Old Curtis Air Compressor

[FarmIT]

This message is a reply to an archived post by Nate88 on August 27, 2014 at 15:56:14.
The original subject was "Re: Old Curtis Air Compressor".

Hi Looking to mod mine, Mine is a Curtis 88 45-3851 3x1 5/8 x3? 300rpm run by a 1941 BS 23B Gas engine. it has the unloader arm assembly running down to the flywheel. I have been told you can put a common pressure switch and needle valve type unloader on your machine and rest easy ***unless** it is one of those Curtis compressors that uses the high pressure exhaust valve as the check valve. In that case, you would need to install an in-tank check valve first, then plumb the unloader line from the switch to the check valve port. You will need to buy some Swagelock fittings and maybe cut and bend a little bit of copper tubing for a new discharge line
Any advise on if what I have is a "high pressure exhaust valve motor" and or what EXACT parts I should be looking at would be appreciated, newby when it comes to compressors, considering always open tank valve as the unit is gas, and my Lab hates fireworks.

 

[Steve@Advance]

The weight operated unloader is only for easy starting with the tank under pressure.

It appears all it unloads is the low pressure cylinder, so the high pressure exhaust should stop the air flow when the unloader is open.

Just be aware, if you take the weights out of the flywheel, what will that do to the balance?

Not real familiar with how the Curtis is set up with a gas motor, but there also has to be some type unloader to regulate the cut out/cut in pressure. Is that component there and working?

 

[FarmIT]

Thanks for the reply Steve, I need to take the head apart today and check it out I cannot do a full rotation either way with the flywheel, it was sitting in the weather and I fear it is quite gunked, Hope it is salvageable! I'll try and post some dirty Valve pics later.
George

 

[Gene Davis (Ga.)]

I have a compressor unit like this one in my shop. It is a 1938 model by Curtis. I emailed them the S/N and they dated it for me. It is powered by a modern 1 & 1/2 hp single phase 220 volt motor. I took it off the original riveted tank and have it mounted on a 60 gallon horizontal tank. Machined 2 V-belt grooves in the flywheel to get away from the old flat belt. All the centrifugal flywheel unloader stuff was missing when I go it. It had a leaking head gasket. I made a gasket out of 1/8" sheet asbestos packing, cleaned the head and valves and lapped them a little with fine valve grinding compounds and it has been a very good compressor all these years. I lapped the valves once more in 2016 as it was beginning to blow back into the intake a little.
I removed the check valve in the discharge line near the cylinder head and installed a 1" inline check valve in the discharge line where it goes into the tank and it works fine and keeps the load off the starting procedure. I also teed the line at this point to install the cut out switches. I have one Square D cut out switch set for 85-100# and a second safety one set to stop it at 140# in case the other one fails.
The original air filter was missing so I adapted an oil bath one onto it from a 6 cylinder Ford engine and it is quite. I turn mine at 490 rpms and it give me ~5 C F M of air and will do it all day. I could run faster and produce more air, but that is about all I ever need. It has been a very dependable machine for me.
Gene Davis (Ga.)

 

[FarmIT]

Gene, Great info thanks! I hope my valve is ok, just saw the price of those suckers.. I was caught up doing other work today and did not get a chance to work on the compressor. Could you take a pic of your set up if you get the chance?
George