Re: Team 1511 Prototype Drivebase CAD
 

Could you explain more about why you are trying out steel? I am all for trying new stuff in the offseason that you wouldn't normally in the build season but this is one of those items I think most of us would say if you are having to try steel you are doing something wrong. Steel isn't the easiest material to work with compared to the ease of aluminum.

I would highly recommend you give this chain spacing calculator a try to properly space your wheels. We used it this past year on 35 chain and after a full season the chains have stretched slightly but they are still in great shape to run. Its been really nice not having to worry about chain stretching out over a season and eliminate some components from the robot. http://www.chiefdelphi.com/forums/sh...8&postcount=10

Also am I looking at the model right that you are using two shaft collars to keep your axles in place? I would recommend using slip rings or tap each end of the axle with a 1/4-20 thread. Shaft collars will come loose very easily and if you don't check them after every match it will come off eventually. Your drivebase is the most important part of the robot that will see the most run time. If you make it as reliable as possible and eliminate as many failure points as you can your pit crew will spend little to no time touching it in a season.

If you keep the gearboxes mounted as they are now you might want to consider running dead axles instead of live axles as you are now. Round bearings are cheaper to buy in comparison to 1/2in hex. Since you aren't directly driving your center wheel there isn't much of a need to go with live axles.

Another thought to consider is how to make each wheel/axle assembly as similar as possible to reduce the number of unique parts and make repairs a lot easier. This past year we made every wheel/axle assembly the same on both of or robots including color coded spacers so all parts were interchangeable between wheels and robots. Of the few times we did have to adjust our drivebase it was an pretty pain free. You can see a picture of one of our drive modules assembled for reference.

Re: Team 1511 Prototype Drivebase CAD
 

A dead axle in this application itself to the use of round bearings, which are more reliable than hex bearings. The dead axle can also help provide strengthening support between the rails of your chassis.

Echoing Brendan's comment, shaft collars are not ideal for this application. The amount of vibration experienced in the drive train will make the collars loosen even more quickly, and you don't want to lose your shaft retention in your drive train part way through a match. I'm no expert in dead axle shaft retention in sheet metal drives, but to my knowledge your options include retaining rings/snap rings (I believe this is what Brendan called slip rings, this is a misnomer as slip rings are an electrical component), drill and tapping each end of the shaft, or simply making your dead axles bolts like in the Kit Bot.

My personal preferences for shaft retention in FRC are to in general use snap rings on the outside of shafts, spacers in the middle, and selective use of shaft collars and shoulders where reliability and maintenance are not negatively impacted but manufacturing and assembly can be made simpler.

Re: Team 1511 Prototype Drivebase CAD
 

I think you would be in good company with using bumpers for structural purposes. I can't find a picture of it, but 1114's 2013 bumpers had some interesting use of aluminum angle which I beleive was for neither weght distribution or aesthetic purposes.