Compressor motor pulley sizing

[allroads]

Fantastic Site! pleasure to meet you all.

Question. All else the same, which is better on an air compressor which is rated 6.5 cfm at 40 psi.

1. A 2 inch motor pulley and make 125 psi slower
2. A 3 inch motor pulley and 100 psi faster.

So, im limited to 120 volt at my place for now. JuST moved in.

I have a sanborn V twin compressor which is 110/220 set at 110.
Hp is 2
Amps are 21 on 110.
Motor is 3750 rpm.
15 amp circuit.

Stock, it came with a 70/100 psi cut in/out.
I bumped up the pressure switch for more air, and found that above 110 psi, it would blow the breaker (bc its drawing more amps?). I had a wild idea, and decreased the motor pulley size to 2 inches instead of three. Now, I can pump to 125 psi and no breaker blowing! Obviously takes more time, but the pump is noticeably cooler. WAY cooler.

Im certainly at the limits of the circuit, but not the compressor. But! here is my question.

For running impacts, a little painting, and blowing out sprinklers, which is better.

1. Having the compressor run slower up to 125 psi with a 2 inch motor pulley or
2. Having the compressor run up to 100 PSI with a 3 inch pulley.

 

[md21722]

It is better to have 125 psi with a 2" motor sheave.

To get the full power of the impact, the regulator, if present, must be adjusted so that the dynamic pressure (the pressure the tool sees) is 90 psi. When using standard 3/8" air hose, this typically means setting the regulator at around 110-115 psi. Using Milton V style air fittings will help minimize pressure drop. They flow about 2x what standard 1/4" NPT I/M fittings will flow. To test actual pressure at the tool, you can rig up a T fitting with couplers and a gauge.

 

[allroads]

I guess thats what I thought( why i did it) but was just wondering....
obv with the 2" pulley/125 psi, I will get more working time but slower recovery/cooler pump and i think cooler pump is way better.
withe the 3" pulley/100 psi, less working time, but faster recovery, hotter pump...
Just didtn want to miss out on anything by the faster recovery time.
I think having the 125 will give me a longer "burst" on the impact which is probably better than a faster recovery. I really only use the impact when im SOL with handtools.

 

[allroads]

Another basics question.
Is it even worth it to run a regulator when using an impact wrench and the pressure switch upper limit is set to 120 or 130? Line drop will make it go down as you said , and lots of people run impacts at 105 or higher to get a bit more power. Think its a wash for weekend use?

I guess thats what I thought( why i did it) but was just wondering....
obv with the 2" pulley/125 psi, I will get more working time but slower recovery/cooler pump and i think cooler pump is way better.
withe the 3" pulley/100 psi, less working time, but faster recovery, hotter pump...
Just didtn want to miss out on anything by the faster recovery time.
I think having the 125 will give me a longer "burst" on the impact which is probably better than a faster recovery. I really only use the impact when im SOL with handtools.

 

[redmondjp]

Another basics question.
Is it even worth it to run a regulator when using an impact wrench and the pressure switch upper limit is set to 120 or 130? Line drop will make it go down as you said , and lots of people run impacts at 105 or higher to get a bit more power. Think its a wash for weekend use?

Short answer? No way - run your impact right off of the tank. I used to work at a shop with a 2-stage compressor (130-150 psi was its on/off range) and my impact always worked much better than at home with 90-120psi.

 

[gdocktor3]

Another basics question.
Is it even worth it to run a regulator when using an impact wrench and the pressure switch upper limit is set to 120 or 130? Line drop will make it go down as you said , and lots of people run impacts at 105 or higher to get a bit more power. Think its a wash for weekend use?

But what are you going to remove the regulator each time you need the impact and reinstall for smaller tools? I have a 30 gallon horizontal that I pulled the 1-1/4" end plug out of, reduced down and ran all 1/2" pipe/fittings, regulator/filter, hi flow fittings and 1/2" hose. So now I run my large air consumption tools off the 1/2" and smaller stuff on the normal 3/8" hose.

 

[allroads]

Well the compressor had some wierd restrictive manifold, so i replumbed it in 1/2 inch, and just before the regulator put in a "t" fitting with one leg going to a regulator, and a second leg going to n unrestricted quick release. Was anticipating hooking up spare air tank back then.
So, i can do either

But what are you going to remove the regulator each time you need the impact and reinstall for smaller tools? I have a 30 gallon horizontal that I pulled the 1-1/4" end plug out of, reduced down and ran all 1/2" pipe/fittings, regulator/filter, hi flow fittings and 1/2" hose. So now I run my large air consumption tools off the 1/2" and smaller stuff on the normal 3/8" hose.