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Unread 30-10-2015, 00:27
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cbale2000 cbale2000 is offline
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AKA: Chris Bale
FRC #5712 (Gray Matter)
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Re: pic: Carbon fiber monocoque drivetrain Top view

Quote:
Originally Posted by Edxu View Post
Any clue on how expensive this would be compared to if it was made out of standard drivetrain steel or aluminum?
Assuming they'd be doing their own layup, and depending on the number of layers it could be anywhere from $100 to $500+ (only for the carbon fiber, not counting the other supplies like epoxy and such). You can get 50" wide carbon fiber cloth for as little as $20 a yard if you look around a bit.

Personally if I were to build something like this, I'd use a high compression strength foam core material rather than building it monocoque (plus it's a bit easier to do the layup). Then simply use a lightweight wood for the center material in areas you need to drill holes (sitka spruce is a good option) and then use just 1-2 layers of carbon fiber cloth. You could also make the walls of this design much thinner using such a method.


Quote:
Originally Posted by Tom Line View Post
The first is to use dry cloth and saturate with epoxy. Generally speaking this is what home-builders use. It's going to be heavier than a well made vacuum bag or pre-empregnated setup, but doesn't require expensive materials or specialized building techniques.
IMO, vacuum bagging gets a bad rap for being too complicated for the average user. Our team managed to build a very simple vacuum bagging table using some non-stick plastic bag material, PVC, sticky tack, and a basic shop air compressor with a vacuum valve.

Quote:
Originally Posted by Tom Line View Post
Your next choice is how to form the parts. Will you make a male mold? A female mold? Use a spacer material like polystyrene that can be chemically removed?
None of the parts we made used a mold, we simply applied the cloth directly to the core material, added epoxy, vacuum bagged, and repeated. This won't work for all shapes, obviously, but for most FRC uses it works fine.

Quote:
Originally Posted by Tom Line View Post
Fastening things in carbon fiber can be tricky. The strength in a fiber structure comes from the fiber itself. The epoxy is merely there to hold the fiber in the shape you need. Fastening to the carbon fiber incorrectly will crack the epoxy and destroy the structure's strength. You also tend to need backing plates to spread the pressure out.
As long as you're smart with what kind of core materials you use and where you use it, backing plates are largely unnecessary, when they are, you can usually get away with some 1/8" polycarbonate. Again, for most FRC uses.

Examples:
www.chiefdelphi.com/media/photos/27823
www.chiefdelphi.com/media/photos/31319

Last edited by cbale2000 : 30-10-2015 at 00:32.
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