[EricH]

Originally Posted by Michael Blake

So, where's the "slippage" provided in this setup?

THANKS!

In the differential gearing. Two of the 4 gears in the inner box are connected to the wheels; the other two are idlers. The relative speed of the wheels doesn't really matter to the idlers; they'll move as fast as they need to.

Hint: Think of this setup as 2 gearboxes. The inner box is the 4 in the middle of the "axle"; the outer is the bevel at the top and the large gear it meshes with.