Quote:
Originally Posted by Kevin Sevcik
That's a friction dependent limit, though. If your wheels aren't slipping, then you're getting 100% of the gearbox's output torque applied to forward motion. Thus, your "efficiency"/pushing force calculation above is bunk. The drivetrain's forward pushing ability is limited to EITHER 80% of the theoretical output torque of the gearbox or 70.7% of the available friction force, as calculated from mu and the normal force. The two limits are unrelated, so multiplying those two numbers together is meaningless.
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I will retract that expression—you're right, that's not valid for the case where the wheels are not slipping, which is most of driving around.
I was mistakenly conflating it with the limiting torque for mecanum wheel slip in forward motion, at which point you've got all of the
available torque at the wheel spinning it, but not all of the frictional force in the longitudinal direction that you'd expect with a conventional wheel. (This is relevant when you're figuring out if your motors will stall before your wheels slip.) And even in that case, as Ether and Kevin noted, it's better expressed as a mechanical efficiency and a geometry constraint. They end up multiplied (or more accurately,
divided) in the equation, but they're not part of the same quantities.