Old Century Polyphase Motor with "Odd" Bearing Lube Scheme

Please excuse me if this is inappropriate for this forum, but I'm stumped.

I've got an old (ca. 1950) Century Polyphase motor, 1 hp. It has what I can only describe as a "unique" lubrication scheme. It has just the one, single plug in the bearing housing as shown in the photo below.

It uses ball bearings, which implies it needs grease. But there's no drain plug for removing the old grease! Everyone tells me to put grease in there, but that doesn't seem right, since there's no way to remove old grease. Also, although I can't see in there very well, I don't see any evidence of any grease ever being in there.

This is an old South Bend lathe motor, and when installed the bearing plugs are pointing UP. I had the motor removed for about a month, sitting with the plugs pointing DOWN, and a small quantity of oil has run out of the bearings through the plugs (which I had loosely installed). I know this could've run out from the grease.

I have obtained quite a few old Century motor documents for polyphase squirrel-cage induction motors from the Smithsonian. But none of the literature describes this specific housing. The literature says the motors either have ball bearings, which require grease, or sleeve bearings, which require oil.

Sleeve bearings have oilers and a drain plug. Ball bearings have 2 drain plugs - one for pumping grease in, and one for draining out old grease. Nowhere is the single-plug housing shown in any of the literature.

I don't want to pump any grease in this thing, so if I'm going to add grease I'll do it in a small quantity by sort of pushing it in with my fingers. The local motor repair shop gave me some old-timey grease that would be compatible with any old-timey factory grease that might have been in there.

But I don't want to install grease if this motor was meant for oil!

Do any of you have any ideas? I'm so conflicted over this!

Ryan

I have a similar motor, that red spot is a press-in plug covering the bearing. On my motor, grease is squirted in via the port, which normally has a screw in it, like yours. If you replace it w/ a zerk and pump in too much it'll pop the plug out. OTOH doing just that to flush out the old grease might be a good idea.

Greg

Of course, the motor could have had the bearings replaced with permanently lubricated sealed bearings at one point. Pretty much gotta go in there and check it out!

Tools

Take off the plug and look in the hole. Do you see any grease in there? Pry off the plug at the end of the motor and look inside. Any grease?

If there is no grease then try oil. If there is some grease then put in more. Don't worry about it, don't think too much about it. Its a small motor and even if you fry the bearings the replacements probably cost $10.00 each.

Move on to more important concerns. Whatever you put in there just make sure that there is enough to do the job. No lube is far worse than wrong lube.

The previous owner couldve destroyed the gits pot and just places a screw there too. Any more pics of the motor( just a fan of the old motors esp century's)?



Sean

Sean, here's a large pic of the motor plate. Not dialup friendly.

Rick, I looked in there and found no grease. But I was able to insert a small pin and dig around until I pulled away a tiny bit of what looked like grease. The plugs definitely look original, not later retrofits.

So here's my theory. The motor is running on the original grease. That would explain why there's no clear evidence of grease packed inside the bearing housings.

It makes sense that grease would never have been added, because the plugs are difficult to access with the motor installed.

So I added a small amount of grease and 2 tiny drops (very tiny) of gear oil to each reservoir.

I should add that these bearings are absolutely silent and smooth running. I merely wanted to add a little extra lubrication to keep them that way another 50 years.

Century called these motors "invincible".

Ryan

On edit: I notice this was moved to the transformers/phase converters/VFD forum...strange. Seems quite off-topic.

We discuss a lot of "old" motors in here.

Many of those old motors used oil lubrication. You can find SAE30 electric motor oil at many hardware stores. The only problem with a threaded port like that is that every time it is removed tens of thousands of metal particles enter the bearing area.

Old oil will congeal like grease.

Ah, well...Rick's right - if I fry the bearings they probably are easy to get and inexpensive. And it would give me an excuse to dismantle the motor and clean it better.

Ryan

"It makes sense that grease would never have been added, because the plugs are difficult to access with the motor installed."

If the plug is a 1/8" NPT, then is may have been intended for "plumbing" to remote, and to more easily accessible grease fittings.

My Monarchs and my Hardinges are like that.

old Monarchs

peterh5322 said:

"It makes sense that grease would never have been added, because the plugs are difficult to access with the motor installed."

If the plug is a 1/8" NPT, then is may have been intended for "plumbing" to remote, and to more easily accessible grease fittings.

My Monarchs and my Hardinges are like that.

Click to expand...

I was searching around for info 0n a 7hp 1955 squirrel-cage motor. I realize your post was ages ago.But I figured I would ask anyhow. the model is sc-254u-fm3-32 (fyi) . Anyhow the motor has two plug screws behind the pully.One on top 1/4 maybe smaller and a larger 3/8 I think on side or 90 degrees apart.The one on top is slotted for a screw driver and the one on side is an allen plug. I do not see how this could be for grease.I am thinking oil. Now what kind of oil is the question? I was hoping you might be able to help me out on this. I know its long winded but to much info is better then not enough.