what does it mean?
 

Hi guys if a motor has a torque rating of 45oz/in , rated at 12v and has a maximum rpm of 4800. Then How do I figure out if it will have enough power to move a 20LB Tank?
Just looking at motors for my tank build and I am lost with the torque aspect. Thanks Anthony
Oh and I want to use the motors to drive the sprockets right from the shaft no gearboxes.

RE: what does it mean?
 

;);)Hi AH64,

The torque rating you have is the maximum rotational force or turning moment that the motor can supply at the shaft at the 12v supply and a rotational shaft speed of 4800 RPM at this voltage........to determine if this motor will move your tank or not, you would could do the following:

a) Build a mechanical engineering mathematical model that reflects your tank design, and from
the results, modify your design accordingly.
b) Put it in the tank and try it.

With electric motors, one can roughly assume that Voltage = speed and current = Torgue
With our tanks, speed is not that critical but torque is, so we want high torque with minium current
drain to preserve our motor & electronics life and give us long duration from low battery drain.
This is why we use gearboxes, since they provide an increase in output torque at reduced current drain but at lower RPM's. Power is NOT increased (A common mis-understanding). It is unlikely that a motor on direct drive will provide enough torque to drive your tank, and even if it did, the current draw could be unacceptably high..........

This is quite a complex area and I have only touched on it briefly as an explanation but I hope it helps

Cheers

CaptainB

RE: what does it mean?
 

It's a classic physics problem with many variables, perhaps too many to model mathematically for an easy answer.

I would suggest having the assembled tanks on the work bench or better yet the terrain type (like dirt) it will be run on and attach a torque wrench to the sprocket an measure the static force and the force needed to get it moving (one track only to simulate power for turns). The moving force will be less than the static force.

A torque test on maximum incline (vertical lifting 20lbs.) would also be advisable to determine the max motor stall current it may experience.