[Madison]

I'm attaching the terrible picture that doesn't show anything just in case in might show something. I appreciate the advice since I've never done sheet metal design in robotics applications -- but I do have a fair bit of experience with it otherwise.

The crossmembers on each end currently pick up the inner vertical flanges, the outer face and the top surface.

Originally Posted by BJC

This looks pretty cool.

I've designed enough complete sheet metal frames that I'm comfortable critiquing this.

The first thing I usually look for in a frame is torsional stiffness. It's hard to tell without seeing the rest of the frame but I think you'll probably have some torsional stiffness issues if you don't add a flange to the outside bottom of the wheel bay going either in or out. How you cap the ends of that drivepod is paramount. You'll need flanges from the outside crossmembers picking up the outside, top and bottom on each end. The giant flange cut out in the middle for the gearbox is also very detrimental unless you can bridge that gap with the gearbox itself. In general putting even a small bend (think 1/4") in a sheet metal part will make it many times stronger. Even after all that I would still put 2-4 box pieces within the wheel bay between the wheels riveted in through the top and sides. That would stiffen this right up.

Some of this relies on your team resources.

-Are you having your parts bent for you or are you going to have to bend them yourself? It would be pretty tricky to bend this part in a bend break, my team hand forms all of our parts and would probably not be able bend this part with the precision needed. You also probably don’t want to try to control the width of your gearboxes and hole alignment with a flange if it’s not bent by a machine.

Everything will be laser cut and bent on a CNC break.

-How thick of metal is this going to be made out of? If you do the above you should be able to use .060” or .050”.

Planning on .060" for as much as possible.

-Another consideration would be chamfering the corners by the wheels. Otherwise as the metal thicknesses stack up there it becomes easier to get stuck on field elements. On a field with terrain this also allows the wheel to contact the slope you’re trying to go up rather than the frame.

Chamfering the leading and trailing edges would make the belly pan part a bit trickier, but is completely achievable. Depends on what sort of field we get.

-It looks like you haven’t decided how to attach the outside axles. If you have the resources to tap .5” aluminum rod I would suggest doing that and bolting into it from both sides. This then acts as another piece of structure and helps pull the frame into alignment rather than being a liability like a like axle there probably would.

We've done this in the past but usually favor using bolts for axles. We might be able to swing making parts on the lathe since we won't have to worry about as much manufacturing as we have in the past.

-You can change all of your 1” flanges to .75” and save a bit of unneeded material and weight.

True story.

-How much is your wheel dropped and are you making it adjustable?

That has 3/16" drop right now; it's dumb and will get changed to 1/8". It isn't adjustable. I'll attach another picture that shows a rough idea for chain tensioners.

Two independent side rails is a good idea that many teams use (including us.) Holding the outside onto the inside with only standoffs sounds like a really bad idea though. I made a drivetrain that is kind of similar to what you’ve got going on about a year ago. If you have any interest I can send you the CAD model.

One of my students had a sheet metal drive done over the summer -- http://www.chiefdelphi.com/media/photos/38121 -- and it's more typical in its design. I'd like to reduce the part count if possible to make life a bit easier for everyone.