More pics can be found here
http://imgur.com/a/1hAlx#0
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Design inspired by 971/488/3847’s 3-piece chassis
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Made using 0.09" thick 5052 aluminum sheet. Based on how well it survived this year’s defense, we definitely could have gotten away with thinner/less material but this was our first sheet metal chassis so we went conservative.
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Designed for 4-CIM mecanum using a direct gear drive similar to JVN’s “Drive in a Day”, with mounting options for a 6-CIM, 6WD as a fallback since this was our first competition mecanum in FRC (we’d done it in VEX before).
EDIT - These are just the sheet metal components as we received them from our awesome sponsor. Here’s a video of it all together and running - https://www.youtube.com/watch?v=Ch7kZrWMYQo (warning - loud).
Nice work! I think this is the closest that I have seen someone come to reproducing our frame correctly. The flanges on the outer edge of the side rails add a lot of strength.
Thanks! I really liked the idea of a 3-piece chassis because of how easy it made assembly. We could have people assembling the motors/gears/wheels on each module independently then they just had to slide it into the belly pan and rivet it in place when they were finished. Having the wheel wells as a single unit rather than 2 panels was also really helpful in terms of strength - using a 1 piece bumper this frame made it through 2 regionals without deforming (at least not that I can tell)
You said we came close to your frame - is it just something we did differently or did you have something in mind that could be improved that I could pass along to my team for next year? (There’s always room for improvement, I’m sure)
Cool to see another va team with a sheetmetal drive. I am curious though, how difficult is maintenance with only being able to access the wheels from the bottom of the drive?
Only maintenance we ever had to do at competition was shoot some grease up into the gears (we drove the wheels using a single stage of reduction with the pinion driving a gear bolted to the wheel), and our robot sits about chest height on our cart with the wheels hanging off the side so they’re not too difficult to access. If we ever needed to replace a wheel or anything though, once the shaft is pulled out, the wheel can just fall out of the bottom. I won’t be on this team next year (heading off to college) but I will certainly keep playing with this design - and shortening the height of the modules so the wheels stick out the top a bit (less material, less weight) is one thing I would change. That would also allow a secondary method to access the wheels.
Since you asked. 
We have had our front and back frame rails bend under hard impacts. If you bend another small flange off of the top flange out there, that will add a bit of strength. We also put a couple ribs in the tubes to give us a nice solid contact point for superstructure mounting and to add some stiffness. Sounds like you didn’t need them if things held up well this year, which is great.
Some of the finer touches are to design in the PEM nuts into the belly pan for mounting electronics, the PD board, and to design in the battery box. Those take a while, but the end result is magical.
