Carbon Fiber Vs. Steel

[valeriemoore]

Has anyone ever used carbon fiber on an FRC bot? How did it work out? Would you use it again?

[mrnoble]

I've used it. The question is, what do you want to use it for? That makes a world of difference in what the answer to your question would be.

[valeriemoore]

Some of the people on the team want to replace our steel axle with carbon fiber. It's a lot more expensive, but I am more worried about what a roll pin would do to it.

[mrnoble]

Ah. Well then, no. That's not a good idea. High grade steel axles will serve you well, and won't suffer from any of the problems carbon might (crush, for example).

[TVwazhere]

If youre using it for any sort of torque application like an axel then no.

In 2008 (keeping with a theme here) Team 20 used carbon fiber hockey sticks for their four bar assembly, saving on weight while keeping a high strength construction
http://www.team20.com/blog/wp-content/uploads/2013/01/2008robot-189x300.jpg

[FIMAlumni]

From Michigan, I know 548 has used it in both 2011 and 2012 as large support feature's for a four bar linkage. http://www.chiefdelphi.com/media/photos/36672 had 2 large bar's as supports and 1 large bar for the arm.
http://www.chiefdelphi.com/media/photos/38031 very similar but the have some smaller tubes for a barrel.

I also remember a 2011 team I met at worlds who's robot was almost completely made from carbon fiber.

[theawesome1730]

We have used carbon fiber sheets (1/8 inch IIRC) for the past two seasons and carbon fiber tube for the 2011 season. Carbon fiber doesn't take torque loads well but it does do well with compression (the tube) and is very rigid. Be aware, cutting carbon fiber is tricky and we use our water jet sponsor to do it. We drill holes in it with carbide drills and even as heavy duty as they are, we dull them very quickly

[RRLedford]

The carbon fiber weight advantage comes with liabilities, as far as its greater difficulties for mechanically attaching it to other structural components without damaging the carbon, or concentrating too much stress in one spot.

I would only consider it for long swinging arm type use where faster speed movement with less torque loading is desired. For use as an axle, especially a power transmitting axle, I would veto that idea.

Is it because the axles are bending, or what other problem are you concerned about with the steel? Weight only? If it's weight, can you just go slightly larger with axle OD and use 7075 or 7068 aluminum?

BTW, you often will need to have some good gluing skills and high performance adhesives available for making any durable & reliable carbon fiber joint assemblies on your robot.

-Dick Ledford

[artdutra04]

7075 aluminum is a much better material for using in robot shafts if your goal is to save weight. Carbon fiber can drastically lose much of its strength if you poorly attach to it (such as drill holes through it) and/or transfer forces into it.