Questions about an Idea for a drivetrain.

[John Neun]

We have used a similar arrangement with good success. Some things we have learned:

I concur regarding drive sprocket chain wrap. Try to approach at 180 degrees. You won't get that much, but shoot for wrap as a single pair. If you use a single chain for both middle and front wheels, you need an idler as suggested to increase drive wrap.

All 035, all the time. Even if you use a single CIM to drive (we use pairs), the 025 will be a thorn in your side. We learned that the hard way two years ago. It's well worth the weight. A robot that can't move isn't a robot. It's just furniture.

We opted to use a "live" center shaft to drive the center wheel last year, and slaved the front and back wheels to the center wheel. This made for a third chain and more complex machinery, but it let us put the transmissions where we wanted them. I think two chains with an idler wrap is a more efficient approach, much as you've drawn. A live shaft is also more complex to build and assemble.

It would be wise to keep the wheel sprocket size a little large, say 30 or 32 teeth. This tends to de-emphasize runout issues in the sprockets.

Good luck!