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Repairing split gears

Started by Desert Rose, February 24, 2023, 11:59:12 AM

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Desert Rose

I purchased 80+ new Bachmann engines - DD40AX, SD40-2 AND GP40's prepping for my retirement. I inspected 30 DD40AX's, 240 drive gears, 42 where split. Inspected 25 GP40's, 100 drive gears, 4 were split. Inspected 25 SD40-2's, 150 drive gears, 0 were split. I am in the aerospace industry and have all kinds of structural adhesives for gluing spars and stuff together. So, in the turbine shop I found a 30+ year old bottle of Loctite 271 thread locker. I'm in the kitchen watching my wife baking cookies, the oven is running about 200°F, this is where I get my lesson in crossover chemistry for model trains. Loctite likes a flat clean surface, the inner surface of the gear hub is flat enough, the outer surface of the wheel axel is flat enough, I cleaned off the gear hub and axel with electro-wash cleaner degreaser (plastic safe) P/N: ES1210. Loctite likes oxygen starved places with tight fits, I put a drop of Loctite 271 in the gear hub and a drop on the axel, with my thumb pressed the axel into the gear hub. Now you have a thin oxygen free layer of Loctite tightly between the hub and axle. Using the NMRA HO standards gauge, MARK IVb I check that the wheel width is correct, now you let it cure overnight. However, I sped up the process so I could see the results. I took the gear drive and chucked it in the oven on the cookie sheet with the cookies for 60 seconds at 200°F then pulled it out and let it cool. I tried to pull the gear drive apart with my fingers, its flipping magic I couldn't pull the gear drive apparat.   

Clean gear drive wheel assemblies with the electro-wash cleaner degreaser (plastic safe) P/N: ES1210. Inspect the outer end of the gear hub for splitting or elongation.

Holding each wheel pull away from each other.

 The wheel in a split hub will pop out.

Apply a coat of Loctite 271 in the clean gear hub axle receptacle.

Apply a coat of Loctite 271 to the clean wheel axel.

Insert the wheel axle into the gear hub receptacle. remove excess Loctite.

Using the NMRA HO standards gauge, MARK IVb check that the wheel width is correct. 
Allow the repaired gear drive wheel assembles to cure overnight.

After running four DD40AX's for 4 years accumulating 50+ hours of run time, all gear drives repaired with Loctite 271 passed the pull test.


To make a long story short, you are basically glueing the spilt hub back on with Loctite. Right?


I know all about the pre-retirement Model Railroad roster bulk-up purchasing. While I had an income to support it all. I built my roster of steam engines up to well over 60, I'd have to count to be certain.  Some of them will probably hardly ever run at all, but I wanted them for so long, I got them anyway.