Good job! Is it your first scene? Can't believe that.
Few suggestions:
Make longer track
Separate bumpers and put it on stretchable hinges (so if it hit the ground it will looks more realistic)
Scale it down to 1:1
That bouncing balls is collision engine (means there is no motors, works as semi-realistic engine, it can stuck, etc.). The rest of magic in this scene is yellow hinge and gray circle - scripts in it reports torque and angular velocity. Yes it can be used in any scene where you need to measure torque. Scales, power meters, anything...
It will never give same 3min result on another PC because scene is to laggy (only 16% realtime on mine) and time balls falls depend on PC's processor power.