Designing and Building my own Carbon Fibre frame

[FilmAt11]

Really great to read about your work. Could you describe the layup, strength considerations, etc? Also, have you looked at 3D printing the lug moulds using dissolvable filament?

[euph]

I have sent off an order for some 3D printed mandrels today. I am going to use one for my BB lug and see how it goes.

Chainstay:

[danny]

Hi euph
I'm interested too builinding carbon frame and I have some experience with carbon bike parts (i have build some carbond saddles).

Why you don't use the bladder moulding system?

[euph]

Hi Danny

For the chainstay I have used a bladder. This I the only part I have made that bladder moulding can be used for as it only needs a guaranteed outer dimension.

The lugs require a guaranteed inner diameter on the other hand. I experimented with bladder moulding them but I couldn't get anything close to the internal dimensions I needed without excessive machining afterwards, which I would rather avoid for many reasons.

This project was my first foray into carbon fibre and I know lots of bits I can do better. However I only have a 9 month timeframe so I am having to work with design choices I made previously! In future I will make more frames/parts under less of a time pressure and with the experience from this project.

Sorry for waffling along! I hope that answers your question.

[dj97223]

I love this thread and what you are doing. Good luck!

[danny]

Euph, i have a old specializied roubaix sworks with a crack on a chain stay do you have some suggestion for repair my self? I have all I need plus vacuum pump but I don't know which is the best solution.

[euph]

Thanks for the encouragement dj97223.

Danny

I don't know how much experience you have with carbon fibre but a cracked chainstay is a great place to start to learn. Have a read through BikeAnon's experience. He documented very well and has pictures of lots of the processes. Shoot me a message if you need any help though.

viewtopic.php?f=3&t=145378&p=1316607#p1316607

Enjoy

[danny]

euph I have buil a few carbon saddle starting from a selle italia slr so I have sufficient skils.

[euph]

Dropout fresh from the mould.

[euph]

All three lugs and a dropout. Need to make a few more pieces and maybe redo the BB lug as I am not satisfied with the wall thickness in some areas. Got my tubes today. Need to build a jig and get something close to a frame soon! Exams and revision are looming so I am cracking on now.

[FilmAt11]

Great! Was the BB lug constructed using a 3d printed mould (PVA?). How'd that work in terms of tolerances, post-machining?

[euph]

I used a 3D printed ABS mandrel for this one. First try with this method and it worked really well. The inner shape is really good and it has picked up all the internal curves very well. Melting it out with acetone worked well enough but did take a while and some extra work. But the time required to pull it out is less than the time and confusion involved in making the mandrel from aluminium. Both methods have there advantages.

I think in future when I am not making such a "prototype" frame I will investigate lost wax mandrels but as I say I am on a time crunch now. So the possibility for experimentation is minimal.

[danny]

You can share also some pictures of construction?

[euph]

Construction of the frame? Not got to that bit yet.

If you mean laying up the lugs I would try and get more pictures but my layup is not the prettiest sight and my hands are gloved and covered in resin so it is difficult. I will make an effort to get more pictures though.

[euph]

Front triangle tests assembly. Weighs 625g

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