Would you guys use this used idler gear?

Wed Apr 21, 2004 3:27 pm

I'm doing a major engine overhaul and bought this used idler gear. In addition to the visable bearing damage there is a slight amount of play when I put the shaft on by hand. Is this safe to use? The alternatives are replacing the bearing for abot $25.00 or buying a new gear from Walt's for about $50.00

Image

Wed Apr 21, 2004 3:33 pm

As long as the teeth look OK - I would get a new bearing.

Look for wear patterns on the teeth - flat spots - cracks - ect.ect.

That will save you 25 bucks.

Wed Apr 21, 2004 4:17 pm

As Oscar said, I would get a new bearing. I think I remember reading that the replacement bearings have to be honed, or bored, to fit the shaft.

Wed Apr 21, 2004 6:03 pm

I just took the bearing out of my original idler gear to see how tuff it would be to replace. Based on that experience and what John said I've decide to buy a new aftermarket one.

Thanks

Sat May 01, 2004 10:09 am

I received a new bearing from Case IH. First of all it isn't split like the original bearing. Second the machine shop ownwer were I got my engine work done couldn't get it to fit. He first tryed to bevel the leading edge which didn't work. Then he put it on his honing machine and the hone shoe ripped the new bearing up. He said the material was to soft. Does anyone know eactly how this is supposed to be fitted? I may have to use my original shaft and another used Idler gear I buoght from Wengers. The fit isn't perfect but Iv'e been trying to get this fixed for over 3 weeks now and done see a nice snug perfect fit in the horizon. :?

Sat May 01, 2004 10:42 am

Steve,

I'm sorry you are having so much trouble.

First thing I would do it find a machinist who understands fitting babbit bearings. Obviously the one I sent is now beyond useable. If he tried to hone it he isn't a machinist, he's a klutz... babbit must be hand scraped to a final fit. Never abrasives of any kind on babbit... they will contaminate the surface.

I'll bet he doesn't even have bearing scrapers!

Sat May 01, 2004 12:23 pm

George,

This process doesn't sound like it would even need to be done by a knowledgable machinist. Is this true and if so do you know were I can purchase the tool to do the job? Also how do you maintain a consistant circumferance when your scaping the bearing?

Sat May 01, 2004 12:36 pm

Steve,
If you have a speed shop near by give them a call.
There is a special reamer for bearings such as you have.
They use them on cam bearings in car engines.

Sat May 01, 2004 12:45 pm

Steve,

The scraping process is used to improve the accuracy of a machined surface. The bearing should first be bored as accurately as possible and then final fitted to the proper oil film clearance with scraping tools. The shaft is coated with prussian blue and the parts trial fitted. The scraper removes all the blue that transfers to the bearing, (only to the high spots) along with a very small amount of babbitt. The process is performed many times... each time producing a truer surface.

Most of my scraping tools are made from old files, but some are factory made. I think the files work as well.

The earliest engine cylinders were made by this method without the use of any machine tools at all.

Sat May 01, 2004 1:57 pm

George,

The process sounds like it shouldn't be attempted by anyone who hasn't done it before. I think I'll get the bushing that came with the gear you sent me and have it reinstalled and go with it. This along with the used shaft I bought from Wengers gives the best fit out of all the combinations I've tried. I was mostly worried about the pitting in the bushing but this may actually make it take the oil better.

Sat May 01, 2004 5:28 pm

I just stumbled on a local veteran machinist who knows about babbit bearings. He said he can do it the original way or he can use bronz. He said bronze would be cheaper to do and feels it would be a good substitute. Should I go with the bronze?

Sat May 01, 2004 9:33 pm

Steve,

A copy of my private message...

Steve,

I'm glad you found this guy! I'm sure he will lead you right. There's no
doubt that a well fitted bronze bearing would serve you just fine. Go for
it!

George

Sun May 02, 2004 11:10 am

There's no
doubt that a well fitted bronze bearing would serve you just fine.


Great! I'm going to drop off the gear and shaft Monday and I expect to have them back by next weekend. I'll let you all know how it worked out .

Thanks again