View single post by Herb Kephart
 Posted: Fri Jul 26th, 2013 02:29 pm
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Herb Kephart

Joined: Thu Jul 19th, 2007
Location: Glen Mills, Pennsylvania USA
Posts: 5873
One other thing that is sometimes noticed in model locos, is that going downgrade they are jerky, whereas going up the same grade they are smooth.

If a conventional worm and gear drive is involved, invariably this is caused by endplay in the worm shaft. Just the minimum of clearance is needed here--and some of the old open frame motors were sloppy in this regard. I've cured many with this problem by adding just enough of the right thickness washers to eliminate all but a little armature endplay.

And Mike is correct about folks setting spur gears too close to eliminate backlash. Nearly all gearing, except for clocks, uses a tooth profile called "involute", one of the features of which is that the gears will be free running with some more backlash than the calculated perfect dimension.


Fix it again, Mr Gates--it still works!"
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