Recently I have been upgrading my non-sound decoders to sound.
The latest version of the SDXH167D sound decoder apparently has better speakers than the previous units.
Also, it comes factory loaded with the ALCO RS1 prime mover and horn sounds. Mountain Subdivision Hobbies has them for $47.97 (+S/H).
I definitely recommend re-motoring.
With DCC the need for flywheels is not as great for smooth running, which leaves more space under the shell for a decoder and speaker.
A-Line/Arrow Hobby offers many options to replace the tube driveline with plastic or metal driveshafts and couplers.
Measure the diameter of the drive shafts from the gear towers to find the couplers that best fit your situation.
I found a digital caliper at Harbor Freight that measures both standard (SAE) and metric. The SAE measurements can be read in both digital and fractional formats. Looking at the photos you posted it appears that the trucks are isolated from the frame with those red fiber washers.
Not knowing if the frame is an electrical path might make isolating the motor/trucks more challenging.
An update on this. It turns out I had a Soundtraxx Econami ECO-PNP diesel decoder from when I did some Stewart loco converstions. I was able to use lead sheet weights to get the motor at the same level as the gear shafts and use silicon tubing to connect to the gear shafts.
Current idea is to use the ECO-PNP decoder and mount it on a strip of Evergren styrene and mount that on top of the flat motor using silicon sealant.
Question: how to mount the decoder to the strip of styrene? This is a plan PCB with no protective wrapping. I have seen other threads that mention using Gorilla clear mounting tape. I’m concerned the tape or whatever adhesive I use in damaging or shorting out the decoder.
Using a multimeter, set to the continuity (beeper function, will help you “trace” the electrical path from the wheels to the wires attached to the top of the gear towers.
Another option would be to use Stanton-type, self-powered trucks.
These can be found a Northwest Short Line; HO Stanton Drives.
It’s a more expensive option but it vastly simplifies converting to DCC as each truck is a self-contained unit drawing power directly from the decoder- -no need to upgrade the motor or drive line and eliminates the gear noise.
Keep us appraised of your progress, and as always…
It was probably me that recommended the Gorilla mounting tape. It comes in a 3/4" wide roll, which you can cut to length. And it has a rubbery silicone consistency with adhesive on both sides. Holds very well and won’t degrade.
Personally, I would skip the styrene strip and mount the decoder directly to the top of the flat motor housing using the Gorilla mounting tape. It will also allow for better air circulation around the decoder.
Before figuring out how to attach your decoder of choice I strongly recommend replacing the plastic/rubber tube drive line with solid shafts and press-fit couplers available from A-Line/Arow Hobbies, Repowering Parts.
These kits have the option of metal or plastic drive shafts that you can cut to length.
The torque produced by the motor and the resistance of the gears might twist the plastic tube creating more problems.
Before mounting your decoder of choice I would pre-wire the decoder and solder the wires rather than using the unreliable slip-on connectors.
If you do decide to use the slip-on connectors I definitely recommend tinning the ends of the wires.
Have you identified the electrical path from the wheels to the screws on the gear towers?
Is the frame used as part of the electrical path to the old motor?
Not properly electrically isolating the motor will fry the decoder and possibly damage the new motor.
Have you considered mounting the decoder on the underside of the shell?
Since you are considering adding LED lights there would be wires from the decoder to the shell; White-F headlight, Yellow-R headlight & Blue-common.
Mounting the decoder to the inside of the shell there would still be wires running from the decoder to the gear towers (electrical path from the rails) and the motor; Red-Right Rail Pickup, Black-Left Rail Pickup, Orange-Motor Positive, Gray-Motor Negative.
