Motor mystery

[Doug G.]

You're welcome.

[mmagliaro]

Tonight , I shimmed the motor with a strip of.025" phosphor bronze. Loco runs very quiet now.
 Those middle gears I mentioned actually have a "spacer" as part of them.
 Thanks again Max!
 Joe D

Thank you, but....
.025" ???   That seems like an enormous amount.  Are you sure that's the thickness of the shim?
It might be working, but I would really try to use a much thinner shim than that.  You could be
pulling the worm up out of the worm gear so much that you'll start beating up the edges of the teeth.
Perhaps try going down to .010" at least, and see if you still have a quiet engine.

[peteski]

Can you guys explain to me where the shim is installed, and what does it accomplish?  Somehow I can't wrap my head around it.

Joe wrote that he has the model made in the early 21st Century.  That is probably this one (Spookshow's images):


Is the shim installed between the bottom of the motor and the frame (to raise the motor slightly)?
I imagine that this model has some sort of drive shafts with universals between the flywheels and the worm shafts. How will elevating the motor cure cyclical noise at the worm?

Even is Joe had the older version of that loco, it also has a "springy" coupling between the motor and worm shafts. What would shimming the motor accomplish?

[mmagliaro]

I for one have been assuming it is a rigid mesh between the worm and worm gear (not like the springy one you showed in the second photo).  So if there is a little slop in the rotation of the truck tower gear, you would get a cyclical bind there if those two gears are a hair too close together.  That's why I suggested a very *thin* shim.

If it's the version with those spring joints between the motor and worms, I suppose it is possible that the springs are slightly bent, and lifting the motor by .025" make them run with less noise.

[Joetrain59]

Max and Pete, I have the loco in the first picture that Pete posted, the split frame version.
 .025" is what the fellow wrote on package for the shim material I used.
 I cut just a little strip, tacked it to bottom of motor with Goo. Let it set up a few minutes,
 then reassembled motor, making sure all clearances looked good. I should be stopping at
 Hobbytown right near me today. I'll see if he has any of the metal packs you suggested, Max.
 Joe D

[mmagliaro]

Okay, so now I'd like to see a photo with the frame halves taken apart and that shim in there.
It just seems to me like jacking the motor up by .025" would separate the worms from the truck tower gears so much that they might be just barely meshing.  Yes, they might be really quiet, but it might also start skipping and destroying gear teeth.

[peteski]

Yes, Spookshow's site does not have a photo of the internals in that loco.  Joe, If you could take photo of what the mechanism looks like with one of the frame halves removed, that would be great. Or at least describe the mechanism.

[Joetrain59]

Photo taken. But the way these, and a lot of other diesel motors are mounted, they have no up and down play.
 Oh, the shim was .005". But I see with Optivisor on, it's not touching the frame below motor. Now that I have taken it apart,
 and reassembled it, the noise is back!
 Photo to be up in a little while.
 Joe D

[mmagliaro]

Okay .005" makes a lot more sense.
And now that I see the insides, the shim would make no difference because the worm shaft is riding in its own bearing and that fixes its location.  So forget the shim.

The fact that the noise comes and goes based on you disassembling and reassembling... sometimes these buggers are devilish to put back together.  The bearing blocks might rotate 90 or 180 degrees on the ends of those worms, and that can make a difference sometimes.  The motor could slightly shift fore or aft in its cavity, and the right flywheel is awfully close to the frame cavity in your photo.   Does it make the noise if you put it back together but leave the screws through the frames a tad loose?  If it's quiet, does the noise appear if you then tighten one or more of the screws?  Are there any shiny spots in there that look like one of the flywheels could be rubbing on the frame?

[Steveruger45]

I’ve been working on a life life gp38-2 which has the same motor mount collars.  The older atlas u25B has the same style of motor mount too.
I see you also removed the inner bearings on the worms.
Yes, it can be frustrating getting this all quiet and yes disturbing them after they are quiet can bring back the noises.
All I can say is be patient and be methodical and try one adjustment at a time, reassemble and test.

One question, is the noise directional?...  The worm shafts will move backwards when loco is going forward and vice-versa.
Thrust washers may help if the worm is binding/rubbing on the bearing block.  Rotating bearing block/s, not only 90/180 degrees but also turning them front to back can change things too.
Worm shaft free play is needed but not too much so adjusting these may help too.

Rotating the motor mount collars may help.  Make sure they are properly seated with their upper an lower prongs in the frame slots.

Good luck

[Joetrain59]

I believe I found the issue. A slight bind in gears in one truck, every revolution.
 I would roll trucks on a paper towel on work surface and never felt any "hiccup".
 Getting bored watching the Islanders/Canadiens hockey game, I picked up a truck
 and rolled wheels with my finger very slowly. Then I felt it. Seems like maybe something in a gear tooth.
 Will tear down truck, wash off lube, and look closely at gears.
 Back to the game for now:(
 Joe D

[Joetrain59]

Seems to have fixed the issue! Did not really see anything in gear teeth, or any flash.
 Whatever works.
 Thanks for all the info.
 Joe D

[peteski]

It was probably some piece of gunk stuck between the gear's teeth and worked itself loose.

[Joetrain59]

At least I don't get cat hair wrapped around axles any more.
 Joe D

[peteski]

At least I don't get cat hair wrapped around axles any more.
 Joe D

You lost your cat?  Sorry to hear that.