I just finished my first sound decoder installation and wanted to share it. Eventually the mechanism is intended for a Whitcomb 70-ton shell. I have posted videos on YouTube. Search for n scale 70-tonner or follow the links below. Let me know what you think. Suggestions and feedback are welcome. Thanks for looking, Mark
Very nice work, excellent execution. I wish I had the confidence to be that neat in locomotives, always afraid I’ll have to go back in or change something so I leave a lot of slack
Thank you. There were several iterations before I took out the slack. No room in this one for extra wire.
For accuracy purposes, that's a GE 70-tonner, not a Whitcomb. Usually I dis on people for putting in sound at the expense of trashing electrical pickup by weight reduction, but jamming the speaker in the cab roof is as good as it's ever going to get. I'm assuming you trashed the Bachmann decoder as you should have. I'm not sure how accurate your sound is and I'm not sure it matters for an FDL6. The Cooper-Bessemer's were a bit of a flawed design anyway. I got to carbide around in the Montreal PQ railroad museum's 95-tonner a few years back, and taking it above the second notch on the throttle revealed the awful banging noises of completely worn-out main crankshaft bearings. That's a sound you don't want to hear! The unit has since been stored for display only, it was on it's last legs then. But if you want to hear one this is a pretty good audio pickup:
Thanks for the comments and sharing the video. I should have been clearer. While I started with the GE 70-tonner mechanism, I added the sound decoder with the intention of putting a Whitcomb 70-tonner on it. Building that shell is my next challenge. The Fox Valley Trolley Museum has one, Warren and Saline River #73. https://www.foxtrolley.org/Resources/Pictures/Cars/0073.jpg I believe it was originally purchased (1948) by Potlatch Forests for use in central Idaho. In The Camas Prairie, Hal Riegger wrote the original power was a Sterling V-8 which was later replaced. However, I don't know when or with what. After exploring a few sound files I chose one for a Davenport. Might change if I get better information. When I get back to the workbench I will try to provide a weight comparison. Adding the keep-alive caps did wonders for the reliability, but not much for the tractive effort. Weight will be a major objective when I build the shell. Actually, I scavenged a few parts from the original decoder. N scale version of the scrap yard.
Nicely done and congratulations on your first sound install! I see you put a resistor on the blue wire feeding the capacitor. I haven’t seen that done before. I assume that to limit the input voltage to the cap?
I followed Zimo's recommendation for the resistor. From the decoder manual, "This prevents any large currents flowing in/out of the capacitor...." Since I have only done this one installation, I cannot speak with authority on the subject. I did notice that Zimo's recommendations vary depending on the decoder family. Some do not need an external resistor. The manual also cautions, "The resistance of course also reduces the effectiveness of the energy storage device, because the voltage drop also limits the available discharge current...(as well as losing about 6V in the process)." In practice, without the caps the loco couldn't go more than a few inches before stalling or going silent. With the caps, no failures after several low-speed runs on my test track.
I have an update on the weight before and after sound installation. The good news it increased, 33.7g versus 32.4g. The bad news is that is not much change. I removed more than a bit of plastic and some metal to get everything in so I am happy to see an increase. Still looking for drawings to start the shell project. Anybody have drawings of a Whitcomb 70DE24?
Mark, Overall impressive! What's equally impressive is the slow speed characteristics of that Zimo decoder. They (obviously) had the correct sound file for this. Although, I'm not sure of their variety of American prototype sound files. Do you have a part number for this file and what speaker did you use. I had a B-Mann 70 tonner and on DC never ran like this! Again, well done....
Mike, Thank you! The sound file number is ZSP00144 - Davenport. It was authored by Heinz Dappen and is the 2015-05-22 version. (There are two Davenport files.) I used the Streamlined Backshop 8x12mm "Sugar Cube" speaker #4069. This model ran well enough on DC for me to tackle the project. It runs much better with the decoder. The keep alive caps made a very big difference.
Mark, Thanks for the info. I have had success with the SBS 8x12 speakers as well. Also meant to ask what part number on the Zimo decoder? This must be a very small "foot print"....
