Air compressor recommendations for home shop

[eKretz]

Try search...

You know the motor RPM.

pulley ratio ?

Does anyone know the formula for calculating speeds from one pulley to another of a different size? Chris

www.practicalmachinist.com

 

[Gordon Heaton]

The above will get you the pulley ratio you need. You can't be too picky about an exact RPM because pulleys come in more or less standard sizes (you could, of course make your own but why bother?).

As for belt size, the typical 4L or 5L series fractional horsepower belts are sized by their circumference. So. if you use a 1/2" wide belt (4L) you can simply wrap a 1/2" wide tape measure flat around your two pulleys and see what that length will be. You want to set the motor toward, but not at, the 'loosest' position while measuring. Even easier is to wrap a rope or rubber tube of similar diameter to the belt and measure that length. 'A' and 'B' series belts are measured differently but a decent supplier can correlate the measurement to the correct size. Either way, you'll only get close and may need to try a couple to arrive at the Goldilocks size.

 

[mmurray70]

Just FYI, any Brunner will be at least 40 years old now, since they went t/u in the early 80s. Good tough machines, but very old. A company called Atmosphair in Toronto advertises spare parts but I can't vouch for availability.

There are single cylinder 2 stage compressors, but they are rare, Puska (Spanish), Heywood (WWII aircraft vintage) and Holman "T" piston compressors. There is a large, flat piston crown riding on top of a much narrower piston body, much like a crosshead. The 1st stage air is compressed above the wide upper crown, and sent through an integrated intercooler, or even through a discharge valve in the piston crown, where it gets trapped underneath the crown in the annular compression cell created between the smaller diameter lower piston body and the wider upper cylinder. As the piston descends, the air is compressed and discharged out the side of the cylinder. Very compact, as you would want on an aircraft breathing air system. If you cut the piston in half vertically, it would resemble the letter "T".

Brunner compressors are awesome. I have a 1946 brunner pump as the main compressor in my shop. I love it. Have another brunner pump for a spare but will probably never get to set it up lol. My main one is almost 80 years old and working perfectly.

I have a Saylor Beale 703 here too that is also great.

Cant beat the old stuff when it comes to compressors.

 

[john.k]

there is a size limit to small motor pulleys ......excessive belt flex and slippage ,and groove wear ......if you want a low rev compressor,you will probably need to buy a low rev motor.

 

[7.3444e]

The above will get you the pulley ratio you need. You can't be too picky about an exact RPM because pulleys come in more or less standard sizes (you could, of course make your own but why bother?).

As for belt size, the typical 4L or 5L series fractional horsepower belts are sized by their circumference. So. if you use a 1/2" wide belt (4L) you can simply wrap a 1/2" wide tape measure flat around your two pulleys and see what that length will be. You want to set the motor toward, but not at, the 'loosest' position while measuring. Even easier is to wrap a rope or rubber tube of similar diameter to the belt and measure that length. 'A' and 'B' series belts are measured differently but a decent supplier can correlate the measurement to the correct size. Either way, you'll only get close and may need to try a couple to arrive at the Goldilocks size.

Thank you Gordon. I just read through the pulley ratio thread , some of it is tricky to understand but I get the gist of it. Do you guys know of a good source for pulleys and belts for Quincy compressors. Wasn't sure if I needed to go directly to Quincy or if you guys knew of a good aftermarket website to order from. I appreciate your patience as I know I'm asking a lot of noob questions. I work on a lot of my own equipment whether it be diesel engines or gas but never really messed with compressors. Was just looking up oil change/maintenance kits for Quincy compressors and damn they are proud of those kits!

 

[7.3444e]

Brunner compressors are awesome. I have a 1946 brunner pump as the main compressor in my shop. I love it. Have another brunner pump for a spare but will probably never get to set it up lol. My main one is almost 80 years old and working perfectly.

I have a Saylor Beale 703 here too that is also great.

Cant beat the old stuff when it comes to compressors.

Thanks, yes this is my plan, just going to get this compressor for now to buy me some time to find one of these older compressors that are still in decent shape. I like the old stuff, both my work truck and personal truck are 23 years old. They don't make them like they used to, especially diesels.....

 

[7.3444e]

there is a size limit to small motor pulleys ......excessive belt flex and slippage ,and groove wear ......if you want a low rev compressor,you will probably need to buy a low rev motor.

Is it doable to make a 1310 RPM pump go down to say 800-900 RPM without changing the motor?

 

[Gordon Heaton]

You can buy pulleys in many places. The best stock in my town is a bearing supply house. McMaster sells them and you might find one at a large hardware store, Amazon or Tractor Supply, etc. I don't know what equipment you have, but it is often most convenient to get the pulley size you want and bore the hub to fit your motor. Stay away from stamped-steel pulleys, insist on cast iron or solid steel.

Whether or not you can get the ratio you want depends on the current drive pulley size and how much smaller you want to go. You can go smaller than you think if you use a serrated belt or a link belt. Even ordinary fractional-horsepower belts have a pretty tight radius limit.

Don't worry about 'genuine' Quincy oil or filters. They're priced for folks who are buying a new, multi-thousand dollar compressor and they make you buy their kit to get the extended warranty. The compressor you're buying isn't new and most likely hasn't seen 'Quincy' oil since the first oil change!

 

[7.3444e]

You can buy pulleys in many places. The best stock in my town is a bearing supply house. McMaster sells them and you might find one at a large hardware store, Amazon or Tractor Supply, etc. I don't know what equipment you have, but it is often most convenient to get the pulley size you want and bore the hub to fit your motor. Stay away from stamped-steel pulleys, insist on cast iron or solid steel.

Whether or not you can get the ratio you want depends on the current drive pulley size and how much smaller you want to go. You can go smaller than you think if you use a serrated belt or a link belt. Even ordinary fractional-horsepower belts have a pretty tight radius limit.

Don't worry about 'genuine' Quincy oil or filters. They're priced for folks who are buying a new, multi-thousand dollar compressor and they make you buy their kit to get the extended warranty. The compressor you're buying isn't new and most likely hasn't seen 'Quincy' oil since the first oil change!

Sounds good I will do some searching around for pulley and belt. Going to pick up the compressor in the morning so once I have it I can get some measurements and find out what pump it has to see how low of a RPM I can go. You are most likely correct about the oil change, heck I bet a lot of people never even change the oil when they're supposed to, or drain the tank for that matter