pic: Pic 2: "caster wheel" crab drive combo

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One of our mentors came up with crab drive using this low cost and easy to make wheel/motor combo. The gearbox pivots on a standard caster-wheel body.

How exactly is it supposed to work on a robot. I understand how the module itself works, but when you put it on the robot ‘as-is,’ wouldn’t it just spin in circles?

Please explain… I’m curious…

I LOVE IT!!! I remember putting a caster over a tough box like that one time, and then not figuring out how to turn it, which is my biggest question…

We’ll try to post more info/pics as it develops. The idea is to link two of these units together with a tie rod as in “ackerman steering”.

Very similar to some ideas that we had for setting up a crab drive or ackermann drive system.

did you try direct driving the wheels rather than using the chain? could save you some weight and be a little cleaner setup - not sure if you would have enough clearance for the caster setup though.

Other than that - I love it.

We’re doing direct drive on our 6wd, which made me think about why they weren’t doing it. I figure that with the direct drive, they’d have to support the end of the shaft to keep from getting any negative cantilever forces on the wheel. Since they aren’t doing a standard crab module, they really don’t have an easy way to support the end of a direct drive shaft.

With the two little side plates going down to support the chain driven wheel, they instantly have a well supported wheel with no cantilevering.

At least, that’s how it seems to me.

-Greg

Yes, I had the same concern with the cantilever affect but I found a way to mount the wheels very close to the toughbox as a direct drive (through some good luck while using Autodesk). with the low friction surface this year and decent weight balancing, I think this will work out fine. But, supporting the wheel on both sides eliminates that concern so it should be more robust with the only real downside being added weight.

my suggestion is that you use wheels that turn under your control, a design like that would have you doing donuts