If a cart with a caster wheel is reversed (fairly slowly) so that the caster wheel has to swivel through 180 degrees, is the force transmitted to the cart from the wheel simply the rolling friction of the caster wheel? (I'm assuming that this happens slowly enough that the torque required to accelerate and decelerate the inertia of the caster wheel assembly is not significant)
You'll also pick up any torque due to friction in the caster bearing as the wheel swivels. On most casters the contact point isn't in line with the caster rotation axis, so unless the wheel skids the cart also will do a small joggle as the wheel swivels, which will impose some inertial loads. Finally, as the wheel swivels it also does some local skidding on the surface, which puts a torque and force into the shaft.
Tom.
Thanks for the input, those still seem like fairly small forces. I had read a paper by Dan Ding, Roy Cooper etc on the "Analysis of Driving Backward in an Electric-Powered Wheelchair" where he showed some measured lateral forces on caster wheels during reversal with forces as high as 40 to 50 Newtons which seemed much greater than the caster rolling friction was likely to be. Andrew
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