Yep my new Connie blew its drive gear. Bachmann is replacing it but in the meantime I'm out of business since this was my first battery conversion. I remember a similar post on the drive gear problem but I don't remember if it was ever solved. Did anyone find a metal gear replacement?
Rex
Barry's Big Trains in Tolleson, Arizona, is working on a metal replacement gear set. The last time I talked to him a couple of months ago he anticipated having something available by the end of the year. You might want to rattle his cage again about the status.
http://www.barrysbigtrains.com
I sent Barry an email as suggested. Here was the reply - quick too.
Rex,
Thank for your inquiry. I have in development a new gearbox which uses the existing axle (without the splines). And this will use my usual seven-pole ballbearing Pittman motor. We're still a few months away from offering this solution. So please bear with me.
The next step is to finish the drawings and six prototypes, submit the drawings to the machine shop and submit a prototype to Dave Goodson for testing.
Barry - BBT
I received the drive wheel/gear set from Bachmann yesterday and its now installed and running. Unfortunately summer is over and we're back in Gold Canyon until spring.
I did remove the plastic/nylon gear from the broken drive set. It is a 25 tooth 5/8" OD 1/4" ID press on gear. I'm going to search for a metal gear replacement starting with the RC car hobby shops. I tried the train shops but they don't carry any repair parts saying that only the manufacturers do repairs or have parts. I'll let you know what I find if anything.
Rex in Pinetop wrote:I received the drive wheel/gear set from Bachmann yesterday and it's now installed and running. Rex
I received the drive wheel/gear set from Bachmann yesterday and it's now installed and running.
What exactly did you receive? Does Bachmann send the gear already installed on the shaft with the wheels and counterweights already installed? I assume the worm is supplied loose.
Walt
Bachmann sent me the drive-wheel-axle-gear assembly. It did not include the counterweights which come off with a single screw each. It did not include the other gears in the motor assembly which were not damaged anyway. The drive gear slips on the axle. It should have been keyed or pinned but it wasn't so when something stops the wheels the motor spins the drive gear then it doesn't go anymore. The whole assembly is only $10 plus shipping so I bought a spare in addition to the one they sent me on warranty.
Right now I'm looking for an after market metal gear to beef up the design or perhaps I'll find a way to key the nylon gear. My gear looks like it broke radially as well so this particular gear is dead for sure. Keying it won't help as its split in 3 places.
I found a couple of metal gears from the RC car and truck world. The gear needed is a 25 tooth metric. The one I found has the right size and number of teeth but the wrong ID. I'll drill it out and cut a key slot in the gear and shaft. I'll make a key out of a washer. If it turns out too sloppy (which I kind'a expect given my lack of proper machine tools) I'll just solder it to the shaft.
The white gear in the center is the broken one. The two gears along side it are from Tamiya RC Parts. They cost me a whole $5.75. The drive wheel set at the top is what needs the gear added to it.
What is the worm gear made of? It looks as though the collar of the metal gears is drilled for a set screw. If so, why not file a flat into the axel under the set screw?
Walt,
The motor/transmission case is too narrow to accept the set screw portion of the pinion gear. There are two bearings that "lock" the drive gear in place on the axle so the gear has to be thin enough to fit inside the transmission bearings when enclosed by the case.
The Bachmann drive gear is made of plastic/nylon as are the rest of the gears in the transmission. The only worm gear is the one on the drive motor. Power is transferred through several gears in the transmission until it gets to the drive gear connected to the drive wheel axle. There is no room on the plastic drive gear for a set screw. That's why I was considering a key.
Hi Rex,
Thanks for the info. I now have two Connies and will probably be facing these problems fairly soon myself. So the worm gear and the spur gear that it is driving seem to be O.K? I guess it makes sense that the gear attached to the axel would be the one to strip or slip since it's transmitting the most torque.
Just a thought ... we had really good luck with a product called lock-tite (made by Devcon, I think). And I know there are other shaft locking products on the market as well. I'd give that a try before trying to fabricate a key and keyway in minature. Although, you might need to smooth out the knurl because most of these products depend on a really close shaft-to-bore clearance.
Neither Locktite nor any other product is going to solve the problem because the Bachmann nylon gears split open from the pressure exerted on them when they are press-fit onto the axle. As Rex mentioned, the slot in the Bachmann gear box is too narrow to allow a replacement gear to have a collar and set screw. I think all Bachmann G-scale locomotives use the same gearbox arrangement and all eventually suffer from a cracked gear. I have two Consolidations with cracked gears.
That's why Barry's Big Trains is having to come up with a totally different gearbox, motor, and main drive axle arrangement just to get away from Bachmann's use of a nylon gear.
What I'm afraid of once I beef up the drive gear is what the next point of failure will be. Barry's solution is probably the best long term fix however I'm guessing it won't be cheap or available for awhile. My metal gear replacement will probably work for awhile until one of the other gears fail. The other gears are not so easy to cobble so they would have to be replaced by Bachmann gears.
Then there is the turn around time. You're looking at 3 weeks to get a manufacturers part. I missed some quality run time with my front yard kids when this gear failed. Now the season is over until spring. Rats ....
Charles,
I'm suggesting that Rex Lock-tite his new metal gear to the axel. Each stage of gear reduction is a torque multiplier so each set of gears going back inward toward the worm has a decreasing torque load. It's possible that the rest of the gears may not fail.
Obviously a well designed gear train with metal gears is the best answer but also an expensive one. I hope Rex's metal final gear proves to be an inexpensive solution.
The shoulder on the drilled out gear turned out to be too thin so I filled the gear cavity with solder instead of making a key. Now its pretty solid. I put it all together as shown in the picture below. I also tested it by pulling the motor/transmission assembly from my Connie and installing the metal gear axle. It ran fine although I was a little worried that I might have been off center a little with my soldering job. It doesn't spin fast enough for my lack of machine tool errors to cause problems. If it were running at 30,000 rpm I might have had a problem.
Anyway it works, its cheap ($5.65 for two gears), and all it took was some time.
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