Just thought I would post up some pictures of the downhill mountain bike frame my partner and I designed and built for our senior design project. Rather than tubes for the top tube and down tube, we designed for them to be open channel sections so that we could easily lay up and cure the whole front triangle in one piece. Enjoy. Sorry, some of the pictures are kind of blurry.
interesting. Is the aluminum just the mold? What travel do you expect out the rear?
Yeah, the aluminum is just the mold. I laid up on the inside surface, envelope bagged and cured it in an autoclave. The rear travel will be a little over 8".
Good on ya! Im in the middle of doing a similar project, but using male tooling.
How did you lay-up the various layers in terms of orientation and
How did you organise ply overlaps with a bag up the middle?
awesome project, well done, im just holding myself back with questions here!
As you can see in the pics (maybe… I’ll try to replace the fuzzy pics with clearer pics soon), the outside and inside plys are 45/-45 twill fabric. Between the twill I used mostly axial uni plys and some transverse plys with respect to the direction of the “tubes”.
Thanks, no need to hold back. Fire away.
If it works well, I’ll take one 
what temp were you cooking at? Did you have any problem with aluminum expanding too much? You must of done it a low temp I would guess. Was it prepreg or just wetlay?
We cooked it at 250 deg F, No problems that I can see with using the aluminum mold, and we used prepreg.
Suppose the fact that there is an open usrface to the mould considerably helps with the reduction of negative aluminium expansion effects.
What stiffness have you modelled / guessed / tested with the open ‘u’ shaped channel as opposed to the traditional closed tubing?
Have you had a chance to field test it yet?!?
I have heard of aluminum molds that would expand, and as the cool the will crush the part. Alot of times the part will be removed hot to resolve that problem. Good job by the way!
Hi,
what pressure did you put on the bladder?
I didn’t use a bladder actually, just envelope bagged. The autoclave pressure used was 50psi, though.
hi eric
wut up?
Not much kenny, found this site I see… It’s a pretty cool group. Some neat stuff on here.
Nice project! Any updates?
Mike
Awesome mold. I’d like to see some updated pics of the finished frame