Algodoo

That's because you have to define the variable (scene.my.rpm) first
Before you will use any of the variables, drop the console and write the name of the variable and the value you want it to have at the beginning (or just 0.0)
So you would write this:
Scene.my.RPM = 0.0
Be aware that writing 0.0 or 0 is NOT the same thing. If you write 0, then if you want to divide the variable, it won't work, so write 0.0! (or 1.0, 500.0 or whatever)

ok thank you so much!!!!