Compressor, will I see the difference with this new motor?

[JonathanLaporte]

Going from a old 1950 brunner motor
3/4 hp 1725 rpm. 8.8amp 115v/230v
TO
3/4 hp 1725 rpm 10.8amp 115v/230v LEESON motor.

Will I see the difference in the power and fill up time?

 

[Tronyadorable]

No. You're spinning the pump at the same rpm.Might have less vibration ? That's about it. I would have just had the old one redone.

 

[angrystroker]

Agreed, need a pump change not a motor.

 

[Miss_Sissy]

You would probably need to change the pump and the motor to get a significant increase in air volume and decrease in cylinder fill time.

If you spin an existing pump significantly faster than it was designed to spin, you are likely to overheat it. Compressing air makes heat and if you you double the numper of compression strokes per minute, you double the heat. It's probably not going to have enough cooling to survive for long.

If the heat doesn't damage it, it's likely to beat itself to death as the piston and rod speed exceed the pump design limits. Basically, it's got a red line just like a car engine does.

If you put a higher volume pump so that each revolution of the crankshaft moves more air, you need more power to spin it, meaning a more powerful electric motor to drive it.

 

[Davefr]

No, you don't necessarily need to change pumps.

Most pumps are designed to operate within a range of RPM's. If you have some range left in the pump's speed, you might be able to increase the speed by changing pulleys and belts to run the pump faster with the higher power motor. (faster = higher CFM).

However if this is an old pump, you might not be able to find the operating specs so you'd be shooting in the dark.

The practical answer is that you're probably wasting your time for only a 2 amp motor difference.

 

[finn]

The only thing different is that the new motor is less efficient, by about 20%.

 

[JonathanLaporte]

Ok I forgot to had, the old 1950 brunner engine broke... the stator is starting to shows some broken fins...

Little bit like that:

http://globuselectric.com/images/mtrfail_str07-f.jpg

So I don't know how to rebuild it. I found a good recent motor for 20$ and bought is... might reset the other one to get fixed...

one thing for sure the old brunner 1950 weight about 150pounds and the newer one about 100-75 pounds...

 

[JonathanLaporte]

The only thing different is that the new motor is less efficient, by about 20%.

Well I think the old motor was a more or so 3/4 and the the 10.8 is a real one.

 

[Miss_Sissy]

No, you don't necessarily need to change pumps.

Most pumps are designed to operate within a range of RPM's.

No, most splash-lubricated, single-stage compressor pumps are designed to each operate at a recommended RPM. For example:

Grainger's SpeedAire Line of Single Stage Compressor Pumps

You will see that each has a single RPM specified.

Run the pump too slow, and you get lubrication problems (dipping slowly does not make much of a splash). Run it too fast, and you have heat and/or structural problems. Obviously the manufacturers allow for for some safety margin, but a safety margin is not the same as a safe operating range.

If you don't know the maximum safe speed for a pump, then it is the speed that it is runs the stock configuration until/unless the manufacturer publishes a different spec or grants you a waiver to run it faster. I recently retired from an engineering position at an aerospace company, so I'm not a "spin-it-faster-and-see-what-happens" sort of guy.

Most compressor manufacturers run the pump at, or very near, the recommended RPM to be competitive in the marketplace. You don't see a manufacturer paying for a 5 HP 700 RPM pump and then running it with a 3 HP motor driving it to 420 RPM (3 HP/5 HP * 700 RPM = 420 RPM).

However if this is an old pump, you might not be able to find the operating specs so you'd be shooting in the dark.

And just because it doesn't immediately self-destruct doesn't mean that you're operating within the range or that it's going to last long.

Ultimately, you gave good advice -- don't waste your time for 2 amps.

 

[zkling]

No, most splash-lubricated, single-stage compressor pumps are designed to each operate at a recommended RPM. For example:

Grainger's SpeedAire Line of Single Stage Compressor Pumps

You will see that each has a single RPM specified.

Run the pump too slow, and you get lubrication problems (dipping slowly does not make much of a splash). Run it too fast, and you have heat and/or structural problems. Obviously the manufacturers allow for for some safety margin, but a safety margin is not the same as a safe operating range.

If you don't know the maximum safe speed for a pump, then it is the speed that it is runs the stock configuration until/unless the manufacturer publishes a different spec or grants you a waiver to run it faster. I recently retired from an engineering position at an aerospace company, so I'm not a "spin-it-faster-and-see-what-happens" sort of guy.

Most compressor manufacturers run the pump at, or very near, the recommended RPM to be competitive in the marketplace. You don't see a manufacturer paying for a 5 HP 700 RPM pump and then running it with a 3 HP motor driving it to 420 RPM (3 HP/5 HP * 700 RPM = 420 RPM).



And just because it doesn't immediately self-destruct doesn't mean that you're operating within the range or that it's going to last long.

Ultimately, you gave good advice -- don't waste your time for 2 amps.

If you limit yourself to lower end pumps, that is true, but not when you get into high quality industrial pumps. Take quincy for example. You can go from mild to wild on the same pump without compromising pump life.

OP, to increase output of a compressor you need to increase the rpm of the pump, to increase the RPM of a pump you need to increase the HP of the motor and the pulley size to get the RPM up into the pump.

To answer your question in a word, No.

 

[VersionOne]

Actually I think you mean decreasing the pulley diameter to achieve higher rpm's, much like one would when trying to increase boost pressure on a supercharged engine.

 

[creativecars]

The first answer it no.
But with a little more information we might be able to actually help some.

What size tank are you trying to fill?
I assume it is a single stage pump since it has a 3/4 hp motor.
Is it single phase or 3 phase.

 

[Miss_Sissy]

If you limit yourself to lower end pumps, that is true, but not when you get into high quality industrial pumps. Take quincy for example. You can go from mild to wild on the same pump without compromising pump life.

It seemed appropriate to limit myself to small, single-stage, splash-lubricated pumps -- the kind that absolutely dominate the under 5HP market. It's a thread about a 3/4hp, single-stage compressor, after all.

Most of us probably have "lower end pumps" on our compressors. If you have a compressor that you bought at a Lowe's, Home Depot, Tractor Supply, or Northern Tool for less than a grand, you have a lower end pump. Nothing wrong with that. Most of those pumps will last for decades with proper care and the kind of intermittent use that home mechanics put on them.