Hello to all. I have a Quincy compressor with a 310 pump. I need to swap out my motor and I have a used 2hp Baldor, that was totally rebuilt. Problem is, the rpm of this new to me motor is 3450, not 1725. So I need to change pulley size. As it sits now, the pump pulley is 14 inch and the motor pulley is 5 9/16". If possible, I would rather change motor pulley, for the ease of new motor is sitting on work bench. Quincy told me that the 310 pump max. rpm is 920. Anyone able to figure out the equations and tell me the correct pulley size? Any help would be greatly appreciated. Thanks
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Quincy comp motor-pulley ??
- Thread starter Bear108
- Start date
21" will get you to just under 920 rpm at the pump.
Looks like the current set-up is only running at 685 pump rpm. To stay at 685 rpm just double the pulley size to 28".
If you go up to 920 you might get increased output. You'll certainly get extra heat. The factory likely set it at 685 rpm for a reason.
Looks like the current set-up is only running at 685 pump rpm. To stay at 685 rpm just double the pulley size to 28".
If you go up to 920 you might get increased output. You'll certainly get extra heat. The factory likely set it at 685 rpm for a reason.
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To keep the same pump rpm, if you double the motor speed, then decrease to motor pulley by half. 2.75 is close enough. If you want to change the pump rpm, you'd have to pull out the calculator and figure out the rpm that you want to achieve. Change the motor pulley size since it will be cheaper. You likely have a quick detachable bore that mounts to a smooth but tapered pulley bore. That will save you oles of money. I'm not sure that a 21" sheave would fit in the pulley/belt cage.
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I got this compressor pretty cheap and it takes well over ten minutes to fill up to 125psi. I would rather push it a bit harder. I agree, a 21" pulley will probably not fit inside the caged area. I not sure the cost is worth it, but what if I changed the pump pulley, as well as the motor pulley?? Any recommendations of both size pulleys and still keeping pump under 920 rpm??
Well, a 3" pulley on the motor would get you 739 at the pump.
3.5" would be 863 rpm.
You should be able to source a 3/3.5" pulley and new belt for just a few bux.
BTW, Bear, this is a simple ratio:
1725 * 5.5625 = 685 * 14
3450 * 3 = 739 * 14
3450 * 3.5 = 863 * 14
3.5" would be 863 rpm.
You should be able to source a 3/3.5" pulley and new belt for just a few bux.
BTW, Bear, this is a simple ratio:
1725 * 5.5625 = 685 * 14
3450 * 3 = 739 * 14
3450 * 3.5 = 863 * 14
I have a 310 also. Pump pulley is 14". The motor is a 5HP, 184 frame, 3510RPM (thats what the tag says), and a 3.5" od pulley. I checked the pump RPM with a hand held tach and it runs about 870 RPM. Hope this helps. Steve
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tkonbass
Well-known member
Here's a handy tool for calculating pulley sizes. I entered your parameters and it came up with a 3.65 motor pully to hit 900 rpm at the pump.
http://www.temecularodrun.com/ref/rpm_calc.asp
http://www.temecularodrun.com/ref/rpm_calc.asp
kams1973
ALLIANCE MEMBER
3.73" motor pulley to acheive 920 pump rpm.
stonesfan68
Well-known member
What horsepower does the compressor require at 920 RPM? If you turn a reciprocating compressor faster then it makes more air but it requires more power to do so. You need to size the motor pulley to turn the compressor at an RPM that requires 2HP or less.
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Thank you to all!!! I would like to say this one more time, just so I have it all correct. On the pump side, I will keep the 14" pulley. The motor I am putting on is a 2hp and spins at 3450 rpm. As long as the motor pulley is i between 3"-3.5", I should be good? Yes???
http://www.garagejournal.com/forum/showthread.php?t=154286&highlight=quincy
Read my response in the above post.
lg
no neat sig line
Read my response in the above post.
lg
no neat sig line
You will be good with anything between 2.75 and 3.75". Your 2 hp motor seems small since the other poster has a 5 hp assuming it was factory installed. I would call Quincy to discuss the finer details of a potentially undersized motor.
Called Quincy. They said that with the 310 pump, the motor is to be a 1 1/2-3 hp.
Now check again and see what the pump speed should be with a 2 hp motor. Your 2hp motor is not going to drive the pump at 900rpm. You will overcurrent the motor trying unless you reduce the cutout pressure a lot.
Once you get the recommended speed for the pump at 2 hp. Take that speed and divide it into the motor speed. That will give you the pulley reduction you need. Take the pulley reduction number and divide it into 14 and you will have the motor pulley size.
motor speed (3450)/pump speed=ratio x
pump pulley size (14")/ratio x = motor size pulley.
lg
no neat sig line
Quincy should have a nomograph for you which compares pump input power to pump speed at a given cut out pressure. Then you can calculate the appropriate drive pulley datum diameter.
The second option would be to ballpark the drive pully size and buy an adjustable pulley. Then, using a clamp-on ammeter, adjust the drive pulley size until the motor draws FLA at cutout pressure.
(Pump input power increases with pump output pressure as pump speed remains constant.)
The second option would be to ballpark the drive pully size and buy an adjustable pulley. Then, using a clamp-on ammeter, adjust the drive pulley size until the motor draws FLA at cutout pressure.
(Pump input power increases with pump output pressure as pump speed remains constant.)
Quincy should have a nomograph for you which compares pump input power to pump speed at a given cut out pressure. Then you can calculate the appropriate drive pulley datum diameter.
The second option would be to ballpark the drive pully size and buy an adjustable pulley. Then, using a clamp-on ammeter, adjust the drive pulley size until the motor draws FLA at cutout pressure.
(Pump input power increases with pump output pressure as pump speed remains constant.)
I concur. Have you ever seen such a nomograph though? The link I posted in bears other post gives min and max so you can kinda interpret what to use.
lg
no neat sig line