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View Full Version : OT - Sears 1 hp Compressor Motor Bearings



asallwey
01-14-2016, 09:37 PM
I have a 1960's vintage Sears air compressor who's motor started screaming, so probably bad bearings. It is a Doerr 1 hp unit. I started to take it apart but didn't get too far, so I thought someone here might have some advice.

I've removed the 4 long bolts and removed the pulley. I need to pull the ends off, but only the end opposite the shaft starts to slide out. Movement this way is only about 1/4", so I figure the electrical connections inside are preventing pulling the rotor out this side. The recommended method of pulling an end off is to tap on the bell edge at the seam to the main case. However is the shaft-end bell is lower than the center case.

Any suggestions?

Alex

Doozer
01-14-2016, 09:50 PM
I'm thinkin' a hammer and a little screwdriver abuse.

-D

Arcane
01-15-2016, 12:51 AM
One of the best (and relatively cheap) tools I've seen for spitting two parts where all you can see is a parting line is a painter's 5 in 1 tool. Use it like a chisel.

http://www.virtualtoolvan.com/shop/images/RP119-b.jpg

darryl
01-15-2016, 01:20 AM
Had the motor out of our table saw a while ago. I used a chisel to raise a bit of a burr on four spots around the endbell so I could get some impact onto it.

lakeside53
01-15-2016, 01:33 AM
Before you wreck it.... a single phase cap start motor will have a centrifugal switch on the shaft that will prevent it from being pushed one way. Some require you to move apart the casing slightly then loosen the switch. Figure out what you are doing before you take the "use a bigger hammer approach".

J Tiers
01-15-2016, 02:19 AM
And, "screaming" may simply indicate that the thing wants oil/lube.

It's common for plain bearings to "scream" when they get dry and the shaft starts to "run around" inside the bearing. If you catch it quick, and oil it, often no harm done.

Screaming ball bearings may also be dry, and you may not need to pull it apart to lube them. Give it a good look before jumping right into a full disassembly.

asallwey
01-15-2016, 07:19 AM
"I used a chisel to raise a bit of a burr on four spots around the end bell so I could get some impact onto it."
This is sort of what I have been thinking of doing. The bell, which is aluminum, is smooth so I would have to put something like a burr on it, and then be gentle.

"Before you wreck it.... a single phase cap start motor will have a centrifugal switch on the shaft."
Yes, I think compressor motors usually have this. That's why I'm going slow, and posted here.

"And, "screaming" may simply indicate that the thing wants oil/lube."
Well, after 45 years I suppose it would be getting dry. Actually it has made noise for the past month (only gets cycled about once a week), but yesterday morning it got real loud and stooped turning. It spins when the belt is off so it's not seized, but I think the front bearing is toast.

Ok, looks like I need to take the shaft-end bell off to make progress. I tried a puller the other day and it just pushed the opposite end out -- should have seen that coming. I suppose a slide hammer with thin finger could grab the bell, but don't have such a tool. If only the bell was above the surface of the case, not below, or if I had won the Powerball yesterday ... .

JoeLee
01-15-2016, 08:55 AM
Before you wreck it.... a single phase cap start motor will have a centrifugal switch on the shaft that will prevent it from being pushed one way. Some require you to apart the casing slightly then loosen the switch. Figure out what you are doing before you take the "use a bigger hammer approach".

I agree.

JL.........

cameron
01-15-2016, 09:17 AM
Before resorting to pry bars, chisels and bigger hammers, I hit the end bell with slanting blows of a rubber mallet. It works often enough to be worth trying.

asallwey
01-15-2016, 09:33 AM
Ok, the bell is off. I did resort to a chisel with small hammer, opened the seam, then continued with a screwdriver so as not to mar the edge too much. Now I have to go find info on how to continue the disassembly since I believe this has a centrifugal switch. My Navy training document doesn't speak to that. Thanks for the help guys!

davidh
01-15-2016, 09:38 AM
quite often with metal parts being stubborn, heat is one of your finest assistants. . . . heat gun preferred but care with a small propane torch is also quite acceptable. 150 degree is something you can just grab quickly without getting burned. . . but quickly. that will usually make a biggggg difference.

CCWKen
01-15-2016, 09:49 AM
Buy a new motor. After 45 years of neglect, it deserves a new life.

ikdor
01-15-2016, 10:07 AM
Buy a new motor. After 45 years of neglect, it deserves a new life.

And while you're at it buy a new car as well, it's not my money anyway......
Maybe we should rename the forum to the Home Shopping Machinist.

Igor

asallwey
01-15-2016, 02:43 PM
Ok, bearings are off. Interestingly they are Nachi from Japan. I would have thought a motor from the mid-1960's would have been SKF or some such.

The front bearing is smooth with no perceptible side-to-side movement. The rear has just as smooth but has a slight amount of side-to-side. Might this be enough to make the motor screech? And then come to a halt? I leaned over the compressor when it screeched and stopped and it was definitely coming from the motor, not the compressor. The compressor turns freely by the way.

There are no worn wires visible. The centrifugal switch contact plate still has spring to the contacting pieces and the contacts are making contact. The collar portion also is intact, and there is spring movement that would press on the contact plate.

A quick internet price check has the bearings for $8+, so pretty cheap. Any thought as to this solving my problem?

J Tiers
01-15-2016, 10:57 PM
What do you call "side to side movement"? If you mean you can move the outer race radially, you should not be able to detect that by hand. If you mean you can tilt the outer race a bit relative to the inner and shaft, that's relatively normal, if not excessive.

More to the point, they may need lube, if they otherwise appear to be free. They can be "Nachi", but they should not feel "notchy" as you rotate them. At 8 bucks you may as well replace them, but they may not be bad.

The screech is puzzling, unless the bearings seem dry. The stopping is more strange if there is no obvious reason, usually that has a fairly clear cause. I believe I would check the compressor, you may have heard a belt-related noise as the compressor bogged down.

asallwey
01-16-2016, 08:34 PM
Been to Cabin Fever today in Lebanon, Pa, it was great. Now back to my compressor. I have a friend that came up with a motor that i can swap in. This will tell me if it's the motor or the compressor. It will take a couple of days, I'll post the results when I'm done.

Thanks for all the help guys!