Ed
Since this thread started I've been reviewing my engine, motor, and hydraulic theory. I'm planning for a fire protection water pump connected to a cistern. Hydraulic theory is the same for water or oil. A small gasoline engine will put out up to its rated horsepower. It has very little torque rise. If a gasoline engine is loaded beyond its rated horsepower it will bog down and stall. If an electric motor is overloaded it will continue to put out an increasing amount of horsepower until it reaches its locked rotor torque. This is how Sears can claim its compressors can "develope" 6.5 HP. However, overloading an electric motor for a length of time angers the god of electric motors and he manifests himself in the form of smoke. A continuous duty 5HP motor with a service factor of 1.0 will produce a constant 5HP without overheating. A 5HP motor with a service factor of 1.15 will produce a continuous 5.75 HP without overheating. I located a single phase 5HP 3450 RPM C face motor with a service factor of 1.15. With the barnes 11 GPM two stage pump I can run it up to 2750 PSI without going into the "red". If used with a 3000 PSI 4x24 cylinder with a 2" rod it will yield the following: at 2750 PSI it will yield 34,500 pounds of force. At high flow the cylinder will take 7.4 seconds to cycle forward and 6 seconds to return. At high pressure the cylinder will take 27 seconds to cycle forward. Assuming that the return stroke will always be at high volume the full cycle will take anywhere from 13.4 seconds to 33 seconds, depending on what point the pump kicks in to high pressure. The pumps are factory set at 650 PSI to kick into the high pressure mode. On a 4 inch cylinder 650 PSI yields 8,164 pounds of force.
I noticed that Barnes has a pump, motor, and tank combo that uses the 16 GPM pump with a 5 HP motor. When I checked the specs I found that the motor was a 3 phase very high service factor motor and the pump was set to kick into high pressure mode at 450 PSI. The pumps are adjustable to kick into high pressure mode at from 400 to 800 PSI. 16 GPM at 450 PSI equated to 5 HP. I think you could use a 16 GPM with a 5 HP single phase motor if you set the cross over point at 450 PSI. At 2000 PSI you would be crossing over into the "red'. 2000 PSI in a 4.5 inch cylinder yields 31,800 pounds of force. 450 PSI in a 4.5 inch cylinder yields 7155 pounds of force. In another thread another poster stated that he put a pressure gauge on his 4 inch cylinder wood splitter and didn't more than a 1200 PSI reading. Someone else stated that they didn't get more than a 1500 PSI reading on their 5 inch cylinder. I think the dynamics of wood splitting a such that the pump is well within its limits 99.9% of the time. Occasionally a tough piece of wood is encountered. I think a 16 GPM pump with the cross over point set to 450 PSI would work with a 5 HP motor. The motor would not go into the "red" unless you were pumping at over 2000 PSI. I think a good quality motor would not be "phased" ( pun ) by an occasional 'blip" into the "red". Because these pumps are positive displacement, the valves used for wood splitters are open center. The ones sold by Northern for wood splitters are factory set at 2250 PSI relief. They are adjustable up to2750 PSI. They are spring centered so that you have to physically hold them on the splitting stroke. They automatically return to center when you let them go. If you stand there holding the valve while the pump is overloading for a length of time, you may anger the god of electric motors. You can set the pressure up high and use the valve to control overloading manually. If you are going to lend the splitter to someone that you have no faith in you can always turn the relief pressure down to 2000 PSI.
I compiled the following figures for a 4.5 x 30 x2 cylinder using both an 11 GPM pump and a 16 GPM pump. 11 GPM: high volume out stroke 11.7 seconds, return stoke 9.4 seconds, high pressure stroke 42.8 seconds. 16GPM: high volume out stroke 8.0 seconds, return stroke 6.5 seconds, high pressure stroke 32.2 seconds. 11 GPM pump: between 21.1 seconds and 52.3 seconds for a full cycle. 16 GPM pump: between 14.5 seconds and 38.7 seconds for a full cycle.
Incidentally, it appears that Grainger no longer carries the C face adapters for hydraulic pumps. Vescor has a full line of adapters.
Sorry for the long post. I had all these numbers rattling around in my head and had to let them out.
RonL
