Back Gear Slinging Oil

The back gear slings oil out when I run the lathe. What a mess! I took it apart (see attached picture). At the bottom of the photo are all the parts I have (other than the pulley). There's a washer-like ring that goes up against the bearing on the bottom left. The next part over looks suspicious. It's a pulley spacer. It's threaded on the inside, and has a keyway. The ID is a bit larger than the shaft; maybe 0.050 or so. The OD is smaller than the hole in the cover plate; again maybe 0.050 or so. Because of the threads on the inside, I'm thinking that it may have been replaced sometime in the past. Because of several marks, hand-made gaskets and a repaired flywheel bore, I know that someone has been in the gearbox before.

I looked over the manual, and I seem to have the right parts. It looks like the way this thing works is that any oil that runs through the bearing hits the large washer-like ring, is slung into a circumferential chamber, and then drains down to the bottom where it runs through a hole back into the oil reservoir in the back gear housing.

When I was working on the back gear, I noticed that there was a gasket installed between the housing and the cover plate. There is a drain below the bearing back into the housing. The gasket covered the drain. I thought that this could be the problem.

So, either the oil was not draining because of the gasket, or it was leaking around the loosely fitting pulley spacer, or I overfilled. Overfilling could have been possible, because it was hard to see through the oil line window. I don't think this was the case, but I cleaned it up so I could see the level better.

I put it back together without the gasket. There was about a 0.02" gap between the housing and the cover plate. This is another place the oil could have been leaking. I made a 1/32" gasket and installed it.

After reassembling everything, I ran the lathe for about 10 minutes. All looked fine. However, when I stopped it, a slug of oil ran out from behind the pulley. Centrifugal force was probably holding it there when it was running. I have not taken it off yet to see if I can see where it's coming from.

Does anyone have any ideas? Should the spacer ring fit better? If so, how much clearance should it have?

Thanks.

The gasket on motor side should have a hole to allow the oil to drain back. I am not sure how much oil would get passed the sealed bearing. It sounds like the oil is leaking past the other bearing on the pulley side. I just finished mine and there are no gaps. I often wonder if gear boxes should breath out when they get warm. Most farm equipment gear boxes have one way valves that release pressure.

If you oil is too thick, it will not have time to bleed trough the passge back into the gear case. It will over run and spread to the spindle thus spinning the oil as you describe.

Paul

There is no seal on the output shaft a Slinger is the thing. It only works when the pulley is turning, Likely overfill or wrong oil.

Having oil that is too viscous not draining quickly sounds plausible. I also understand how overfilling would result in the oil running out of the assembly. However, it's not over filled, and I used Mobil DTE Heavy Medium Oil. The manual calls for SAE 20, and posts I've seen call for the DTE Heavy Medium.

Should I be using a SAE 10 / DTE Light Oil?

Does anyone have a cross section of the back gear box, so I can see some detail on the assembly?

DTE Heavy Medium should be just fine.

I already sent you the only cross section drawing that I have, but it's not the one for your gearbox.

You mentioned a collar against the slinger that has a keyway and an internal thread. I don't see anything like that on either the old drawing or parts sheet 101. AFIK, the slinger is sandwiched between the inner race of the outer bearing and end of the pulley itself. Maybe the ring was added as a spacer for some reason. The pulley should stick inside the big stationary cover ring with the 4 screws. If the spacer is proud of the cover ring, the keyway would allow oil to walk out along the shaft. Someone with more knowledge of the unit will have to say for sure. Dave?

Maybe the slinger plate is damaged? Is it a close fit to the shaft? Does it have a step on one side for the inner bearing race?

Cal

More info about parts

Here are some pictures. Perhaps someone "modified" the assembly in the past.

In order from inside the housing to outside, I have:
inner bearing
spacer
outer bearing
oil slinger
spacer
pulley

The oil slinger looks like a big washer. It is smooth on both sides. There are no grooves or raised sections.
The spacer is threaded on the inside, and has a keyway. It fits loosely on the shaft and in the housing. It's a right handed thread, so it would tend to move oil out of the housing when running in forward.
The pulley sits on the spacer, and does not have a nose that extends into the housing. It has been repaired with a new sleeve, held down by four screws.

Back view (side closest to back gear housing) of the pulley, with the spacer and oil slinger:


Front view of the pulley:


I did some experimenting this morning. With the pulley and spacer removed, I ran the motor forward, backwards, and at various speeds. I turned it off and on several times. It never leaked. I put the pulley back on and ran it once. It leaked about two or three tablespoons from behind the pulley when I turned it off.

The problem arises from the altered pulley and spacer. In an original assembly there is no spacer between the slinger and pully hub, the hub butts directly to the slinger. Something bad must have occurred in the past to require such an extensive pulley alteration. Your spacer appears to have been made from a piece of scrap, a proper spacer would not have an internal thread. The joint between the hub and spacer is outside of the slinger cavity, any leakage from that interface would be expected to have a portion of the leaked volume find its way to drool out.

Perhaps someone has a spare pulley that they can provide hub dimensions from or better yet sell you. I have one packed away somewhere but can't recall which one of the 400+ boxes and crates from my recent shop move it's in.

My pulley is 1.3" deep from front to back.

I vote for a vent for the assembly as we discussed at Noon.

It should not leak. An easy place to put a vent is on the filler plug.

Granger sells them:
Gearbox Vents - Grainger Industrial Supply and here
LUBE Relief/Filler Vent Plug, 3/8-18, 1.19 H - Breathers and Vents - 1U577|PRV103-2 - Grainger Industrial Supply

They are used on bearings, gear boxes, reservoirs, and anywhere pressure or vacuum relief is necessary. They can also be used as filler plugs. This vent plug features a splash deflector to prevent liquid from spilling into the vent hole and outside.
Vent Plugs and Filters on Oil-Rite Corporation

Solution to Oil Leak

First, thanks to everyone that helped. I got a lot of ideas of things to investigate. It turned out to be something completely different.

First, I found a cross section of the back gear. There was nothing in the 1939 patent or the 1942 version of the manual, but there was one in the 1965 version of the manual that was almost identical to the one I had:



I kept thinking that it was odd that I had no leak when I removed the pulley, even after several starts, but I got one on the first start when I put the pulley back on. Looking at the cross section, I could see that the output shaft with the gear squeezed the two large bearings when the pulley assembly was made up. I could also see that the drain hole was behind the gear inside the housing. I wondered if the gear was being pulled so close to the housing that the drain was plugged. That would fit all the symptoms I saw.

I took the whole thing apart again. And I found the problem. There was an old home made gasket between the housing and the cover. It was roughly cut, and extended under the gear. A notch had been cut for the drain hole, but I could see that the gear had been rubbing on the gasket, which made a seal!

I trimmed the gasket. It was so old that it crumbled at the top. I made another gasket. Here's a picture of the old gasket. You can see where I cut it out, and you can also see if you look closely where the gear was rubbing.



I put it back together and ran it. No leak!!

An easy solution to a hard problem!