(Older) Atlas SD50/60 Gear Noise -- How to fix.

[learmoia]

I've got several Atlas SD50s and SD60s that I'm selling.  Never run them - all NIB but testing them as they get sold at the buyer's request.

The New Run (Slow Motor) locos run great (and relatively quiet)

However I sold one of  the Older Run (High speed motor and molded plastic packing) units 3 out of 4 tested ran great but had an intermittent high pitch squealing noise when running both directions.  (The buyer will be getting the quietest of the 4 that I tested)..

But what is the fix for the other 3.. (and maybe the 2 others that I didn't test yet.)  Is it a 30-45 min break in thing or is something out of alignment?

(I tried to search the archives but didn't get anything or "Atlas SD Noise")

Thanks.. ~Ian

[Plumcrazy]

i Would put  a couple drops of oil behind the fly wheel on the motor where the bushings are located to stop the squealing noise.

[Doug G.]

Yeah, a high pitched squealing is always motor bushings/bearings, possibly worm bushings/bearings as the shafts turn just as fast there as at the motor bearings. Lubrication fixes it.

Doug

[atsf_arizona]

learmoia,

I have found (with help of others here on TheRailwire) that there is one other common possibility for squealing mechanisms, that has nothing to do with dried-out motor bushings/bearings.

The other possible reason for the SD50/SD60 'squeal'  is that one (or both of the trucks) is missing the 'mounting tab' that the split-frame chassis is supposed to sit on.  Check out the following and see if this is the cause of your 'squealing' SD50/SD60.  (or Atlas SD7/SD9 or other similarly constructed trucks).

See this thread, specifically, page 6:  https://www.therailwire.net/forum/index.php?topic=40758.75

In which I discovered that my Intermountain SD45-2 / SD45-T2 / SD40-T2's were squealing... because excessive "push-down" when putting the shell back on these locos.... had broken off the "mounting tabs" that the  split-frame chassis is supposed to sit on.  The Atlas SD50/SD60 use exactly the same trucks and can have exactly the same problem.



Thus that end of the mechanism, with nothing holding/preventing the gear tower to keep it separate from the worm, causes the top of the gear tower gear teeth in the truck..... to bottom out in the worm in the mechanism.... thus causing continuously squealing sound.   The gear and the worm are supposed to mesh only.   It's clearly wrong to have that gear rub continuously on the worm, and the the gear/worm bear the weight of the mechanism.   See the photo above.

After replacing the 'missing tab' truck with a 'proper tab' truck.... the IM SD45-2 mechanism with "good trucks with mounting tabs" now runs practically silently!

Anytime you see someone put a shell back on a split-frame N scale diesel by "placing the mechanism on a table then pushing the shell back on top firmly"..... you see exactly how these small somewhat fragile mounting tabs  in the trucks can get broken off.  Don't put your shells back on that way.   Instead, hold the mechanism by the fuel tank area in the middle and then push the shell back on. This is a long known issue and problem....but not everyone knows of this.

I've seen the same squealing sound caused by "broken tab" issue, with Atlas SD7/SD9/SD35 trucks and with Intermountain 6-axle diesels. 

Getting replacement trucks is the fix if this is your problem.  And now knowing this,  being more careful in the future when replacing your shell on the mechanism.

I hope this helps. 

Missing the mounting tab:


Truck with the mounting tab intact:

[learmoia]

Great info on the trucks - Never knew that..

I sat down and inspect my locos, and all trucks are intact.. (When I pressed shells on, I would use my index finger on the shell, and thumb on the fuel tank and put force there.. (I always suspected I could damage the trucks.. )

Also checked the trucks, clear rolling with gears.. Reassemble - test - still noisy..

So back to the lube..

I put a drop of lite Labelle oil on each motor bearing, and at each worm gear bearing.. and a strip of gear oil across the worm gear and that solved it..

Thanks all!! ~Ian