any air compressor guru's lurking?

Japedo · Post by **Japedo** » 09 May 2010, 17:03

Hello folks, just though i'd make a post as I just got a good sized air compressor and don't know much about them.

I baught a used compressor the other day from my co worker's parents, it had been sitting for 5 years and was baught by them at a military auction. I knew it was missing a few things but brought it home and cleaned it up as it was cheap 200$

Never haveing a compressor before I had no idea what I had untill I got it home in the garage and cleaned it up a bit.
-1960 60 gallon tank "military green"

-a matching military green 1.5 HP motor 230V, unknown what year it is.

- 1999 two stage quincy QR-25 model 310 'rated for 9.3 cfm at 175psi'

So after doing a bit of reading it seems quincy compressors have a good reputation, and the compressor was still bright blue under the dust and had clean oil in it. builds 22lbs of oil pressure on guage "quincy says 18 to 20 is good"

I took everything apart, sprayed two cans of black rockguard on the tank, flat black paint on the motor, taped off warning stickers on compressor and repainted blue. Along with new regulator, pressure switch, air pressure guage and a couple new copper lines for the hydraulic unloader. Looks like a great unit for the 400$ I have invested

What I am wondering is how much better would the compressor work with a 3hp or maybe larger motor turning the belt?

Best part, buddy of mine that uses my garage quite a bit baught a 60 piece airtool set for the garage. Just a cheap walmart set, but seem to work well. Friends are good.

Japedo

Post by **JDS60R** » 09 May 2010, 17:21

Make sure to change the compressor oil and drain the air tank. You can set up a bleed valve at the bottom of the air tank and blow out the water once a week. Make sure to have a catch can or box as the air comes out under pressure and will have rust particles and rusty water in it.

A 2 stage is more efficient and usually quieter. If you need to, build a case to deaded the noise.

It took a 2 hp motor as that is all that is needed to spin it at the right rpm. A 3hp will not help or hurt you unless it runs at the wrong rpm which can lead to heat (thermal runaway) in the chamber.

Keep the tank and compressor oil clean and it will serve you well.

Congratulations !!!

Japedo · Post by **Japedo** » 09 May 2010, 17:41

JDS60R wrote:Make sure to change the compressor oil and drain the air tank. You can set up a bleed valve at the bottom of the air tank and blow out the water once a week. Make sure to have a catch can or box as the air comes out under pressure and will have rust particles and rusty water in it.

A 2 stage is more efficient and usually quieter. If you need to, build a case to deaded the noise.

It took a 2 hp motor as that is all that is needed to spin it at the right rpm. A 3hp will not help or hurt you unless it runs at the wrong rpm which can lead to heat (thermal runaway) in the chamber.

Keep the tank and compressor oil clean and it will serve you well.

Congratulations !!!

Thanks, i did drain the tank out well amd there is allready a drain cock under the tank. Although I haven't drained it under pressure so the bit on putting something under it will save me a cleanup. thanks
I also agree on the HP thing, I guess I need to calculate what rpm the compressor is spinning at, it has a minimum rpm rating of 400 and a max rating of 920. Seems quiet enough for now but if I find it annoys me it's going in the basement under the garage.

I haven't changed the oil yet, as I am waiting to get a new filter. It has a screw on filter like a car, as well as an oil pressur feed line to the head. Seem's to be very well built..... I just told the wife I could do car repairs quicker with air tools so i can spend more time in the house

Whats with justifying spending anyway?

Japedo

Post by **JDS60R** » 09 May 2010, 22:25

Ooops - I said 2 hp when it had a 1.5hp. The rpm is crucial here. Back in 1960 if max rpm was 900 that meant when it was going to blow up. Trust me -I've had a few. If you can determine the rpm it is running at now and replace the motor with a 120V modern motor turning a similar rpm it will serve you well. As far as the compressor oil goes - use a top quality synthetic. Its sooo worth the extra money - they purr on sythetic compressor oil . I rely on Amsoil for this type of application. Its cheaper as you don't have to cahnge the amsoil as often as regualr oil.

If you can't determine the operating rpm then keep it low. Maybe 500 rpm max. The compressor I got from my grandfather spun very low in the rpm range. I think when I got it the spec was 400rpm and it spun 380. I am sure you can find a modern 2+hp with a speed control and rpm meter and most any electronics repair store or online. These like to chug along and as they got older did have some issues with the stock motor. I think a 5hp with speed control would be nice.

Japedo · Post by **Japedo** » 10 May 2010, 19:42

based on a little math and the fact that the tag on the motor says 1700rpm, I should have 513 RPM at the compressor flywheel.

This is a bit low as the minimum RPM for the compressor is 400 and max is 920 according to it's specs. If I had a 3200 RPM 3hp motor to turn it I would be cutting the time it takes to fill the tank in half. And although the tank is a 1960 the compressor is a 1999 that hasn't been used since 2005, so should be able to handle some higher rpm's.

I checked a local farm equipment store and I can get a 3hp 230V 3200rpm motor for 199$, but ill prolly cheap out and get a second hand one. But haveing double the CFM would be handy for running an orbital sander or something like that.

I drained the tank like you mentioned, and had a small amount of water come out. Still haven't been in town to get a filter yet, and will take the advice on synthetic oil. Haveing a speed control and tach at the motor would be pretty decent. Have to look into it.

Why would recomend 120v? doesn't 220v run these things more efficiently/cheaper? Someone told me that anyway and since I had a 220 plug I wired it that way.

japedo

Post by **JDS60R** » 10 May 2010, 20:30

You should have told me about the 1999 compressor from the begining.

Recommended 120V as most don't have a 220. If you do have 200 then great.

A 1999 is a compltely different beast than a 1960. This should be great for you.

I still do not recommend going higher on the rpm. 9.3 cfm at 175psi is alot of compressor. I don't think you will want for more. You will run most of your stuff at 90 -100 psi and the turn on switch is usually set at about 125psi for a 175psi unit.

I would leave it be. I think it will be more than you need. It will keep a few bucks in your pocket . If the motor on it runs and you alrady have 220V then I would fire it up right after the oil change. If you think you need more then you can always upgrade.

Japedo · Post by **Japedo** » 11 May 2010, 07:56

Hello again, I actually did say it was a 1999 quincy QR-25 model 310 in the original post

But I am guilty of missing stuff I read all the time as well, it happens.

Also the 9.3 cfm at 175 PSI is a rating when the motor is spinning 920 RPM according to manufacturer, and 400rpms gives it 4.3 at 175psi. So with the 513RPM that the current motor is providing it is probably about 5 cfm at 175 PSI.

I know that at a lower PSI there are higher CFM ratings not sure of the formula to calculate this, I setup the pressure switch to kick on at 110psi and pump the tank to 140psi.

I need to get some drippless undercoating and a spray gun to undercoat the vehicles now that I have air.

Japedo