# filament winding progress



## Drew Diller (Jan 4, 2010)

Making tubes has finally become something of a convenience, given the right tools: a winder, a large-enough heating appliance, some "towpreg" from TCR Composites.

I don't even know how many years my X-Winder has been collecting dust for a litany of reasons. I ordered it during the crowd funding phase at version 1, so I got it for a song. They're rather expensive now, which makes sense considering what they can do.

You can see some flaws. The Dunstone shrinkage tape is tricky to use. It wrinkles too easily, which are the surface deviations imprinted in the finish where there is intense light reflection mostly toward the left where it is catching my ceiling lights. There are compression and expansion alternatives I have yet to try.

Another thing I need to sort is _rewinding_ the carbon spool during certain kinds of direction reversal. Sometimes it matters. In the first two images you can see some slight lack of tension pre-cure. That's no good. The compression is meant to be the final step, it's bad to have the fibers move very much. There is evidence of fiber "crimp" in certain places despite the overall good looking finish.

Good progress - but I can do better. I wanna see some steel front triangles with carbon rear swingarms that I'm gonna build. Can't wait!


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## Drew Diller (Jan 4, 2010)

Also, the middle wheeled support is there as a "zero day" fix for the notion that an 18mm OD polypropylene tube is SUPER flexible. I managed to yank it out of the chucks sans support.


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## Cord (Dec 10, 2006)

I know nothing about this, but find it really interesting. Please keep updating.

I wanted a filament wound seat tube for a frame I’m making, and in the process of nibbling info I found a German guy on Instagram who made them. He wanted €400 for a single tube, I instantly redressed my “need” for filament wound.


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## Drew Diller (Jan 4, 2010)

Cord said:


> I know nothing about this, but find it really interesting. Please keep updating.
> 
> I wanted a filament wound seat tube for a frame I'm making, and in the process of nibbling info I found a German guy on Instagram who made them. He wanted €400 for a single tube, I instantly redressed my "need" for filament wound.


Yeah, that is a bit steep. Towpreg is approximately $30 / lb. Assuming you wanted a 1 lb seat tube (somehow I doubt it), the labor is not massive. I'm guessing his process involved high precision chromed mandrels and he needed a new size, which would be an expensive up front thing, but any consecutive tubes thereafter would be much cheaper. I'm wanting to avoid that material choice for avoiding that kind of catch-22 economics.


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## Drew Diller (Jan 4, 2010)

I almost forgot: Cord, in the mean time, why not use Rockwest Composites bike tubes? If you only need a small quantity.


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## Cord (Dec 10, 2006)

Rock west had the size I wanted, or the finish I wanted, or the length I wanted. Unfortunately not all 3 at the same time. I ended up discovering a local company that specialise in fishing rods (tri-cast) to make almost exactly what I wanted for £110.

The €400 was with a mandrel I was supplying, the metal part of the process was the only bit I could do. I politely declined, obviously.


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## Drew Diller (Jan 4, 2010)

Ok so what do we have here. Experimented with a different mandrel.

Previous mandrels have been with a polypropylene rod as I mentioned briefly. The trais of using PP (plus + for good, minus - for bad) are as follows:

+ Large thermal expansion makes for a grow during heat / shrink during cool effect that can be used as a cheap "inflation bladder", albeit on a smaller ratio of expansion compared to an actual air membrane. Kind of a big deal, because the fibers retain good tension from being pushed outward during cure.
+ Does not bond to epoxy.
+ Relatively easy to machine, but the swarf sure is weird.
- Bendy.
- Will undergo plastic deformation if not stored perfectly flat or hung vertically from something.
- There is a practical limit to the thermal expansion effect - since CTE is a ratio, if your overall base unit (diameter) is small, then the amount of diameter lost during cooldown is not great enough to pull out easily on its own.

So, to some extent, screw using PP for covering great distances with a small diameter. It is good for large tubes where the rod diameter is such that the flexibility is not very important.

What to do then for small tubes. This time, tried a steel rod surrounded by Teflon. The idea is to wind, cure with heat, cool, pull the steel core out, then stretch the Teflon by pulling on it.

And that's pretty much what happened.

Only problem? There's no significant expansion. All the fibers get pushed inward from the outer pressure membrane (in this case, Dunstone shrink again). My fear here is that the fibers will lose tension slightly and make little wavy motions.

And that's pretty much what happened.

So what needs to change with my winder? I think the low-friction eyelet surfaces need to change to rollers. The towpreg is crazy tacky compared to wet winding. Also, I think the amount of tension is too low - friction alone does not seem to be working right. You know how when you peel packing tape or duct tape from a fresh roll, and it makes that peel-pause-pop-pop-pop-pop-peel sort of pattern? Like a ... seismograph - in terms of tension? The feed looks like that.

You *don't want to bounce the line*, just like when towing a vehicle with a tow strap in an emergency situation. You want to ride the brakes. Except, in this case, the mass involved is so freaking small that riding the brakes isn't doing the job. I think I need a rewinder device on the gantry. A bunch of stuff I've been reading about filament winding makes similar claims: tension must remain even.

Apparently there are yet other reasons aside from just keeping the carbon tight for good loading: if the tension is too low, the angle of separation of the towpreg coming off the spool can micro-crack the carbon fibers. An ideal separation angle is tangent. What I'm getting is more like 45 degrees. I'd be happy with a small number of degrees because tangent ain't about to happen.

In other words, a stock X-Winder can make _good_ parts but not ideal parts.

On the plus side, I'm starting to learn sequencing. Note the Charlie Brown wavy pattern of the fiber crimps. Fewer of them than last time, woot woot.

I'm still not too keen on the Dunstone stuff. The epoxy spirals on the surface don't look cool and retain a bit of mass. Maybe I'm applying it wrongly. Maybe it isn't _meant_ for tapering wall thicknesses.

I think dr welby said something once about hating your equipment for years. I'm grateful for my current equipment set --- but it needs improvement if I'm going to reach *predictable* strength numbers.

Images show: Charlie Brown patterning, under-tensioned carbon tows, surface air pockets doing a poor job of escaping (tiny white scratch mark lookin things), epoxy pool spirals. Second image shows ridiculously bent first attempt with a long polypro mandrel compared to the absolute straightness of using a thick as possible steel mandrel core.

Sorry not sorry for novel. Apparently filament winding is more than just putting a string around a tube. It's putting lots of weird strings around a tube in a hyper specific fashion.


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## Cord (Dec 10, 2006)

Charlie Brown pattern? Eh? Who? What???

Don’t apologies for the novel, it kept me entertained. Any chance of a video of the machine so we can see the unwinding seismograph in action.


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## dr.welby (Jan 6, 2004)

Ha yeah, "You will hate yourself and all your tools for your first 10 frames."


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## Drew Diller (Jan 4, 2010)

Cord said:


> Charlie Brown pattern? Eh? Who? What???
> 
> Don't apologies for the novel, it kept me entertained. Any chance of a video of the machine so we can see the unwinding seismograph in action.


Like Charlie's shirt. Pattern highlighted by pink line. Red splotches indicate air flaws at surface.















A high class example can be found at carbonfibertubeshop.com as follows:









It means the pattern is extremely uniform and well covered. When the tows tuck under each other and make that pattern, it is a crimp in the fiber. Fewer crimps = better. An even better situation would be to eliminate the crimp completely, which would involve running the mandrel backwards as the carriage changes direction at either end. This is hard to do, but not impossible. The pattern I'm chasing can be thought of as a very-very-very-good compromise done at medium effort.


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## Cord (Dec 10, 2006)

Charlie Brown, i like it!

So your pink extended "W" shows 4 tows passing from right to left over/under woven with 4 tows coming from bottom to top. Presumable the more even and uniform your W, the flatter and more consistently your tows have been laid/woven. And i guess a tow is a group of fibres together, like a strip of tape? 

Sorry to pester you with basics, it's all new to me, but very interesting!


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## compositepro (Jun 21, 2007)

Dunno if you have access to ground rod we used to use or place UHMWPE around a ground steel mandrel won't whip and deflect at high rpm there's a ratio of diameter to length and rpm where things get lairy when tension winding


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## Drew Diller (Jan 4, 2010)

compositepro said:


> Dunno if you have access to ground rod we used to use or place UHMWPE around a ground steel mandrel won't whip and deflect at high rpm there's a ratio of diameter to length and rpm where things get lairy when tension winding


The one test I've done with a steel mandrel indeed showed incredibly high stiffness. I tried a PTFE tube over that, and that worked pretty well, except that it was slightly oval cross section. The stiffness of the steel mandrel revealed the weak points in my winder, specifically the gantry, wherein the tension is not maintained at every single moment. I had a thought the other night, you know how with derailleurs on bikes, the tension arm is built really light weight with a strong spring to quickly take up the slack from moving chain mass. And now clutch derailleurs are more likable because their tension abilities are even stronger than the previous generation. Maybe an analogy to the light weight tension arm also applies here.

The way I've seen some winders use REALLY long gaps between idler wheels to naturally baffle the tension variations, but I don't have the room for that. I think my shop is 13 feet across given the rest of the tools/storage already present. So I need some compact way to maintain tension so that I can do a good job of winding on a non-expanding mandrel.

I'll try the UHMW, thanks for the tip.


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## Drew Diller (Jan 4, 2010)

Despite my relative discomfort with recent things with Walt leaving these online shores, I guess I'm gonna keep posting here.

I another test with a centerless-ground steel mandrel wrapped in a PTFE tubing layer. One thing I noticed with the previous molding in this manner was that the OD of the PTFE had changed after one processing cycle. It's a relatively thick bit of tubing.

Well - after a second cycle it got screwed up even worse. Observe the interior surface of the tube. Twirling the PTFE tubing under the light reveals such warbles in its reflection as well.









It is becoming deformed well below its melting temperature.

Unfortunately, after looking closely at UHMWPE as a low friction liner option, it doesn't have the temperature rating needed by my current client. Gotta stick with PTFE, but maybe a thinner layer of it. But it is giving me a rough time, I wonder why? After talking with a guy, apparently PTFE has some funny behavior -- a very low softening temperature but a high melting temperature, and poor stability in a thick solid form, which contributes to it generally being used as a surface treatment. So I'm going to try silicone backed PTFE thin gauge tape. Applying it in a spiral with zero gaps is going to be... pppppfffffttt... well, that's why I tried the tubing, basically. Denial, bargaining...

I also figured how to apply more even tension on the tow spool with my current supplies, which... promptly resulted in applying so much torque that the carriage belt stepper motor started losing position, resulting in wrongly sorted filament wrap and exposed zones. I inquired for tech support from X-Winder, and Turner responded (PARAPHRASING) that the default config of the machine is for wet winding, and that adapting the machine to towpreg is possible, but don't expect it to do that in stock form. Which, hey, I'm fine with that now that I know for absolutely certain what angle to attack.

The centerless steel core approach really is great for linearity across a distance. 1.5m pictured:


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## Feldybikes (Feb 17, 2004)

Have you tried an Al mandrel? I remember hearing from someone who knows what they're talking about that steel has too small a CTE to release well but Al works well.

Also I’m happy to collab on a FS frame when you get to that point.


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## compositepro (Jun 21, 2007)

Never caught you were curing past 90 deg c


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## Drew Diller (Jan 4, 2010)

Feldybikes said:


> Have you tried an Al mandrel? I remember hearing from someone who knows what they're talking about that steel has too small a CTE to release well but Al works well.
> 
> Also I'm happy to collab on a FS frame when you get to that point.


Makes sense to me, I'll try an aluminum mandrel in the near future. Heard of one guy that uses dry ice to shrink his AL mandrels out. Client wanted to try with steel first for sake of high stiffness over significant length at small diameter. Kind of a moot point now that I've figured it's relatively easy to support the suspended mass along the middle with rollers.

@compositepro: well, I probably didn't mention it -- mea culpa. In this case it's not a bicycle tube, but, whatever I learn from this implementation can benefit future bicycle specific tubes.


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## Drew Diller (Jan 4, 2010)

I received some very-thin PTFE taped back with silicone adhesive, so it will be tolerant of a lot of heat. As I feared... even at this thin, it is very _unlike_ packing tape for example. Packing tape is useful for making very straight lines with little effort because it is stiff along its width. This PTFE stuff is more like a gum in tape form. While I do not exactly need to handle as if it is _extremely_ fragile, it is also pretty easy to pinch fingers, pull, and watch it distort readily while the silicone whitens. This is going to be incredibly hard to apply to the mandrel without any gaps or overlaps, and I already have doubts about it being a successful experiment. Will know soon enough.


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## Drew Diller (Jan 4, 2010)

_OKAY_, so, time to break down the good, the bad, and the changes of the recent test.

Changes:

New software installed. Carriage speeds reduced. Teflon tape applied to all contact points along the towpreg path.

Not changed:

Towpreg tension problems and Dunstone related spiral compression problems yet remain.

Good:

The ordering of fibers was much improved. The most recent software allowed for some carriage motor tuning, which eliminated the over torque / missed steps problems (which probably had everything to with the fiber ordering). Lots of chevrons / Charlie Browns. Woo woooooo

Bad:

As I expected, hand application of wide (2") teflon tape is a nightmare, the finished tube had visible tiny grips to hold onto. I could see them, I could feel them with my fingernail through a nitrile glove. Maybe I should try again with a narrow tape that's easier to handle, and spiral it into a sort of makeshift screw thread... but... I have reservations about trying it.

This got me to thinking, anyway. My bladder molding stuff has been pretty successful. While that process may have involved resin transfer, it obviously translates to prepreg stuff very well, that's how almost everyone else does it after all. So, maybe I need to take my bladder related knowledge and apply it to making straight tubes. I didn't _want_ to involve that level of complexity... but maybe it's what I need to do. @#$*

There's still a few things to try, such as the aluminum mandrel idea. I could spice up that notion with a few details, such as a VERY slight taper, and/or some lengthy polishing until I can see my face in the surface. The idea is to make it more slippery than an oligarch.

But... when it comes to making slightly curved shapes (such as chainstays), the slippery mandrel thing just isn't going to work. I need to make mandrels that either mold in place permanently like I've done with my handlebars, or I need to make some dissolvable tooling ($$$$$$$$$), or I need to make trapped rubber tooling.

View attachment 1296781

View attachment 1296783


At any rate, I think this thread has largely run its course, and it was to answer this notion: can you, for a budget of less than $10K, get into high quality filament winding at home? Yes you can. Should you? Ehhhhhhhhhhhhhh... just because it's going to fit my future situation _very_ well doesn't mean it's worth it for everyone. I know one guy selling his winder so YMMV.


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## dr.welby (Jan 6, 2004)

Drew Diller said:


> or I need to make some dissolvable tooling ($$$$$$$$$)


Could you 3d print PVA tooling?


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## Drew Diller (Jan 4, 2010)

dr.welby said:


> Could you 3d print PVA tooling?


That is a fine idea, though I lack a functioning printer. I'd need to own one for that approach to make sense. Buying anything at all is suddenly questionable after my wife was just delivered news a few hours ago that her job (along with hundreds of her peers) is gonna disappear in February.

If we were to pretend cost is no object, print speed is still a concern. So if I could mill a negative of a mandrel and cast something in it that is stiff-during-layup and soluble-after-cure, that would be ideal for curved shapes. There is a substance for doing exactly this but I think it got bought out by the US military, though I cannot seem to get a straight answer on the subject. At least I have not gotten killed for asking, hooray for speech.


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## Drew Diller (Jan 4, 2010)

Pleasant surprise: after some cold treatment, the dimply steel mandrel covered in wrinkly teflon is moving after some hard strikes on the ground. Moved it all the way to where pounding simply wouldn't push any further because the carbon is contacting the ground. Well, then, Teflon. You win this round. This tube should _not_ be coming off, but it _is_. That's just *weird*. Gonna make myself an improvised mandrel pusher. I've used a bottle jack and a large syringe to do resin transfer -- I want to find out what a bottle jack and a bit of sturdy hardwood can do.

I guess this reinvigorates my willingness to experiment with Teflon tape -- albeit of a different size, next time.


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## dRjOn (Feb 18, 2004)

Drew Diller said:


> There is a substance for doing exactly this but I think it got bought out by the US military, though I cannot seem to get a straight answer on the subject. At least I have not gotten killed for asking, hooray for speech.


its always fascinating following your progress but when it gets spy vs spy, it's getting serious! cheers and sorry to hear about your wife's job - that level of uncertainty is never good....


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## Cord (Dec 10, 2006)

.

View attachment 1296781

View attachment 1296783


.[/QUOTE]
Attachments don't work, is it just me?


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## Drew Diller (Jan 4, 2010)

@Cord -- yyyyeeeeah I don't know what's going on with that. I attached images in the usual way. Maybe next post I'll use my own website host to store the images

@dRjOn -- to be fair I wouldn't trust my own memory on this. I think that's what I read in some press clipping, but... *fuzzy*, and at the end of the day I still don't have the material in my hands. There's a few other materials out there that I am already qualified to buy, but the minimum order size and expense is CRAZY. Like if you're doing something other than building race cars or aircraft, don't bother asking. Which is a real bummer because some of those advanced materials can handle compression forces and bike frames have all manner of zones that obviously deform in compression.

Regarding my wife's job, I think her circumstances will allow her to land on her feet, but the situation pains her emotionally because it has been her one and only professional job, she was there more than a third of her life so far. She doesn't call them coworkers, she calls them friends. She feels sad for other people more than she feels bad for herself.

Just means I need to get product out the door all the more swiftly.


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## compositepro (Jun 21, 2007)

You need a mandrel puller

Honestly there's also a cheap ass way where you have a threaded collar on the mandrel , two flats to get a spanner on and pop it off that way


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## Drew Diller (Jan 4, 2010)

Mandrel puller, eh? I was like hmmmmm... I have a half-ton rated little hoist that I use to get my winder table off of my main table and up along the wall (the winder itself is relatively flat).

I took the hoist off the wall and found some heavy lumber, fastened some blocks to constrain the end of the carbon tube. Things started moving right away, hot damn! Not much effort. It was harder to manage the chains, as I quickly found that the hoist wanted to choke on its own guts due to the lack of gravity that would otherwise be keeping the chains relatively oriented toward their inlet.

Let's see if pic attachment works this time.


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## Drew Diller (Jan 4, 2010)

BTW, getting the animated GIF to show up in the previous post was a chore. Upload limit for GIFs on this forum is 879kb, I had to make a custom video output in Kdenlive and then run the resulting GIF image through EZgif. Total chore.


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## Cord (Dec 10, 2006)

Drew Diller said:


> BTW, getting the animated GIF to show up. Total chore.


Worth it, look at all that Charlie Brown!


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## Drew Diller (Jan 4, 2010)

Cord said:


> Worth it, look at all that Charlie Brown!


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## Drew Diller (Jan 4, 2010)

More observations:

I ruefully must turn my back on polypropylene mandrels. I noticed they were changing shape each cycle, lengthening slightly and reducing OD slightly. What was once 19.05mm (3/4" on the nose) is now 18.5mm after a dozen cycles.

If I'm doing internal-overlap lugs (and I am), what good is it to me to have tubes whose ID changes the more they're made?

I had one mandrel pull that was so much force that the lumber bent like a Pringles chip, and I had to fixture the puller to a sturdy trussed table. Even then, the softwood of the puller base started absorbing the fasteners. Note the chain tension.









The thing that REALLY got my goat was when I realized the remaining mandrel material on the far end is bigger than the actual mandrel surface material. This meant that upon removal, the carbon was being _forced_ to a larger diameter, and this is bad because epoxy carbon laminates really really really don't like plastic deformation. That was the final thing for me, no more polypro   

So I had a chat with this one outfit that does centerless bar grinding. As it happened, he already had a prior customer that does filament winding, and they are picky about straightness and surface finish, and they had already established that surface RMS 16 is "good enough" for release qualities, but I can order up to RMS 8 if it makes me feel any better. Handy, I'll take the free advice-by-proxy!

I'm gonna go ahead and admit that my mind is in a really dark place about this whole project. I feel like I'm four-and-a-half years behind my envisioned original timeline, and I've spent what I think is a large amount of money (although some people would laugh at the figure, depends if you're driving a Tesla or not)... and I just don't feel good. Like how many ways can I @#$* this up. A lot apparently. I mean my signature says 2016 but since then I've been straight obsessed with safety and @#$*ing heck man it was more difficult to certify than welding some steel together.

And my shop roof is showing water damage and my air compressor broke and it's a bad week man. Bad week. At least my car isn't on fire but hey, who knows, right.

And then I hear some things about the work life of someone I care about that I'm legally obligated to not repeat and I'm like... damn... ok ok yeah I'll stick to my numbers-obsessive job that lacks middle management, thanks.


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## compositepro (Jun 21, 2007)

Drew Diller said:


> More observations:
> 
> I ruefully must turn my back on polypropylene mandrels. I noticed they were changing shape each cycle, lengthening slightly and reducing OD slightly. What was once 19.05mm (3/4" on the nose) is now 18.5mm after a dozen cycles.
> 
> ...


Don't be ****ing stupid ...you have actually learned more than most will ever by doing this work yourself

Sure we could have told you a steel mandrel with a 1 in 1000 taper is not even noticeable but you need to mark the fat end and put the popper on the fat end but you wouldn't have learned anything .

Believe me in my career ( admittedly highly funded by a few companies) the fun part was learning what doesn't work ....now it's almost as good watching the internet experts tell you why without actually knowing themselves.

Hopefully you will stick with it till you realize you can earn far more money using what you learned and applying it to something else.


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## Drew Diller (Jan 4, 2010)

compositepro said:


> Don't be ****ing stupid ...


Sorry dude, moment of weakness on my part. I have been getting a steady trickle of other BS just going wrong, the most present is a roof leak in my shop. I just climbed up into the truss work while wearing a bunny suit and got myself a good look. Thankfully the leak is only on the un-finished / un-insulated side, so very little is going to rot and I can delay that significant cash expense for another day.

And I just hate December in general. So many businesses on which I rely go dark for weeks. Not too fond of Giftsmas for ...reasons... Maybe I should get one of those indoor UV lamps.


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## Drew Diller (Jan 4, 2010)

I tried a new technique. The intended goal was to create a "flashing-less" outer mold, so that ALL sanding and polishing work can be eliminated.

Did I get there? Ehhhhh... no. Close! Close indeed.

Did I get an improvement? YES.

Will it substantially reduce sanding and polishing time? Yes, the high spots are lower.

It's almost too much compaction pressure: the surface is totally dry of epoxy. There's little stray carbon fibers floating about the surface which I was unable to photograph as well as my human eye could see. Subtle flaws are revealed in my remaining not-quite-tense-enough winder configuration. It's like I've traded parting lines for a different kind of flaw that is evenly distributed.

I'm glad to see a pattern free of Dunstone spirals for the first time. Second image has a Dunstone compressed example for comparison.

I'm reticent to go into process details because I'm not sure if I've reached a "convergent development" with an existing patent or not. It follows the typical composite rules of one soft side VS one hard side (in most cases).

Overall I'll give myself a B+ on this one. Room for improvement is dwindling.


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## Drew Diller (Jan 4, 2010)

One heck of an update!! Getting out of the way the bad news first, I've been... really sick. So sick. Diverticulitis. I'm too young to have it, but I caught it early enough, and I don't have "complications" other than mind altering extreme pain, exhaustion, and confusion. Technical tasks seem overwhelming. Augmentin is helping a lot so far, and once I'm done with the regimen I need to drastically alter my diet.

GOOD NEWS is I tried a new (to me) release compound. Maverix Solutions has this stuff called 954ML (which is not a measurement). They make some pretty bold claims: incredibly low surface energy, non transferring (for good secondary bonds on the released surface), pretty fast cure (several coats five minutes apart followed by five hour cure), can pull several parts in between a single coat of refresh. It is transferred by solvent, VOC breathing protection definitely required because it smells awful during application.

This stuff... really delivers. OMG it delivers. A treated bare mandrel is difficult to _hold onto_ when gripped vertically. I tried removal by hand and simply couldn't get a grip. I put it in my extraction fixture and LAUGHED MY BUTT OFF when I observed how little force was needed to extract a one foot length at approx 3/4" diameter.

Simply _incredible_. Screw giving this an A, it gets an S+. I'm using it on a steel mandrel polished to RMS 16, and it works just *so good*. So good. Did I mention it is *SO GOOD*?!

It's kinda expensive, but worth every penny. I have not yet tested if it can be used as a general purpose release on convoluted shapes. I'm guessing it will be useful for that; I was able to _blow_ off some of the epoxy swarf at the ends of the part. Like not with a compressor, but with my piddly little lungs.

Wow.


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## Drew Diller (Jan 4, 2010)

HAW HAW, so, if something can go wrong, it eventually will. Made another test tube with shrink tape as the compression method. Once cooled out of the oven, I put the tube in a vise and tried twisting one end of the mandrel with a small hand vise grip. Rolled really smoothly. Nice. The surface was still working, and the advertised claim of pulling more than one part per refresh seemed legit.

Cool.

So I put it in the extraction fixture, and started pulling it some inches. The extraction force was indeed low. All right. Started pulling more quickly. BAM - sudden stop. In frustration, I pulled a little harder. Disassembled everything, and it appeared as though there was some shrink wrap debris that had pulled over the lip, into the inside diameter of the carbon. Suddenly a slip fit became an interference fit.

Turned everything around, and tried back it out. Haha, nope. Chain that tethers the winch to the mandrel end just up and broke.

OK, write it down: ... shrink wrap debris can and will jam into the carbon tube if the end of the carbon has a concave face... put in little rubber end grommets ... or just stop using shrink tape even for tests.

(face palm)


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## Drew Diller (Jan 4, 2010)

Some updates since I've been doing this more often of late.

I still cannot fully quantify this number, but I've made a number of adjustments to my winder, almost all related to tram/gantry/whatever belt tension. It now twangs like a guitar string. No more stuttering, and I can run the machine twice as fast as before.

I've also noted that the handling temperature of the towpreg _really matters a lot_. 75°F is barely useful. 77°F is okay. 79°F is the good stuff.

Using rubber stops on either end was useful for more than just debris management. It also had a lot to do with initial "bite" because the Maverix coating is so impossibly slippery that the first layer just won't stick. I made custom rubber stops (PlatSil 73-60) where the ID of the stop is very slightly undersized compared to the mandrel, and there's a little hole in which compressed air is blown. Similar to the old shop trick of removing stubborn MTB grips from handlebars.

The rubber stops also had a useful unanticipated benefit regarding extraction, in the waste material region at either end.

One thing that is a bummer is the high spots. It appears I'm going to need to sand the outer surface at least a little bit no matter how fancy the compression method used. @#$*. I'm trying to figure out what to do there. Centerless grinders are WAAAY outside of my budget (I'm not the Fed, I can't just print money for billionaires). I did a cheapo test with a dummy spindle and a portable belt sander, with a gap so that the carbon tube can slide back and forth across the spindle for the purpose of sanding both ends of the tube. Honestly? It worked, lol, better than I thought, but that doesn't mean it works very well. I can get things round, but the diameter variation along the length is far too vulnerable to my human error.

I've been warned by an acquaintance that towpreg will naturally be more testy to wind with in terms of final outer appearance - the profile of the tow is not as flat compared to dry tow mixed on the fly with wet resin. My sanded results lately appear to validate his warning, which I'm not sure how to describe.

One thing is for sure: these tubes are STRONG!

EDIT - forgot a thing - the addition of back pressure on my dust capture device, by way of adding a conventional large diameter shop fan, was _very_ good. It works. The carbon dust just disappears.


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## Wombat (Jan 25, 2004)

Thanks for taking the time to document your progress and downfalls. I find it fascinating to see how this is going, and how you've solved your various problems.

I hope your health has improved. 

Keep it up!

Tim


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## Drew Diller (Jan 4, 2010)

Appreciate the kindness, Wombat. I am doing a touch better. Been experimenting with foods of late. A bit irritating when the conventional wisdom doesn't apply. Newest research suggests everyone's a little different and you have to just try things with your own body. I've got it to the point where even if I am having a flare up, I can mostly manage it to the point where I'm able to get some work done, even if I am not at peak efficiency.

Oh and I forgot to mention that I think the interference-fit rubber end pieces, how they move on and off aided by air pressure. I _think_, but am not sure, that the air pressure has a momentary influence on the static friction of the mandrel. The mandrels have been coming out by hand lately. With one arm!


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## Cord (Dec 10, 2006)

Keep it up. I have no input, but I appreciate the updates.


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## Drew Diller (Jan 4, 2010)

The fun thing about tuning is that sometimes you get to (have to) _tune again_. Since I tightened up the gantry drive tension, I was allowed to increase the spool sliding friction to get closer to towpreg manufacturer tension spec.

Well, at certain angles and speeds, the bearings on the gantry that came stock with the X-Winder design are proving to be not up to the task. There are new shuddering patterns, and it puts these tension spikes onto the carbon spool itself, breaking the fibers! FULL STOP, ADDRESS THAT.

The gantry needs better bearings that can tolerate torque for winding towpreg at proper tension spec. The end. Do that.

Between my lack of need for transport and my wife suddenly needing emergency surgery (successful op, btw, she's tough like Rosie the Riveter) and my desire to make this winder stronger than stock form, I decided to sell my beloved WRX. I'll miss it, but at the end of the day it's a box on wheels that I have anthropomorphized for emotional enjoyment at the expense of high continual operating costs. So, I let it go, not only to get some extra operating cash, but also to avoid costly maintenance that would be needed in the next 20,000 miles (or sooner, or later, and I greatly feared the "sooner" possibility). I can always get another toy car when the finances are better. What made it easier to part with is the guy I sold it to was really nice and I'm ok with sending it to a good home.

So, with those funds on hand, I'll be swapping out the gantry bearings for a legit linear guide, with the four-contact recycled ball bearing cartridge design. compositepro was kind of enough to instruct me on how to install them accurately.

I'm also giving up on the belt drive entirely and I'm going to swap out for a chain drive. Chains work.


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