# Custom Carbon Fiber frames? or whats wrong with the c.f bike industry



## bhsavery (Aug 19, 2004)

Carbon Fiber is a great material and it seems bike makers are finally beginning to truly figure out how to use it (see the number of carbon ROAD bikes at interbike this year). However I think theres alot of more uses for it espescially in the mt bike world. I have an idea for making carbon fiber frames that I want to bounce off you guys. I've done a lot of work in the boat world with composite construction and want to bring something new to the bike world.

To me theres a few problems with carbon fiber mountain bikes:

1. Cost OR lack of VALUE
2. Strength and weight issues i.e. engineering
3. stuff that makes people want to buy a bike. like custom sizing, colors etc

Basically theres a few ways bike makers make carbon frames. One is they take carbon tubes and glue them together at the joints and call it BONDING like thats something fancy. The other is they make the bike in halfs in a mold and then carbon fiber them togethers. A little better but you have a seam running down the middle. 
There are problems with these types. To keep the production cost down makers will only make a few mold sizes. Trek for example only offers OCLV frames in three sizes. Also there doesnt seem to be a bike I've tried that they've combined light weight with the rigidity that an aluminum bike has. This is supposed to be what carbon fiber is good for! Moreover why does someone want to spend so much on a cookie cutter flexy carbon fiber frame??

My idea is make carbon fiber frames a different way. Use moldless construction (in which you lay carbon fiber over a foam shape and then remove the foam). This way you can custom build bikes to whatever size and specs you want. Want a bike without canti brake studs? no problem. Want one with a long top tube? no problem. Custom painting etc, also wouldnt be a problem as it is when a bike is put in a mold. Basically I think you could put more into the bike.

My question is: do you guys think this is a good idea? would people go for it? Is there a market? PS I'm already bulding a prototype hopefully I'll have that to show in a month or so


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## mattsbored (Mar 23, 2004)

There's a market for everything, but custom carbon work is something extremely boutique. But if you're willing to put in the time and can build a proven design...you'll make a few bucks.


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## 20.100 FR (Jan 13, 2004)

Scott USA, and GT thermoplastic used different processes.

you may check this project :
http://www.bme.szm.sk/carbonframe.htm


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## @dam (Jan 28, 2004)

That is a good idea. You could have the foam mold CNC machined to whatever custom dimensions you need, and then just lay-up over that. A CNC to machine foam would be much cheaper and faster than one to machine metal. However, you'll need to find a foam that...

Can easily be machined
Won't melt on contact with resin
Is strong enough to resist the forces of vaccum bagging
Is light enough to leave in the mold, or find some way to break it up and remove it from the mold
Will stand up to the temperatures of the autoclave
Has some way to hold the threaded, metal interface bits and the headtube, bb, dropouts, etc.

Also, you'll have to have a skilled labor force to tweak the CNC design (customize), do a lay-up, paying attention to thickness and fiber orientations, and do a good, wrinkle-free vaccum bagging job on this complex shape.

Also, carbon fiber combines light weight with high STRENGTH- not necessarily the same thing as rigidity- especially since CF is only strong along the direction of the fibers.


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## bhsavery (Aug 19, 2004)

I was looking at a process called "Lost Foam" which you make the shape out of polystyrene foam, cover it with plastic, laminate the carbon and after curing use acetone to melt the foam. Pretty cool stuff



@dam said:


> That is a good idea. You could have the foam mold CNC machined to whatever custom dimensions you need, and then just lay-up over that. A CNC to machine foam would be much cheaper and faster than one to machine metal. However, you'll need to find a foam that...
> 
> Can easily be machined
> Won't melt on contact with resin
> ...


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## Ohio_Huck (May 13, 2004)

yup, thatas definatly the way to do it. leave the foam in. foam doesnt melt with epoxy, just polyurathane resin. and its surprisingly strong under vacuum bagging, even if its light weight. and if you used a foam like those in some skis, it would acctually add strengh to the finished product. sounds sweet, go for it.


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## rideit (Jan 22, 2004)

*How to make a million in the Bike Industry...*

DRUM ROLL

START WITH TWO!!!!!


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## bhsavery (Aug 19, 2004)

http://www.bme.szm.sk/carbonframe.htm

yeah so basically I'm thinking similar to this guy only I'm using pre-impregnated unidirectional fiber and vacuum bagging it

Oh and I think the foam will come out of the main triangle tubes, maybe not the chain/seatstays


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## elistan (Jul 3, 2004)

good luck


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## MTBDOC (Feb 28, 2004)

As a 29er rider, I have wondered when one of the big players (Giant?) would step up to the plate and start building CF 29ers. The 29" frames require LONG downtubes, and this is problematic as there are not a lot of choices in bicycle-world. I have a Titus Ti custom 29er hardtail, and the downtube is HORRIBLY expensive compared to standard length stuff. And you don't want flex...anyway, you get the picture.

So, a CF framebuilder who could build a strong and durable 29er frame could find quite a market out there. Add in the combined ride benefits of big wheels AND CF...and you have a winner!


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## bhsavery (Aug 19, 2004)

so I finalized the design in solid works (see picture). I have been talking to machine shops, and I'm getting the foam made for about 100 I think.

So it adds up to: 
$100 for foam
$100 for materials (carbon fiber and vacuum bagging)
$25 for bottom bracket shell and dropouts and brake bosses

should be too bad


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## Ohio_Huck (May 13, 2004)

no, i think you should rethink this. this technique is a good one, but you should make a design that is more suitable to the material (and make it look cool  , something similar to the monoque intense bikes ect. plus, your definatly gonna be spending more than that. and the foam will not come out. (leave it in, you could laminate carbon across it, so you would have cross brases for your main tubes. you should probably try something like a big triangle, and a small section cut out of the middle. and definatly go with directional carbon fiber. it is way stronger across distances. that stuff is for non load bearing parts and smaller items with very dificult wraps. what ever you can afford, but quad or triaxle is the way to go. you are gonna want to keep the head tube area pretty reinforced.


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## Warp (May 24, 2004)

Cool. As my first try I would use more metal at the BB. That would save you some wraps around complicated ares.

Keep it going!!!! Send pics of the process!!


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## bhsavery (Aug 19, 2004)

Yeah I definitely wanted to stick with a traditional double triangle design. I was planning on using unidirectional CF. 

The bottom bracket shell is going to be metal that I'm going to lay up the carbon around. You think more bracing (ie fillets ) at the joints is nescessary?


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## bhsavery (Aug 19, 2004)

keep in mind also that that design is for the INSIDE of the tubes. That the design of the foam that the carbon fiber will be layed over.


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## Warp (May 24, 2004)

bhsavery said:


> Yeah I definitely wanted to stick with a traditional double triangle design. I was planning on using unidirectional CF.
> 
> The bottom bracket shell is going to be metal that I'm going to lay up the carbon around. You think more bracing (ie fillets ) at the joints is nescessary?


Not necessarily. But some raccords at the BB and heat tube should be good for the first try. You know, even if you're a experienced fiberglass worker, CF gotta have its own "tweaks". So, if you want increase your possibilities of succes (reduce problematic areas), you could use raccords at those points (even if you trhow later one or two layers of CF to make it look good).

Being so manipulable the CF, you can shape the foam to make the downtube oval at both the headtube and BB shell. That would wouk out wonders for stiffness.

Some ideas I got in my mind while thinking at it. Keep it up, man!!!!! Don't get discouraged at the making.


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## 20.100 FR (Jan 13, 2004)

BB and Head tube are by far the more stressed area in a diamond frame.
Be sure to add a lot of layers in theses areas.

I was planning on building a custom 29" in the spring (aluminium) but Mtbdoc got me thinking. Carbon... why not !

Have you calculated the loads on the differents parts of the frame ? Downtube as a lot of torsional load, seat tube as flexion loads, etc...
This whould translate in the direction of the fibers you are going to put.

Keep us updated.


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## bhsavery (Aug 19, 2004)

Warp2003 said:


> Being so manipulable the CF, you can shape the foam to make the downtube oval at both the headtube and BB shell. That would wouk out wonders for stiffness.


In fact I copied the down tube design from a specialized S-Works I have. It is horizontally oval at the BB and vertically almost rectangular at the head tube. I don't know how to make it curve like specialized does in solid works, so for now its straight.


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## Bortis Yelltzen (May 18, 2004)

bhsavery said:


> In fact I copied the down tube design from a specialized S-Works I have. It is horizontally oval at the BB and vertically almost rectangular at the head tube. I don't know how to make it curve like specialized does in solid works, so for now its straight.


Ok, you all are running amuck designing what we engineers in the composite industry call black aluminum. This is by far the worst way to go about designing composites as you will never get the full benifits of composites. Never ever use geometry from a metal part to dictate the geometry of a composite part as youa re doing with your tube geometry, this is the #1 composite design mistake. Key composite benifits are stiffness (not to be confused with strength), specific strength (strength to weight ratio, this is where composites kill AL, steel and most other materials), part consolidation (3 metal parts combined into 1 composite part with no bonding or welding etc..), fatigue resistance, high frequency vibration dampening, and thermal stability to name the main ones.

Now bhsavery, you are obviously somewhat inteligent and have demonstrated some engineering knowledge by being able to create a frame design in SolidWorks, but you are totally going about designing for composites completely wrong in my opinion (and my opinion is that of someone who has spent the last 7 years as a mechanical design engineer in both aerospace and automotive composites).

It is cool you are learning how to use photoworks to show the composite weave too but you specifically mentioned you will be using uni prepreg. In order to design a quality composite part you need to design for composites at the very begining. Someone up above mentioned using a design more like the Intense frames, this is a much better way in my opinion as well. Also, uni prepreg is great if you know your loads and where they act, you can then design an optimized lay-up and put fibers only in the direction they are needed. Do you know the loads on that frame design, both magnitude and direction? If there is any doubt you are better off using a woven material to cover your a$$ for the loads in directions you forgot about or didn't expect. What are your plans to comu up with the lay -up? How are you going to lay up continuous fibers around the headtube and BB, how are you bonfing the metal inserts to the composites? How are you controlling the vacuum bag surface thickness (you are going to have a bag surface on the outside? not good thickness variation in composite laminates lead to stress increases which lead to microcracking of the resin and eventually catastrophic failure of the part) what do you know about balanced laminates, if you laminate is not balanced you part will warp and bend during cureing.

I could go on and on all day but I have to get back to work. THe main reason there are not too many good carbon bikes out ther is simple, it is hard to make a good carbon bike affordably. And if you go about your wash-out foam method you are going to get hurt, I could be wrong, but from what I have seen you need a lot of help in your design, you are not going about it the way people int he industry do, and in fact you are making many of the most common composite structuaral design mistakes. Composites are very tricky materials to work with and gaining the necessary knowledge is hard and expensive.

I would be happy to chat more and let you know my $0.02 cents if you are serious about moving forward, I have been desiging composite parts in CAD (SolidWorks and ProE and Catia) for 8 years now and performing FEA analysis on the components for laminate optimization (Using NE/Nastran, Patran laminate modeler, ansys, algore, and CompositePro) for the last 4 years. If you are serious about designing and making composite bikes you need to do it right, and you are right, no one is making a good carbon bike right now.

I am sure you learned a lot working on the composite boats, but for the most part boat makers use very limited amounts of advanced composites (unless you worked on boats like the ones in the Americas cup, they are more advanced than any other composite structure) but if you were mainly making spray up glass boat hulls, there is a lot you need to learn before jumping into uni directional carbon. 95% of the load in a composite part is carried by the fibers, the longer the fiber, the better the load transfer, you had better know where you are putting those fibers and why, otherwise you are bound to be disappointed or injured.

Let me know if you want to chat more.

B


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## Bortis Yelltzen (May 18, 2004)

bhsavery said:


> In fact I copied the down tube design from a specialized S-Works I have. It is horizontally oval at the BB and vertically almost rectangular at the head tube. I don't know how to make it curve like specialized does in solid works, so for now its straight.


oh yeah, if you want to make that tube bend in solidworks you need to use the loft tool and use a guide curve to make it follow the bend you want, set up the tube geometry at the head tube with a sketch, then at the BB with another sketch, then use a guide curve to connect the two, then loft the tow sketches together along the guide curve. Should take 2 minutes to do it and about 6 clicks.


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## bhsavery (Aug 19, 2004)

check your Private messages Bortis, i left my email


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## mikedesign (Jan 25, 2004)

*if you want to build frames*

its easy when you know how


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## Bortis Yelltzen (May 18, 2004)

*Is that RTM?*



mikedesign said:


> its easy when you know how


It is easy of you know how and have access to $50,000 tooling, resin injection equipment, a press of some sort, and maybe a cutting table to cut the dry carbon preforms to be laid into the mold. What method was used on that motorcycle frame? Loks to me like it had to be RTM to get the smooth finish everywhere and to get all those inserts molded in. Or is it a multi peice autoclave cure part that is then secondary bonded into the final structure? I don't see any bond lines.

Just curious how it was made and for who. Was this for Ducati? Luckily motor cycle frames only come in 1 size. If that part was made via RTM there is no way you could build mountain bike frames in multiple sizes and still justify tooling cost, not unless you sell lots of bikes or don't change things every year.

That is one damn fine looking motorcylce frame and one of the coolest composite parts I have seen. Good work if you made that.

Cheers,
B


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## mikedesign (Jan 25, 2004)

i wish i did have access to 50k tooling but i dont have that big a budget

we develop production techniques for producing high quality carbon fibre and basically started doing this to prove people wrong the black magic material isnt such a black art if you understand it which im sure you are well versed on the subject


i cut my teeth making aerostructures for europa aircraft kit planes and was shocked by the mother of invention techiques employed to produce high quality parts at low cost

this led me to research into making parts without autoclaves and the like we primarily use rtv bladders and female moulds but have a sneaky technique of filling the bladder inside the tool with low melt alloy 40 deg melt this means we can wrap the bladder outside the tool and make monocoque structures

when the bladder goes in the tool it is pre heated , the alloy melts and goes out of a small hole in the pressure seal bulkhead once its out ,in goes 120 psi just above autoclave pressure though with steel tools you can hit 200 psi but then you have resin fibre ratios etc to consider and all the other bits that go with making structural cfrp 

so all thats needed then is an oven to cure the job

we are looking at bicycle frames at the moment but due to geometry varience as stated this is a bit of a way off yet


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## Bortis Yelltzen (May 18, 2004)

*Damn sneaky!*

Very clever, is the rtv bladder re-usable? Is the low melt temp alloy re-usable? What types of conumables (bagging material, sealent, tape, etc..) is required with this process? How long does it take to make a frame?

You mentioned with steel female molds you could increase to 200 psi, is your female tool aluminum or are you using composite tooling, if using AL tooling do you have any CTE issues during the oven cure that effect final cured part dimensions? How are you cutting your fabric preforms to drape into the mold, start with a big sheet of fabric and as you drape using darts and what not or are you using more sophisticaed techniques like a cutting table and draping software to create the fabric peices to place into the mold? What is your scrap rate for the fabric (material is the most expensive part usually, how much do you throw away)? Is this wet lay up or prepreg? I am guessing that part has a solid foam core, right?

Just curious if you don't mind me asking? I am working mainly with thermoplastic and carbon for high volume automotive structural parts and I am always curious to hear how others are taking the cost out of making complex advanced composite parts. Could your process be used to make 50,000 parts per year affordably in an automated environment?

Cheers, 
B



mikedesign said:


> i wish i did have access to 50k tooling but i dont have that big a budget
> 
> we develop production techniques for producing high quality carbon fibre and basically started doing this to prove people wrong the black magic material isnt such a black art if you understand it which im sure you are well versed on the subject
> 
> ...


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## bhsavery (Aug 19, 2004)

ok so mikedesign I'm really impressed. So the reason I started on this was that I was looking for a way to make a cheap bike frame, and also I was curious about whether this construction method would be efficient enough to make a frame that doesnt require tooling such as a steel or aluminum mold. Whether or no one could take a custom frame design and rapidly turn out a carbon frame.

Now clearly I'm not going to have the surface smoothness using the method I'm planning but what do you think about my construction method? Any suggestions that I could improve on it? I noticed you mentioned you worked on kit planes, its funny because i got the lost foam idea from a site about making model airplanes.


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## mikedesign (Jan 25, 2004)

ill try and answer these in order

yes the rtv bladders are reusable we use different shore hardness dependant on application
and to avoid bridging in the tool rtv think of blowing up a baloon in a square box
you can buy them from a company called aerovac sytems we make our own

there are no consumables the bladder is reusable and there are no requirements for bagging film sealantetc the usual consumables in the process we removed all possibilities of surface problems and mark through on thin 35thou parts by using an undersized bladder
to make a frame actual layup time is about 50 minutes the preforms are cut by hand simply because it costs no money to do this way, from data produced using Pro composite one of the surfacing functionalities of Pro E wildfire

aluminium tooling is avoided unless we can use sub 60deg cure pre preg aluminium might be good for wet layup parts but all our tooling is 12" thick prepreg carbon, cnc machining is just out of our reach financially and for one off applications
we could probably make cheaper tooling using carbon fibreglass but as its pressurized and heated carbon was safer, one point to note though there is a tendency for weave marking in the finished part

scrap is pretty low its quite hard to get it wrong as a lot of this is manually done it is really down to who is laying up the part components usually come out pretty much correct

this was pre pregged though wet layup still provides good parts as the pressure of the bladder compacts everything so well if its wet layup we often leave blled holes in the tooling to prevent air entrapment between the carbon and mould

could it be used to make 50 00 of what motorbike frames no way but the cycle time is short roughly 4 hours which isnt bad for a complex piece

if you need to discuss anything else im one of those guys that doesnt really keep secrets im not that anal


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## mikedesign (Jan 25, 2004)

bhsavery said:


> ok so mikedesign I'm really impressed. So the reason I started on this was that I was looking for a way to make a cheap bike frame, and also I was curious about whether this construction method would be efficient enough to make a frame that doesnt require tooling such as a steel or aluminum mold. Whether or no one could take a custom frame design and rapidly turn out a carbon frame.
> 
> Now clearly I'm not going to have the surface smoothness using the method I'm planning but what do you think about my construction method? Any suggestions that I could improve on it? I noticed you mentioned you worked on kit planes, its funny because i got the lost foam idea from a site about making model airplanes.


when i said kit i meant the kind you build sit in and fly not models think rutan and the like

the method your using is fine it is one of the fundamental methods of making strong carbon parts most people leave the foam in the other fundamental you are lacking is
pressure and heat these two are a prerequisite in most case to get a good quality carbon part

vacuum bagging is a good method for basically de bulking carbon and removing air from the laminate for the most part it will probably strong enough if you put enough material in

once you start losing material all the other elements come into play if your building monocoques i once read an article about a guy who made a 3.5lb frame by wrapping carbon round a foam core then using tape with pin holes in it to wrap around that laminated material very low tech but it worked he just sanded it smooth

anothet misconception is that a beutiful looking finished part are some of the strongest high perfomance low weight structures are just matt black and the weave is compressed so tightly that the optimum ratio of resin to fibre volume is acheived resin rich parts are usually the nice looking ones

as for building customs we havent figured a good way of doing this yet

i could go on and on but i dont think this is the place


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## bhsavery (Aug 19, 2004)

sorry when I said beautiful looking i meant surface consistancy. I'm just worried that even with the vacuum baggin I'm planning I will have ripples and such in the surface, of course I can sand them out after.


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## 20.100 FR (Jan 13, 2004)

so how is the project doing ?


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## bhsavery (Aug 19, 2004)

20.100 FR said:


> so how is the project doing ?


 good actually,

Update... The cnc'd foam is on the way from the millers and I just today got the titanium BB shell and headset cups and drop outs and brake blocks from Paragon Machine Works who supply alot of Ti frame building parts. Not really much to show, but I'll post pics once I get the foam in and mount them on there.

I also have the unidirectional pre-preg ready from a company that sells airplane and glider building supplies. But I'm waiting for the other stuff to be set before having them shipped because that has a shelf life of about a month to get used up so I want to be all ready.

All in all its actually coming together for cheaper than I thought! The Titanium parts were really cheap (40) and the foam machining cost about $100 The carbon will be about 100 too. I'd love to learn how to do the foam myself, but this was easier to have the pros do it precisionlike.


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## 20.100 FR (Jan 13, 2004)

Nice !

Could you explain me the difference between your process and the one used on the site i gave you (BME) ?
I don't understand how the vaccum thing works.


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## bhsavery (Aug 19, 2004)

I actually spoke with that guy on the BME site. 

Theres a few differences in what I"m going to do.
1. He shaped his foam by hand rather than have it cncd
2. After the carbon fiber is done over it I'm going to remove the foam from mine.
3. He machined his own dropouts and stuff out of some weird aluminum
4. Ok so he didn't "vaccuum bag" but did something similar. When doing composite construction, one has to apply heat (sometimes) to help with curing and pressure to keep everything tight and in place. It also helps to squeeze out extra expoxy (glue) from the fabric. The way he did it is by the homemade way of wrapping inside out elecrical tape around the frame to compress the carbon fiber while curing. Vacuum Bagging makes it more even and consistant and basically works by wrapping the bike in plastic and hooking it to a vacuum pump.


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## 20.100 FR (Jan 13, 2004)

Thanks.
- Are you going to vaccum it for each layer, or are you only going to vaccum it when all layers are finished ?

- Do one need a special pump and plastic houssing to do the vaccum thing ?

- How are you going to deal with the insertion of metallic parts ? Is there a special process to help them *glue* together ?


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## jeepin-paul (Jun 8, 2004)

20.100 FR said:


> Thanks.
> - Are you going to vaccum it for each layer, or are you only going to vaccum it when all layers are finished ?
> 
> - Do one need a special pump and plastic houssing to do the vaccum thing ?
> ...


Make sure that you thoroughly clean the metal part & rough the surface to be glued with course sandpaper to give more scratches to bond into.


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## bhsavery (Aug 19, 2004)

jeepin-paul said:


> Make sure that you thoroughly clean the metal part & rough the surface to be glued with course sandpaper to give more scratches to bond into.


 of course. actually the BB shell comes knurled so I dont need to rough it up


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## 20.100 FR (Jan 13, 2004)

Thanks,

What about my question 1 and 2 ?

I'm starting to be really interested in this, i think i will try to build a frame with your process after christmas.


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## bhsavery (Aug 19, 2004)

*answers...*

oh yeah so about your questions.

No you don't have to vaccuum bag for every layer. The cool thing about prepreg is that it doesnt cure till you apply the heat, so you have plenty of time to put on 10+ layers and bag it before it cures. Sometimes I've seen people bag after 4 layers or so when they do a wet layup. Also Bortis Yeltsin suggested using shrink wrapping stuff instead of bagging.

If you want to know more about it, I'd suggest researching on google or asking someone who REALLY knows what they're doing.


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## mikedesign (Jan 25, 2004)

*heres a few pointers and im not trying to put you off*

i admire someone whos still prepared to have a go

heres a US based supplier of shrink wrap tape we use this in the uk and it is good

and some thoughts on the process

whilst you are using prepreg ill point out some other areas you may have a problem

the guy who built a bike in his garage used wet layup heres some suggestion why

firstly you are using foam cores this is good but depends on the cure temperature of you resin if its near 90deg as most structural prepregs are they will most definitely distort if not melt

secondly there will be a very structured cure cycle to allow the prepreg resin system to flow, allow for debulk, gel and cure this creates additional exothermic heat in the layup if you have thick parts this can be a nightmare expect 250 deg in the part and if it exotherms that badly you will have waste to dispose of

vac bagging will typically allow low pressure compaction though it is more for debulking than final compaction if vac bagging learn about gel time and debulking and what the advantages and disadvantage of these things are

typicall y pressures developed are
around 14.7psi at full vacuum ive seen even this pressure squeeze and distort foam
shrink tape specifically designed for composites will achieve roughly 200-2500 psi be carefull a good link below has some guidelines

http://www.shrinktape.com

might i suggest another way of doing it and buy some tubes from somone like maclean quality composites mitre them in the traditional frame building way wrap the joints with enough fibres then shrink wrap the joints

now that not quite the way SCOTT do it they use special moulds at the junctures but its probably as near as dammit to a high performance frame that your going to get using the technology you have available to you 
and on top of that you only have to worry about getting strong bomproof joins and learning how to prepare the joints rather than concentrating on the entire thing

sure you could progress to making special profile tubes at a later date but my advice would be to take small steps and learn as you go


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## Bortis Yelltzen (May 18, 2004)

mikedesign said:


> i admire someone whos still prepared to have a go
> 
> heres a US based supplier of shrink wrap tape we use this in the uk and it is good
> 
> ...


Good info Mikedesign. I have been in contact with bhsavery and told him about the shrink tape as well. I like the idea of buying tubes from MQC (I almost worked there but chose my current job instead), they make the tubular filament wound and roll wrapped parts for a lot of carbon bike makers (Trek for sure).

Filament wound tubes would be very strong, they (MQC) have several stock sizes and lay-ups, and if you do like mikedesign said and miter/lug this thing and wrap the joints with shrink tape I think you'll get a pretty stout ride, just make sure you spen lots of time researching how to prep for bonding and make sure the adhesives are well speced. This way you would only have to focus on a few parts and you could learn there, instead of having to learn all things at once.

I would also use a combination of unidirectional and a woven fabric as well, put a layer of woven, then a couple layers of uni, and then a final layer of the woven on top, this might help cover some of the loads that are missed by the uni. Just my $0.02 on this, but I don't think you have a clear enough idea of how to really use a pure uni construction technique and the work involed to do it right, use a woven, cover your a$$.

And as for the prepreg cure, see if you can get one specifically designed for ambient (room temp) cure, be very careful of exotherm as mikedesign said, I have seen plastic cups or catalized resin melt and smoke due to the heat given off during the cross linking chemical reaction when epoxies cure. If you are not careful this is a good way to burn down your garage. Mikedesign has a good point, often prepregs are designed to have a programmable oven cure them, so you can bring the part up to a certain heat and let it dwell so the resin can flow and wet out the fibers, then it ramps up to a gel temp and has another dwell, then it will ramp up to a final cure temp and dwell for a while, then drop back to room room temp or so. This insures that the part is cured throughout, you may have bad results if you try to cure one of these types or resin in an ambient environment. Shop around and get something tailored to what you are doing.

Thanks mikedesign for putting in your $0.02, it is good info.

B


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## bhsavery (Aug 19, 2004)

I have no problem doing a wet layup, but it would certainly be easier and more controlled I think to do prepreg. Although I see the issues you bring up about temps. I'm going to look into the heat properties of the foam I'm usiing. 

Is there such thing as a room temp activated prepreg? Maybe wet layup is the way to go.

I looked at a solutions such as getting the tubing and then bonding. Problem is the tubing is expensive and not really serving my purpose. I'd still have to make the lugs and worry more about the bonds.


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## mikedesign (Jan 25, 2004)

bh im kind of getting the impression you have answered your own question at the start of this topic

undoubtably you have found through your own research what is wrong with the composite frame industry and something i discovered a long time ago and that is that whilst the materials may be cheap the cost comes in the process used to get it right and make something from what effectively is 200 year old idea

you seem to have arrived at the same house every other composite manufacturer has
and to get a decent quality product take a lot of research, time and knowledge to do it propererly


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## Bortis Yelltzen (May 18, 2004)

mikedesign said:


> bh im kind of getting the impression you have answered your own question at the start of this topic
> 
> undoubtably you have found through your own research what is wrong with the composite frame industry and something i discovered a long time ago and that is that whilst the materials may be cheap the cost comes in the process used to get it right and make something from what effectively is 200 year old idea
> 
> ...


Eggggzactly! And once you get the process figured out and molds/whatever the process needs purchased the material cost usually drives the price of the bikes, but you have to sell a lot of bikes to pay off the molds/initial set up cost.

I have been making complex composite structures fo 7 years now, the honest reason I have not made a carbon bike yet is that I have yet to learn of a better cheaper more flexible way than what Kestrel and Aegis and Specialized and Scott are currently doing. I don't consider my time to be free, and by the time I buy materials, design the bike, and manufacture it I have paid 10 times what I would have if I had just bought it. I use what I call the BBP method, Buy, Build, Or Partner, and it has done well for me in my career on projects from fighter jets to golf club shafts. If you can buy something that fills a need you are almost always better off doing this, if nothing is available then you try to partner with someone doing something similar, and if you can't do either of those then you build it. Remember, in the real world and especially in the manufacturing world time is money. So if it takes you 2 months of weekends and evenings to build this, what is your time worth? Even at $1/hour your "cheap" home made carbon bikes is still going to be pricy. If you can't find a carbon bike with the geometry/features you want, call Kestrel, or Aegis, plead your case, work together, maybe they will partner and deliver a wicked custom ride.

"Just because you can doesn't mean you should." My favorite quote from one of the people I have learned the most about fabricating composite structures from.

Cheers,
B


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## 20.100 FR (Jan 13, 2004)

Hi guys,

After reading this post and looking around on the net i decided to also make my own carbon frame !

This project will cost in time for sure, but the joy of ridding my home made bike is what pushes me forward. I like to create much more than buy !

I have found and intereseting article about a nice full suspended carbon mtb here:
http://www.machinedesign.com/ASP/viewSelectedArticle.asp?strArticleId=55763&strSite=MDSite
(may 2003)
1- What do you think of it ?
2- I wonder why they use so much kevlar....
3- Wouldn't the kevlar be more suited as an external layer to protect ridder skin from carbon shards if the frame fails ?

I've got another question for you guys. I'm finishing a PhD in mechanics, so i have some theoritical background. I even worked some years ago on the FEM analysis of a carbon brake disk for aiplanes, but haven't done any work in this domain since. So im planning to do some calculation before building, but don't really know where to start.

4- I would like to know wich software would you recommend me to use to evaluate the strenght and rigidity of the frame (ansys abaqus, .... ???)
5- Is there a soft that can help me design the number of layers and the direction of the fibers ?

A final question : You spoke about buying carbon tubes and bonding layers to connect them. 
6- Wouldn't a continuous fiber running throught the tubes and around the inserts be better ?

Thanks,
Vincent.


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## Bortis Yelltzen (May 18, 2004)

*Here is my point of view/opinions*

I'll put my thoughts under your questions.



20.100 FR said:


> Hi guys,
> 
> After reading this post and looking around on the net i decided to also make my own carbon frame !
> 
> ...


Over and out,
B


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## datako (Aug 27, 2004)

*Moncoque cf frames*

Take a look at E-PX

I've got a couple, but they don't really seem to have any advantage over my Surly 1x1 in handling or feel. No real advantage in weight either.

Not sure if they are still available.


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## bhsavery (Aug 19, 2004)

datako said:


> Take a look at E-PX
> 
> I've got a couple, but they don't really seem to have any advantage over my Surly 1x1 in handling or feel. No real advantage in weight either.
> 
> Not sure if they are still available.


 link?


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## The_Real_Cyclesmith (Apr 1, 2004)

*economics*

The problem is there is just no market for Farbon Ciber (aaahemmm I mean carbon fiber  ) mtb frames. The market for high-end mtb's just isn't there. Oh, I know that is blasphemy in this forum...but its true. The high end road bike market constitutes a far larger market than the entire mtb market...let alone full-suspension, high-end, or carbon mtb's on their own. It's simple economics...when enough people are willing to shell out the big bucks for ultra high end mtb's on a large scale, then the market will be flooded with product to satisfy that niche. But the fact is that niche is not nearly big enough for people to invest a ton of money in catering too. Most of the engineering and technical aspects for Carbon use in bikes has been solved on the road side of biking. It just not too many people are focused on making the mtb bikes.


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## 20.100 FR (Jan 13, 2004)

Thanks Boris !

I think that i'm starting to see the big picture now.

Now i need to to clear out some more specific points :
-which foam to chose
-prepreg vs wet
-how to deal with the inserts (long continuous fiber? kevlar like in the greek proto ? just bonding ?)
-what is the best lay up for a torsional load (on the diagonal tube)
-do carbon fibers are good in compression ?


Bhslavery :

how is your proto doing ?


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## Bortis Yelltzen (May 18, 2004)

*See below for my comments.*

I put my comments below your questions.



20.100 FR said:


> Thanks Boris !
> 
> I think that i'm starting to see the big picture now.
> 
> ...


And now the main reason there are not more carbon fiber mtb bikes. It is easy, manufacturers make more money selling road bikes. Think about all the outside parts the manufacturer has to buy for a full suspension mtb; a fork form Manitou or RS or Marz and a rear shock, components, bearings, disc brakes, wheels, tires, and all the added engineering and manufacturing time for the more complex parts designed for much more abuse and much more liability. Now look at a road bike, it is pretty simple really, a frame, fork, components, wheels, tires, and that is about it, there is not the abuse of an mtb, so less engineering, you can put a really fancy frame on a road bike and sell it for $5K, and make close to $2K profit, that does not work on an mtb, you only get about half the profit.

It is all business people. It is that simple. It is all about making the most money for the least amount of work. There is less design, engineering, and outside parts on a road bike, and it still sells for the same price as a high end mtb, so they get more $$ from road bikes. This justifies the added cost of molding CF bikes. The economics just don't work out for high end MTB carbon bikes..........yet. Don't get me wrong, CF road bikes for the most part are well designed, but there is still a ton more work involved with mtb design.

Cheers,
B


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## 20.100 FR (Jan 13, 2004)

Boris,

I agree with your view on the problems involved with composites.
But contrary to bhslavery, i'm not fulled by economics, but by the will to learn new technology, the joy to design something, and the future proud of ridding my own frame...

So i won't quit ! I will build ?several? frame(s) ! And if this takes time, that is not a problem because i rather spend time doing this than watching my skis waiting for the snow to fall.... or my bikes waiting for the mud to dry... 

Expandable foam while heating is a smart idea ! Nice !
I have to find some people selling this kind of stuff to get more info. (even if it's in the us, is not so problematiq, all the more as my girlfrind gonna be in the US in march).

I was also thinking of another way to prevent the foam from folding while putting void. May be it's stupid. give me your opinion. here is how i see it:
Shape the foam, then put a plastic sheet, then put the laminate.
Put everything in the vaccum bag, and try to make the void only between the inside plastic layer and the outside vaccum bag, so that only the fiber is compressed.
I don't know if that can be easily done.
Using a prepeg, it might not allow the fibers to follow the shape of the foam ?

About prepreg, you say it's nicer. Ok, but does it abolutely needs hight temperature to cure ? home made temperature controller may be out of my reach...
Is it possible to put a lot of layers in one time ? won't the thickness lead too high temperatures with the exothermic reaction ?

For inserts, let's be more specific.
Greek proto as explanations for the dropouts, ok.
Let's now think of something not to complicated : the area of the frame where the seatpost inserts, for a mtb with no seatstays nor seattube (trek Y, i-drive, FSR...)
The goal if to attach the metal insert to the carbon beam top tube.
For lateral loads, Would it be good if the fibers comming on one side of the top tube just take the turn around the seatpost and come back on the other side or the top tube ?
For vertical loads, the fiber on the top of the down tube whoud wrap around the insert vertically and then come back at the bottom of the top tube ? May be we need +20s orientation to do this ?

For a quasi isotropic laminate, what are the difference in bahaviour between a [0,60,120]s and a [0,45,90,135]s ?
Edit : auto answer:
I found some interesting information on the giant web site. The use 0 for pull loads, 45 or 60 for torsional loads, and 90 for avoiding that the tube will compress on itself.
No the new question is : in what order shoud this layers be put ? [0,45,90,135]s or [0,90,45,135]s ?

Bad compression behaviour is problematiq. How do carbon fork makers proceed to avoid the buckling of the fibers and get a good rigidity ? The seatstays are another place where we are going to find compression loads...

Such an interesting topic !


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## 20.100 FR (Jan 13, 2004)

Hi guys,

Found and interesting document :
http://calfeedesign.com/Calfee_TWP.pdf

Bhsavery, looks like you chose the perfect material for your inserts !
Titanium does not corrode with aluminium, and has thermal expansion characteristics very close to carbon/epoxy.

How is your project doing ?
I'm still looking for info for mine, i have started nothing yet.

Could you give me the contact information of the shop where you bought your titanium inserts, please ?

I've got a new question to add to my list :
What would be the best path for the fibers of a simple bar under compression loading ? (for example seatstays on full suspended).


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## Bortis Yelltzen (May 18, 2004)

*More info*

My comments are below yours.



20.100 FR said:


> Boris,
> 
> I agree with your view on the problems involved with composites.
> But contrary to bhslavery, i'm not fulled by economics, but by the will to learn new technology, the joy to design something, and the future proud of ridding my own frame...
> ...





20.100 FR said:


> I was also thinking of another way to prevent the foam from folding while putting void. May be it's stupid. give me your opinion. here is how i see it:
> Shape the foam, then put a plastic sheet, then put the laminate.
> Put everything in the vaccum bag, and try to make the void only between the inside plastic layer and the outside vaccum bag, so that only the fiber is compressed.
> I don't know if that can be easily done.
> Using a prepeg, it might not allow the fibers to follow the shape of the foam ?


Not sure about this. It would be very hard to do and would most likely pull the material away from the foam leading to problems. You want the vacuum to allow atmospheric pressure to push the laminate against the foam core which is essentially behaving like a mold or mandrel. If you do it the way you are talking about, this will not happen, there will be no pressure forcing the laminate against the core which is supposed to dictate the part shape.



20.100 FR said:


> About prepreg, you say it's nicer. Ok, but does it abolutely needs hight temperature to cure ? home made temperature controller may be out of my reach...
> Is it possible to put a lot of layers in one time ? won't the thickness lead too high temperatures with the exothermic reaction ?


Yes, most prepregs need high temp (90 C or higher) to initiate the cure, that high temp starts the chemical reaction called cross linking in epoxies, low temp freezers is how you store Epoxy prepregs, the low temp keeps the reaction from occuring.

And if you have access to a programmable oven or autoclave and a bunch of vaccum fittings and a nice vacuum system prepregs are much "nicer". You get much better resin distribution, consistent cure, and less mess. With composites there are a lot of what is often called "comsumables", things like vacuum bagging material, sealant tape, shrink tape and on and on, if you have all of these things it is pretty easy to make parts, but all these things add up and there is a lot to keep track of. However, you will need a lot of these things and many others for wet lay-up as well. Prepreg just saves time and consumables to some extent.

I wouldn't worry about thickness issues and exotherm too much, be aware of it, but I have only seen that in very thick large laminates (12.5 mm or more) and your laminate should only be about half that at the thickest areas. Try not to use too much resin. You want a composite that is roughly 55%+ fiber by VOLUME, not mass. According to CompositePro if you use a standard modulus fiber such as AS4 and a epoxy resin, to get a 55% fiber VOLUME you need to have 63.5% fiber by mass. So for example, if your final frame (not counting inserts) weighs 3 pounds, 1.905 pounds of that should be carbon fiber. So mix up 1.2-1.3 pounds of resin, and evenly distrubute that onto the carbon as you lay it up, once you apply pressure you can usually squeeze (bleed) out the excess resin.



20.100 FR said:


> For inserts, let's be more specific.
> Greek proto as explanations for the dropouts, ok.
> Let's now think of something not to complicated : the area of the frame where the seatpost inserts, for a mtb with no seatstays nor seattube (trek Y, i-drive, FSR...)
> The goal if to attach the metal insert to the carbon beam top tube.
> ...


Not sure what you are saying here. I am a visual person, a picture is worth a thousand words. Geometry often dictates fiber paths.



20.100 FR said:


> For a quasi isotropic laminate, what are the difference in bahaviour between a [0,60,120]s and a [0,45,90,135]s ?
> Edit : auto answer:
> I found some interesting information on the giant web site. The use 0 for pull loads, 45 or 60 for torsional loads, and 90 for avoiding that the tube will compress on itself.
> No the new question is : in what order shoud this layers be put ? [0,45,90,135]s or [0,90,45,135]s ?


Yes there is a huge difference. 0's in tension is pretty self explanitory, pulling on a very strong string, the carbon fiber rather than the matrix (resin) handles all most all this type of load in this loading condition in a composite. The 90's are often used as you mentioned, they ass what is often called "hoop strength" to tubular structures. THey also add a little strength if you try to compress the tube a long the long axis of the cylinder. I have done a lot of filament winding and there are tons of things you can do to make a strong tube. I would be worried about the head tube and BB junctions.

As to what order. The layer furthest from the centerline has the largest effect on the component due tot he fact that the furthest ply has the largest moment of inertia. So the loads on the part generally dictate your laminate archetcture. Whatever the directions is of the load with the highest magnitude, dictates the outer most ply orientation (and inner most, both are the furthest from the laminate centerline), however there are always exceptions to the rule. It is hard to teach 7 years of what I have learned about composites in an mtbr chat room.



20.100 FR said:


> Bad compression behaviour is problematiq. How do carbon fork makers proceed to avoid the buckling of the fibers and get a good rigidity ? The seatstays are another place where we are going to find compression loads...


The hoops I mentioned earlier help, and most forks (and seat stays) are mainly loaded in bending, not pure compression, in bending some of the part is in compression, the rest in tension or under lateral loads. The part laminate is over designed in the tension aspect and lateral aspect most of the time so it can handle the compressive load (you always design a part to handle the weakest link, in this case compression). Part geometry plays a huge role, the "aero" look on road forks also adds strength in certain dorections due to the elliptical and tapering shape. It is not just the material properties that make a strong part, it is how you shape it as well that gives the high strength at a low weight, part geometry is a huge player in this composites game. The Wound Up road fork is an exception, that one is just over built in terms of tension so it can handle the compression loads.



20.100 FR said:


> Such an interesting topic !


It is hard to teach 7 years of what I have learned about composites in an mtbr chat room. I am happy to help where I can, but you are getting into stuff far to complex to explain here. I am learning new things every day, and there is still tons about Composites I have not yet learned. Composites are a relatively young and new frontier, and there are a lot of closely guarded secrets by the people that do this work. If you are really this interested I would highly recommend you look for a job in the industry as a technician or hang around a shop to see how it is done, there you will learn all the tools you need to do this stuff. I can only TELL you so much, you are at the point where you need to SEE it done. I'll help where I can. You are asking all the right questions. You are just getting to the point where it gets hard to explain with out showing you how it is done. A lot of this stuff is also not in books, so much is learned by simply doing it.

You also asked a question in a later post about what would the best fiber path be for a seatstay in compression, it is pathS, not path, this is a laminate and you need to taylor it to the loads. In a Pure Compression condition as you asked, I would run a lot of 0's and 90's, something like [90,0,90,0,90,0,90], by sandwiching the 0's by the hoop 90's the 0 degree fibers will not be able to buckle as easily when the load is applied. Again, a seatstay is not under pure compression loads, it is a combined loading condition, bending and compression.

Good luck, and keep up the research. I'll continue to try to answer your good questiuons.

B


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## bhsavery (Aug 19, 2004)

you know, actually I was thinking about this project today, havent been able to work on it much as I just took a new software job with a "large CAD firm". Anyway, I'm starting to see that the carbon tubes joined together with carbon might be the most performance/ease way of doing this. Bortis didn't you suggest this all along?? I should learn to listen more.

Also someone sent me that calfee design paper that said basically the same thing. You can premake the tubes whatever size/shape you want to custom design but it could probably work well.

Random thoughts....
PS... loving the new job, I get to play with CAD software AND use my programming background


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## 20.100 FR (Jan 13, 2004)

Bhslavery :
yep, but you miss the "monocoque" properties...
And it must be more costy too, but you have a nicer tube (best compression, fiber already under tension....

Boris:
Thanks a lot for your imput !
I learn a lot from you, and you help me very much.
I think i begin to have a big picture of the thing, and will try to switch to a more concrete thinking now, applicated on the frame.
I will post the news here, and continue to ask you stupid questions 


In the white paper, the guy speaks about "boron", saying it's stiff in compression and can replace aramid for shocks absorption.
Any one has info on this fiber ?


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## bhsavery (Aug 19, 2004)

boron as in the metal? Dont think its in a fiber form. 

Yeah I realize that I'll lose the monocque porperties, but it was just going to be too hard to bag and do a whole foam core at once, and with some tests I'm not sure the foam is going to hold up. 

I'm thinking at least for the front triangle I could buy premade top, seat and head tubes, and use my foam downtube shape. Rear I think best way would be to do the chainstays and seatstays each one piece. 

By the way you're doing a Full suspension not hardtail? You might think about finding another design to copy first like a FSR or whatever, and just make the front triangle to the same specs.

Brian


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## bhsavery (Aug 19, 2004)

*About face!*

Hey all
I've decided after much deliberation to make an about face in my design.

Instead of going with the onepiece construction method, which is going to be difficult to acheive high quality with, I'm going to think about a lugless reinforced carbon tube method.

Reasons : First of all the benefits are laid out in that calfee paper. It can be strong and light but not always the most aero.

Less oportunity for failure.

Premade tubes although I might make my own downtube

Theres so many people making custom steel or aluminum frame with this same method. And I can use traditional framebuilding tools like a jig to set the tubes up before they are reinforced. So heres a question. Whos a good supplier of carbon fiber tubes?


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## kustomz (Jan 6, 2004)

I tend to agree that the Calfee method is going to be the best, or at least that is the style I have been planning to build. I have thought of buying my tube from Maclean, but my biggest concern is design of the seat and chain stays with straight tubes! What type of riding will you do with you frame, XC, CX,...? My intensions are a single speed 29er based on a Gary Fisher Supercal geometry.


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## bhsavery (Aug 19, 2004)

I was thinking about custom making the stays, I do have the foam shape I got machined. I dont know havent thought about that yet, could do straight ones.

Theres a few steps I'm working out first, like redoing the design and figuring out the ply layers on Pro|Engineer and doing structural simulation. Cool thing is that the composite ply design is very easy to do in this


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## mikedesign (Jan 25, 2004)

bhsavery said:


> Hey all
> I've decided after much deliberation to make an about face in my design.
> 
> Instead of going with the onepiece construction method, which is going to be difficult to acheive high quality with, I'm going to think about a lugless reinforced carbon tube method.
> ...


scott and a whole bunch of others have stated using this method the new scale bike is a very light but primitive way of reinforcing joints at their junctures using carbon personally i like it but it takes about 25 hours of full on processing(read all done in a semi cured state)


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## bhsavery (Aug 19, 2004)

what does that mean exactly in non composite engineer english? How do they do the joining? Wet layup or prepreg? and what about compression? Do you think for my purposes its feasible? I was thinking cut the patterns I generate for the plies out of prepreg and use that shrink wrap stuff for the reinforcements.


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## mikedesign (Jan 25, 2004)

bhsavery said:


> what does that mean exactly in non composite engineer english? How do they do the joining? Wet layup or prepreg? and what about compression? Do you think for my purposes its feasible? I was thinking cut the patterns I generate for the plies out of prepreg and use that shrink wrap stuff for the reinforcements.


well in non composite engineer speak

joint intersection becomes more critical its not something thats easy to perfect tubes on the whole are mitred quite precisely and you must remember that the carbon composite must be in what is loosely termed a green state, whats that mean,all resin systems be they prepreg or wet layup will have a mid cure stage where the resin system is not fully cured around 75% of full cure this means the composite is still more elastic than full plastic but the key thing is that the full crosslinking of its chemical make up isnt done.

how this is an advantage is that you are not relying fully on a good bond surface prep to allow the resin to leech in mechanically instead it will bond chemically and the resin wil eat into the green state top layers whilst not a foolproof bond it will then rely upon physical laminate layup properties to do the structural work so instead of a full monolithic monocoque imagine it as a semi homogonous structure

the best way i can describe the method is that of filament winding the joints kind of like you would a stick tent but remember that the resin wil be eating in also to make a solid junction, filament winding then finishing means that there is little compression needed as the fibre resin at the junction will be in tension as its wound(remember scott also pre tension the fibres to increase their stifness characteristics)

if you go down this route it would be a better method at your level of experience to use preforms or patterns of cloth and wrap the junctiuons just remember to do it a long time before the full cure ie read the green state bit above

then shrink tape the lot around the junction ive seen motorbike guys hold gp chassis together instead of a weld on alloy tubing so its a proven method but on alloy remember it
comes down to prep then to get the composite to bond with the alloy

the new tarmac and six 13 are roughly based on this principle but also have tubes that interlock into their shape to remove the chance of carbon aluminium seperation at the joint

gt learned a lesson from this on the sts with wobbly head tubes twhich would deform at the interlocking band allowing the joint to become loose the point im trying to make her isnt that it can be a nsty horrible mess if you get it wrong obviously you have to research the media you are working with to get a good result and the interactions of shape and materials if you are going to have a go at doing it this way


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## bhsavery (Aug 19, 2004)

very interesting mike! 

So what if I'm using premade tubes here? Like if I buy the carbon tubes from somewhere won't they be fully cured and it will be a strictly mechanical bond? Or are you saying that the different layers will chemically bond? And yes I was thinking for this method using cut sections of cloth rather than filament.


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## mikedesign (Jan 25, 2004)

bhsavery said:


> very interesting mike!
> 
> So what if I'm using premade tubes here? Like if I buy the carbon tubes from somewhere won't they be fully cured and it will be a strictly mechanical bond? Or are you saying that the different layers will chemically bond? And yes I was thinking for this method using cut sections of cloth rather than filament.
> 
> ...


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## Samu Ilonen (Jan 13, 2005)

Hi!

You are talking about prepregs and I'm very interested on them. But I asked few questions from my frien abut using them...he poined few things.

Is this correct:

-prepreg hold air between layers easilly because prelaminated expoxy will not let it go trought the layer easilly as wetted building? So vacuum needet any way...least ~ 0.5 bar?
-they are quite stiff when aplying to mold. So no tight curves and lot of pressure?
-lower curing temperature=shorter storing time...higher curing temp of fine but most cores will melt...

That weight prepreg would be good to try? For laminatin tube junctions. ~250g/m2 based prepreg?

I'm trying to build road time trial bike. Just because nothing seem to be designed as I want. Cervolo P3C and so was old Tre Team Time Trial but they could do better...

I will make molds for tubes and bond them together ala Scott. Female mold and simple "male mold" that has pressure bag over it. CF will be laminated to male mold (only slightly smaller to fit in), put it in side female mold and pressurise bag. There are few small drain holes for excess epoxy to come out.

I did this way seat post tube yesterday and it looked pretty good. And easy to do many...

Fibers are UD string and twill sock. Unique parts, just for me and for fun.


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## kustomz (Jan 6, 2004)

Samu Ilonen said:


> I did this way seat post tube yesterday and it looked pretty good. And easy to do many...
> 
> Fibers are UD string and twill sock. Unique parts, just for me and for fun.


Can you share pictures of your molds, bag, and pump, for those aspiring to do this type of project? It would also be very helpful for all to see the finished product so we know what is possible.

Anyone else have pictures of your projects to share?


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## Samu Ilonen (Jan 13, 2005)

*Just basics...*

I don't have digicamera but may be I can get some pix..

-Mold is basic simple glass fibre mold,2 piece. This can be done from plastique filler to be simplest. Wax it also..
-"bag" is 400mm long piece of road innertube with 18mm copper tube inside, piece of plastiqiue rolled outside to avoid epoxi sticking to rubber
-pump is Silca track pump...

So roll Cf+epoxy around "bag",put it to mold,thighten mold together and pump some pressure...epoxy will flow out from small holes in mold. Simple? Preheat tube ~60C overnight to add heat resistance for summer. Ready?

Look your epoxy data sheet for temperature. Don't fry it!

I have done TT-bar,one prototype seat and I design and produce some light ti parts. Like 143g 27.2X350mm mtb-seatpost,TT-bar,road, track,mtb frames etc.

CF TT-bar:

https://weightweenies.starbike.com/phpBB2/files/dsc00373_842.jpg

Ti-TT bar:

https://weightweenies.starbike.com/phpBB2/files/dsc00385_123.jpg

I'm still taking my first steps with CF so I have lot to ask...


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## bhsavery (Aug 19, 2004)

nice, now what about for the complex shape like that TT bar? what method did you use for that? 

In terms of making an entire bike, its easy enough to make tubes, but what about when it comes to making shaped downtubes or seatstays? Its harder to make female mold from those shapes. Thats why I'm thinking about using a MALE mold

Have you done anything with male molds? Not really that much harder.


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## bhsavery (Aug 19, 2004)

*Interesting paper...*

http://www.specialized.com/OA_MEDIA/pdf/Witchcraft.pdf


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## Samu Ilonen (Jan 13, 2005)

That Spezialized link is good!

The TT bar was made simply Rinaldi's way. That ugly tape way, you know.

Core is 6mm Debron etc.+1,5mm balsa wood sheet on both sides glued with tubular glue. 

 

Weights 20g and balsa keeps it straight. Glue them agains straight table..

There are balsa sticks on rear and front sides. Stem and tubes are alloy. Sandet with wet epoxy and glass fibred.

Keep mind that tape will not compress straight areas well so I addet more pressure with pressing hard foam (like camping pad). 

Taping was pain in a$$ due to shapes of wing. It tend to slip away...something to sand. It take like 10 rolls of take but it's only 4€...

There is also Kevlar band on front of wing. Safety belt...

Base wing has 3 layers, stem and tubes have like 5-6 and one layer at last totally over it. Everythinf is 250g/m2 twill. But next time I but some UD just below finishing layer. Lighter and more stiffer.

Elbow pad are simply copied from 3TTT hero bar between two pieces of plastigue pag...not elegant but say fast? Again pressure was addet with camping pad and piece of 3" plastique drain tube (inside of cource).

There are ~300g alloy parts and bar weights 603g.


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## Samu Ilonen (Jan 13, 2005)

*Twill only tube...?*

One basic question:

IF I do tube with twill socks ONLY so there are only 30-60 decree fibres, I will get tube that bends easilly but is torsinally very stiff?

I will use UD also but down tube is 80X30mm...so could I put UD only to 80mm sides (agains side bending)? Or least lesser on bottom of tube to avoid that I will be ripper apart from them.

Any input?


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## loosch (Feb 16, 2005)

Here are a couple of photos of one of my homemade bikes.

They aren't very good photos, I really should take some more. I have had this bike for about 4 years and race it often. I made all the tubes separately then wrapped them to make a frame.
I have made 8 bikes over the last 15 years, some road some mtb and have tried many different methods of fabrication.


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## Vulcan (May 22, 2004)

wow... Thats a swwet ride.


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## bhsavery (Aug 19, 2004)

Vulcan said:


> wow... Thats a swwet ride.


very nice, how did you mold the tubes?

How strong/light?


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## loosch (Feb 16, 2005)

[Tubes were made by resin infusion with uni and braid, front triangle in female molds stays over aluminium mandrels. Bare frame weighs 1.27kg, wing bar about 650g, I have raced it in TTs from 10k to 80k on some rough roads and fast descents it handles nicely.
Here is another pic I found.


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## 20.100 FR (Jan 13, 2004)

impressive.

did you also made the fork ?


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## Davide (Jan 29, 2004)

*Here you go*

Found an Italian manifacturer that makes costum sized road/mtb carbon frames:

http://www.hbm.it/

http://www.hbm.it/prodotti.html

site is in italian ...  see also

http://www.ciclismonline.it/edispor...6BFBBC806828695FC1256FB3003E429D?OpenDocument


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## applegreenheckler (Feb 26, 2005)

There are 2 ways to make carbon bikes. 
Method 1: Lugs, just like bikes of old stock tubes are glued into frame lugs. Fairly easy to make but not really all that great if performance because of the process of bonding the c/f tube to the lug(which can be any of a # of materials i.e aluminum, carbon, steel, ti)
Method 2: requires a $500,000 mold so not really all that practical in the custom market and that would be used to make a molded frame that has less joints so it is stronger and lighter.


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## mikedesign (Jan 25, 2004)

applegreenheckler said:


> There are 2 ways to make carbon bikes.
> Method 1: Lugs, just like bikes of old stock tubes are glued into frame lugs. Fairly easy to make but not really all that great if performance because of the process of bonding the c/f tube to the lug(which can be any of a # of materials i.e aluminum, carbon, steel, ti)
> Method 2: requires a $500,000 mold so not really all that practical in the custom market and that would be used to make a molded frame that has less joints so it is stronger and lighter.


not quite true up to now i know of about 5 methods of making bikes and believe it or not if designed and bonded correctly you wont see a bond fail but you will see the material fail
adjascent however production bonding isnt the same as bonding a wing skin to sub structures so this is probably why bonding gets a bad rap

the majority of builders are using carbon lugs nearly eliminating the problem that lugs and tubes bonded together were heavier than a welded or monocoque frame

the carbon motorbike frame on page 1 of this thread used no where near 500k in tooling and its a seamless monocoque a bike is far simpler sure its a one off but most people in here want to just have a go and not make 600 frames a year if they did then yes they probably would spend in the region of 100k on a cnc machined heated die


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## 20.100 FR (Jan 13, 2004)

Davide:
yep, i think they use the same process as in scott frames.
There are 3 little us producers that also do custom carbon bikes.

On my side i still need to decide if i'm gonna use one process or the other
-the tubes + overlaping at junctions seems easier and well adapted to an classical hardtail
-the 3 monocoques (main triangle, chainstays, setastays) bonded together looks a bit more performing
-the full monocoque looks nice for the front triangle of a full suspended frame.


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## BranoM (Aug 5, 2004)

to bhsavery: any progress with your cf frame?

B.


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## TM1 (Aug 9, 2004)

*Here's one. VERY special, very nice ...*

a guy I know, an engineer here in Israel, built his own bike from CF.

now he is offring to guild YOUR next bike. custom build, tailor made.

I have seen the bike (6.6 nude) in action and it look cool.

http://www.dekelbikes.com/


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## 856er (Jul 16, 2005)

A friend of mine got permission from K2 to make mould of there K2 Oz Carbon bike circa 98/99 model,So he did and made a seamless copy using modern carbon material,
here it is.


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## 20.100 FR (Jan 13, 2004)

856er said:


> A friend of mine got permission from K2 to make mould of there K2 Oz Carbon bike circa 98/99 model,So he did and made a seamless copy using modern carbon material,
> here it is.


 I can't see any picture ???


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## 856er (Jul 16, 2005)

20.100 FR said:


> I can't see any picture ???


Opps it was there,
try again,


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## 20.100 FR (Jan 13, 2004)

856er said:


> Opps it was there,
> try again,


 I see it now.
Very nice !
What process did he exactly used ?


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## 856er (Jul 16, 2005)

20.100 FR said:


> I see it now.
> Very nice !
> What process did he exactly used ?


To be honest I haven't seen him for a while (and he's moved)
but I do recall him mentioning the WEST SYSTEM,if you would like more details of the process used and how the mould etc was made I can copy and paste some details here or give you a link to info he posted on another site.
I also know he intended to make another one as he used too many layers on the one pictured (heavier than intended),


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## 20.100 FR (Jan 13, 2004)

856er said:


> To be honest I haven't seen him for a while (and he's moved)
> but I do recall him mentioning the WEST SYSTEM,if you would like more details of the process used and how the mould etc was made I can copy and paste some details here or give you a link to info he posted on another site.
> I also know he intended to make another one as he used too many layers on the one pictured (heavier than intended),


 The west system is the one used by reinard i think.

I would be very interested in having more info, thanks.

V


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## 856er (Jul 16, 2005)

20.100 FR said:


> The west system is the one used by reinard i think.
> 
> I would be very interested in having more info, thanks.
> 
> V


Here's some info he had posted.

The use of Gel coat is only realy used in the repair of yachts though it is used in manufacturing items, but do bear in mind that there are many types of Gel and for many diverse applications. 
I would avoid the use of them in mould making. 
Polyester resin is quite good enough for the making of moulds because using West System to make a mould is a very expensive way to go. 
Please do not mix the two of them because they do NOT like each other and if you spend hours making an item it will be a pain if you have to start again. 
Also remember this when using Polyester you must use some MW solution, it is liquid wax, and you will need to mix this in with your resin when making batch's of resin for making the mould. 
Otherwise you will not be able to seperate the frame from the mould. 
You see MW solution as the resin dries rises to the surface to form a non sticky surface. 
West System already has the wax in it and depending on how cold it is you may get a leaching from it where the yellow'ish wax rise's to the surface, this may be removed with warm soapy water. 
Dont be deterred. 
Now your question, well yes Joe Bloggs could do this with determination as there's no great skill to it. 
Practise this first. 
Get a 3x3 sheet of glass and clean it on one side. 
Lay it down on a flat surface. 
Coat the glass with re-lease agent as i discribed. 
Having cut your carbon matt already to size say 2.5 ftx2.5ft. 
15 sheets should do. 
This will give you a finish of say 8mm thick. 
Have some three inch paint brush's handy, rubber gloves and acetone or nail varnish remover to clean up, and a roller which has special groves cut in it for working out bubbles. 
Apply your resin then lay a sheet onto the glass and paint on gently more resin. 
work the surface with the roller. 
Apply another sheet and repeat and so on. 
Then have a firm sheet of Formica with a smooth finish the same size as your carbon matts. 
When your done lay the Formica sheet onto the resin soaked matt applying release agent to the surface that is on the matt. 
Place a flat but not too heavy object onto the Formica the same size again. 
Leave to dry say 5 hours. 
Remove the flat plate and peel off the formica and you should with gentle persusion be able to remove you finished product. 
Clean back the edges with a cross cut saw. 
Your finished product will look like the dogs danglies.

Earlier i said Polyurathane ignore this i meant to say Polyester.

Once you have your sheet of carbon made you will be able to cut it to any shape using a scroll saw. 
West is not UV resistant you must if liveing in a hot country or not spray on a lacquer to stop it breaking down.


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