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#1
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pic: Carbon fiber monocoque drivetrain Top view
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#2
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Re: pic: Carbon fiber monocoque drivetrain Top view
Guess I'll take the obvious first question: How much does it weigh?
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#3
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Re: pic: Carbon fiber monocoque drivetrain Top view
That's hard to say, as inventor doesn't have a material for carbon fiber in its default library. By setting the carbon parts to the closest material I found, it says 28.5 lbs.
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#4
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Re: pic: Carbon fiber monocoque drivetrain Top view
Very neat. Any idea on how one would build this? Have you done any simulations to check the stress resistance compared to the "standard" aluminum chassis?
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#5
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Re: pic: Carbon fiber monocoque drivetrain Top view
I have ideas. Part of the reason I CADed this was so that I could learn how to make it easier to manufacture. Team 2471 recently had a visit from a new sponsor who might have the resources to make this chassis. I used the information they gave us abut what is easiest for them to make, but that doesn't mean that it is optimized for ease of manufacture.
currently, it is made of five peaces. One C channel on each side, and a dropped center piece that would be vacuum molded into a "top hat" shape. Quote:
Based on the sample peaces I have seen from our sponsor, I think that this would be very strong. |
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#6
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Re: pic: Carbon fiber monocoque drivetrain Top view
No.
Based on the sample peaces I have seen from our sponsor, I think that this would be very strong.[/quote] It will also be a major pain to drill any holes in. |
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#7
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Re: pic: Carbon fiber monocoque drivetrain Top view
Definitely. Make sure you get all the holes in the original design!
And, OBTW, what's plan B if it does actually break? I was nervous about our welded aluminum chassis in 2013 (though not as nervous as I should have been now that I know more about aluminum grades and welding and heat treating), but this is a whole 'nother level of "no way to repair". |
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#8
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Re: pic: Carbon fiber monocoque drivetrain Top view
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But really, carbon fiber is quite the science. I'd recommend checking out acpsales online as they have decent guides on carbon fiber. Consider a filler material like foam or a hex shaped layering for some added strength along the rails. You want carbon fiber to have some flex, but not too much. Also be careful about hole placement. |
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#9
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Re: pic: Carbon fiber monocoque drivetrain Top view
From what I remember from talking to a team that does a majority of their robot out of carbon fiber, that seems to be the main drawback.
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#10
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Re: pic: Carbon fiber monocoque drivetrain Top view
Any clue on how expensive this would be compared to if it was made out of standard drivetrain steel or aluminum?
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#11
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Re: pic: Carbon fiber monocoque drivetrain Top view
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There are a number of ways to fabricate carbon fiber structures. 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. 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? 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. Then there's cure times, cure temperatures, mixing ratios, substrate materials...... Starting around 2:10: https://www.youtube.com/watch?v=504I_hJDFck Wet Layup - what many FRC teams would do in their shops: https://www.youtube.com/watch?v=-sOU3zEigt0 Vacuum Infusion: https://www.youtube.com/watch?v=hEyF5KOkhUY The last two months of my life finally coming to a close (and why I know so much about fiber construction): ![]() |
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#12
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Re: pic: Carbon fiber monocoque drivetrain Top view
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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:
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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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#13
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Re: pic: Carbon fiber monocoque drivetrain Top view
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The gearbox plates would be cut from stock plate on a CNC router. Quote:
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#14
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Re: pic: Carbon fiber monocoque drivetrain Top view
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You can also use a space heater and half of a cardboard box to speed up the epoxy setting process if you want (don't leave it unattended though, for obvious reasons). In the case of your design, you could use this method to basically make the whole thing with 5 pieces (or as one big piece if you were feeling really ambitious) and you wouldn't have to make the frame walls so wide (leaving more space for electronics and such). And now for some related old pictures... 1, 2, 3, 4 Edit: After re-reading your previous comment a few times, I'm thinking you might have been referring to how the construction method would be used in this situation, and not so much how it works (correct me if I'm wrong)... >_> Answering that question might require some CAD work to explain unfortunately. Last edited by cbale2000 : 30-10-2015 at 21:40. |
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#15
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Re: pic: Carbon fiber monocoque drivetrain Top view
This is how I've personally done a few of our parts, it uses really only 4 +-2 layers of carbon fiber and is much easier to shape your parts. We just get the desired shape we want and make it out of foam core, plan around hole placement and how much carbon fiber needs to be in the pockets, and then lay the carbon fiber. I'm not sure how it would work on a frame of your size, but it can help with rigidity and cut costs.
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