Hi 3-d Joy - Its that physics stuff - I think "torque" falls under "for every action there is an equal and opposite reaction" Assuming the same rpm, and taking the same shape of the props for comparison, the value of the equal and opposite reaction is reliant on the wieght of the prop. One of the equal and opposite reactions to a propeller spinning is torque. These are just my findings from trial and error and may not be correct - I know theres much more knowledgable people who can explain the physics behind it.