Using two CIMs in the Banebots Transmission

[Joe Johnson]

Originally Posted by Justin M.

Hmmm...after some thought I think I just might get two more gearboxes, with a total of 4. The robot design would be for 4WD, so now that I think it would make more sense to have each wheel be powered by it's own independent gearbox/chain geardown. It'll wind up costing us almost double, but worth it. Double the strength and reliability, with the same current requirements as a doubled gearbox.

Back to Autodesk....

This is an age old design choice. In general, I come down on the chain between the wheels camp rather than independently driving each wheel. It boils down to this: When you are pushing against another robot, your front wheels tend to lift and your back wheels tend to get more weight on them. This means that your front wheels are likely slipping and your back wheels are doing most of the pushing. In the independently driven wheels case, only your back motors are doing any useful pushing. This is not why you wanted 4 motor drive! So... whether you buy 2 planetary gearboxes or buy the adaptor to drive 1 planetary gearbox with 2 CIMs, I highly recommend that you consider having chain link all your wheels (and by the way the right number of drive wheels is 6 -- FYI).

Joe J.

P.S. It is my considered opinion that the Banebot 56mm gearbox is sufficiently over designed for 1 CIM motor that it can easily accept the load of 2 CIMs. In fact, I think it be converted to accept 2 CIMs AND a Fisher Price in case you are in the Team 25 Camp (a.k.a. The 3-Motors-Per-Side-Minimum Camp)

[Justin M.]

Originally Posted by Joe Johnson

This is an age old design choice. In general, I come down on the chain between the wheels camp rather than independently driving each wheel. It boils down to this: When you are pushing against another robot, your front wheels tend to lift and your back wheels tend to get more weight on them. This means that your front wheels are likely slipping and your back wheels are doing most of the pushing. In the independently driven wheels case, only your back motors are doing any useful pushing. This is not why you wanted 4 motor drive! So... whether you buy 2 planetary gearboxes or buy the adaptor to drive 1 planetary gearbox with 2 CIMs, I highly recommend that you consider having chain link all your wheels (and by the way the right number of drive wheels is 6 -- FYI).

Joe J.

P.S. It is my considered opinion that the Banebot 56mm gearbox is sufficiently over designed for 1 CIM motor that it can easily accept the load of 2 CIMs. In fact, I think it be converted to accept 2 CIMs AND a Fisher Price in case you are in the Team 25 Camp (a.k.a. The 3-Motors-Per-Side-Minimum Camp)

Thanks for the tip. I was considering doing that to distrubute pushing power among all the wheels. Just run a chain from the output shaft to the wheels, then attach an additional sprocket to the opposite side of the wheel, and run a chain connecting the two wheels together with the same size sprockets.

[Billfred]

Originally Posted by Justin M.

Can you attach two sprockets to the AndyMark wheels in the kit?

I haven't tried it with these exact wheels, but last year 1293 ran two sprockets off of an IFI wheel in their 6WD setup. You've got to put a little space between the two sprockets through your choice of method (either bolt them on both sides or put a spacer on the bolt holding them on), but it's entirely possible.

[Justin M.]

Originally Posted by Billfred

I haven't tried it with these exact wheels, but last year 1293 ran two sprockets off of an IFI wheel in their 6WD setup. You've got to put a little space between the two sprockets through your choice of method (either bolt them on both sides or put a spacer on the bolt holding them on), but it's entirely possible.

I answered my own question shortly after typing it...

The AndyMark wheels have holes in a circular face pattern for a sprocket. You have to tap the threads into the hub yourself, which makes it 100% possible, you just need to use >.5" long bolts on each side for a tight fitting of the sprockets.