It's all three bearings on the sprocket / drive shaft. There are two "donut" bearings and one large "double-size" bearing. The one that is the worst is the large one but the other two go bad as well.
When they do go bad, the projector starts sounding like an old washing machine. I've been told that there was an incident where one froze up mid-show. When you take them out to replace them, they feel like they are full of gravel and often they have leaked black grease all over.

I am told that every projector in the place has had at least one bearing job. There was one incident where the new ones went bad just two weeks after replacement.

I replaced the bearings in one projector this week. I made sure to be as careful as I could:
I carefully knocked the old bearings out with a spark plug socket and a hammer. I made sure they were seated perfectly straight using the same method in reverse...tapping gently and making sure to only apply force to the outer rim only. I cleaned all the parts as thoroughly as I could and made sure there was absolutely no grit or dirt on anything. I deburred any parts that wouldn't fit together with hand pressure, test-fitting everything before final re-assembly. I didn't open the packages to the new beraings until the last second before I needed them to make sure they weren't contaminated by grit. In short I was just about as anal-retentive about it as I could be.

I have about 50 Simplexes in my area and these are the only ones that do that. (Although I must admit half of them are practically new "Milenniums".) I have made similar repairs in other locations but none this severe and none so chronic... There's GOT to be something wrong here.

I suspect it might be just a bad run of bearings but that doesn't explain why it would continue for 5 years unless Strong is having long-term "quality" issues with suppliers. Second I'm trying to rule out poor workmanship on another person's part, as you've read above. What else could it be?

 |  IP: Logged

Still I did my best to make sure that things weren't put toghther all cockeyed so that there wasn't any lateral pressure on the bearing races.

The larger bearing on the outside is sealed, as I remember, have to check when I get back to the office. This is a very heavy bearing and the only thing that should make that fail is excessive tension. When we "chatted" about that the other night, tension didn't sound like a problem.

The only other thing is that the bracket and/or its mounting bosses are really tweaked. Let the bracket "find" it's location by spinning the shaft before really clamping down on the two screws that secure it. Does the bracket seem square to the rest of the shousing?

With everything mounted up, does the shaft free-wheel easily? A little spin by hand should let it spin for a long time -- a minute sor so, depending on how hard you spin it.

Make sure your crew isn't spraying things down with WD40 or cleaning with 409. That stuff drives the oil out and will cause that. I was once complimenting a theatre on how clean everything was until I saw what they were using...

After a long, drawn-out process of elimination, I finally discovered a bottle of XeKote in the cabinet with Renovex in it.

After a long, loud "training session" with the booth people, I locked up all of the chemicals.

But the damage was done, and I ended up replacing the drum bearings on all 6 projectors.

I also let all the parts find their own "home". All parts were hand fitted before final assembly and then put together loosely before tightening. All the screws were tightented in stages.

Since the shaft is loaded by way of a "wave washer" I found it hard to get the black bracket on without putting lateral force on it. Every time you press on it to get it in position it would want to shoot off to the side. I put the bracket on but left the last big bearing loose. (There is a set screw on the bottom that tightens it in place.) Once I was sure that everyting was centered I pushed the bearing in by hand and tightened the set screw. The last thing was to make the final turns on the screws that hold the bracket. (I left them a couple turns loose, too)

I was able to turn the shaft with just finger pressure but it wouldn't spin for more than a rev. or two. Then again I didn't have the last gear / pulley on yet either. Once it was all back together I put the belts on and tensioned them. The projector would turn over just as easily as any. Just fingers is all it took.

 |  IP: Logged

Now, I can't speak for the other 9 of them. When I took this first one apart it was okay. (It was done previously by the NCS "guy".)

 |  IP: Logged