Many years ago, when they first came out, I bought a Bachmann 2 Truck Shay with every intention of making my grand garden route. Life got in the way and during some leaner times it was sold. Last Xmas, my two grown boys rekindled the dream when they bought me a NOS Shay that had never been out of the box (included VHS instructional tape.) I set up an oval of track and proceeded to turn into a child. On the third outing with almost no weight in tow, it broke the final drive gear on the rear axle (which I now know they are prone to do.) Since parts are hens teeth and I really didn't want to pony up multiple $ hundred for new trucks, I decided to see if I could fix it. A friend who had been into R/C cars noticed how much that gear looked like a pinion gear so the search was on. We came up with a steel gear with the right diameter, pitch, and number of teeth to match the BS plastic one that broke except the axle hole was 5mm and the Shay axle is 6mm. Getting the axle out was quite the adventure with the pickups and all (thanks to those that helped here). Found a 6mm bit and drilled the gear out on the drill press. Pressed off the bearing and chucked the axle up in the DP so I could file down the knurling for the old gear. Made a flat spot with my Dremel to accommodate the set screw of the new gear and then pressed it all back together. With some adjustment and tuning I now have a fully functional Shay once again and I will be damned if that gear will ever break again. Did the second axle in that truck and ordered 2 more gears to do the front truck. If anyone wants pics and details I can provide em.
Definitely, and part numbers! I've replaced a fair number of Shay trucks for other folks, so I've got wee bit of a stash of 1st-gen Shay trucks here to keep my 1st-gen Shay running for a while, but with metal drive gears, that would be a fix I'd make once and not have to worry about again.
I got the gear from Amazon, search: Hot Racing NSG3222. I got the 6mm drill bit from McMaster-Carr (great service). I also damaged one of the bearings pressing it but those are the same as ones used in skateboards and available everywhere but also from Amazon, search: 625zz Bearings.
Note: When notch the axle for the set screw, make sure the set screw goes in deep enough that none of it protrudes above the collar on the gear. If it does, it will hit the worm gear on the motor when you cinch down the cover.
I will do pics and procedures when I get the gears for the front truck. I am NOT taking those contacts apart any more than I have too. If I were doing this more often, I would make some sort of jig or clip that holds the pickup balls in while I take out the axle so as to not have to muck with taking the contacts out to keep em from flying across the room.
I did this mod using a drill press, a Dremel tool, hand tools and my highly calibrated eyeballs. You machinist with your fancy lathes will probably get a few chuckles. Drill out the gear: I started by making a jig to hold the gear while I drilled it out. This made things easier and safer. With a ¾” spade bit in the drill press (DP), drill a hole in a piece of scrap wood the depth of the teeth on the gear. Switch to the 6mm bit and drill the center of the hole through. Clamp the jig to the bed of the DP. Remove the set screw from the collar of the gear with an Allen wrench. Place the gear in the jig, collar up, and grab the collar with a small pair of locking pliers to keep it from spinning. Drill out the center hole to 6mm, cutting oil is good but not mandatory as you aren’t removing much material. Remove the axle from the truck: You Shay veterans probably know this step and can skip ahead. I placed the loco upside down in its original packaging foam to cradle it. Remove the 6 screws from the motor cover. Backing off the contacts is a pain but best to done to prevent loss of the ball bearing. Remove the tabs with the wires (1) and spread them out to the side. Remove the 2 small tabs (2). Pry the spring shims (3) up and out. Pull the pressure springs (4) in toward the center of the truck. I placed a small rare earth magnet on the springs to keep the ball ‘attached’ to the end (5). Gently pry the axle up and out. Strip the axle: Remove the small screw and washer from the center of each wheel. Remove the wheels. Remove the plastic spacer behind the wheel. You will need to press off the bearing on the gear end of the axle and the gear (if it is still there). If you have a bearing puller, I hate you. I used the drill press. Put a 6mm open end wrench around the axle next to the gear. Put the other end of the axle through the hole in the DP bed. Press down on the end of the axle with the chuck until the bearing and gear pop off. You can leave the other bearing on. Remove the knurling from the axle: Chuck the non-gear end of the axle in the DP. Turn on the DP and run a flat file up and down the axle until the new steel gear will slide smoothly all the way on. Avoid the very end of the axle where the wheel and bearing mount, it is already 5mm and sized to fit them. Notch the axle for the set screw: Align the steel gear to its approximate position on the axle. With a sharpie, mark the set screw hole on the axle. Remove gear. Using a Dremel with a bur grinding bit, make a flat spot at the mark on the axle. NOTE: It is very important that the notch is deep enough so the set screw does not protrude above the collar of the gear. If it does protrude, it will hit the worm gear on the motor when re-assembled (ask me how I know). Put the set screw back in the gear, tighten it on the axle, and use you sense of touch to check it is flush. Re-assemble the axle: Leave the gear loose on the axle. Press the bearing back on the axle. I used the DP once again by placing the non-gear end of the axle on the bed, opening the chuck so the axle will go in but the bearing won’t, and Press the bearing on with the chuck. Position the gear and tighten the set screw. For positioning, compare it to the axle that still had a gear but if you don’t have one, space it about 1mm off bearing using the calibrated eyeball method. Install the plastic spacer, wheel, washer and screw on each end (the wheel with the gear goes on the end with the new steel gear on rear truck, opposite for front). Double check that the bearings spin smoothly, I damaged one of mine with the pressing on/off. They are cheap and readily available so replace any that aren’t silky smooth. Do the other axle: Rinse, repeat. While the truck is apart you may as well upgrade both axles. I found another broken gear and a cracked one.
Test for binding and clearance: I did a quick test to be sure they ran smooth. Snap the axles back in the truck. Using jumper leads, run power from an old track power pack to the two wires that were un-clipped from the contacts. Check for binding. If you hear a ticking you probably did not get the set screw notch deep enough and it is impacting the worm gear. If it is quiet and smooth, grease it up. Re-assemble the Contacts: Just do the dis-assemble in reverse. Those little clips are gonna be a booger especially for old eyes and shaky hands. Close up the trucks and test: Put the cover on and carefully tighten the 6 screws. Do another run test by touching the jumper leads from the Power Pack to the wheels or use your fancy run in station. Listen closely for any ticking that would indicate you have clearance issues with the set screw that will ruin your day.
Last edited by EDHRailroad; 05-17-2020 at 08:55 PM.
Reason: add pix
I too have the very first release.
I too had the gear break during the first hour of use, running light.
glad to hear of your clever fix.
never the less, I strongly suggest that you keep an eye out for the metal replacement trucks, hopefully at a decent price. The difference they make is worth the money, imho. (I bit the bullet , and just bought them for $59.00 way long ago, didn't want to mess with warranty and shipping it back. I know they are a lot more now, and will likely increase, I think).
Simply, Bachmann G scale, and the Shay is no more, parts are difficult and , the loco is delicate to say the least, in terms of parts, and thin styrene. Not to mention, they cannot take moisture.
The problem with the original trucks is that the plastic is very brittle and eventually will crack around the screws. Also, the ball bearing contacts against the back of the wheels were pressing way too hard, creating a good deal of drag. I too have my old set. got 4 replacement axels from Bachmann, but still bought the metal version. It changed my mind from hating the loco to loving it.