...resistance to flow develops pressure.

Yes Fernando, what you said is very correct. Today being Saturday, let me take off totally Off-Topic !

Since you seem to be comfortable on the hydraulic funda, read my earlier post giving the cycle details with the following defenitions :

1. The motor that I was referring to is an electric motor and this was driving an hydraulic pump. The pump is the one used in automotive power steering circuits. These have a speed - flow characteristic that is linear upto 0-1000 rpm and thereafter kind of "flatten out" or enter the regulated zone upto 6000 rpm. The test rig is to test this performance against varying loads - so both rpm and outlet pressure (load) are programmed variables. Two US auto majors when they entered the Indian market also brought in the temperature as another variable - these pumps are tested at 120 to 135 deg c endurance cycles. Normally they clock 2 to 3 million cycles like this easily - so the next time you are negotiating that U-Turn on a hill, with your family in the car, on a hot Indian afternoon ( 40 deg C ) - rest assured the steering pump can handle it.

2. When I said "the pressure also cycles in its own loop " what I meant was the maximum set value of pressure. This is done by switching in relief valves (connected to the test pump delivery line ) that are set and locked for different values. We normally use this "pressure cycling " terminology often. The correct way to say that will be " cycling of the resistance parameter in the flow line " . Now thats a mouthful and more ;-)

Have a nive weekend.

Raghu