Pulley Question from a Farmer
Pulley Question from a Farmer
(OP)
Hello,
Is it possible to move a 50HP motor requiring 3600RPM with a 1HP 1800RPM motor?
I'm not an engineer but I have a big irrigating water pump that requires 50HP 3600RPM to move and I've heard of people doing it with only a 12 VDC 1HP motor by using pulleys.
Does this sound possible? If so, can someone tell me how or where I could find how to do it?
I already have the pump which I move with a gas powered 45HP engine but would love the idea of doing it with a 12 VDC 1hp motor.
Thanks,
Andrew
Is it possible to move a 50HP motor requiring 3600RPM with a 1HP 1800RPM motor?
I'm not an engineer but I have a big irrigating water pump that requires 50HP 3600RPM to move and I've heard of people doing it with only a 12 VDC 1HP motor by using pulleys.
Does this sound possible? If so, can someone tell me how or where I could find how to do it?
I already have the pump which I move with a gas powered 45HP engine but would love the idea of doing it with a 12 VDC 1hp motor.
Thanks,
Andrew





RE: Pulley Question from a Farmer
RE: Pulley Question from a Farmer
I don't have any electricity but have plenty of 12DC batteries.
Thanks,
Andrew
RE: Pulley Question from a Farmer
73 ft-lbs of torque to turn it at that speed. A 1 HP motor could be connected to a pulley system to deliver that much torque at a lower speed, but it will never be able to deliver 73 ft-lbs at 3600 RPM. So you can probably use the 1 HP motor with pulleys to run the pump at a lower speed. Just figure out what speed the 1HP motor runs at, calculate the torque at that speed, then create two pulleys with a ratio that will increase the torque to what you need to turn the pump - which will be something less than 73 ft-lbs at a speed lower than 3600 RPM.
Power = torque * speed
1 HP = 550 ft-lbs / second
3600 RPM = 377 1/sec
50 HP = (50 * 550)ft-lbs/sec = 27500 ft-lbs/sec
torque = (27500/377)ft-lbs = 73 ft-lbs
For the 1 H
RE: Pulley Question from a Farmer
If I increase the RPM on the 1HP could I turn the pump? I kinda get the formula but not sure how to figure it out.
Thanks,
Andrew
RE: Pulley Question from a Farmer
But...the fact that the output torque of the 50 HP motor produced 73 ft-lbs of torque at 3600 RPM means this drive was designed to deliver so mant gallons of water per hour at a certain pressure. By turning the pump with the small motor at the greatly reduced speed would reduce your flow rate to trickle if it move the water at all depending on how far the delivery is.
RE: Pulley Question from a Farmer
To get your torque up you'd have to slow the pump speed even more and you would probably end up with almost no flow by the time you got something to work.
Find out more about the other applications - I think there is a big difference between yours and anyone's who is using a 1 hp motor (maybe they have a much smaller pump).
RE: Pulley Question from a Farmer
RE: Pulley Question from a Farmer
Can you turn it with a bar or anything?
RE: Pulley Question from a Farmer
The original pump ratings may be for maximum combined pressure and flow. If the pump has a much easier job to do than that, then much less power may be required to get the actual pump performance you require.
See if you can get some pump curves from the original manufacturer. That will show how much Rpm and drive power is required for different combinations of flow and pressure head.
Hook it all up and see how it goes. There will be a rating plate on the motor that tells you how much current the motor will draw at full rated horsepower.
Measure the current and see how that compares to the motor rating. That will tell you how heavily loaded the motor is. If it is overloaded (too high a running current) slow down the pump. If running current is very low, speed up the pump a bit to get the motor working harder.
A small speed increase will give a fairly large change in motor current. It may be roughly cube law. So 20% more pump Rpm may be roughly (1.2 x 1.2 x 1.2 = 1.73) 73% more motor current.
As you can see motor power varies a lot with only small changes in Rpm. It may be quite possible that a 50Hp pump can run at only 1Hp and still work quite usefully.
If you cannot find any pump curves to initially get you started, jut try it and see what happens at a fairly slow pump speed. As long as you check actual motor current, there is no harm in trying.
All motors draw very high current when first starting up, it is the current draw once it has reached final steady speed that is important.
RE: Pulley Question from a Farmer
1000/3600 = 0.277
0.277 x 0.277 x 0.277 x 50Hp = 1.06 Hp
Then experiment from there.
RE: Pulley Question from a Farmer
are you useing a single impeller pump or a multie stage centrifical?
answer some of these and them some of the calculation will tell you that 1hp probibly will not work, it may take 5 hp just to turn the pump
SBI
Central Ne.,USA