Film-Tech Forum ARCHIVE: Need advice on special replacement motor

This is topic Need advice on special replacement motor in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=009234

Posted by Bill Enos (Member # 440) on 04-08-2008, 03:21 PM:

The motor that needs replacement is a 1/3 hp three phase with 1/2 inch shaft 6 to 8 inches long. Frame 1445. It is a sleeve bearing motor with a fairly heavy blower impeller on it. 1140 rpm +- made in 1928. It is electrically OK but in need of bearings again. It runs from opening to close every day ventilating restrooms. It lasts 2 to 4 years between bearing replacements. I am thinking a ball bearing motor might support the weight of the impeller better and last quite a bit longer. Single phase 110 or 220 would be OK.

Anybody know a source for this? Shaft length is the issue, could turn down a larger shaft if length is in the range. Can adapt mounting.

Grainger draws a blank.

Posted by Stephen Furley (Member # 1277) on 04-09-2008, 01:26 AM:

Sleeve bearings should be lasting longer than that. We have large fans up in the roof space of our college doing the same job; there are four wings in the building; the plant in one of them was replaced two years ago, the rest is original, but about to be replaced. They are sleeve bearings, and I don't think they've been replaced since the place was built, in the late '50s. They certainly haven't been replaced in the eighteen years that I've been there. It sounds like something is wrong with your system, incorrect clearance between shaft and bearings, poor lubrication, shaft out of balance, worn shaft or poor quality bearings.

I haven't seen a standard motor of that size with a shaft anything like that long. I suppose you could make up an extension shaft for a standard motor, but you'd really need to turn it between centres, case harden it, and then finish by grinding between centres, while mounted on the motor shaft, to get it really accurate. The case harding would need to be deep enough to not be removed by the final grinding, so not something you with a solid box type system; you'd need a cyanide bath or reducing gas atmosphere furnace; it sounds like a lot of work.

Have you considered trying to obtain ball or roller replacement bearings for the existing motor, or what may be the best solution, replace the whole fan assembly with a modern one? Even if the existing ductwork is a non-standard size it would be a fairly simple job to make up suitable adapter ducts to fit a standard fan; any HVAC contractor would be able to do this. You're talking about a standard supply, so obtaining a new fan assembly to run on it wouldn't be a problem.

Posted by Bill Enos (Member # 440) on 04-09-2008, 10:22 AM:

Stephen, you're correct on most issues. The last shop that reworked this motor made a new shaft on a lathe to what they said were very close tolerances, pressed in slightly undersized bearings, then align bored the bearings to the proper clearance for the shaft, new felt oil wicks etc. etc. This is a large industrial motor shop that has a very good reputation. When I picked the motor up, the shop manager asked about what was going on the shaft, when I told him he suggested replacing the motor next time, that this motor's bearings were too small for the load.

I'm also considering using a ball bearing pillow block and belt driving it.