The worm wheel in one of the powered trucks on my Williams GP9 is slipping on its axle. Do I have to replace the whole truck or is there a relatively easy way to make this repair?
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The Bachmann Williams shows the GP-9 geared truck available as an assembly with the coupler for around $42.00. About two years ago the helical gear and drive axle joint failed, helical gear was free spinning causing no motor torque transfer from the worm gear on the motor shaft to the wheel axle, after disassembling the motor truck assembly the teeth on the helical gear and motor pinion gear looked okay. I used a Locktite Bearing Retaining compound to bond the gear to the motor shaft, this must be done after reassembly, both the gear bored hole and shaft must be clean for this retaining compound to bond. I recommend using a micro brush to apply this retailing compound to the contact surface of the gear and shaft, side the gear sideways to increase the bond contact area. Do no allow this retaining compound to flow into the adjacent bearing area of truck block if done properly the shear strength of this retaining compound will transmit the required torque. Allow 24 hours for this bond to fully develop. I did not want to use a Locktite retaining compound that requires heat to break the bond. Replace helical gears are available from Timko.
@John Ochab posted:
The Bachmann Williams shows the GP-9 geared truck available as an assembly with the coupler for around $42.00. About two years ago the helical gear and drive axle joint failed, helical gear was free spinning causing no motor torque transfer from the worm gear on the motor shaft to the wheel axle, after disassembling the motor truck assembly the teeth on the helical gear and motor pinion gear looked okay. I used a Locktite Bearing Retaining compound to bond the gear to the motor shaft, this must be done after reassembly, both the gear bored hole and shaft must be clean for this retaining compound to bond. I recommend using a micro brush to apply this retailing compound to the contact surface of the gear and shaft, side the gear sideways to increase the bond contact area. Do no allow this retaining compound to flow into the adjacent bearing area of truck block.f done properly the shear strength of this retaining compound will transmit the required torque. Allow 24 hours for this bond to fully develop. I did not want to use a Locktite retaining compound that requires heat to break the bond. Replace helical gears are available from Timko.
John, thanks for this! I did see the truck on the Bachmann parts site, but since the worm cylinder and worm wheel gear seem to be in good shape, I'd like to avoid replacing the entire truck, if possible.
How did you remove the drive shaft (axle for worm wheel gear) and worm wheel gear, which presumably you must to clean the surfaces adequately? And reassemble? Is the silver retaining collar on the drive shaft (on the opposite side of the truck from the external gears) press-fit on?
Matt, sorry about a late response, I am retired and working on other projects.
Remove the motor and wire connects to the truck. Also remove both side frames and the motor plate.
You do not have to remove the coupler, the helical gear that meshes with the motor pinion gear is brass.
Look at the drive axle that this gear is attached to, on one end there is a spur gear that drives both geared wheel assemblies.
On the opposite end their is a bearing assembly for this drive shaft. Using a small piece of wood support both wheel axles on the geared side by turning the truck vertical. On the bearing end of the drive shaft I used a nail punch and ball peen hammer to gently tap downward to drive out this shaft. One this shaft moves a fractional distance the spur gear comes out and the helical gear will fall out of the truck block. Clean with alcohol the portion of this shaft and brass helical gear of all grease and oil.
I purchase a small bottle of Loctite 641 retaining compound to bond the helical gear to this drive shaft. I purchased this retaining compound on Amazon or Ebay.
If the teeth on the brass helical gear are not nicked or worn reuse the gear. Frank Timko at Timko's Repair Depot has replacement brass helical gear, I brought some spares from him.
Now the reassembly, hold the brass helical gear in the truck block and slide the shaft from the spur gear into the truck. The brass helical gear should slide easily unto this shaft. Continue pushing this shat in until the spur gear on this shaft meshes with the two integral spur driven wheel gears. Now comes the critical part, center the brass helical gear in the truck block and apply the Loctite 641 retaining compound to the brass helical gear hub bored hole and the shaft. Do this in small amounts using a micro brush, insert a .010-.015 shims both sides of the brass helical hub to prevent the retaining compound from weeping into the truck block to prevent shaft seizure. Once the shim are in place gently slide the helical brass gear left and right and rotate this gear this should help to draw the retaining compound and capillary draw this retaining compound to bond the contact surface of the shaft and brass helical gear hub. Let this assembly bond at least for 24 hours cure time. If the gear breaks free again repeat this total procedure, it failed for me after two months use, the second time I cleaned the axle, brass helical gear and bored hole on the truck both with alcohol and blew it out with compressed air. Contamination of the retaining compound was the issue, these three item must be clean.
This seams like a long procedure, but after the second application, my old Williams Milwaukee Road GP-9 works with no issue pulling 15-20 cars with a caboose on upgrades. For maintenance the Jerry Williams Williams engines that I purchased years ago are very easy to grease and oil.
Sounds like a lot of work to avoid buying the available power truck.
Except that I had pulled the parts and cleaned them, disconnected the motor and was running the locomotive with just one powered truck and the same thing happened to that truck. The disassembly and cleaning is done and I'm looking at about $12 in retaining compound versus $82+shipping in new trucks.
Edit to add: As much as the cost savings, the idea of tossing otherwise perfectly good parts, particularly when there's a straight-forward-sounding fix, doesn't sit right with me. If I mess the DIY repair up, then I won't mind picking up new trucks.
Reply to gunnrunerjohn and Matt. First response to gunrunnerjohn when the helical gear connection to the shaft failed I just wanted to buy the geared truck assembly Bachmann had no assemblies for a long time probably two years ago. I disassembled the truck with the failed gear connection and being familiar with Locotite products from work I chose to purchase the Loctite 641 retaining compound to bond the helical gear to the axle. Now the response to Matt, I chose this retaining compound when comparing the shearing strength of similar Locktite compounds based on the torque necessary to shear this bond. If the brass helical gear teeth fail, Frank Timko had the replacement brass helical gear, I purchased 5 for spares. You can use other Locktite products but remember the higher the shearing strength of the compound the disassembly will become more difficult.
Reply to Matt, on the gear side of the truck block three steel gears mesh, the geared center shaft is driven by the brass helical gear, the driver is the motor pinion gear. What I did was to stand gear side of this truck, wheel faces bearing on a wood block, the opposite end of this shaft is in a bearing housing(part of truck block), gently tap with a small pin or nailset using a hammer, I used a small ballpeen hammer, to start the removal of this axle on the steel three meshed gear side. On reassembly reverse this removal procedure.
I ended up getting a 10 mL bottle of Vibra-tite 530, a general purpose retaining compound, which with a shear strength of 2300 psi is a little stronger than Loctite 641. @John Ochab, I think you point about removability of the medium-strength Loctite 641 is a good one, however, I went with the Vibra-tite, because I could trust the legitimacy of the product and I don't trust the vendors selling the Loctite on Amazon and Ebay. The Vibra-tite 530 is comparable to Loctite 609/675 and its shear stregnth is on the low end of the product range.
Late yesterday afternoon I applied the compound using a toothpick—the tool at hand—and today I reassembled the trucks, lubed everything and now they're waiting for the another six hours to finish curing. I'm pretty sure that I cleaned all of the surfaces sufficiantly. For this first attempt at the fix, I used a minimal amount of retaining compound, hopefully it will be enough.
Thank you, John, for sharing your wisdom! This kind of knowledge sharing is a large part of what makes OGR a great forum.
When I reassembled the locomotive, it ran a short distance and then stopped. It could go in the opposite direction a short distance before stopping. The worm wheel and cylinder were binding. The cause, and I'm confident the cause of the original slipping on the drive axle, each worm wheel had a fine crack causing the worm wheels to be out-of-roundl and thus bind.
I'd noticed a line when initially disassembling the drive, but overlooked it as the cause of the problem, since it seemed to be an odd type of failure, and assumed it to be a mark from the manufacturing process. Indeed Frank Timko had never heard of such a failure, but he promptly sent me replacements.
The replacement worm wheels have been installed with a sparing amount of Vibra-tite 530 retaining compound, the locomotive reassembled, and now runs fine.
FWIW, the parts bonded with Vibra-tite 530 were easy to free with a ballpeen hammer and punch.
The cracked worm wheels (they were much less noticeable prior to using the retaining compound):