Quincy 310 Compressor Questions

[rustyjames]

I picked up a sweet Quincy today that the owner said takes forever to build any pressure. It was listed on CL as a parts unit. The motor was replaced with a 1 HP Dayton with a 3.75 diameter pulley. I have a nice old school 2 HP to upgrade it. So, my questions:
--What would be the proper diameter pulley to spin this pump?
--What should I be looking as far as the low output/recovery?

TIA

 

[oldmachinenut]

I have a 1947 Quincy 310 that I have used daily since I got it in 1981. They are great compressors and if you keep oil in it your grandchildren will use it some day. I have a 2hp Dayton motor on mine, I am having some back problems but I will try to go out and measure the motor pulley. I think one of the websites has the minimum/maximum rpm’s listed.
400rpm minimum, 920rpm maximum

 

[The Cobbler]

this will help you https://www.blocklayer.com/pulley-belteng.aspx
you need to know the motor rpm as well

also look for leaks in the pump and discharge lines etc. it may not be the motor causing the slow build up

 

[yelchevelle]

I would try lapping/rebuilding the valves. Also, 1.5 hp is going to be on the low end of what can run that compressor. I will try to remember to measure mine tomorrow. Mine had a 1.5 hp motor when I rebuilt it. I swapped it to a three and I think that I am in the 800-850 rpm range now. Builds up a lot faster.

I have seen/rebuilt two 310’s and both had worn out wrist pins on the smaller high pressure piston. I had a machinist put a bushing in both pistons and make new wrist pins.

I have a 1947 Quincy 310 that I have used daily since I got it in 1981. They are great compressors and if you keep oil in it your grandchildren will use it some day. I have a 2hp Dayton motor on mine, I am having some back problems but I will try to go out and measure the motor pulley. I think one of the websites has the minimum/maximum rpm’s listed.
400rpm minimum, 920rpm maximum

What record of change is your 310?

 

[oldmachinenut]

Mine is ROC 14, splash lube

 

[rustyjames]

I have a 1947 Quincy 310 that I have used daily since I got it in 1981. They are great compressors and if you keep oil in it your grandchildren will use it some day. I have a 2hp Dayton motor on mine, I am having some back problems but I will try to go out and measure the motor pulley. I think one of the websites has the minimum/maximum rpm’s listed.
400rpm minimum, 920rpm maximum

Thank you, but you don't have to go out of your way to get that. Take care of that back!

this will help you https://www.blocklayer.com/pulley-belteng.aspx
you need to know the motor rpm as well

also look for leaks in the pump and discharge lines etc. it may not be the motor causing the slow build up

Thanks for that link. At the moment it's apart, I asked the guy selling it if he would dismantle the pump/motor for easier transport.

I would try lapping/rebuilding the valves. Also, 1.5 hp is going to be on the low end of what can run that compressor. I will try to remember to measure mine tomorrow. Mine had a 1.5 hp motor when I rebuilt it. I swapped it to a three and I think that I am in the 800-850 rpm range now. Builds up a lot faster.

I have seen/rebuilt two 310’s and both had worn out wrist pins on the smaller high pressure piston. I had a machinist put a bushing in both pistons and make new wrist pins.



What record of change is your 310?

Thank you for that information. The ROC is 25. The tank was made in 1980 so I figure the unit is around that age.

 

[MacMcMacmac]

Low output is almost always caused by valve wear or breakage. The other posters are correct that 1.5hp isn't going to get you much air no matter what pump you have. Is there a safety valve screwed into the head? If so, remove it, put in a 60psi pressure gauge and see what it reads. You should have a consistent reading below final discharge and above zero. It might fluctuate a little, but it should not go to zero. This would indicate low pressure valve problem, while full discharge pressure would indicate high pressure valve problems.

Edit: Ok, I blew up the picture and saw there is no relief valve in the cylinder head. There is a square headed pipe plug in there, just above the intercooler on the right side in the picture. Put a gauge in there and see what you find. If you get a consistent pressure, around 40psi if I recall but I might be wrong, your valves are probably fine.

 

[rustyjames]

Thanks, Mac, I'll try that.

 

[MacMcMacmac]

I should clarify that your interstage pressures should settle out to these figures once your final discharge pressure has exceeded this value. While it is coming up from 0psi this test will not be valid.

 

[rustyjames]

Understood, Thanks again, I appreciate your input.

 

[rustyjames]

So, I finally got a chance to start working on this compressor. I think I found the obvious cause of the slow air buildup. On the pump discharge there's something I've never came across before. The supply line is around 3/4" connects to some kind of "thingy." The output line from this is reduced down to 1/4" to supply the tank. I'm assuming this compressor is purpose built for whatever? See pics, and any input is sincerely appreciated.

 

[joe121]

d

 

[yatg]

Have a similar "thingy" on my 325. Believe its some sort of dryer or buffer, can't remember. Also have that smaller line, about 3/8, going to the tank.

 

[Jpkimmel]

I know it’s an old thread but that “thingy” is called a cushion chamber. It’s used to lessen the incoming air pulse into the storage tank so the output of the tank is more consistent and smooth.