[Ether]

Originally Posted by Nate Bloom

What's the math for a traction limited drive?

If:

- the wheels are all the same type and diameter and are chained (or belted) together on each side, and

- you are powering each side with a single gearbox with N CIMs, and

- you assume that traction force = normal force * coefficient of static friction (where coefficient is a constant), and

- the center of mass lies along the vehicle longitudinal axis,

then:

A = [(4*D/G*Istall*mu*W)/(eff*Tstall)]/N

where:

A = amps per CIM required to break traction and spin the wheels

W = weight (lbs) of vehicle

mu = coefficient of static friction

D = diameter of wheel in inches

G = the total speed reduction gear ratio from motor to wheel (including sprockets/pulleys)

eff = drivetrain torque efficiency fraction

Tstall = CIM spec stall torque (oz_in)

Istall = CIM spec stall amps