Carbon Fiber Chassis

[JJD]

Why isn't it used? Is it a matter of availability and cost, or is there some weakness I'm completely overlooking...

[vivek16]

Availability, cost and it's hard to work with. Some teams have done it with great success but for most, it's a lot easier to drill some aluminum.

-vivek

[JJD]

But if you have the resources, it would make a very good, lightweight and durable frame yes?

[sporno]

Ive always enjoyed the good ole KOP frame. Carbon fiber is a great material to use if you can use it right. Ive seen too many teams try to use CF and it looks horrible and is very misshapen.

[dtengineering]

Wood is nature's carbon fibre... look up "wood chassis" or "plywood frame" and you'll find lots of teams that use it.

Other than us, that is.

Jason

[JJD]

Not talking about wood lol

[artdutra04]

Carbon fiber is expensive, needs resources (curing oven) beyond what most FRC teams have, and is heavily weakened by drilled holes (oops, we mounted our thingamajig in the wrong spot, time to move the hole). So yes, it's lightweight and strong, but it comes at a steep price.

Besides, this is the year I think teams will want their center of gravity as low as possible. Using a carbon fiber frame only invites them to put more weight in things that raise the center of gravity.

[synth3tk]

Originally Posted by JJD

Not talking about wood lol

Well, he's suggesting an inexpensive and widely available solution. Don't chew out a helping hand.

[Jones571]

Originally Posted by dtengineering

Wood is nature's carbon fibre... look up "wood chassis" or "plywood frame" and you'll find lots of teams that use it.

Other than us, that is.

Jason

This is our 10th year using a euro ply chassis. Never have had an issue knock on wood

[Al Skierkiewicz]

Teams have used carbon fiber in the past but one must remember that the equipment and materials needed for repair are not allowed in the pit. They also require some serious personal protection when working with the materials. You can make the frame at a facility that satisfies all these but you won't be able to fix a major break at a competition. With this year's game, repairs may be a much higher priority.

[Bongle]

In the past, I have heard of teams using broken carbon-fibre hockey stick shafts as structural members to get around the cost issue. If you've got a fairly high-level hockey club in your town (WHL/OHL/AHL/QMJHL), you might be able to pick up the shafts and process them into strong, light frame or superstructure portions.

[Pausert]

I like the hockey stick idea!

Everyone continues to talk about the strength of carbon fiber, but I would think it's too delicate for use in an FRC 'bot chassis. I know carbon fiber is used in all sorts of military applications, but my personal experience with carbon fiber RC cars has me convinced that an FRC chassis built of carbon fiber would tweak, torque, and slowly splinter apart.

[jimbot]

We made a mechanism out of composits (kevlar) a few years back. By no means was it too weak. The issue was that in order to mount anything, some solid backing was needed, like wood.
Haveing played lacrosse, I have seen composits fail. They don't bend like aluminum, when they fail, they go completely.

[BenX02]

I think for most for most teams it's availability, cost, and the fact that it is extremely hard to work with.

Our team has access to it, as well as composites, but the fact that it is so hard to work with that keeps us from using it for our chassis.

[cbale2000]

Team 703 has actually used Carbon Fiber on 2 of our robots in the past and it works out quite well.

Our 2007 Robot featured Carbon Fiber ramps and top structure, and our 2008 Robot featured Carbon Fiber on the manipulator and the base of the robot supporting all of the electronics (hard to see in the picture, might get a better view in this one).




*** Warning - Wall of Text ***


*Note* Below are my thoughts based on my experience with using Carbon Fiber on our team, I do NOT claim to be an expert in the matter, nor can I say I was 100% involved with all aspects of the purchase, use, or construction of all of our parts on all of our robots, read "with" (not "at" ) your own discretion.



The cost is significant but can be mitigated by shopping around (We found our Carbon Fiber from a vendor on E-bay for significantly less than most others we looked at). We used a divinycell foam (High compression strength) for the core, and wood in places we knew we would have to drill in to.

It's not particularly difficult to layup if you use a "vacuum bagging" process and there is no special equipment required, all that's needed is an air compressor with a vaccum valve attached to it, though it can be VERY time consuming depending on how much you want to use and how complex the part it, as well as how much workspace you have and how many people are working on it.

We would layout the parts like we wanted them, wrap the parts in carbon fiber (1 layer), cover with epoxy, cover the epoxy with a "no-stick" cloth and a few layers of paper towels (to absorb excess epoxy, saving weight).
We would cover the whole thing with an airtight plastic covering and seal to the table, essentially with sticky-tack (It wasn't REALLY that but was basically a stronger equivalent), and insert the "sucking end" of the compressor vacuum hose to suck out the air.
Leave overnight, pull out the next day, and if you're not satisfied put it back in for a few hours with an ordinary household space heater blowing on it; though make sure not to leave it overnight with a spaceheater due to the fire risk it could potentially pose though. If you want to make the surface a bit smooth and shiny as well, you can add a simple clear coat to it.

The end result is a VERY strong piece that can support many times it's own weight (our 2007 ramp bot could EASILY hold 5+ large adults at one time without a problem. The main weakness to the parts we used was that they were weak to any "puncture" force applied to them, so while you could not take a piece and break it with your bear hands, you could stick a pen through it with relative ease. This problem can however be avoided, it's all dependent on what you use for the interior "sandwiched" material. That said, while Carbon Fiber can be a nice, lightweight component to a robot, it does have limitations, for example, I wouldn't use it as an outside plate on the frame, nor would I recommend using it to support ANY kind of axle.



Again, this is just an example I have seen other teams that have used other processes and materials besides carbon fiber and have gotten similar results, it really just comes down to what you want to make with it.
Don't forget there are a TON of online resorces you can find on how to use these "composite" materials, Google is your friend.


Hope that helps, sorry for the long read.