For those of you who have followed this blog for a while you’ll perhaps be aware that all my locos are fitted with DCC decoders and that I use an NCE system to drive my trains. I have sound and lights in all my locos and wouldn’t have it any other way. In fact DCC sound was one of the prompts that pushed me to switch scales many years ago. I wanted to fit sound to all my locos at the time I was contemplating the scale switch and figured that getting a nice big speaker into an O-scale loco would be a lot easier than into an HO equivalent. I had decoders in all my HO locos but none were sound equipped and if I was going to have to start from scratch I figured I may as well do this in my new scale rather than go back and retrofit them into my existing HO fleet.
As I’ve worked on the 20 I’ve been planning and cogitating on the way I was going to install the decoders (I need two to get enough function outputs) and just as importantly the speaker. I’d been back and forth about where to put the speaker but I hadn’t contemplated the fitting on my standard choice (a small Jaycar speaker that is not longer available) of which I have a small supply salted away. This was mainly because I hadn’t considered there was sufficient room for this speaker in this model, that was until I was persuaded otherwise by my DCC adviser John. He convinced me to try fitting this relatively large speaker between the tanks and lo and behold the following is the result.
After I decided to go with John’s suggestion of fitting the larger speaker into the space between the tanks I had to mill a large slot out of the boiler. The speaker is enclosed in a thin styrene box the edges of which have two screw holes drilled through to allow the assembly to be secured to the bottom of the boiler. The decoder of choice is an ESU V4 but not the XL version. A decoder with a lower power rating will be more than adequate in this application. This will be supplemented by a TCS function decoder which, when added to the function outputs on the ESU decoder, will allow me to install the functions for two dual coloured marker lights front and back, a head light front and back, a glowing firebox and a cab light. I picked up the TCS decoder for less than $US20 by buying a five pack from Litchfield Station.
John has kindly offered to work out a wiring diagram for the loco which will probably look remarkably similar to those he produces regularly for articles appearing in 7th Heaven. You can get an idea of what this looks like at the Aus7 Blog. Most of his wiring articles are available as back issues and can be easily adapted to other locos with similar needs. All that really needs to be adjusted is the size of the vero board circuits. One of the things John tends to recommend is the use of multi coloured strap wiring in combination to the mini pin strips. I have a stock of these components too.
One of the challenges of this project will be to get these strap wiring run from the rear tank to the decoders in the boiler but happily a solution suggested itself today. There will be a need for 7 wires (or this may possibly be five) to run from the tank to the decoders and normally this would pose a challenge because the cab is in the way and there isn’t a great deal of room below the footplate to allow the wires to pass unobtrusively between the two. However the damage I inflicted on the rivet strip the other day left a small oblong shaped section exposed inside the cab that was just about the right width for the amount of wring that will need to pass along the loco. Upon examining prototype photos I discovered that there is a wooden inset floor in the cab that sits above this damaged area giving me a perfect mask for the wiring run that can easily pass under this wooden floor and will mask the wiring all the way from the tank to the boiler.
So the rear headlight and both marker lights will be hooked up to a vero board circuit as designed by John and the connection to the decoders will be made via a 7 line run of multi strand cable that will run unobtrusively under the wooden floor I’ll install in the loco at some point down the track.
I won’t be installing any DCC decoders or other wiring for quite a while but I am close to installing the light castings to the rear of the water tank and I also need to cut the slot in the bottom of the tank to allow the multi strand wires to run under the floor. Now is the time to do this, I don’t want to have to come back and chop up a painted loco later.