[trilogy2826]

This general topic has been discussed several times before. General theme: Use the right tool for the job. If you understand what material types can be used where, you can get away with a robot that has no business weighing less than 120 lbs. Not saying we have it all figured out. We still have a lot to learn, but here is what we have learned during our short time in FRC.

We just started using the FEA tools embedded in Inventor this last year and this helped shave our sheet metal thicknesses by at least 20 %. We also found a couple problems with fatigue and were able to fix it before we even manufactured a single part.

2828 converted over to 7075 AL hex shaft in 2010. We have used .375, .5, .625 and .75 for anything from gearbox shafts and cantilevered axles to arm joints and shooter axles. All of these had e-clip style snap rings as the main retaining fastener. We had one issue this year that was similar to the OPs shear at the groove, but it turned out to be that the material used was accidentally 2024 instead of 7075. After the switch, no problems.

I highly suggest purchasing from onlinemetals.com. They have a great selection, fast shipping and prices that are hard to beat.

If anything, please don't "just go to steel". In most cases it isn't necessary.