[Tom Saxton]

mNm is milli-Newton-meters, that is thousandths of a Newton-meter, 1000 mNm = 1 Nm. A Newton-meter is about 0.7365 foot-lbs.

Force and radius are inversely related at a given level of torque. One foot-lb of torque with give you a one pound force at the rim of a wheel with a one foot radius, or two pounds at the rim of a wheel with a six inch radius.

Torque and speed (RPM) are inversely related. Gear boxes generally gear things down to a lower speed and higher torque. So, the globe motors with the gear boxes have a slower speed (RPM) and higher torque than the motor without the gearbox.

There are also inefficiencies, frictional losses, in gear boxes. So if you cut the speed in half, you'll get a little less than twice the torque. The losses depend on the type of gearing, but generaly get worse with each stage of gearing.

Electricity is a pretty broad subject. Is there a physics teacher you can ask? If you have a specific question, post it here and someone will help.