Compressor question

WolfGT

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#1
I have a small hobby project I am working on that has nothing to do with Jeeps, offroading or even vehicles. But I have a technical question that deals with air compressors and I thought this may be the best place to find the technical know how to find an answer. (move my post if you need to).

My project has the need of compressed air. Somewhat high pressure (100psi) but very low volume. The biggest concern is noise. I want to be able to have a small tank (maybe 1 gallon) that can be charged slowly. My question is: can I take a regular small air compressor that is capable of 100psi and put a slow turning, high torque motor on it that will charge the tank over a long period of time (like 12 to 24 hours). That way reducing the noise level to about nothing. If there is no technical restriction to this, where can I find the parts? This will run indoors so the capability to operate on normal household current is a must.
 

LBarr2002

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#2
Well, I don't know what your project is, but if you're talking really low volume why not use a storage tank (high pressure nitrogen like paintball tank or a CO2 powertank) and refill it as needed? You can get 4500 psi 68 cubic inch paintball tanks that would probably last a long time.
 

WolfGT

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#3
Yeah, I could do that. But this is one of those projects that if it goes the way I want it to, it could be marketed and sold to consumers. So I want it to be self contained. Just plug it in and use as directed. Not have to worry about some idiot that doesn't know an air canister from a propane tank doing something stupid.
 
#4
I dont know if I have ever seen a slow turning high torque electric motor? if you have a one gallon tank could it recharge like once a day?
 
#5
A low rpm high torque motor is 99% of the time a high amp draw. There are a few electric motors on the market that would do what you want, but amp draw and heat soak will be hard to overcome.
Most motors will be high rpm high torque, and to some degree will sustain the rpm & torque from centrifical force. It takes far less amps to maintain a high rpm than a low rpm motor.
 

WolfGT

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#6
I say high torque because I assume that is what it would take to charge a tank to That psi. I could be wrong. I don't want to put in a standard compressor and set it on a timer. That is just bypassing the issue and not many people will like a compressor running in the house no matter how short of a time it is.
 
#7
I say high torque because I assume that is what it would take to charge a tank to That psi. I could be wrong. I don't want to put in a standard compressor and set it on a timer. That is just bypassing the issue and not many people will like a compressor running in the house no matter how short of a time it is.
something like a small ARB compressor could be mounted in a closet in a sound insulated case and be barely audible, plus it would fill up the gallon tank in about 5 minutes and you would only need to fill it up once a day.
 

WolfGT

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#8
How about a higher speed motor geared down. That way the motor could spin at an RPM that it is used to but the compressor would rotate slowly not making much noise. Maybe a flywheel to keep it going past the resistance of compression.
 
#9
That's possible.
I saw something about a house. Is this 12v or 120v?

120v motors can be low rpm high torque and still lower amp draw. I assumed that we were talking about 12v motors.
 

WolfGT

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#14
Just thought I would update this thread. I presented this question to my brother a couple months ago and asked him to keep an eye out for something that may work in this situation (slow turning, high torque electric motor). And he came back a couple days later and said .... "treadmill". I thought, holy cow, he's right. If a treadmill motor can move a 250lb person at a walking pace for hours at a time, that is exactly what I need.

I just spent the evening tearing a treadmill apart. I now have a 3.5hp motor and all the electronics to go with it (and I gained some pretty heavy duty steel for my stock pile). Who knows how I can rig this motor up to just be turned on by a switch and run at a specific speed?
 
#16
Who knows how I can rig this motor up to just be turned on by a switch and run at a specific speed?
The industrial version of what you want is called a "variable frequency drive" (VFD). It allows motors to be run at different frequencies (AKA, more or less rotations) without forcing the motor to commit suicide. Mainly used on AC motors and primarily for 440v stuff, unknown if they make it for smaller stuff. So a VFD, you put it in between your control panel/switch/2 dangling wires and your motor, and it can make a motor spin slower or faster.

So I would go back and look at the treadmill, see what VFD they are using. Can probably look it up online somewhere since it is typically a stand alone module. Or you can start looking at new units. I know Allen-Bradley makes a mighty fine unit but they might be a little bit on the pricey side.

Also look around and see if there is a VFD off of something else that is easy to get ahold of.
 

WolfGT

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#17
I'm guessing that treadmill wasnt direct drive though, was it?
Not sure what Direct Drive is...

The industrial version of what you want is called a "variable frequency drive" (VFD). It allows motors to be run at different frequencies (AKA, more or less rotations) without forcing the motor to commit suicide. Mainly used on AC motors and primarily for 440v stuff, unknown if they make it for smaller stuff. So a VFD, you put it in between your control panel/switch/2 dangling wires and your motor, and it can make a motor spin slower or faster.

So I would go back and look at the treadmill, see what VFD they are using. Can probably look it up online somewhere since it is typically a stand alone module. Or you can start looking at new units. I know Allen-Bradley makes a mighty fine unit but they might be a little bit on the pricey side.

Also look around and see if there is a VFD off of something else that is easy to get ahold of.
I have all of the electronics from the treadmill. I was very careful not the damage anything. I could plug it all up and run it right on my bench as is if I wanted.
 
#18
Not sure what Direct Drive is...



I have all of the electronics from the treadmill. I was very careful not the damage anything. I could plug it all up and run it right on my bench as is if I wanted.
does it have a gear reduction at all, i'm guessing that the motor spins pretty fast, and there is a gear reduction to slow it down.
 

WolfGT

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#19
It's a belt drive but the size difference in the pulley's are not extreme. I would say 2.5 to 1. But I will look it up. But even then, I was planning on gearing it down anyway.
 
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