new gears-no backlash : LUSENET : Elevator Problem Discussion : One Thread

I am working on an old (20's?)Otis basement drum machine,in which I have installed a new bull gear and worm. I am not able to lower the drum all the way down-I run out of back-lash.The drum bearings are poured babbit.There is no provision to move the the worm away from the bull.Can I replace the lower half of these bearings and achieve the proper clearances? Can anybody explain the procedure needed to get the machine working with the gear set I have? I have never poured a bearing before,and I don't know the backlash spec.

-- Chuck (, March 23, 2000


Chuck, you wouldn't want to lower the gear all the way to the root of the worm; that is called bottoming. There must be some clearance.

If no adjustment is provided, shimming would be the way to set the clearance.

Backlash is the end thrust and is another matter. It is the AXIAL clearance, whereas clearance is the vertical.

Some babbit bearings were made in two halves like a hollow tube and split horizontally so as to be replaceable. A poured in bearing was typically poured around a mandrel and then finish sized by reaming.

Pouring babbit bearings is somewhat of an art, but I'm sure there are some old timers who still know how, but it also takes special tools (e.g. the mandrel, the reamers, etc.).

If memory serves (and sometimes these days it doesn't) typical back lash settings are .003" to .007".

What else might ths old jewel need? Is it time for a new elevator?

Good Luck --!

-- John Brannon (, March 24, 2000.

Chuck, I reread my prior answer and it is confusing at best.

Backlash is the "play" betweeen the worm and gear axially. Clearance (center distance) affects it. Thrust is something else entirely.

You probably know that. Don't know why I even got into it as it was not responsive to your question.

-- John Brannon (, March 25, 2000.

i neen to no waht reasons for gears bachlash

-- w.r.s (, May 04, 2004.

Why bother...if your sales guys are good enough, just get rid of the junk and upgrade....

-- dayle (, May 05, 2004.

who is asking?

-- thomas (, February 25, 2005.

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