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Al, It can be done. 1 horsepower = 33,00 FT-LBS/Minute. The units in hydraulics are directly convertable to horsepower because it's pressure X volume. If you take the equations and begin multiplying and cancelling terms you get the following: Lbs/Sq In X Gallons/Minute = Lbs/Sq Inches X Gallons (231 Cu inches/Gallon)/Minute = Lb-Inches/minute 12 inch-lbs = 1 foot pound, therefore divide the equation above by 12 to get ft-lbs/min. For a 40 HP unit, you can set the equation at 40HP and work it backwards. It looks as though you'll need around a 70 GPM pump @ 540 RPM. Since most pumps are made to fit 1800 RPM electric motors you'll need one rated at about 225 -250 GPM @ 1800 RPM. If you run the pressure system at 2000 PSI, the pump can be a 35 GPM pump @ 540 PTO RPM. You can stack smaller volume pumps on a common shaft to get the volume and plumb them into a common piping system. Ordinarilly, you should have a reservoir about 4-5 times larger than the GPM = 300 gallons. The piping size should limit the oil flow to about 20 ft/second. The gear pumps will have to be routed through a very large heat exchanger with forced air circulation or circulated water. Unless, you have a lot of this stuff laying around the garage, plan to spend about $20K-$50K new. Alternately, a large generator would work, but you'll need about a 40hp X 746watt= 30 KW generator that is geared for the 540 RPM. To it, you would need a bank of resistors and a tremendous heat-sink. I've gone to some tractor shows in Ohio/Indiana. There's a fellow that shows up there with a generator equipped with a flat belt. He tests the steam engines. Alternately, you can build a prony break. It usually consists of a brake on a shaft with a lever arm. The leverage of the arm is on a scale. Thus the length of the lever arm X the pounds on the scale X RPM = horsepower. Again you'll need to cool the brake, but it's the simplest form to make a dyno. Ken McWilliams
Dayton, OH
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