Wow, thats a ton of CIM motors. I really like the layout of the side modules and the gearbox in the frame.
A few comments/questions:
How do you plan on retaining the bearings and locating the module axially?
The shaft that drives the module is going to be really difficult to do the way you have it. I'm assuming there's 3 bearings supporting it, two on the inner frame part, and one on the outside. If you had only two, I'd worry about the shaft bending. It'll be tough to get those three holes aligned with each other, especially if you're welding it. If one of those holes is in the wrong spot, you'll "overlocate" the shaft and it'll bind up. You do have the advantage of using hex bearings, which usually have a pretty sloppy fit.
If your frame bends at all, your center wheel won't touch the ground. The slots that have been cut out to let the chain by are weakening your center module. These wheels are usually articulated so that you have enough force on the wheel so that it won't slip. You also want to avoid the opposite, where the robot rocks side to side and one half of the drivetrain is off the ground.
Quote:
Originally Posted by Orion.DeYoe
This is impressive. I really like it. I'm assuming you want suggestions so here are a few:
1) I would change the framing to 2 x 1 x 1/16 tubing (someone pointed out to me that this is lighter as well as stronger than pocketed 1/8th material).
4) I would take your high gear speed down to 16 fps. Just my preference after running a 20 fps drivetrain this past year. We made the change to 16 fps and really liked it. That was with 4 cims though so you could save weight by taking 2 out or leave the ratio the same and using 6.
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2 x 1 with .063" wall box tubing is a pain to find and is weaker than I'd be comfortable with for a frame. We used .125" thick on our robot, in roughly the same configuration as show above but with a bellypan and we still managed to get bent.
If you want to save weight, you could get .100" thick tubing from vex pro. If you're really desperate, you could probably put some lightening holes in the sides.
You said you had the ability to adjust the drive ratio with the sprockets on the wheels. I'd wait until you know what distance you want the robot to travel quickly, then gear to get the best acceleration for that distance. That being said, 20 fps is on the fast side. If you do go to four CIMs, I'd take gear to go slower, but that's my opinion.