Algodoo

WARNING : contains hundreds of circles. I guess a weak PC won't like it!!
If you can't get it running smoothly, i apologize. Simulating fluids is always a problem...

Simulates the functions of a torque converter similar to the ones used in automatic transmissions (not 100% accurate due to 2D and some simplifications).
I could not really figure out, whether this simulated thing really increases the torque (3000nm going in, moving 4000nm, but is this because of the real effect?). The principles are well to see , i think.
I don't want to describe a torque converter in this small window, if you like to, look at wikipedia.