Mrs B has been making Lego models with a kit lent to us by one of our friends. Here is on of the models that she has made.
We got the motor going and it does go forwards nicely. The motor drives two flexible rods that each drive a wheel. So the motor delivers torque to the wheels. Torque is a concept that seems quite slippery. Books and exam papers use the words moment and torque interchangeably quite often. I thought I'd boiled it down to the idea that torque is what produces pure turning but that you couldn't really use torque for something that causes a cartwheeling motion. I got this from usage of the words on exam papers. But perusal of Wikipedia. suggests something different, although acknowledging the semantic difficulty associated with the two words.
When a torque acts on something, it makes the mass the move accelerate, so we would say that there is a rate of change of angular momentum, angular because it is turning in a circle. If there is no change in angular momentum, then there is no torque. So a turning force that acts but cause no motion can't be called a torque. A torque is a motive force.
Below are photographs of how the torque is delivered from the motor to the wheels.
The kit came from Oxfam in Wigton originally. A great place to shop!
