same speed as the rotor and vanes, but there is a very slight 'walking behind' of the vane contact area and there is a very slight speed slippage which results in the inner belt wear being spread out and this results in much longer belt life. Also, the belt set now confines the pressure and speed-squared forces like a pressure vessel and the potential speed of operation is very much higher. The result of all this is to raise both the operating pressure and the operating speed and this amounts to a 10 times increase in hydraulic packaging density and similar decrease in weight per unit power.