Hi
I have an old Bachmann GP36 or 38 single drive with pancake style motor. It has sufferred the infamous clicking noise from broken gear problem. I am not sure if I am not searching correctly but I just cant seem to find any parts or spares even in the classifieds or sales. Is buying another parts donor locomotive (which needs to be in working condition otherwise how would I know the gears arnt broken in the donor too) , the only way to restore this broken locomotive ?
Its the two step up/down gears that are broken. If anyone have any spare gears please let me know.
Thanks.
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These gears have been out of production for about 20 years and were never sold separately, so taking them out from another motor is probably going to be the only option unless someone else has some good spares for you.
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Forum member rbturner has a good repair method for these he's shared in the past elsewhere:
Here is how I do it.
This is the cracked gear from a Bachmann something or other. The knife is in the picture to help the camera focus.
Measure the shaft.
Next I press the crack together to see if will lay back together well and make the part a candidate for repair.
Select a bit that is a couple thousandths over. This allows for no outward pressure on the repair. In this case the bit in my Harbor Freight set that was best was marked #44. But I always measure with the micrometer because the HF bits are not always the size my Starrett chart shows them to be.
Once reamed out, I generally simply slip the shaft or axle in and add a small amount of super glue. In this case I am not sure where the gear should be positioned on the shaft so I just left it out.
I add a bit of glue then quickly squeeze it together and put the clothes pin back on. I also add a bit of accelerator to glue to speed up the process.
I always run the bit back through the hole while still clamped to remove any glue that sneaked in the hole.
Next I take a mating gear and test how well the repair will work. Many times it will mesh perfectly and you're done.
If you have trouble or there seems to be a 'bump' as you roll past the repair I do the following;
Sometimes the repair leaves the two teeth; one on either side of the repair a tiny bit wider than they should be. As the mating gear comes around the teeth on it will hit the tops of the repair teeth. Scraping or filing the very tops of the 2 crack teeth down a bit will allow the mating gear to contact the repair gear further down the tooth and this will stop the clicking and clunking.
I use Loctite Pro thin liquid glue. I have learned to avoid my tendency to 'ensure this fix works by using a large amount of glue'. This is especially true when working on Athearn type gears. I had some trouble early on. I found I was using too much glue. When I had the first axle in and went to the other side I was adding a large drop to the inside of the gear hole. When I pushed the second axle into the gear this excess glue had to go somewhere and it went out the crack; re-opening it and spreading the crack out. So, use very tiny amounts of CA. Too much spoils the repair.
I have recommended using a file to flatten each tooth side on the teeth on either side of the crack if you have clunking after the repair. I have wondered why, after the repair which should eliminate the crack, it comes back sometimes? I believe what is happening is when gluing the second axle half into the gear there is no where for any excess glue to go so it goes to the area of least resistance; the crack. Here, it oozes out the crack, spreading it slightly and causing mesh troubles. So today I experimented with drilling relief holes at the bottom of the teeth on either side of the crack. I used a .015" drill.
Success! I repaired 7 axles and they all meshed fine with my test gear.
-Peter. Mantua collector, 3D printing enthusiast, Korail modeler.
Just throwing this out there - you might look at just buying a newer Bachmann GP and swapping the entire chassis. That way you get a smoother running engine with a better motor. TrainWorld has a new GP38 for $79.99, and you can get a DCC-equipped GP30 or GP35 for $99.99. (Not sure about the GP38, but I know the GP30 and GP35 use the same chassis.) You might find a better deal on new or slightly used engines on Ebay.