Ed
Sure nice to have someone with an extensive back ground in hydrualics here on the forum. This way from time to time I can ask some dumb questions and know I will get a an informed answer
Tony
I wish you good luck on that one Tony
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If a 200 pre-rotator rpm is acceptable, then I agree with Vance above. With the blades lifting at 200 rpm, a 22' rotors drag may require about 4.4 hp max. I don't know if this will help anyone but this is how I would figure the required pump and motor for this job, as an example.
Using those noted gerotor Parker pump and motors, I would use the largest 2000 psi motor (.58 cu.in./rev) and set the system relief valve to 2000 psi, to allow the highest continuous torque available.
Using the standard rotorhead gear set; say the P.D. (pitch diameter) is 12" and 1.5", so the motor must rotate at (200 x 12) / 1.5 = 1600 rpm.
The motor torque is (.58 x 2000) / 6.2832 = 184.62 in.lb. and the hp is (184.62 x 1600) / 63025 = 4.69 HP….so this motor should drive the rotor at 200 rpm.
If this gerotor motor efficiency is 90% then it will require a pump oil flow of (1600 x .58 x 1.10) / 231 = 4.42 gpm. The pump efficiency would be the same, so the pump rpm must give a flow of 4.42 x 1.10 = 4.86 gpm or 4.86 x 231 = 1122.66 cu.in.
Using the same motor as a pump, the needed pump rpm would be 1122.66 / .58 = 1935.62 rpm.
The next smaller pump (.45 cu.in./rev) would need 1122.66 / .45 = 2494.80 rpm.
I would choose the .58 cu.in./rev pump with 1 to 1 pulleys from the prop shaft to the pump clutch or belt tightener unit and increase engine rpm from idle up to 2000 rpm. One could use a smaller displacement pump if using a step-up pulley drive, but I don't like them
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This hydraulic circuit may need a dump valve or an accumulator for a soft start. It also should have an oil tank, an oil filter and possibly an oil cooler if the system will run long enough to heat up. And a good grade of anti-wear "hydraulic" oil.