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Electric motor bearings

Ultradog MN

Aluminum
Joined
Jun 14, 2020
Have a noisy bearing in a 7 1/2 hp electric motor. It has zerks and greaseable bearings in it. Took it apart yesterday and cleaned half a pound of excess grease out of the end bells. These bearings are open on one side, sealed on the other. Other than they generally cost a bit more is there any reason not to replace them with sealed bearings? In my farm mowers, etc I always get a lot more life out of sealed bearings. And no greasing or big mess when you need to replace them either.
Thanks
 

neilho

Titanium
Joined
Mar 23, 2006
Location
Vershire, Vermont
If they're greased just a little bit, regularly, they'll last longer than sealed bearings. But....hardly anyone does, often for very good reasons, so it's often better to use sealed.

Cleaning and regreasing the noisy bearing may extend the service life considerably.

Installation labor is often more important than the open/sealed issue. If the bearings are cheap, and the motor hasn't been reassembled yet, it may be best to buy new sealed ones.
 

wood2steel

Aluminum
Joined
May 17, 2013
Location
georgia
Ultra,
Its perfectly OK to put double sealed bearings in the motor but be certain they are premium brand and not a china import. I've got Powermatic machine motors that are 25++ yrs old that are still with their original motor bearings, but only because they used high grade bearings with a special grease that would not solidify in a few short years. Just remember, excessive grease added to open bearings can cause premature failure as well
 

GregSY

Diamond
Joined
Jan 1, 2005
Location
Houston
Excessive grease won't really hurt the bearings. What it does hurt is wherever it winds up....like on the motor windings.
 

MwTech Inc

Titanium
Joined
Feb 6, 2005
Location
Fishersville VA
Use a Nachi ,NTN or even SKF sealed and you will never have to deal with the problem again......
unless it runs 24/7...lol

Call Accurate Bearings...pick the quality you want....(std disclaimer)
 

Shaybuilder

Cast Iron
Joined
Sep 24, 2006
Location
Nevada
Put in sealed bearings and forget about lubing them. We had a 25HP vertical turbine pump motor that hadn't run for over 3 years but the maintenance card said to grease weekly which the operators did. When we finally tried to turn the pump on the grease had all gone into the motor windings.
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
I replace always with sealed.

What you should do is clean everything up. Grease up bearings from the open side. Install bearings with open sides on the outside of motor rotor.
When end bells are installed you plug the Zerk holes. Now you have sealed bearings.

I was doing this stuff years ago and a Motion Industries sales person persuaded me that the grease/Zerk way of doing things is not the best.
He knew a lot about bearings and I always talked with this guy every time I was fixing a motor.

In my opinion the Zerk idea is good for a armored tank. Easy to grease everything up and invade your next door neighbor.
 
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Ultradog MN

Aluminum
Joined
Jun 14, 2020
Thanks folks.
I went ahead and replaced them both with sealed bearings.
Local bearing house had 'em in stock.
$46+tax for the pair. I always specify non China bearings. These are Nachi - made in Japan.
I just bought this motor at the U of Minn surplus outlet. It was on a pump platform. Paid $20 for the whole thing so now I have a nice quiet motor pretty cheap - and some scrap.
I replaced the idler on my RPC with it.
 

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Bill D

Diamond
Joined
Apr 1, 2004
Location
Modesto, CA USA
Modern grease and modern rubber seals are much better and longer lasting then what was available 50 years ago. So go ahead and use sealed bearings if you are over 40 years old. If you are under 40 you may want to pump in some fresh grease in 40 years.
Bill D
 

whj

Plastic
Joined
Sep 11, 2017
Modern grease and modern rubber seals are much better and longer lasting then what was available 50 years ago. So go ahead and use sealed bearings if you are over 40 years old. If you are under 40 you may want to pump in some fresh grease in 40 years.
Bill D
Have a noisy bearing in a 7 1/2 hp electric motor. It has zerks and greaseable bearings in it. Took it apart yesterday and cleaned half a pound of excess grease out of the end bells. These bearings are open on one side, sealed on the other. Other than they generally cost a bit more is there any reason not to replace them with sealed bearings? In my farm mowers, etc I always get a lot more life out of sealed bearings. And no greasing or big mess when you need to replace them either.
Thanks
Most motor bearings that are greaseable has a plug opposite the grease fitting that can be removed to allow excess grease to escape to keep from filling the motor.
 

guythatbrews

Cast Iron
Joined
Dec 14, 2017
Location
MO, USA
Excessive grease won't really hurt the bearings. What it does hurt is wherever it winds up....like on the motor windings.
Well not exactly.

Excess grease causes bearing overheating if it can't escape. I guess it usually can in a motor so it causes problems elsewhere, so true in this case.

Bearings require very little grease. My dad was a smart guy but he was of the school more is better. He had a travel trailer and repacked the wheel bearings, and I mean full. Bearing got hot enough to fail and cut the wheel hub half in two.

Sealed bearings, yeah. If there is a zerk there don't farmer grease it.

Apologies to you farmers.
 

beckerkumm

Hot Rolled
Joined
Aug 5, 2014
Location
Wisconsin Rapids WI
A sealed bearing will run hotter than a shielded or open but mainly an issue when running a motor under load for long periods. New small frame motors tend to run hotter to begin with so the added friction of a sealed bearing and resulting heat can be an issue but not for my use. Still, an open bearing with a exit for excess grease and a decent maintenance schedule will give the motor the longest life. Dave
 








 
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