_ the mold up... a little up over here, get something to hold it in place, a little up on the other side, get something to hold it, repeat.

I dunno if that was helpful, if you have any specific mold making questions do go ahead and ask.


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## Drew Diller (Jan 4, 2010)

*C is for Compromise*

I did a dry test fitting for the first time. I made the straight sections recently, using a caul plate design. Basically the tubes are just half tube profiles, they're going to be secondary bonded, and later overwrapped after... well, lots of secondary (third, fourth, etc) bonding is going to happen.

It's not ideal, but it moves the ball forward for me. I lack a BUNCH of composite-specific equipment for machining, and I want to move at high speed, so there's a little rock and a hard place thing going on there. So, for now, right, use a caul plate so that the interior tube is known, the exterior tube is known, the parting plane is known (friendly to bond flat), I can use the frame components themselves to aid in alignment.

The slip / "shunk" noise that the last socket made was viscerally pleasing, like letting go of a bowling ball and your arm KNOWS that something cool is going to happen, even though you can't really touch the ball anymore you still WATCH the damn thing go.

Note the vertical seat tube socket (short stay design) and pronounced belly (gotta make room for an IGH to fit where a normal down tube would be).

I find the caul plate thing a little cumbersome in terms of effort per yield, but WOO the interior and exterior results are convincing, the resin ratio is convincing. Tedious but works firmly.


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## bluechair84 (Sep 30, 2008)

Drew Diller said:


> After all, if it is possible to do open shell vacuum bagging with a natural limit of a touch over 14 psi, then it follows that you could feasibly do it with a bladder.
> 
> It's just, I had trouble getting it to work. I tend to use a little too much temporary tack adhesive. One or two little puffs covers a surprising surface area. If the plies are stuck together too firmly, they won't want to slide along each other during compaction. If the plies are not stuck together at all, it's absurdly difficult to get the preform into the mold... like bathing a cat, or trying to put an angry baby squid into a jar.
> 
> ...


We're definitely on the same page regarding a few things - I'd also taken 14psi as the (atmospheric) pressure used in compressing open moulds. The only problem with this is they are often cured in autoclaves which raise the pressure further I think. I've seen other no-clave cures and vac-bagging so I'm pretty confident it'll be reet.
I hadn't considered the need for the sheets to slide along each other during compaction - I can see why this might be relevant for the changing circumference of curvatures for each layer. It's something I'll look at in the first trials!
Because I'm not currently planning on a preform (I will be wrapping some Alu mandrels for the bearing faces) I shouldn't have your 'baby squid' problem. 95% of my fibre is going straight into the female mould and the bladder will be the only internal shaping force.
As for the dowels, I might have a solution. I'm planning on running a 'bead' around the face of one mould and have a concurrent groove in the other mould. This will mean that there is very little height to clear when separating the moulds, but there will be a full seating guide all the way around.

When you are combining your halves, are you using an internal flange on one side that is pressed against the other half via the bladder? Or are you wrapping the two halves externally?
You've given me some confidence to share what I'm doing, so I'm going to revist an old thread and put up some details of jig and blank. Keep your eye out


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## Drew Diller (Jan 4, 2010)

bluechair84 said:


> We're definitely on the same page regarding a few things - I'd also taken 14psi as the (atmospheric) pressure used in compressing open moulds. The only problem with this is they are often cured in autoclaves which raise the pressure further I think. I've seen other no-clave cures and vac-bagging so I'm pretty confident it'll be reet.
> I hadn't considered the need for the sheets to slide along each other during compaction - I can see why this might be relevant for the changing circumference of curvatures for each layer. It's something I'll look at in the first trials!
> Because I'm not currently planning on a preform (I will be wrapping some Alu mandrels for the bearing faces) I shouldn't have your 'baby squid' problem. 95% of my fibre is going straight into the female mould and the bladder will be the only internal shaping force.
> As for the dowels, I might have a solution. I'm planning on running a 'bead' around the face of one mould and have a concurrent groove in the other mould. This will mean that there is very little height to clear when separating the moulds, but there will be a full seating guide all the way around.
> ...


Gotcha, I misunderstood a few things. I think you have a realistic course ahead of you. I was getting confused where you were using "bladder" and I think you meant "vac film". I'm splitting hairs of course, both of them act as flexible-membrane-soft-clamps. Just one type is a balloon, the other type relies on a sealing flange.

My halves could be called half/full (different than half-full). Part is laid in the mold in halves. Part is laid on the bladder as a complete unit, but "complete" is still a relative term here since we are talking about plies of overlapping fabric.

That said, a mating flange is a legit way to do it as long as there is some overwrap. 3M secondary adhesives are really something, but even then they are not really designed for peel strength. The caul plate tubes I made just the other day are mated in this same flange-y kinda way, and will be over-wrapped at the seam later.

Regarding autoclaves, yeah it is basically for the ease of use with vacuum bagging, but goes well beyond the atmospheric pressure limitation that otherwise goes with vac bagging. For your purposes, I don't think you need it. Does your first part _need_ to be perfect 38% resin? Nahhhh. If you're trying to make some world record road bike --- it's been done. Make now with whatcha got, autoclave later.

I like your groove idea for the registration.

Have you purchased a vacuum pump yet?


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## bluechair84 (Sep 30, 2008)

I won't need a vacuum pump as I'm using a pressurised bladder inside the tubes. The bladder will likely be left crusoe'd inside the frame but, I'm not bothered about saving a few grams to get it back. The process I'm planning on is to lay up mould A to the edges, lay up mould B to have a few inches of overlap, place the inflation bladder into mould B beneath the flanges and fold them down onto the bladder. As the bladder expands it'll press the flanges onto mould A. 
It does leave me with a problem though - how to get the atmospheric air out of the frame as the bladder pressurises. If I don't remove it I run the risk of dissolving it into the epoxy. It's a big advantage your vac bagging has!


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## Drew Diller (Jan 4, 2010)

Ahhh, ok, I misunderstood twice! Gotcha. You're worried about that trapped air, give one mold face some cardio lines. I don't know how well this applies to close mold wet layup, but once piece of advice I read was "if the epoxy doesn't move, the air bubbles won't move". Some feed lines to the outside world will give a path of least resistance when you inflate the bladder. They don't have to be deep channels, because air pressure finds a way.


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## bluechair84 (Sep 30, 2008)

Hey that's not a bad idea at all... You know, I was going to run some full length cable guides inside the frame. They can be multi-freakin-purpose! If they are porous, the air can escape through the internal cable inlets. That's bloody genius.


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## Drew Diller (Jan 4, 2010)

That thing I was saying, about caul plates being accurate...

Caul plates are accurate.


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## bluechair84 (Sep 30, 2008)

They're fantastic, nicely done. I'm looking forward to see how you're going to bond them!


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## Velobike (Jun 23, 2007)

bluechair84 said:


> They're fantastic, nicely done. I'm looking forward to see how you're going to bond them!


I'm watching with interest too.


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## dandelave (Apr 12, 2016)

bluechair84 said:


> Hey that's not a bad idea at all... You know, I was going to run some full length cable guides inside the frame. They can be multi-freakin-purpose! If they are porous, the air can escape through the internal cable inlets. That's bloody genius.


bluechair - If you are only planning on 14PSI (same as 28 inches of Vacuum) I think you have to seriously consider using a vacuum bag. If you are making a mold that is able to take a bladder then you will be able to use that mold with a vacuum bag. The added advantage will be to use a breather cloth and padding backing in order to suck out all bubbles.

To do this you would make the bag part that goes inside the closed two piece mold similar to the shape of the bladder you are expecting to use. Then there is the outside of the mold to worry about. Make another part of the bag that fits the whole mold. The only issue is that you have to connect these two pieces with a length (through your pressure opening) that will be able to close it all to take the single line vacuum. So the vacuum will be pulling on the inside of the mold as it pulls on the outside of the mold. Imagine it appears as a bag inside a bag. Without the mold halves in there it would look like an empty balloon if vacuumed down. As mentioned before make sure you have no sharp edges.

If you are not interested in buying a vacuum pump consider getting a Venturi Vacuum Pump from Harbor Freight for about $20 (Vacuum Pump - AC Vacuum Pump w/ R134A & R12 Connectors).

Later,
Dan


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## bluechair84 (Sep 30, 2008)

Thanks, I understand the process. thinking about it the benefit is that my clamshell mould isn't having to hold in 14psi. I do need to leave access to the in and out of the finished frame to remove the the vac-bag when actually I want to create a complete, almost fully closed frame. The theory is that without large holes needed to remove the vac-bag, or a 'monocoque' design, the frame will be stronger. 
To do the vac-bag technique I'd need to leave a hole... possibly inside the headtube... I'll consider it for sure.


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## dandelave (Apr 12, 2016)

Drew Diller said:


> Thank you for the encouragement! I was hoping to impress, this niche has been kicking my ass for too long.
> 
> Improving my bamboo frame building craft was the original goal.
> 
> Once I started getting closer to high quality carbon, the thought crept in "I could use this for a lot more than bamboo bikes", so the motivations morphed.


Drew Diller: I have been on a similar path to what you are doing for quite a while. I started a long time ago with latex bladders that did not last past a one time thing that took a while to make each bladder. I then started making plastic film bladders using a soldering iron to seam them...works great. I have been successful making parts with pressures up to 60 PSI. Also failed with high area parts using 10 PSI.

I would encourage you to take a look at Adam Pequette's video on Inflation Bladder Molding (



)

Later,
Dan


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## dandelave (Apr 12, 2016)

bluechair84 said:


> To do the vac-bag technique I'd need to leave a hole... possibly inside the headtube... I'll consider it for sure.


Even if you used only the inflation bladder you would want to get it out of the inside somehow. The inflation connection width may be big enough to dig out the bladder.


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## Drew Diller (Jan 4, 2010)

dandelave: you're spot on regarding the positive-air-source vac pumps, I love them. Solid state, zero maintenance, no bad smells or bad compounds in the air other than what is produced by your compressor.

The near-full-vac one really gulps down air, though.









Regarding the seam film bladders, I believe they work and I'm glad you go them to do so, but I always had one tiny spot that would hinder an otherwise good bladder. I had previously followed exactly with Adam's techniques. If you can get the seam strong enough, I have no doubts that it works.

The reason I went with 3D bladders is that I knew I wanted deep V and U type shapes. The down tube I built the other day is 56mm viewed from the top, 38mm from the side. I knew I wanted something that would take a near vertical angle straight away from the parting line, which is why I turned away from the seam bladder approach.

EDIT: I would even say that the film bladders are better in some respects, for instance they have lower friction under pressure. Whereas my silicone bladders tend to be high friction under pressure, a ply can get dragged elsewhere under pressure if I do the layup poorly, which can lead to cuts and eventual rupture.


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## dandelave (Apr 12, 2016)

Drew Diller said:


> dandelave: you're spot on regarding the positive-air-source vac pumps, I love them. Solid state, zero maintenance, no bad smells or bad compounds in the air other than what is produced by your compressor.
> 
> The near-full-vac one really gulps down air, though.
> 
> ...


Drew:

They do take a fair amount of air compressor time but they are cheap.

Sorry to hear your luck with the film badder technique. I would only occasionally have issues with them, and that was always spelled out when I tested them, before putting them in the mold.

Lately I have really liked oogoo for making bladders, easy cheap, strong, holds a pretty good shape when not inflated, and easily repairable.

Later,
Dan


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## Drew Diller (Jan 4, 2010)

dandelave said:


> Lately I have really liked oogoo for making bladders, easy cheap, strong, holds a pretty good shape when not inflated, and easily repairable.


Clever, I'll have to try it.


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## Drew Diller (Jan 4, 2010)

I'm no longer embarrassed by sharing failed parts. This time, I used too much temporary tack adhesive during dry layup. Doing so creates a condition where the plies have too much shear friction for the bladder to break apart and flatten. The fiber bundle doesn't quite make it to the mold cavity surface all the way - sometimes by 2mm or more - and the epoxy is given no incentive whatsoever to continue infusing. It just fills the empty space, path of least resistance.

On the upside, I did achieve the possibility of daisy-chained molds. I can now make parts that are twice as long as the cutting envelope of my CNC.

I'm really kicking myself over using too much tack, I've done this before, absolutely a repeat failure. It's a skill, usually I nail it, sometimes not. Much to learn.


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## Drew Diller (Jan 4, 2010)

I made some superior pressure bladders, hooray, and got some decent handlebars as a result.

Note I say _decent_ and not _good_ or _great_ or even _commercially viable_. It's a decent, but ultimately scrap, part.

So I cut it into many pieces and looked at the insides. It was mostly really good, with two symmetrical bad parts. The bad parts were, happily at least, free of any air, but they were bogged in excess epoxy that is just sort of... _there_, not doing anything.

The aspect of this part that I'm really happy about is the minor Z flashing at the middle. This was made with four molds, like A1-A2 meets B1-B2, all hydraulically linked. The theory works, which means I can now legit make parts that are larger than the size constraints of my CNC mill. While this may be a scrap part overall, what is represents is _huge_: *this paves the way to true monocoque front triangles for full suspension frames*, because I could feasibly daisy chain more than two molds in this same fashion. It could be _N_ number of molds, it just comes down to how much fancy BS am I willing to do / how motivating is the part in question.


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## Drew Diller (Jan 4, 2010)

Forgot to note, the thicker flashing along the length of the bar, currently it is there as a crutch. Initially, I thought it might be some competitive advantage because it decreases overall infusion times, but... it's actually not a good thing. The reason they persist for me at the moment is lingering shortcomings in my layup technique - the channel gives an emergency exit to little wild hair fibers. If you DON'T account for these loose fibers, they mess with the hydraulic seal of the mold. They are very hard to keep track of, and until I am able to track them all, I need the training wheels mode with the seam relief channels.

Also, the flashing left behind is extra work to clean up. It'll be better once improved technique nearly eliminates one task.


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## Velobike (Jun 23, 2007)

I can see some nice tapered carbon curved fork legs that fit into a lugged crown in the future...


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## Daniel Thomas (Aug 1, 2015)

Congratulations on the progress! Did you determine the fiber volume content that you achieved?


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## Drew Diller (Jan 4, 2010)

Daniel Thomas said:


> Congratulations on the progress! Did you determine the fiber volume content that you achieved?


On this one, wasn't too concerned since scrap, but the ugly answer before chopping it up was greater than 50%.

Good infusion of lugs usually gives somewhere around 41%. It may be a reality where I *never* hit 38%, and based on the stuff I've seen so far, I'm not too concerned about that 3%. I'm MUCH more concerned about the bladder mortality rate.


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## Daniel Thomas (Aug 1, 2015)

I'd be fine with consistently getting 41% (resin weight percentage I assume)! It is more important to a have reliable results than saving an ounce of weight at the risk of having dry spots.


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## Drew Diller (Jan 4, 2010)

So Daniel Thomas, I thought about what you said and tried a literal application: I used a _very_ low cost, recyclable, and _mildly inaccurate_ method of internal compression. To elaborate on that last notion, the ply compression is well-enforced in the Z direction of the mold, and poorly compressed in the X and Y directions. The X and Y are expected to take up some "fat" or excess resin pockets.

I made a bar the other day that turned out heavy, relatively speaking - something north of 47% resin.

That said, it doesn't feel like a boat anchor. It is _light enough_ for me, sure. Like Walt has correctly said ad nauseum, the weight weenie game is stupid. The way I see it, thanks to the wind turbine industry, there is all this standard modulus carbon fiber available for low cost now. Why not make some affordable and light enough frames? If you want to throw in oodles of the super-high-tech carbon fabrics to chase ultra low weight, then you have to pay for it.

I want to take the notion of forced elitism out of carbon. I'm sick of the superiority complexes, I just wanna make some weird shapes, all right?

So I was thinking a bit - for the oddball customer who *doesn't* want a super shiny and well painted expensive result... rather, they just want to test an idea and they are willing to exercise their bicep muscles... is there any way I could provide a sort of "C grade" prototype.

It would need to check the boxes:

Light enough?
Strong enough?
Reasonably not-ugly enough?









This handlebar checks the light enough (well, according to me) and attractive boxes. The real question is, does the mediocre X and Y compression make for a *weak* part? This remains to be seen, I expect the answer is yes but I hope it is no.

In this way, I hope I can appeal to more than one kind of customer income bracket, while still making a livable income myself.


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## Drew Diller (Jan 4, 2010)

I tried attaching a metallic logo / clamp anti crush zone thing today.

Ehhh it went okay for a first attempt. Not bad. There was an air inclusion which messes with the flatness of the logo surface. I went very modest with the secondary bonding adhesive, too conservative. With no abrasion, most of the clamp surface was acceptably close to spec, but one section at the strip meeting point, that was 0.1mm out of round.

I tried straight filament winding over top twill fabric - I don't really care for it. I'm going to take a tighter pattern with the straight filament instead, make it one smooth continuous thing. I don't much care for the twill fabric finish, it makes me a little dizzy / vertigo sensations. I'd rather chase after a "grayscale mallard plumage" tone.

330 grams in all at 760mm wide... time to put it on an epoxy diet to some degree, and more importantly fix the flashing problem.


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## Drew Diller (Jan 4, 2010)

July was cruel to me. I thought there were things I was "over", apparently not! Vac and bladder leaks of new types, one of which was cause by the instability of my main work table. Some moments were mean enough that I was contemplating those dark "Am I good enough to hack this? I need to pay some friggin bills" moments.

August is being slightly more kind so far. I've taken some heavy handed steps at fixing the new leaks, and they're working well.

That said, I did something stupid this morning. I had a legit handlebar laid up and infused, and I repeated an old mistake by demolding too early. The epoxy was still considered an extremely high viscosity liquid and I didn't realize it. The carbon decided it liked the hydro lock of the mold on either side a lot better than the epoxy wanted to stay in one piece, and I was rewarded with a bad stretching goopy sound instead of the desired cracking popping sounds. I could get the halves out as they were stiff enough once carefully handled, but it was clear that they would still self-stick in a very slightly gooey way.

It ended up being a good mistake, oddly enough. In this manner, I could see some interior fiber warp, indicating bladder stress. This was location matched to white-opaque (micro tearing) zones on the silicone bladder. So I gotta figure out how to artificially increase wall thickness in certain zones without changing much about part strength or weight, ONLY for the sake of the bladder being asked to do something sane and achievable.

Thankfully, when it comes to adding artificial thickness for the sake of interior flatness, boat hull builders are already on that like flies on sh!t. My naive past self used to look at those filler materials all "Why the heck would you want to do that?" and here I am again with another "Oh. This is why."


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## Drew Diller (Jan 4, 2010)

Like I said, August has been more kind. Feel like I am touching rubber to the road again. The epoxy I used in this one is harder to work with, but it has a usefully high service temperature. 297 grams pictured with flashing, with just barely enough room to stuff a smidgen of extra carbon in for the next bar.

First carbon part I've made where I've struggled to make it heavy _enough_.

Zero mold damage. After a solid month of fails, feels damn good to have a win.









EDIT - forgot a major thing. This is a 39% resin content bar. I did it!! I think I'm going to plump it back up to low 40% because I really really like the look of carbon veil surface compared to the twill look, and that stuff is really epoxy-hungry.


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## Drew Diller (Jan 4, 2010)

Had a failed bar, oh well. Repeated an infusion mistake based on some new advice. Turns out it was only half-good advice, so time to head back to the notion of "nothing is true, everything is permitted".

I used to think one vac gauge was good enough, by the time I'm done here there will be five gauges.

So I decided to take this most recent bad bar and chop it up. What did complete looks pretty good. It certainly is *thick* and that's to keep me from having to honor warranty claims. I want it to be where I don't process any warranties because hardly anything comes back to me.

The light colored ring around the donut hole is a single layer of aramid fiber. Wow, now THAT stuff is a pain in the ass to work with.


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## Drew Diller (Jan 4, 2010)

Well since no one posted to this subforum over the weekend, here's a scene from the shop:









I like to supervise the filling of a box mold (with machinable wax) by witch wanding with a heat gun on full blast. It makes the top surface cool in a relatively smooth way.

In the future I'll have some snazzy auto-heated boxes to offload this process away from me, but I cannot afford that yet.

A few more steps after this image, and the resulting blank can be CNC'd.


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## compositepro (Jun 21, 2007)

Drew Diller said:


> Had a failed bar, oh well. Repeated an infusion mistake based on some new advice. Turns out it was only half-good advice, so time to head back to the notion of "nothing is true, everything is permitted".
> 
> I used to think one vac gauge was good enough, by the time I'm done here there will be five gauges.
> 
> ...


dude that thing will take a plane landing,


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## Drew Diller (Jan 4, 2010)

compositepro said:


> dude that thing will take a plane landing,


See that's exactly what I'm after. I've been told "you shouldn't sell carbon bits to people who crash a lot".

I crash. I'm clumsy. I'm inattentive. Sometimes, I become *enraged* and resemble someone high on PCP. I want carbon bits that will survive the worst of my human faults.


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## Drew Diller (Jan 4, 2010)

I had an idea after looking at my epoxy catch pot too many times. I noticed that the wasted epoxy resin was "neat" or free of gas bubbles. And they call this *waste epoxy*?!?! How about perfect epoxy that is stuck in a bad place?

What if I could pause / open up the infusion pathway for a short time, collect wasted resin _that has been immaculately degassed after being forced through the fine mesh of carbon fiber_, and then put it back in at the beginning of the pathway? Feasibly, I could recirculate resin through the system with very little waste, as long as the pot time of the resin was still alive.

Seems to work. I'm using an extra slow epoxy on this one, so I can't view the result til Saturday. I'm guessing I recirculated 30 grams or more out of a 250 gram resin payload.

Basically this custom catch pot that I made is an unexciting shallow tub with five holes in the back for various tubing lines and a gauge. The slanted line with seemingly nothing underneath it is a small pool of epoxy with no visible gas in it.


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## compositepro (Jun 21, 2007)

Drew Diller said:


> I had an idea after looking at my epoxy catch pot too many times. I noticed that the wasted epoxy resin was "neat" or free of gas bubbles. And they call this *waste epoxy*?!?! How about perfect epoxy that is stuck in a bad place?
> 
> What if I could pause / open up the infusion pathway for a short time, collect wasted resin _that has been immaculately degassed after being forced through the fine mesh of carbon fiber_, and then put it back in at the beginning of the pathway? Feasibly, I could recirculate resin through the system with very little waste, as long as the pot time of the resin was still alive.
> 
> ...


IM NOT SURE WHAT YOU MEAN BY OPEN UP eeek Pretty much once its sealed you want it to stay sealed 30grams of resin is a good sacrifice for a part you know is free of air?


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## Drew Diller (Jan 4, 2010)

compositepro said:


> IM NOT SURE WHAT YOU MEAN BY OPEN UP eeek Pretty much once its sealed you want it to stay sealed 30grams of resin is a good sacrifice for a part you know is free of air?


I cheated for this test, see what I get kinda thing. In the future one of the extra tubing lines is only for clamping, so I could isolate the mold from the catch pot for a time, maintaining the vac integrity for the part while relieving the pot in order to drain it.

Either way, the feed line stays clamped so there's no start point entry of air.

Not sure what I'm going to get!


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## compositepro (Jun 21, 2007)

Drew Diller said:


> I cheated for this test, see what I get kinda thing. In the future one of the extra tubing lines is only for clamping, so I could isolate the mold from the catch pot for a time, maintaining the vac integrity for the part while relieving the pot in order to drain it.
> 
> Either way, the feed line stays clamped so there's no start point entry of air.
> 
> Not sure what I'm going to get!


roger roger , i read it wrong


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## Drew Diller (Jan 4, 2010)

Pretty okay result. I made some human errors during layup (again). The inlet side showed better infusion than the outlet, which suggests I might want to just recirculate longer.

The sharpie points to said human error, basically there is a limit to how far the bladder is allowed to expand, on purpose. I didn't fill it out properly, capillary action was missing. Consequently, the fiber volume fraction is not what I wanted, a rather unexciting 50/50.

Gettin' closer. Time to try (yet) again and concentrate on my weak zones.


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## Drew Diller (Jan 4, 2010)

Found myself arguing with a friend the other day about me being ready for production. I was claiming to be not ready yet, based on my acceptable parts vs crap parts ratio being way too low.

So I snapped this pic, and realized that I had saved more failure / learning pieces than I thought. At least two others weren't pictured, so I guess that makes fifteen failures of some kind or another between June and now.

I'm unamused, but at least I gleaned important info from each. Some over compression here, under compression there, leaks here, a different kind of leak there, a resin batch that was inappropriately fast curing, a *third* kind of leak...

Pareto principle all up in here.


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## compositepro (Jun 21, 2007)

"I'm unamused, but at least I gleaned important info from each"

And with that you can say each was a success ,your learning very well


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## Drew Diller (Jan 4, 2010)

After damaging a mold component, I had to mill a replacement, delaying a second test of the epoxy-recirculation idea until recently.

Looks pretty good to me. There are a few lack-of-capillary problems again, but this time I am pretty sure it is because the bladder ruptured some time during the night. This was the bladder's seventh pressure cycle. Next goal: twenty cycles.

Each bladder costs me about $20 in materials, so if I can have them cost $1 per use I'd be pretty okay with it.

This is also the first bar that I've made where both the left grip and the right grip are properly registered. I can clean this bar up and actually put things on it. Neat. That much closer to gettin' paid.


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## Drew Diller (Jan 4, 2010)

Forgot to note: the resin recirculation has been a huge success in my eyes. I got some bits of data, the most fun aspect is that the ENTIRE batch of resin was recirculated in 30 grams increments.

This is one of those fun times where "on paper this should work" and in real life IT DOES!! Some months ago I was reading about how air bubble "spontaneous nucleation" is a problem for resin infusion, and one way to deal with it is to include a fine mesh screen in the degassing pot. I was like "Fine mesh screen you say?" .... what if the part _itself_ was the fine mesh screen? POW!

I will allow myself this momentary victory. Now, the next thing...


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## cartographer (Jun 20, 2006)

I understand virtually none of this, but really appreciate your sharing your work. It's always exciting to see those moments of inspiration turn in to something functional!


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## Drew Diller (Jan 4, 2010)

The last three bars in a row have turned out fine. Phew.

It's time to move on: clean 'em up, badge the stem clamps, and start bend testing them. I've already done the thing where I hang them on an overhead beam and I do rough-shod pull ups with them. Buuuuuut that's pretty unscientific.


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## Velobike (Jun 23, 2007)

Looking good Drew.


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## dubthang (Apr 2, 2009)

Bars look great. Is there a possibility that the metal clamps could cause stress to the bars? The metal looks to ride in a slightly narrower section for a flush fit. Would bar flexing cause the carbon to rub the metal resulting in a premature failure?


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## Drew Diller (Jan 4, 2010)

dubthang said:


> Bars look great. Is there a possibility that the metal clamps could cause stress to the bars? The metal looks to ride in a slightly narrower section for a flush fit. Would bar flexing cause the carbon to rub the metal resulting in a premature failure?


The bars pictured are unfinished, as they sit, the stem clamp zone doesn't reach 31.8mm. Once I bond a 26 ga sheet metal strip (new ones have self alignment wobbles), the 31.8mm will be reached, and there will indeed be a flush zone across, there's a 75mm length of straight tube sharing that same 31.8mm OD (I like my headlights to point _forward_).

I'm not too worried about it, due to the ball nose end mill I'm using for the mold making, there's a little pocket between the edge of the metal sleeve and the nearby carbon surface, which I'm going to fill using chopped fiber and thickened epoxy.

Further, the wall thickness in the area is excessive.

Even so - that's what testing is for, I'm just going to have to see what develops there.


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## dubthang (Apr 2, 2009)

Cool. Best of luck with the testing.


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## Drew Diller (Jan 4, 2010)

Yarrr, testing be a harsh mistress...

I didn't do very much science here. Just took a standard aluminum bar that came off an unnamed mountain bike, and gave it a full bore test, which it failed. My first visually passable bar also failed, in that pleasantly disgusting way that carbon likes to do.

Time to build a better bar. If I can pass the Too Powerful For The Standard Bars test, I'll sleep easy at night.


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## Drew Diller (Jan 4, 2010)

Forgot to note, the snapping failure mode shown by my first tested bar is totally unacceptable to me. I know some very, very big men who are interested in being customers. Regardless of what point it breaks, I want a carbon bar that is going to bend.

I've seen a composite that does this: bamboo. I'm convinced there is a way to dope carbon + epoxy with an additional ingredient for the sake of a safety oriented failure mode.


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## Eric Malcolm (Dec 18, 2011)

How are you doing the test Drew? By lifting the bar to a certain height and dropping it so the clamp hits the block of wood? The weighted ends then having a flexual moment beyond its capablities? SNAP.

Eric


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## Drew Diller (Jan 4, 2010)

Eric Malcolm said:


> How are you doing the test Drew? By lifting the bar to a certain height and dropping it so the clamp hits the block of wood? The weighted ends then having a flexual moment beyond its capablities? SNAP.
> 
> Eric


Correct. In the future I want something like a very strong spring pad that would compress over a very short distance, enough to still cause the same kind of failure, but usable for maths.

I'd be able to say the bar is surviving ______ newtons. This is currently a knowledge hole I need to fill.

I am working on testing samples of aramid / fiberglass / Innegra for more likeable carbon failure modes. I'm also cutting new molds that have gentler features and will produce less fiber warp.

Of the aluminum reference bars I've tested so far, a Race Face bar was very impressive. I could keep on bending it repeatedly, and it never snapped. That is the kind of performance I wish to imitate.


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## MannaDesigns (Mar 5, 2013)

Looking forward to what you come up with.

From my experience in aerospace with Carbon, I think it'll be tough to replicate a failure mode similar to aluminum... mainly by the nature of material. As you're well aware I'm sure, the stress/strain curve of AL has a much longer "yield" area before failure, whereas carbon, while fantastic in fatigue - tends to creep up to that limit and fail catastrophically... Part of why on new airplanes they don't do the full wing static test to failure like the metal wings of past. Partially due to the mode of failure being gnarly.... I think that is why you tend to see just a huge amount of safety margin built into the carbon stuff in recreational applications...(that's just IMO though...)

regardless of my jibberish, definitely enjoy seeing what you're doing, and maybe there are some cool layups you can play with to get it closer...



Drew Diller said:


> Correct. In the future I want something like a very strong spring pad that would compress over a very short distance, enough to still cause the same kind of failure, but usable for maths.
> 
> I'd be able to say the bar is surviving ______ newtons. This is currently a knowledge hole I need to fill.
> 
> ...


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## Drew Diller (Jan 4, 2010)

MannaDesigns said:


> Looking forward to what you come up with.
> 
> From my experience in aerospace with Carbon, I think it'll be tough to replicate a failure mode similar to aluminum... mainly by the nature of material. As you're well aware I'm sure, the stress/strain curve of AL has a much longer "yield" area before failure, whereas carbon, while fantastic in fatigue - tends to creep up to that limit and fail catastrophically... Part of why on new airplanes they don't do the full wing static test to failure like the metal wings of past. Partially due to the mode of failure being gnarly.... I think that is why you tend to see just a huge amount of safety margin built into the carbon stuff in recreational applications...(that's just IMO though...)
> 
> regardless of my jibberish, definitely enjoy seeing what you're doing, and maybe there are some cool layups you can play with to get it closer...


My brain agrees with you. I chose the word imitate carefully, as I think you're correct that I will not be able to replicate aluminum in the ductility department.

But I do want to imitate it. At least to the extent of sending the end user a visual cue of "this is still mostly in one piece but you should really stop using it immediately".

The snapping completely off behavior is @#$&ing scary.


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## Drew Diller (Jan 4, 2010)

*Continue testing.*









Recent bars are not yet quite strong enough, though they are certainly much stronger. I'm fairly certain this is because my winding angle is not correct, due to some dumb ass calculations on my part when ordering carbon sleeving most recently. So the next two weeks are going to be spent cutting new molds while I wait for stuff in the mail.

Interestingly, the carbon sleeve approach has a "rescue" failure mode, I'm not sure what to call it exactly. It's not yielding, it's not ductility - technically it is fracture, but only some of the fibers failed while others did not. Once it goes limp from an initial overload, the subsequent repeat (and increased) loads didn't rip off the flimsy limb.

I think I need to take some material out of the wall thickness as it approaches the stem clamp. My hunch is that area is being too stiff, forcing the secondary bend on either side to shoulder an excess load.

One thing I'm still missing from my test jig (aside from a proper twin-rail setup that doesn't rotate) is a means of measuring contact time. The falling-impact formulas use time as one of the components. I know the impact speed and the mass, but not the duration applied. Changing the value even slightly in a theoretical environment drastically changes the peak load, so I'd *love* to know what it is.

Or I could throw (increasingly scarce) money at an impact sensing instrument.

Up next, construct different internal pressure tools (this part is getting easy, hooray!), use more appropriate winding angle.


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## dr.welby (Jan 6, 2004)

Why not just use an air cylinder? I broke a lot of handlebars with that, an adjustable regulator, and a ruler to measure displacement.


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## Drew Diller (Jan 4, 2010)

dr.welby said:


> Why not just use an air cylinder? I broke a lot of handlebars with that, an adjustable regulator, and a ruler to measure displacement.


I was advised by a vastly-more-experienced-than-me composites guy to use a method that involves sudden shock rather than gradually reaching ultimate strength. Going beyond strength limits with a large displacement will tell a more visceral story about its post-failure behavior.

As a bonus, it makes for an easy to understand visual that will be useful to me later for marketing purposes.


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## jgrano (Dec 5, 2011)

Off chance have you considered integrating some Innegra fabric in your bars? It is supposed to dampen vibrations but does a pretty good job for impact resistance. Hai Velo is using it with some good results it seems.

innegra


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## Drew Diller (Jan 4, 2010)

jgrano said:


> Off chance have you considered integrating some Innegra fabric in your bars? It is supposed to dampen vibrations but does a pretty good job for impact resistance. Hai Velo is using it with some good results it seems.
> 
> innegra


That's the plan for the near future, yes. I've received mixed recommendations from some acquaintances ("it's great" VS "don't bother at all"). So that pretty much means I must try it and judge for myself.

As far as suppliers, no one braids it. There are some that say they do, but they steer me in the direction of similar-but-not-identical fabrics. I kinda get it, I've read that it can have a twisting premature failure from improper human handling.

I suppose it's kinda like buying aramid, you don't literally have to get it from DuPont at this point.


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## jgrano (Dec 5, 2011)

In a previous life I made a ton of test samples for a big bike company. I don't think they ended up using it or anything but some of their now ex-employees have seen a ton of value in it apparently. 

Might be worth doing a non-sleeved layup. If there was a fail safe in carbon handle bars that would be a great thing to bring to market.


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## Drew Diller (Jan 4, 2010)

Testing and re-building of molds continues. What I've changed recently is a slight increase in minimum allowable stem length (70mm, an increase of 10mm), the effect on the mandrel is that the double-S-bend is less extreme. This change helps with sleeve layup and UD layup alike.

Another change is a more sudden transition from 31.8mm OD to 22.2mm. It used to take all of the length of curvature in the bent portion of the handlebar, now the transition length only takes 30mm. It is subjectively uglier, less flowy, but the first test pull looked mostly fine (which I totally screwed up by using *really old* epoxy that I didn't date check because the canister looked so new, @#$*ing idiot).

One thing I dislike as an end user about the shorter transition is that it allows less length of a 31.8mm OD, which means less real estate for bolt-on gadgets.

The purpose of the shorter transition is to create a thicker wall along the outer reaches of the bar, and initiate flex closer to the stem, sorta like a diving board. ALL of the bar failures have happened at the same spot near the grip. This leads me to think the middle of the bar is over-reinforced while the grip areas are insufficiently reinforced.

It also would appear as though I have wasted _months_ of time on a certain epoxy formula that my current heating device will simply not cure completely enough. I did some tests on some "neat" slabs of epoxy, and just face palmed upon seeing some obvious strength differences. I'd been using ProSet (high temp) for some time now because of its super low viscosity, long gel time, and high post-cure heat deflection temperature (for the sake of people who live in hotter climates than where I live).

After re-reading the specs on the stuff, it seems that the real cure quality comes from the higher temp cure schedule, which is out of my reach for the time being. See, I'm simply using hot water to cure, so I'm theoretically limited to 212F but _practically_ I'm limited to 160F. And that's not enough to get a strong result out of that particular epoxy. So, in the mean time, it seems I will have to stick with an epoxy that has easier / lower temperature post curing requirements (AdTech 820) before it reaches a strong result, with the trade off being a lower heat deflection temperature. Until I get a proper oven, I'll just have to warn users in very hot climates to be careful about leaving their bike in the car. That part doesn't feel particularly good.

I've been admonished by my local composites supplier that I am overthinking things with the heat deflection concern. "We have a lot of customers in motorsports, and we haven't heard complaints about this stuff that you consider low temp."

And I'm like, "I'm not making an aerodynamic fairing, I'm making a structural component..."

Last few months have been a struggle, but I'm past the point where I see light at the end of the tunnel. I'm nearly outside and the high contrast is starting to morph into details. The bars have become stronger while also becoming lighter, but none have passed the gravity sled yet.


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## Drew Diller (Jan 4, 2010)

I encountered a sort-of-new kind-of-not way to cause an infusion to fail. What's familiar is the symptom: a blockage in the fast-travel zone around the parting line. The blockage forces epoxy to take the looooooong route through the entire volume of the bar (or, in this case the entire volume starting from the stem area to the end of one grip).

What is unfamiliar is the root cause of the blockage: a dry gasket that wandered even when it had a registration groove. The gasket grew in width beyond what I expected when it was clamped.

Note the slightly zoomed in photos that show the flashing. The functional zone has clear resin, indicating an "artery" function. In the incomplete half of the bar, there is no clear resin, because the gasket was pushing directly against it.

So, now I know why D-profile gaskets sometimes use two Ds. That's what I'm going to switch to, and I will likewise increase the relief area to allow for a wider channel.

To further highlight just how far the gasket encroached, I had a little tab on the gasket near the end of the bar, which is *meant* to pinch the resin flow at that point, so that the resin doesn't have a reason to just... exit the mold, as opposed to flowing through the laminate.

It's the same theory as MTI tubes for open-shell vacuum bagging. I simply don't have the room, so I have to emulate it. Kind of a problem when I pinch off one of the tubes, so to speak.


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## Drew Diller (Jan 4, 2010)

Now we're TALKING.

I'd been out of commission for a little bit because I lightly injured my shoulder. What I'd been doing was dangerous, and I knew it, but ignored it egotistically. It's about a 60 pound load for the mold uppers, and I had been straight-arm supinating them.

We're not meant to pick anything up that way.

I invested all of $45 into auto-glass movers and a bicycle lift. Healed up mostly, I'm back at it.

And HOW.

I trimmed the gaskets by hand with extreme caution, and gave the epoxy fast tracks a bit more volume. It @#$&ing paid off. Look at those clear runners! The resin infusion itself was fast, there was sign of epoxy exit at THREE MINUTES, and it was completed at 20 minutes.

Also noteworthy is my new vacuum canisters. It's a see-through sandwich of polycarbonate -> polypropylene frame -> polycarbonate. The polycarbonate is insulated from the epoxy with clear packing tape. This arrangement (emptied as pictured) gives me an incredibly clear picture of how much resin has been consumed, and it is easy to place close to the mold for the sake of using a minimal amount of vac tubing.

Been a good week. It's going to be easier / faster / cheaper to make these bars pretty soon.


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## Eric Malcolm (Dec 18, 2011)

Keep up with those good weeks Drew.....

Eric


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## Drew Diller (Jan 4, 2010)

Kind of a bummer: the latest bar failed testing, due to an insufficient-infusion zone that was so subtle that I didn't really notice it until well after sanding. The watching of water evaporating can occasionally show stuff. The cause was over-compression of fiber in one small zone. All familiar.

I need to reduce the sensitivity to human error. On the one hand, solid mandrels are great in terms of positive fiber alignment. On the other hand, air pressure membrane (bladder) is more reliable in terms of avoiding over-compression. How to combine best of both worlds?

It's time I move on to an idea that is similar to how Felt does their frame moldings. They combine a semi-rigid thin jacket that vaguely represents the finished interior shape of the part. Through that, they thread a conventional pressure bladder. The teamwork provided by both tools makes for easy layup and consistent results.

The way I'm going to do it is to simply make the thin jacket out of carbon, and it'll bond directly into the final product. Two jackets, actually, so that they can be split apart a small amount on compression.

For some time now, I've wanted to avoid taking this labor-intensive route, in part because of a type of mold that would need to be involved, which would require a _lot_ of roughing time on the CNC mill. Well, I watched my wife catch tiny fish on a river over the weekend, so I had a lot of time to think about how to get around that kind of milling. I think I have a solution that will involve less milling altogether (even compared to my current method, yay).

Aside from the main goal of avoiding over-compression, I need a compressive element that is easy to remove. The current way I'm doing things with the solid rubber core isn't so friendly given the very small exit diameter at either end of the handlebar.

EDIT - The failed bar at least showed a friendly failure character. Like trying to break a thin tree branch that is still alive and green, it needed to be forcefully twisted back and forth several times after initial failure.


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## Drew Diller (Jan 4, 2010)

No pictures for the most recent handlebar because it looks like the previous one (I ACCEPT).

I stumbled on something neat regarding resin infusion: if you have a mold with an unacceptably high leak rate, and - AND - you have a "moat" around the entire carbon preform (mine is in the form of the epoxy fast-channels), you can suffer a vacuum leak at the edges of the mold, so long as the epoxy injection site is located at the part interior and the injection site has an otherwise acceptable leak rate.

Basically, if the incoming air flaws going past the outer "moat" seal are given an attractive path out of the mold, that's where the air will go. It'll go around the part.

I mean, it's not ideal, it's undesired. But it's tolerable, to some extent, provided you have a leak rate that can be compensated by an intermittent vacuum top-off.

Also, the experiment of imitating Felt with their compound inner compaction tooling, that paid off. Good compaction. (I'm trying to figure out how to photograph this properly.)


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## Drew Diller (Jan 4, 2010)

"An attempt was made" at shining light from one end of the bar.

I'm not sure what the black vertical bar is to the left. Otherwise, the bright epoxy indicates the presence of the 0.25mm thick carbon skins that kept the bladder in a bent and reasonably supported shape during layup. Note that they expanded slightly unevenly, which will create some amount of fiber warp.


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## Drew Diller (Jan 4, 2010)

Ah wow, I feel good today. A friend came over and gifted me with an armful of donor bars to test. Some reputable, some knock-offs.

I won't name names out of both (1) respect and (2) fear of liability, but my rig busted a nice handlebar. *Oh.* Okay. My rig is pretty harsh, perhaps too harsh.

*wrings hands*

Going to mod the rig with a high tension impact spring next. Cautiously optimistic about this development.


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## Drew Diller (Jan 4, 2010)

Briefly: I think I should say that Felt _used to_ do a similar approach to what I'm doing right now. Apparently they are now using the solid core polystyrene thing, which if done right gives crazy good compaction and all the positives that go with that... but as I've learned, is quite difficult to do right.


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## compositepro (Jun 21, 2007)

Drew Diller said:


> Briefly: I think I should say that Felt _used to_ do a similar approach to what I'm doing right now. Apparently they are now using the solid core polystyrene thing, which if done right gives crazy good compaction and all the positives that go with that... but as I've learned, is quite difficult to do right.


You should have said i developed systems like that for the taiwanese and before that the F1 folks


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## Drew Diller (Jan 4, 2010)

compositepro said:


> You should have said i developed systems like that for the taiwanese and before that the F1 folks


My mistake dude. I know that I stand on the shoulders of giants.


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## compositepro (Jun 21, 2007)

Drew Diller said:


> My mistake dude. I know that I stand on the shoulders of giants.


No man I meant if id known this was your preferred method we could have had that running in hours .....hence the history explanation...sorry chap


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## Drew Diller (Jan 4, 2010)

Man, I had another @#$*ing case of what I think is over compression, which *doesn't even make any sense*. I should be OVER this.

Vacuum leak-down (or is it leak-up?) was acceptable, 0.3mmHg/hour. Bladder leak-down was acceptable - there's a _possibility_ there's another leak apart from the air compressor quick connection naturally leaking down because that's what they do.

See the blue specks? Part of the wax mold was damaged. This screams over compression. I'm just not sure how to process that because I'm using a sort of "soft mandrel". It's squishy before layup _specifically to avoid over compression_.

I kept the bladder air pressure below what I've learned is a threshold for over compression. After infusion was done, I increased pressure slightly, still below threshold.

The stuff coming out of the exhaust tubes looked the way it should.

_Curiously,_ I heard a familiar noise, but in an unfamiliar context: the high pitched whoosh of a small volume of vacuum being refilled by atmospheric pressure, _while demolding_. Uhhhh... _*what?*_

I've done some solid gains in process control of late, and this has me utterly baffled. I'm so pissed off that I'm considering making my own room-temp prepregs and side stepping infusion entirely.


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## Drew Diller (Jan 4, 2010)

My best friend has a saying when someone makes a claim about the accuracy of their actions:

"*DID YOU?*..."

I have learned to repeat it back to myself after I assert some claim, whether said claim is directed at someone, or if I'm trying to convince myself in order to grapple with uncertainty.

After inspection of the damage, I found "print-through" of twill carbon fabric on the surface of the mold flange juuuuuust outside of the damaged mold area. This means stuff not meant for the flange got in the flange. This means that the fabric thickness was just too much for the bend zone. (It also means I should increase the flange thickness to prevent mold damage in case of future human error, which is likely based on evidence.)

"But, brain, I swear I checked all the major spots with a caliper and subtracted by 1mm. I checked the bend."

*DID YOU?*...

...

_Maybe I didn't, and just think I did._

...Crap. Time for a plain ol' redo.


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## bluechair84 (Sep 30, 2008)

I love these little mantras - I have some for teaching which I say to students every time they have a question about their work. Eventually, they come to realise that if they ask themselves the mantras first, they can usually proceed without needing me to come and pander to them. My private mantras are far more detrimental and only said within inner-monologue... they probably do more harm than good


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## Drew Diller (Jan 4, 2010)

The unsaturated zone was indeed over-compressed. I made another bar and it infused fully.















Some funny stuff happened with this one. I took (what I thought was) an extreme aversion to over compressing the layup. This was effective, too effective in the stem area, to the extreme that the outermost fiber didn't reach the mold surface all the way (even though the pressure bladder DID cause the laminate to grow slightly).

This one-time result is that the epoxy injection had a huge amount of room to play with, and I had to inject a lot. This (presumably) caused the interlaminar lubricity to increase, causing the fiber stack to expand, displacing a LOT of resin. Overnight, as the epoxy was gelling, the vacuum tubes were forcefully expelled. _Weird._

Even with that bit of drama at the stem area, the bend zone over compression _persists_ in being a problem. This time I got a clearer look at why. It has to do with avoiding warp in the fiber as it is being laid down. Not only does a thicker fiber stack result in that area overall, but it is not 100% as orderly as wrapping around a completely straight cylinder. It stands to reason that this small amount of chaos increases the fiber thickness further in that area.

As temporary relief before finding some better solution, I'm going to change the guide-skin-mandrel-things such that they have an inner diameter reduction in this problem zone.


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## Drew Diller (Jan 4, 2010)

I was wrong about the leak rates I quoted of my various canisters and the molds in particular.

I'm at something more like 0.9mmHg/min rather than 0.3mmHg/min. So I'm not quite at NASA spec yet for leak rate, while previous I thought I was. Dang.

I spent some time doing isolation tests, as finite as testing a solitary short bit of vac tubing with a gauge on the end. I learned to apply mastic tape to the gauge itself (you get what you pay for, they're cheap gauges).

It's all well and good if I test the mold cavity by itself, but supposing I make a mistake in sealant *after* disconnecting those isolated test tube fittings, or while fitting in the replacement hoses that are going to be doing the actual infusion?

No thanks. I'd rather just leak test while the functional system is in place. Even if that means accepting a higher leak because there are more joints to manage.

That in mind, here's my current preferred vacuum catch can. It is sealed with a rubber gasket (I cast one) and a thru-bolt. There are rubber gaskets around the thru-bolt, and the huge washers have a thirty degree cone surface on the clamping/business surface. It seems to do a good job of smooshing the gasket inward toward the thru-bolt.

They're otherwise made of PVC cap and polycarbonate, and are tiny and easy to evacuate in _two seconds_.

The polycarbonate looks a bit chopped up because that's what I did to it. Used to be a large rectangular plate. I did the math, and I could get a slight boost in surface area while shedding five clamping bolts.

In the future, the only mod I'm going to do is having them held together *WITH MAGNETS*.


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## Drew Diller (Jan 4, 2010)

Did I say 0.9mmHg a minute? Cripes. I meant 0.9mmHg an hour.

Still not perfect, but perfect isn't achievable with polymer based vac equipment.


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## Drew Diller (Jan 4, 2010)

compositepro said:


> No man I meant if id known this was your preferred method we could have had that running in hours .....hence the history explanation...sorry chap


You do not owe me any apology, nor did *I* really know that the expanding split mandrel was my preferred method.

Turns out, it isn't. I had more consistent success with the solid mandrel method (despite my habit of damaging mold edges using that method). The issue I've been having with the split mandrel is seam misalignment, which has often resulted in _severe_ under compression.

So -- how to return to the solid mandrel stuff, while avoiding some of the pitfalls that I experienced with solid mandrel.

I pondered some alternative cores - different waxes for instance, but that would involve a machinery addition I cannot yet justify.

What I really need is a zero-day fill-in element for a solid mandrel.

HELLO, why not just one of my already functional pressure bladders, except just... don't treat it like a bladder in terms of compaction. Rather, just treat it as a large physical volume where epoxy isn't allowed to travel.

I've been trying to poke holes in the logic for a few days. None found, so I'm going to push out a few in this manner.


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## Drew Diller (Jan 4, 2010)

Tested some of the more recent bars vs some older bars vs some donor bars.

I did break some eBay carbon bars -- yikes that was scary how thoroughly and suddenly they snapped.

I broke some of my older bars, wasn't surprising, though they were a step up.

*Happily*, my most recent iteration of bars reflected the following falling object setup many times:

1 meter drop, payload ~9 kg, spring tension ~109 N/mm (spring spec by manufacturer 62.4 lb per 0.1"), spring travel limited to 19 mm. This is the first time I've had the necessary values available, I *hope* I did the math correctly.

I increased the drop a few cm such that the spring bottomed audibly (I do not have sensitive equipment for measuring this but I know what I heard). The bars survived this. I increased a few more cm and that was met with failure.

Testing isn't close to done (is it ever?), especially since none of the above informs me of what has happened inside the laminate, but I am finally getting near acceptable peak strength values.

Which is good because I have debts to pay.


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## compositepro (Jun 21, 2007)

Drew Diller said:


> You do not owe me any apology, nor did *I* really know that the expanding split mandrel was my preferred method.
> 
> Turns out, it isn't. I had more consistent success with the solid mandrel method (despite my habit of damaging mold edges using that method). The issue I've been having with the split mandrel is seam misalignment, which has often resulted in _severe_ under compression.
> 
> ...


this one falls into the realms of advanced stuff we use to use to make turboprop blades , one of these methods was to fill the bladder with low melt alloy , effectively meaning you have a solid mandrel at wrapping and a liquid one that you could pump air into to remove the alloy through a valve when you were at ramp temperature, we did try using the fact bismuth expands as it cools but it didn't provide enough compaction on thicker laminates though was very good at thin ones ,the alloy also meant it had a very good temperature gradient inside the part as well as the tool side


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## Drew Diller (Jan 4, 2010)

Hey compositepro, I had another idea and I'd like you to shoot some holes in the logic.

It's been ... well I lost count, almost 20 bladder cycles since I've had a positive air pressure rupture. The other day, I had a slow-flow but high-pressure leak. The way I had set up the closed mold was a bit different so I had no way to gauge this. (Mea culpa.) I was leaking 90 psi through a pin hole. The infusion went pretty well, and my goal at the time was to up my game with respect to waste material, by cycling acetone through the exit epoxy lines, which happen to be the longest lines.

I learned a lesson the hard way about applying TWO clamps on either side of a cut before cutting a line with liquid in it. Highly pressurized epoxy sprayed all over the place, thankfully away from me, generously skinning a brand new aquarium dosing pump with a glittery pattern of epoxy dots. The pin hole positive air pressure leak happened to be located outside of the part (why the infusion went ok), but inside of the vacuum seal (why this did NOT affect the initial pressure rise test is currently confusing me). Once a free escape was made, the flash/runners were the path of least resistance.

So, in the vein of simplicity - I'm trying to make these bars inexpensively because that's what I want to buy - what if I had *nothing* inside the mandrel of the bar? What if it was just an enclosed envelope of nominal atmosphere pressure? Cap the ends with fast epoxy sort of thing, to be later snipped off during finishing work.

The risk is that absolutely capping the ends precludes me from measuring the air pressure inside to ensure that it is not messing with the partial vacuum environment of the infusion process.

An alternative question: is it possible to do a mock infusion to measure the volume of, say, water actually absorbed during the flow process, and then be able to get ALL of that water OUT of the mold before infusing epoxy / some other resin? Doing so would bypass the need to check the mandrel interior pressure.

I realize I'm obsessing over this a bit and I should just accept the occasional 5% defect like any other manufacturer. But that ticks me off and I want 99% reliability damn it.


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## Wacha Wacha Wacha (Sep 27, 2017)

I love hobbies.


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## Drew Diller (Jan 4, 2010)

Drew Diller said:


> I realize I'm obsessing over this a bit and I should just accept the occasional 5% defect like any other manufacturer. But that ticks me off and I want 99% reliability damn it.


I did an isolation test the other day. I reproduced a problem that I suspected, but sounded too crazy to be real.

It's real.

My inflation bladders are produced with a very soft silicone rubber with a 1,000% elongation-at-break rating. In reality I subject them to 200%. Like other silicone rubbers, they will run if a small tear is started. Supposing a partial pinhole gouge was made in the surface. Then suppose 100 psi air pressure was directed at the surface for the purpose of cleaning particulate so a good vacuum seal would take to the surface. Could the high air pressure create a pocket or tunneling effect in the surface, enough to pry open the hole and create the runaway tearing condition?

Yyyyyyyyyep.

Behavior change: I now clean the ends of the bladders with packing tape. The same idea behind using those little tape strips on a roll when you need to clean pet hairs off your clothing when leaving the house. This is a win, as the tape is faster / more complete to clean with anyway.


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## Velobike (Jun 23, 2007)

Drew Diller said:


> ...Like other silicone rubbers, they will run if a small tear is started. Supposing a partial pinhole gouge was made in the surface. Then suppose 100 psi air pressure was directed at the surface for the purpose of cleaning particulate so a good vacuum seal would take to the surface. Could the high air pressure create a pocket or tunneling effect in the surface, enough to pry open the hole and create the runaway tearing condition?...


It's always the details, the little things that you don't know that you don't know that get you.

Practical knowledge versus theory.


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## Drew Diller (Jan 4, 2010)

What follows will probably be the most useful thing I've posted in this thread specific to handlebars or other quasi-single-tube inflation design, assuming any other CF newb ever reads this and wants to retrace my steps.

Tygon 3350. It's a pre-fab silicone tubing that has been cured to extremely high purity, and I'm assuming used for medical purposes. A farming scientist buddy of mine uses it for making tight bends in vacuum lines. Unlike the vast majority of pre-fab silicone tubing I found out there, _this_ one has a usefully high ultimate elongation at failure (how far did it stretch when it ruptures) of 770%. This is a downgrade from the stuff I was making (1,000%), however, it's good enough.

As a bonus, the slightly higher durometer makes for easier insertion of inflator fittings. Once inserted, they sort of hold themselves in temporarily while awaiting a retention device prior to full inflation.

I made some mandrels with it, at close to road bike tire pressures.

Caveat: it's expensive. (On the other hand, it's durable.) #worthit

https://www.usplastic.com/catalog/files/specsheets/FT-Tygon-3350.pdf


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## Drew Diller (Jan 4, 2010)

Feels like I should update. Latter half of December and all of January sucked. I made a few bars and they were nice, except for when they weren't. If I look at the data, the reliability ratio is CRAP (less than 50% keep).

Then had some multiple computer equipment failure. Then spent a few weeks being sick. All better now, boots on the ground. The bed time gave me some non trivial hours to think.

I suspected that the small bladder inlet diameter coupled with the inlet being a boring ol' cylinder shape made for a leaky combination - occasionally a leak that would blow bubbles directly into an infusion.

...At a slow enough rate to be considered part of the natural leak rate.

So I was like SCREW IT. If the use of a bladder only nets me a small % bump in fiber volume fraction, for parts of this size why even use a bladder at this juncture? I've had that thought before, and have also thought of using just a filler for the mandrel during layup and epoxy transfer.

Now... now I just had a lot more motivation. Just remove the chance for air intrusion entirely, and circle back later on with a revised custom inflator that is suitable to the small inlet diameter. So the problem is then WHAT filler specifically to use, something that I'm sorting presently. This filler nonsense is a step I'd rather not have to take, and will remove down the road, but right now I'm into the "extreme circumstances" line of thought.

I also determined that the use of mastic tape in a hard-mold-against-hard-mold situation is not a good idea. Mastic tape really should only be used for its intended application, with a hard mold on one side and a film membrane on the other. The deformation of the membrane prevents the tape from liquefying and migrating as it had been doing for me. A vacuum seal needs to be good for potentially unlimited hours, not just "very good for four hours and then suddenly not good at all".

So I did a vac drop test with a revised mold with nothing in it, using only rubber gaskets at a prescribed loss in thickness upon compression. Yeah... yeah that'll do. Hardly a noticeable pressure rise in a 48 hour period! Are you KIDDING me? How long have I been blowing bubbles into otherwise perfectly good-- you know what, NEVER MIND, I don't want to know, let's just move on!

So hopefully the next few bars will be "lit" as the kids say these days and I can move onto the gearboxes already because I don't even give a 57!t about these handlebars beyond their value as a litmus test as a single-point-of-failure manufacturing exercise.


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## Eric Malcolm (Dec 18, 2011)

Man, it's going to be fun watching you do a drop test on a lug. Remember, you started doing lugs? Ha. When are you going to do 'that' bike Drew?

Eric


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## Drew Diller (Jan 4, 2010)

Eric Malcolm said:


> Man, it's going to be fun watching you do a drop test on a lug. Remember, you started doing lugs? Ha. When are you going to do 'that' bike Drew?
> 
> Eric


I think I could take what I've learned and make a better lug, though, at this point, I could either take it or leave it with respect to lugs. I remember WHY I started with lugs, and that still makes sense, but I have less motivation to make stuff from bamboo. "Less" is not to conflated with "no motivation".

THAT frame, are you referring to the one I wanted to make that is the same tack as how Zerode started with the Alfine jackshaft, before they moved on to the Pinion design? If so... that ship has sailed, for a very specific reason. Shimano. They were a contributing reason to my favorite bike shop deciding to close down. It was a unique shop where you could walk in with a cheap bike or an expensive bike and the owner would take you seriously. My blood pressure always lowered.

So emotionally, screw Shimano. Objectively, also, screw the Alfine design. I took one apart in the intervening time and I was like WHAT, this is what's on the inside?? How do these go anywhere at all? Some of the small torque transfer cogs were _toys_ to my eyes and not in the good way.

I decided I want to make my own gearbox instead because I'm a control freak. An affordable one. I've been told - by someone indeed, who would *know* - that what I have in mind is going to be high budget. Personally I took it as a challenge even though I'm sure he did not intend for that. The way I see it, the gearbox market is still very very young, and you have these extremes of almost ineffective range at a quasi-affordable price (Patterson 2 speed, Efneo 3 speed) VS amazing performance at absurd price (Pinion). Must there really be NO middle ground? Really?

Rrrrrrrrrreeeeeeaaaally? *I REJECT THIS.* I want a gearbox bike that can get stolen and it won't break my heart if it does because the 'box only cost a few hundred bucks.

I've been told by nearly all industry folks "Well Drew you're not going to make money that way". @#$**@&%&@#* if I wanted to make money and only make money, I'd go back to writing software for manipulative information merchants. On the other hand, when I find one of "my people" and make my elevator pitch, not only are the keen on the idea, but they start describing the idea _to me_ in fine detail. Clearly it is wanted, and clearly it does not have a great profit potential, but I'm focusing on the "clearly it is wanted" part. I can make money from bikes in other ways (such as refining custom handlebar production to a degree where they are easy to make and can be pumped out in quantity).

Sorry for vent.


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## Eric Malcolm (Dec 18, 2011)

Gee, I was just hoping to see some interesting Carbon and Bamboo put together in a very innovative way...Lol.

Anyway, I am enjoying the thread, just wondered where the bike thing was going for you.

Eric


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## Drew Diller (Jan 4, 2010)

Eric Malcolm said:


> Gee, I was just hoping to see some interesting Carbon and Bamboo put together in a very innovative way...Lol.
> 
> Anyway, I am enjoying the thread, just wondered where the bike thing was going for you.
> 
> Eric


It's going places, just with these long standing pauses to deal with the occasional, I don't know, _fundamental processing flaw_. Sorry if I'm making this out to be a catastrophe, I walked past the pile of "good enough to drop test" bar and it was not exactly _empty_:








I'm dissatisfied because that's the kind of output I'd like to see *in one week*. ...Not the better part of a friggin year.

Regarding the bamboo stuff, I'd like to keep those to either of two extremes: (A) high-fashion "finish carpentry" type build where the carbon lugs would be minimal or invisible (underneath with an overwrap of nearly invisible fiberglass) and mini slabs of bamboo would be glued and turned and polished and lacquered and all that shiny BS, vs (B) low-fashion intentionally hippie these-were-some-plants-that-came-out-of-ground-and-made-into-a-frame-and-it-looks-exactly-like-that. Specifically on the notion of a (B) build, I have a down tube in mind that weighs _five pounds_ for the down tube _only_, and that takes a certain kind of customer.

Is that innovative, though? Ehhhhhhhh.... *shrug* depends on the viewer.


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## Drew Diller (Jan 4, 2010)

Finishing up a nearly week long melt cycle. The last job of melt / pour iterations is less picky about having things crunched up into tiny chunks because the large volume of not-quite-drained molten wax makes for a quick re-congeal and melt compared to starting when cold. Sometimes I like to play puzzle while waiting impatiently for the heated spigot to unclog.

At some point I'd like the "gun" like accessory where the wax is moved along by a fairly strong pump, instead of currently having to rely on gravity loading from a very full vat in order to achieve a fast pouring rate. It's inefficient to wait for the *entire* vat to become molten. But those guns ain't exactly cheap soooooo it's on the back burner.

EDIT: I've figured out how to keep my hands free and clear of a hammer-and-chisel arrangement, but sometimes the pieces come apart at high speed, slip off the table, and hit me in the knee. At some point I'll have a coarse grinder bin to remove the risk - I would make sure that it is analog / human powered.


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## Drew Diller (Jan 4, 2010)

*Some good news.*

I have established with some degree of certainty that my bladder-related vacuum leak-_up_ rates are small but significant. Tiny but intolerable.

After much hand wringing, I did my first infusion of a fully solid filled mandrel with the new vac gasket design. It's pretty easy to put together, the leak-up is very slow. Critically, the epoxy fast travel zone on the inlet side came out as pure epoxy.

I also tried to employ an external resin brake - it kind of worked. Epoxy didn't quite reach the exit / recirculator zone, but a small amount of did come out of the mold.

Unfortunately, the filler still needs some tuning. All the fillers I have tested so far experience volumetric shrink or warp or porosity. The result is extra resin ingestion, such that the fiber volume fraction is 48% rather than the desired 60%. I thought that it is about time to try compositepro's suggestion of using a low-melt alloy what with its neutral or backwards CTE. ...Unfortunately, with the large amount of indium present in Field's Metal, and with indium being more expensive than silver, it's not something I can quite justify at the moment.

This means I need to revise the small-diameter bladder inlets such that they do not exhibit blow-by. I think this also means I should soon invest in a very fine resolution vacuum gauge, something that can tell me within minutes of a fine vacuum leak instead of having to wait several hours for a leak-up to show some tangible pressure rise.

In the immediate time frame, I'm going to try a multi-phase approach to a paraffin wax filler. The hope is that gravity fed castings will bleed around the small gaps left over from the shrinkage of the previous gravity casting.

I'm _over the moon freaking *happy*_ to know that my vacuum integrity problem has been diagnosed, and that a solution is around the corner.


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## Drew Diller (Jan 4, 2010)

Drew Diller said:


> This means I need to revise the small-diameter bladder inlets such that they do not exhibit blow-by.


I think I've accomplished this in an isolated test mold with a super tiny vacuum envelope volume. Finally. The solution's shape is kinda like the wine-cork design of the larger bladder inlets, but in the form of a press-in rubber washer - well, two of them, of different hardness - with a bit of mastic underneath where the gasket cord pokes out.

The compression force is enough to nearly close the bladder inlet such that the bladder hesitates to inflate until some significant pressure is introduced. Cripes. Now to mill some new molds with this change in mind and *move on*.


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## Drew Diller (Jan 4, 2010)

*A "Sad Trombone" moment.*

So I've been having this recurring issue lately with continuous profile gasket cord where they exert what appears to be a pressure hot spot, causing the relatively soft wax mold material to fracture.

This fits with some of my intentional fracturing of the mold, where once the tiniest crack begins, I can just sit there with even torque on a chisel, and the crack will just spider, and spider, and spider...

Anyway, the cracks unsurprisingly let air in. This particular _version_ of mold fracture is relatively new, and didn't happen in this way with the older flat gaskets.

So, back to flat gaskets. Found a faster way of makin' em. Yay. Leak-up rate tested out okay. Yay. Started an infusion job last night, and it was good until suddenly it wasn't.

It appears as though an inlet tube liner (present because it eases the removal of epoxy from the inlet and outlet tube sites) got sucked too far into the mold, and bent into an L shape, cutting off inlet flow. The epoxy inlet side channel was almost pure epoxy, indicating very low vacuum blow-by. And the epoxy seemed to spread evenly across the inlet flashing. However, the infusion just... stopped halfway. I was unable to extract the tube liner on the fly, and I could not blame things on a sudden spike in epoxy viscosity from premature polymerization. It was just... jammed.

I might need to make a custom liner that has a little butt at the end with a C shape to let the epoxy through while also not traveling _with_ the epoxy.

Whomp whomp. I tried to validate what I could of the revised gasket design - there were no visible traces of epoxy blow-by.


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## Velobike (Jun 23, 2007)

When you get all this sorted you may be better off building for the aerospace industry than the bicycle.


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## Drew Diller (Jan 4, 2010)

Velobike said:


> When you get all this sorted you may be better off building for the aerospace industry than the bicycle.


If the bike industry pisses me off I'd probably gravitate toward motorsport or boating firmware.


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## Drew Diller (Jan 4, 2010)

@Velobike: also, this latest flub is probably why other molding outfits use a side-entry injection port. During clean up, you just pull two halves apart. Easy peasy. I'm doing the top-down approach because it makes my particular assembly easier and the feed lines much shorter. And my way *appears* to have a slower vac leak rate, except for the part where it gets, ah, _overzealous_ like this.


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## compositepro (Jun 21, 2007)

Velobike said:


> When you get all this sorted you may be better off building for the aerospace industry than the bicycle.


that is the best advice anyone has ever given on a forum related to bikes.....


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## Drew Diller (Jan 4, 2010)

*Woo!!!*

YEAH.









*YEAH!!!*

This bar worked by the thinnest of margins! Literally - the gasket wandered and almost occluded the fast track *again*. Damn thing needs a retention channel.

*Now I get to move on to the next thing.*

EDIT for some stats:

- Resin content ~42%
- Pulled the deepest and most stable vac I've yet seen
- Gaskets migrated SEVERAL millimeters
- Infused _without_ explicit degassing at the start (???)
- All surface features intact across entire bar


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## Drew Diller (Jan 4, 2010)

More good news: pulled three bars in a row with identical cosmetics. 99% free of surface blemishes, all within a few grams of each other. I managed to stuff a few extra grams of carbon into one of them, which resulted in a 1% lowering of resin content.

Next step: make this sort of consistency _old hat_.


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## Drew Diller (Jan 4, 2010)

Five in a row. Three of them in an every-other-day pattern.

At present, the only thing keeping me from one-a-day is how fast the mandrels cure. I'm using Kwik Kick epoxy for that task, as it advertises one hour cure. Unfortunately, with the 0.3mm wall thickness of the mandrel, the exothermic reaction of the epoxy doesn't really stand a chance because there's no volume to work with. So it takes six hours.

So, I basically need to find a very fast cure epoxy that is longer than the handful-of-minutes epoxy one can find at the hardware store. It seems I'm having trouble finding that happy in-between.

I am feeling *pretty jazzed up* at the moment. Five in a row!!! They all weigh within a few grams of each other. I'm estimating cut and trimmed mass will be around 260 grams.


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## Drew Diller (Jan 4, 2010)

*Dozen+ in a row*

My standards are shifting a bit. I've made a bunch in a row, so that's no longer a neat trick.

What's next? Can I make them:

- stronger/lighter?
- cheaper?
- faster?

I don't really think I can make them cheaper. This is about as low investment as I can figure. I started it that way.

Stronger it is, then. I paid attention to some advice given elsewhere by compositepro, and I implemented it in the form of additional fibers wrapped around the bar circumference rather than along its length. An analogy to how human skin restricts and focuses the force of human muscles.

Wow, yes, that is very strong, and buckling upon failure is reduced, all without special materials. I built a stupid little "pre-test" test that is nothing more than a lumber-platform with a hole in it, into which I place a sawed-off 1-1/8" steer tube, to which a stem and anti-rotation blocks are attached. I had a 210 lb guy stand on a handlebar so I could watch the deflection. Fascinating, easily more than an inch deflection at the ends.

I wanted to try some specialty materials (boron) that can reduce buckling by handling compression loads (and reduce the amount of carbon needed, thus, lighter). Yiiiiiiikes. That looks like an exclusive club to be in. Shelving that for a later date out of raw lack of influence and investment cash.

So I guess the next most approachable thing to do is start putting CNTs in my resin. And I don't think I'm yet tooled up for that in terms of air flow management - important not just for my health but also because the stuff costs $30 a gram.

With the undesirable notions in mind, I suppose my only option for improvement right now is to make them faster. Indeed, with the practice of so many failed bars, I and the inclusion of some very high areal weight UD fiber that has a friendly warping character (or, as friendly as it gets...), I can now do layup in just less than an hour.

It takes me longer to align, close, connect, and pressure test the mold components. That'll need some work. I think this means I have to (grumble) yield on some previous held notions regarding mold-cavities-per-volume-for-milling-efficiency. The driving force is that this latest mold set didn't get killed by anything and has done dozens of pulls, which means the milling-time-per-part is no longer a lead factor of the economy.

...Which means I'll need a new mold to test some of the fast mold assembly things I have in mind.

Been playing with polishing a little bit too. Almost out the door with this stuff.


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## Eric Malcolm (Dec 18, 2011)

Thats looking pretty good.

Are you selling these now?

Eric


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## octanejake (Oct 11, 2010)

Looks fantastic Drew! This has been my favorite thread to follow along.

Are you still infusing? I was under the impression that CNTs don't work with resin infusion.


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## Drew Diller (Jan 4, 2010)

@Eric: very close now. The last safety check I wanna do is send it out for someone to X-ray. Just how bubbly is it on the inside? 2%? 10%? Inquiring minds wanna know.

@octanejake you know that doesn't surprise me to hear - the epoxy barely makes it through on its own, why would thickening it make it any easier? I've been thinking of moving to DIY prepregs. Been thinking that a while, honestly, but was encouraged privately to avoid it on the notion of "you keep moving little pieces around, just perfect this one thing first".

Bearing in mind I must keep the room temp cure for the extremely CTE-fickle wax mold material, DIY prepregs have some things going for it:

1) I get to skip all the vac setup and validation nonsense, this is currently the biggest pain to me
2) Reduction of waste epoxy
3) Lack of the liner film waste that keeps mass-manufactured prepreg from sticking to itself

Another practical limitation that made me choose to avoid testing DIY prepregs was my table space. A single layer of 150g/m^2 carbon takes up a lot of freaking area just to make a handlebar. However, with the recent inclusion of the 373g/m^2 stuff, that number changes to a figure that can fit on my existing layup table.

Perhaps the time is right. Vacuum infusion sucks (haha whomp whomp).


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## Drew Diller (Jan 4, 2010)

*Moar*

Been keeping my head down lately, and have come up with a reasonably consistent routine. I had fun taking this picture, my apologies to the handful of you who've already seen it.

I made a bunch of friggin bars so far in July. Zero count of total rejects. WHOOOOP.









Also, I have a question for anyone willing. First, I need to detail something about my infusion setup. I'm using a cheap peristalsis pump meant for aquariums. This completely forgoes the catch pot on the pull side of the infusion mold, whatever comes out goes back into the injection source pot. The peri pump is three-headed so it holds vacuum (relatively, depending on the age and quality of the tubing) even when not rotating.

The thing here is that I do not have a vacuum gauge that can withstand direct contact with epoxy, and then separate after epoxy has cured, and have the gauge continue to function. So what I've been doing is verifying vacuum holding with a temporary gauge directly on the inlet tube, then clamping the line and removing the gauge. This effectively means that during the actual infusion, I'm running with no gauge at all. Today I noticed something, after verifying an unusually good seal (for once). After letting the peri pump run a while, there was - what looked like - kind of a fog on the inside of the exit tubing on the exit side of the peri pump.

My question is: does this happen to be water content that has boiled off from the dry laminate preform, and then condensed in the tubing once the water vapor was confronted with atmospheric pressure again?

I ask because the peri pump does not hold a particularly deep vacuum, I assume because of the distance between the impeller cylinders letting in at least a smidgen of atmosphere every seal / unseal event.

In the photo below, you'll see two opaque silicone lines crossing each other - that's what goes in the peri pump - the exit PVC tubing is heading south or towards the camera. What I'm guessing is the condensate is just a small puff leading from the silicone-to-PVC black coupler.


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## Feldybikes (Feb 17, 2004)

Disclaimer: I know about making bikes, and I know about high vacuum systems. I don’t know anything about infusion. So with that mega-caveat, what you describe sounds plausible. Between low vac and ultra high vac, water adsorbed onto very surface is most of what you’re pumping. I assume the condensate goes away after you wait a bit? If so, what would it be besides water? It’s not like epoxy would condense and then go away.


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## Drew Diller (Jan 4, 2010)

Feldybikes said:


> If so, what would it be besides water? It's not like epoxy would condense and then go away.


Yeah, that's... kinda... what I was guessing. The epoxy isn't even entering the mold at the time pictured.

The only other thing it could really be is maybe some condensed off gassing from the spray tack adhesive, but, the folks who sell the stuff said "nope" to that inquiry.

I don't think it's a big deal, but...

Hmm.

I appreciate the input!


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## Drew Diller (Jan 4, 2010)

*Time for something else*

Here's the first pull of a 27.5° swept flat bar (vs a 20° for reference). 240 grams @ 760mm wide.

There was a small amount of surface fuzz that needed to be touched up, but the numbers and the tap sound feedback was good.

I no longer get an excited feeling from pulling a good bar - now it is all about hard examination of minute defects, things being slightly out of round or too thick etc. I guess that means it's time to move on to the next thing, which means drop bars that will be three-piece-bonded, partially because I have to what with my very limited CNC table envelope (especially in Z-axis), partially because I will be able to vary the flare from bar to bar based on customer preference. They're going to be *slightly* heavy due to the overlaps required, but I've received enough requests for drop bars that I cannot say no.


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## Drew Diller (Jan 4, 2010)

Iiiiiiiiiiiiiii am feeling a little buzzed on autonomously dosed adrenaline. I was so worried that I was making garbage. Got some results from Delphi Precision today.

Good results.


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## octanejake (Oct 11, 2010)

Congrats man!


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## Drew Diller (Jan 4, 2010)

I don't think it is fair to only post successes, so let's mix the bad with the good.

I had a JRA the other day! I didn't even make it a block after installing a new bar. It... just _didn't occur_ for me to at least do a standing weight test before its first use. I didn't even make it a city block, it broke while I was accelerating away from a complete stop using the out of saddle position. Same with the other side once I got it back home, I put the bar in a clamp and pulled on it like I was picking up a grocery bag full o tomato sauce cans. Crunch! HOLY CRAP THAT IS FRIGHTENING.

My mind started to race, "I thought this was from the batch of bars that imaged well? What the heck?"

Grabbed the computer and looked through every last photo. There *was* one bar that looked like crap. 1 outta 7 failure rate is perhaps acceptable to some, but not to me long term. I recalled making a mental note not to ride the bar marked. So why'd one bar that I expected to be strong end up failing so miserably?

I looked at the photos really hard, like just sat and stared as I was suddenly having a whole lot of anxiety about opening up for official advertising and shipping. I didn't want to hurt anyone, and my insurance policy is meant to be never used, in the same way I put on a seat belt but drive my car carefully. My palms were sweating. After enough staring, I realized I had mislabeled one of the bars. The imaging service merely sent back the information based on what was provided to them. The way I determined this was via ephiphany: the dark striations are fiberglass! That's an older method I used just to get rid of some material I didn't want anymore! DUDE! The oldest works were better than the most recent? They were! @#$*. @#$(@&#%(*@#^*($^@ you don't want to regress, man!

Go outside and test the bar that you labeled as the weak one. Yyyyyyup, strong as heck.

Kinda gave me a gut check ("Am I able to organize anything?") because I had made an association with bad clerical accuracy leading to someone's deeply unwanted injury. Did NOT feel good.

One silver lining came out of the experience. I had a test bar on my personal bike for a while that I hadn't swapped out for a while, to which I guess I hadn't paid any mind. I wanted to give my bars the most abusive life possible to simulate what might happen in the hands of a 2nd or Nth owner, so I didn't use a torque wrench and just went monkey tight. When removing this bar, I noticed a little bit of dimpling. It still looked pretty safe, I know there's a lot of meat in that section specifically.

That said, I didn't _like it_. I'd rather have someone inevitably just monkey wrench and bolt everything up in the wrong order, and be content in this future person surviving despite their lack of awareness of modern stem clamp care. So I'm gonna use a metal sleeve. I want it to be mad abuse tolerant.

Yeah, it'll add weight. Worth it.

Felt the need to talk about my failings here because there aren't many people in my personal life who get it. They just think "Oh Drew's just doing his dream job, his lack of interpersonal conflicts means his job is super easy." I don't even need a response, because the correct response is "do better". I just wanted to say it here to people who know.


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## Eric Malcolm (Dec 18, 2011)

Man, you have matured. You used to Rant for Food. lol.

Good admission. Keep working at it.

Eric


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## duandr (Jan 7, 2016)

Drew Diller said:


> I didn't want to hurt anyone, and my insurance policy is meant to be never used, in the same way I put on a seat belt but drive my car carefully.


I won't go into details but know the feeling. The mind races contemplating the ugly possibilities. For me, I just need to stop trying to over optimize.


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## dRjOn (Feb 18, 2004)

as someone who is patiently (- ish!) waiting for you to be ready to sell the 27degree version, i apprecioate the candour - its all very interesting and i salute yoru efforts!


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## Drew Diller (Jan 4, 2010)

Ok I think I figured it out.

I went through all the X-ray bars, and the oldest ones were strongest, newest ones were weak like papier mache as far as structural needs go.

I had one where I couldn't even support my weight when gently transferring that weight. Yiiiiikes.

What do the new ones really have in common? A new (to me) fiber type. What attracted me to its use was the notion that the tows - about 3k wide (3,000 fibers) each, or a few millimeters, depending - are allowed to move relative to the neighboring tow because the binding fiber is flimsy and only runs in one direction and is only held in place by friction. So, practically speaking, I could take a 20mm wide tape of 7 or 8 tows, and "bend" it around a corner, all while keeping tension in check.

So why are they so awful in my application? It is possible that the manufacturer claims of infusion-friendly processing are either (A) exaggerated, (B) false, or (C) greatly dependent on a specific process. It is further possible that the increased areal density takes longer to get through. It is further possible that the lack of "sizing" (this is proprietary information that I lack, but you can see it up close, it looks like salt) is a problem. It is further possible that combining two different types of infusion rates in a single laminate can lead to complicated flow issues, like (sorry, John) a rally car needling through a chicane, when really you wanted a bus to just knock the hay bales out of the way. Maybe not the best analogy, but, @#$* you I'm so angry at the moment.

That in mind, next steps are to politely harass most recent supplier, and to revisit the Zoltek specific fiber that has apparently been far more reliable.

Boy are my ears red with embarrassment. Do not believe manufacturer claims, Drew, test them yourself.

EDIT - I think the science terms for this flow problem I'm experiencing are "intra" fusion versus "inter" fusion. The idea of getting epoxy *into* the fibers (rather than just _around_) is critical.


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## Drew Diller (Jan 4, 2010)

It took me a bit of time to think about the point of having done the X-ray images taken, if they were ultimately ineffective at identifying weak bars vs strong ones.

In defense of the outfit that did the imaging, *they did warn me* that detection of total void content and location was not a feature of X-rays. Only gross misplacements of fiber, and thickness variations, would be detectable.

If I wanted void content data, I'd have needed multi section CT scanning, which is considerably more expensive.

The images are also decent marketing material, if only for the notion of pursuing diligence.

Gonna send the crap bars to someone who does ultrasound - if those results are at all informative, then I can evaluate what to do from there in terms of long term habit.


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## Drew Diller (Jan 4, 2010)

Rather than continuing to *roll my eyes* at the various interpretations of "Catcher in the Rye" with the thread about college-based frame building classes, I thought I'd post a recent challenge and resolution.

I had an infusion go sour last week - like double-yew-tee-eff, why is it so dry? Only the grips infused. I remember being at this stage of development, that is a huuuuuuge regression! Even bigger than the preceding regression.

Figured it out the next morning: the resin source pot had melted, leaving behind a hardened mess. So... the source pot exotherm'd? Yeah, yeah I guess it did. That would explain why the infusion seemed to slow early - I had assumed at the time that it was done. Nah, it wasn't done, the resin itself had occluded the inlet by way of early gel stage.

But why? Well, I have been doing some unusual amount of office work. It could be that the epoxy sitting in quick pumps, with the tip of the resin and the hardener being exposed to atmosphere, could have aged one or both components, such that runaway exotherm could happen earlier than expected.

Bah! @#$*

Now what?

Well, for starters, I've complained in the past that there is no room for MTI tubing, which is true. I came up with the perimeter distribution scheme, and that was a boon. But I need *more* even flow throughout the pesky transition from 22.2mm OD to 31.8mm OD.

What of some additional channels on the outer surface? I hate sanding, and channels would make for more sanding, but I hate making scrap parts even worse than I hate sanding.

So I scratched some in manually with a thin screwdriver.

Also, I tried to imitate the low tech form of a continuous injection machine, by splitting up the epoxy source pot into small batches.

This appeared to work - now to wait a few days for the the epoxy to reach full strength, and see if it _really_ worked.


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## bme107 (Jul 23, 2008)

Drew Diller said:


> I hate sanding, and channels would make for more sanding, but I hate making scrap parts even worse than I hate sanding.
> 
> View attachment 1224573


Now I finally see how much that you need to sand. (re: Abrasive thread) How long would that take you to clean up and what grit progression?


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## Drew Diller (Jan 4, 2010)

bme107 said:


> Now I finally see how much that you need to sand. (re: Abrasive thread) How long would that take you to clean up and what grit progression?


Less than ten hours, more than one. Don't have enough data on that yet to really say.

I am definitely going to buy a tube polisher as soon as I can afford it.

Thankfully, the new epoxy lanes ingest less fiber compared to the perimeter. EDIT: This means that I can just snap some of them off, minimizing extra sanding.

I'm _told_ that higher viscosity resins _tend_ to be tougher, so it is interesting to me if I can get more arterial flow in general.

One caveat that should be obvious: my scratching in the lanes manually, I made one with some undercut. This was bad, and traumatic to the mold upon removal. I'll have to get a teeny tiny end mill with a slight taper.


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## Drew Diller (Jan 4, 2010)

To illustrate the "just snap em off" idea. This is after some manual attention with a flush-edge pliers type cutter. Doing this is not so horrible compared to the perimeter flashing. The perimeter has way more carbon in it which makes things difficult for high speed removal.

So, ehhhh, I'll live with it for now.

Additional data gathered is that the manual carving made for lanes that are 2mm wide. This is excessive. I measured one lane (a product of two lengthwise molds being joined with a set gap, to avoid mastic tape minimum thickness problems) as being 0.5mm wide. This gap did the job just fine. So I aim to mill a really, _really_ small lane. The wax material is soft, so removal isn't going to be a problem at first, but chip removal may be a problem. First milling experiments along this line of thinking are going to be conservative, slow, plenty of air.


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## dRjOn (Feb 18, 2004)

....bump....? any updates? ive been fascinated following along...


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## Drew Diller (Jan 4, 2010)

dRjOn said:


> ....bump....? any updates? ive been fascinated following along...


Appreciate your concern dRjOn. This year has been a bit of a misadventure, I am in large part - but not wholly - responsible. I had some things happen on a personal level, traumatic-like, witnessing unsuccessful suicide attempts of people I care about type of thing. I took some time off to just to, like, be alive, take care of myself, spend time with my wife, ride bikes instead of design them. If I had an employer I'd be taking some FMLA time, it was that bad.

I've been riding, and thinking, thinking, riding, thinking, thinking, thinking, and a lot of CAD. (Speaking of, FreeCAD is up to 0.19 and is remarkably stable and useful compared to just a few years ago.)

Practical problems: My handlebars take too long to make and give me very few options in terms of epoxy selection. My gearbox design is going to be more expensive than I wanted it to be. Course adjustments, I have had lengthy conversations with people who are both friends and successful business people, and through those talks I've come up with some plans. These plans involve using some of my existing tools in ways they were not originally intended, but will work well enough.

Some of _those_ mild course adjustments required some rearrangement of my shop, which, conveniently, are nearly ready.

Honestly? The time off helped. I'm willing to brag that I have a strong work ethic, in two decades I have rarely had time off. But if your mind has been injured, work performance suffers until you heal. It hurts to see how many Americans are working themselves to death. I was in a position of privilege to heal up, and I took it. If you can find a way to heal, you take it. I'm done recuperating. I'm ready to get back at it.

Want to hear some *REALLY GOOD* news? This will take a minute. Some context is that one of my 2019 misadventures being a foray into crowdfunding that failed before I even published it. This was surprising to me, as I have seen some genuinely uninspired garbage succeed via crowd funding, so why I was I rejected while presenting a decently useful idea? I talked to someone who has done a great deal of crowd funding, it is not unheard of for projects to be rather arbitrarily cancelled.

I went looking for other sources of funding. My patience for getting this gearbox off the ground is wearing thin, and despite being graciously kept alive and housed by the kindness of my spouse, I don't have purchasing power on my own for a fully detailed and vetted metallic functioning prototype. As a shot in the dark, I applied for a small business grant. Happily, I am shocked and humbled that I was awarded a growth grant by the NASE (National Association of the Self Employed). I'm going to remain a member with them out of gratitude, as long as it takes to pay back the grant.

I have lined up a manufacturer who will make a one-time-only prototype, they're not interested in serial production, but they're really high precision people and that's what my concept needs. The first example needs to be flawless, and that costs money. It just _so happens_ that the NASE award amount (four thousand USD) matches the verbal agreement between me and the manufacturer. _What are the chances?_ It feels like some kind of dream.

I'm deeply grateful to have been given a financial boost. I'm grateful to have been given some time to just be alive. I'm grateful this gearbox thing will be *happening in mere months from now if not sooner*. I'm grateful for the privileges I've been afforded. I'm grateful for a lot of things.

TLR I'm working on an acrylic 1:1 model of the gearbox, I'm working on getting thicker resin (tougher) into my handlebars and that's almost ready, some really cool small business sympathizers gave me some money that I'm going to try to figure out how to pay it forward some day.


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## dRjOn (Feb 18, 2004)

sounds like a rough time - im glad there is some light at the end of the tunnel - the prototype sounds exciting! looking forward to seeing it ~


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## Drew Diller (Jan 4, 2010)

dRjOn said:


> sounds like a rough time - im glad there is some light at the end of the tunnel - the prototype sounds exciting! looking forward to seeing it ~


Me too!! MAN I cannot wait to ride it for the first time. The approach I'm taking is fanatically dedicated to high-resolution engagement while downshifting under torque. "You're not supposed to do that on a derailleur anyway" BZZZZZZZT WRONG ANSWER, people do it all the time on mountain bikes. Today's derailleur hardware does an admirable job *coping* with the hardship (until such time where the derailleur is ripped off by tall weeds, in my case of living in overgrown marshland river valleys).

Basically what I've been observing is a legion of mountain bikers making excuses for their hardware because they simply don't have options and they're trying to make do, because that's what humans do.

To that end, after uncountable dozens (maybe hundreds?) of conversations with perfect strangers, I've figured out what to talk about VS what to avoid discussing. My guerilla market research conversation script these days goes something like this:

"If it is true that a single speed is the ideal low tech setup that is un-manageable by the imperfect legs of many cyclists, and if it is also true that every multi-gear-ratio bit of hardware added is another chance for mechanical failure and increased cost, what is the smallest *number* of gear steps you could deal with across a total end-to-end range of, say, 400% to 500%?"

Some people want a 4 speed, some want an 8 speed, some want 12, some don't want to answer out of fear of hurting my feelings (????). I can tell people really start to think hard about it when confronted with the notion that every gear in a gearbox is just another ~1% power loss. The fewer gears, the better, but there has to be enough to be useful.

I also take great care to pscyho-analyze the person being interviewed, as fast as possible. Clothes, bike they're riding, demonstrated fitness, bike handling style, any stickers that might be present. It's a lot of people watching with a good intent of making a fine product. I don't approach just anyone. People are fascinating.

I could have, probably some time ago, just designed the metal parts myself and paid any old machining company to make the parts that I cannot make in my shop of finite abilities. But, that will not do! Many prior attempts have been made by others to get gearboxes to work on bikes, few have succeeded so far, and the bike industry is full of marginal gains. I feel compelled to focus on *one critical behavior, which is extremely high resolution shifting response*, to make a _non-marginal gain_.

For a time, I was trying to do this all with extreme economy. "$100 per gear is the goal" was my mantra. I was raised lower-middle class, so this was important to me. After some talks with business people outside of the bike industry (and inside of it), I've decided that a multi-tier system is best. For instance, now that 1X drivetrains are a thing, is there anything I could do to "harden" traditional derailleurs now that the front chainring size is a non-moving target?

Well... yeah. Yeah there is. And it would not cost a lot of money.

So, the plan moving forward is to have the torque-tolerant-downshift gearbox be my flagship, and it will be expensive as it needs to be in order to work at high pedaling efficiency and have lengthy service intervals (and THAT is where the costs go up), and not everyone will need it, and that's okay. Once it is out, open-source the plans because it is based on technology from the early 1900s, and let other people manufacture it. From there, move on to the bottom-tier product that does a fair amount of effect for minimum cost (and involves any kind of cassette in terms of consumables / replacement access). From there, move on to the mid-tier solution that will, honestly, look a little off the wall but once you ride it a few times people will go "ohhhhhhhhhh I get it!" (and this, again, will use cassettes).

So, yes, I'm really excited! I'm PUMPED. Specifically for you dRjOn I'd be glad to make some handlebars with exactly the right bar ID to fit your DeWidgets, I've been paying attention on instagram 

One personal satisfaction I'm going to get out of the gearbox thing is in succeeding at something that "can't" be done. I've been ingesting a great deal of information from the car racing industry. The ingredients are right there for bicycles. If I were to compare recently successful mountain bike products to other things, ahem:

Thru axles? Motorcycles had that down pat long ago.
Dropper posts? Adjustable airfoils.
Lauf forks? Many a year of modern Corvettes would like to have a word with you.
Extremely high output brakes? Pffffffffft too many to name.

Hard-shifted gearboxes are simply the next thing to be applied to mountain bikes that *hasn't been tried yet* and _will succeed because it is based on proven technology_.

The primary difficulty I face has everything to do with longevity and low angle of contact. At this point I see it as being almost trivial to make a gearbox that will downshift happily under torque. It is more difficult to do so at an extremely low lash / free spin angle, and on top of that, making such a system continue to work 50,000 miles or whatever can be achieved.

The whole reason I did this carbon stuff is for credibility. I had this gearbox idea years ago, hell, when I was 13 years old I was thinking about cone clutches (btw, that approach will not work). I figured at the time that the adults would wise up and make gearbox mountain bikes. Nope, bike industry is very complacent. Problem was, even six years ago I could not start a conversation with anyone in a position of manufacturing power because I was a nobody in the bike world. No I'm a somebody, even if my "somebody-ness" is very, very small, it is more than nothing.

And that credibility has already been used. I carefully, carefully spent it in January of this year. The way that conversation went was ... ethereal. I was ecstatic. After leaving the site, I found the nearest patch of gravel parking lot and gleefully whipped all kinds of donuts. I had been *heard* by someone who *knows*. The rest is just details and precise execution!

My extended family and in-laws think I'm bat @#$* insane, but the way I look at it, I'm going to do something useful and cool before some idiot kills me via texting while driving.


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## Drew Diller (Jan 4, 2010)

In other words, We've Got To Try


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## octanejake (Oct 11, 2010)

Drew Diller said:


> So, yes, I'm really excited! I'm PUMPED.


Wow, quite the news. Sorry to hear about the rough personal stuff, really glad to hear that you're moving forward and in a better mental place. Looking forward to to see what you're cooking up with this gearbox! Best of luck.


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## Drew Diller (Jan 4, 2010)

octanejake said:


> Wow, quite the news. Sorry to hear about the rough personal stuff, really glad to hear that you're moving forward and in a better mental place. Looking forward to to see what you're cooking up with this gearbox! Best of luck.


Again, months have passed, and no result. Why? My brain is fine (now). My body is not. I have diverticulitis. It is incredibly painful and my capacity for creative reasoning is severely impacted. The easy way out is strong antibiotics, but I not want to ingratiate myself to antibiotic resistance. There are other reasons for being unwilling with the antibiotics, I did one round and had these strange, irrational, homicidal thoughts. There are other options from here.

The point is that this, now, is taking a LOT of time.

Some positives to offset this bummer:

- I'm younger than 40, creates surgical options as being (relatively) safe.
- My wife is awesome, I cannot imagine (gesticulates wildly) _doing any of this_ as a single man.
- I recently acquired a used B grade inspection plate for $200!
- I'm soon acquiring a Light Armor LA2500, so, prepreg options of long length will be in my not too distant future - relevant for a thing I want to do with marketing suspension swing arms to other frame builders. The nice thing about the LA2500 is the very low amperage requirements.

While these compound delays are frustrating to my core, one common thread about my disease is that keeping stress very low will reduce the severity and frequency of acute episodes. So I'm trying to be kinda zen about the delays. The Earth continues to spin.


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## Cord (Dec 10, 2006)

Missed this little update. Keep on trucking man!!!!


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