old style 70 ton diesel switcher conversion

[gmpender]

I am trying to convert an (old) Bachmann two motor 70 ton switcher to DCC, and have not found anyone, as yet, that has tried to get them running with in DCC. I already have the new Bachmann 70 ton engine and do not like it because it is very noisy. My old one does run very quietly, and for that reason I would like to try to get it running again in DCC. However, I would like to try to get the original two motored engine switched over to DCC rather than change it out for a newer model. Would you be able to help me in getting this done? Could you let me know the best way to go forward in getting this project done? I would like to do this on my own rather than send it in to have you work on it. I would need some assistance on how to prepare the loco for DCC. I would also like some information on if there is a standard decoder I can use that will not make the diesel loud when it runs. If you still have a diagram of this engine, that would help immensely as I bought it on line and do not have any of the paper work.
Could you help me with this project?
Thanks,
George Pendergraft

[railtwister]

Hi George,

The dual motored Bachmann GE locos were known for having problems due to weak motors, usually one motor would burn out, effectively relegating the loco to the scrap line until a replacement motor could be found. As for converting one of these to DCC, having two motors to control may pose a problem for the decoder which is designed for operating a single motor. Even if the two motors together don't cause an overload, having two of them could be a problem with any decoders using "back emf" motor control. before trying it, you probably should check with the decoder manufacturers to see what they say.

As for your newer version of the 70 tonner being a noisy runner, the noise may be caused by one or more of it's gears developing a split through the hole for the axle. This is a common problem with both the 44 ton and 70 ton models, and is currently being discussed in another thread on this group. If your loco has developed "split gear syndrome", it should be fairly easy to diagnose and fix, because the cracks are usually quite visible to the naked eye, and Bachmann has replacement wheelsets available. I have a 44 tonner which has basically the same drive, and I am impressed with how smooth and quiet it is, so I don't think your noise problem is the norm if the gears are good. Just be advised that some of the replacement wheelsets sent out by the parts department have arrived also split, so you need to place your order with a live person over the phone, and ask them to please inspect your replacements before sending them to you.

I think fixing your newer 70 tonner is a better option than trying to fit a decoder into your older unit.

Regards,
Bill in FL

[richg]

I have put a Digitrax DZ125 into a two motor 44 ton that is essentially the same design as the 70 ton. Just a little smaller.
I have an article from a 2001 Model Railroader magazine that showed the 44 ton install and should work for the two motor 70 ton.
My two motor 44 ton would have a brush hang up on one motor which "looked" like a burnt out motor. Touch the brush holders and the motor would run for a while. A continuity check with my ohm meter showed the motor to be ok.
Isolating the motor required me to remove the motor from the trucks, clip off the contacts and solder #30 insulated wire to the truck pickups. Solder wires to the motors and slip the motors back into the trucks. Follow the directions that come with the decoder.
My single motor 70 ton runs very nice and has sound. No cracked gear issues.

Rich