SP Jawbone Branch (Part 45) - DDC Control Planning & Engine DCC Ponderings

Time for a quick update on my electrical planning and DCC command system for the Jawbone Branch.  Until now, all testing was done with straight DC power from an MRC 1370 throttle.  I hadn't bothered to hook up the DCC system to the layout yet.

First DCC Engine at Owenyo!

SP 5301 is the first DCC equipped engine to be test run on the Jawbone at Owenyo on March 12, 2024.

The NCE PowerCab system, while allowing walk-around with the command station throttle, doesn't allow it to be unplugged at any time.  So my plan has always been to keep the 'hammer-head' PowerCab throttle plugged into the Mojave Yard throat area, where the heavy restaging switching will be done.

March 2024 DCC plan and cable connections.

Originally, my plan was to use a tethered throttle, such as NCE's 05 or 06 throttle to walk-around the layout for the road job around the room to Owenyo, unplugging and replugging as the train progressed. However, the challenge of rigging the phone-cable command and throttle power bus between each module and across the east doorway will be a bit of a pain, requiring more hardware and connectors.  I've talked it over with a couple of friends, one of whom offered me a 05/06 radio throttle for the road crew to use.

I didn't plan to use a radio throttle system, as the layout's not that big, however I'm now reconsidering the merits of a radio throttle in terms of the cost savings of the layout wiring and additional connections between the modules.  For the cost of the radio base station, not command station, I could jump straight to operating the layout, with only the track power bus wires through my already planned Molex Pin connectors between the modules, which will also handle the LED strip lighting for the staging yard and any under-layout lighting I need, over the workbench below Mojave mostly.

Yes, I still need to finish running the rest of the wiring for Mojave Staging Yard, lighting wiring, etc through the Molex connectors.  I was planning to do that later last year, but as I discuss in the next section, I wasn't able to do gripping, stripping wires, and crimping of cables in the later part of 2023.  So now it's mid-2024 before I'll be able to get back to the wiring again.

Time to DCC the Jawbone's Engines?

For the last six months, since my trip to Owenyo, the following my right thumb's tendon flame-up, which has made basically any modeling or machinist work exceedingly painful. I've not been doing much on the physical Jawbone Branch construction or the models.  A bit over three weeks ago, I received an injection to my thumb to try to get the swelling under control and permit better healing.  I have to wait a total of six weeks, and then see how it's doing.  But I'm hoping that in a few weeks time, I can start dipping my toe back into doing some gentle modeling work again.  

Hopefully soon I'll be able to DCC a Mike or two, like the SP 3203, so I can run them around at Owenyo!

I don't feel I really need sound, but subtle sound would be nice on the single-engine trains that will be the regular operations of the Jawbone branch.  Hopefully, I will include being able to get DCC sound chip installing and setting up of at least one or two of my Mike's for the Jawbone Branch, now that I could run them on DCC!  I've been planning to use ESU LokSound 3.5 decoders that I bought from a friend as new-old stock back in 2018.  I was also able to get some 100-ohm Bass Reflex speakers from Railmaster Hobbies to use with the older decoders (modern decoders use higher power 8-ohm speakers).

DCC Settings on the Engines

I really don't need much of the functions of the modern decoders, or the extra channels for sound.  Plus I still have the LokSound 3.5 custom sound programmer and software to map the sounds how I want them.  The v3.5 decoders were also about the first decoders that had good quality B-EMF reading of the motor so that a sound cam on the drivers or axles wasn't required. i.e. if the engine slowed or stalled, the sound of the exhausts beats would also correspondingly slow or stop. The B-EMF would also help adjust the volume of the engine's exhaust beats as the engine works upgrade or backs off to a softer volume as the engine is drifting down grade.  I don't know how much this will be noticeable on the 1.25% grades that I'm planning to use on the Jawbone, but I can always mute the exhaust only for times I really want to drift downgrade.  However, unlike operations at LMRC, the prototype sections of the Jawbone that I'm modeling are much flatter even than 1.25% grades required by the no-lex design that I'm using.  So having the engine lightly working most of the time on the prototypically nearly flat Owens Valley, would be appropriate.

I will have to see how much momentum I can stand to have in the models while doing all the switching at the various towns, I may choose to have much more acceleration momentum, so that the decoder will realize that the lag and make the starting exhaust louder.  Switching with excessive deceleration momentum on selectively compressed layouts has always been my main concern with being able to get models to stop and not just over-run the mark, shoving cars out the end of a track, etc.  Yes, I plan to have effective wheel stops/tie bumpers, etc and containment to keep cars from getting off the layout if they were to run hard into an end-of-track situation.

In Closing

I am planning to write a blog post covering the installation of DCC decoder, speaker, lighting, boiler weights, etc to the Mikes, as I've not done any DCC installs since starting this blog.  

Showing example of "tight" wheel gauge, in this case a GGD sample coach from 2017.

One of the other challenges to getting any of the steam running on the branch is that I still need to regauge the drivers and wheels for operation on the Jawbone Branch. - Many older brass models have 'tight' gauge by about 0.015" to as much as 0.025" on their wheels and drivers, which will cause issues on my properly gauged hand-layed switches, binding up on the guard rails or derailing.  Many pre-built switches on the market have extra narrow gauged guardrails which can take the narrower wheel gauges from ~30-40+ years ago.  Also with my hand issue, I've not been really wanting to do the regauging, as it is risking making my hand injury worse.  I'm sure I'll be using some wheel-puller jigs when I do get around to doing the gauging work.

Jason Hill

Related Articles:

Jawbone Branch Engine Roster - All the engines I plan to one day have available for operations on the Jawbone Branch.

Modeling SP 3266 (Part 1) - History and Fixing Frame Damage - Starting work on my 3266 conversion by fixing some broken frame solder joints.

Modeling SP 3266 (Part 2) - More History & Installing Clam-Shell Smoke Stack - Time to refit the 3266 to have the clam-shell smoke deflecting stack.

Modeling SP 3266 (Part 3) New Drawbar Mount for Athearn-Genesis 120-C-6 Tender - Time to catch my 3266 up and modify the tender mounting on the A-G tender. - I stopped short of doing the DCC installation and doing the rest of the fitting of the boiler weights, speaker, etc in the boiler.

Modeling SP 3237 (Part 1) - Ex-Arizona Eastern Mk-4 - First look at the SP 3237 from a Sunset Models engine.  Clam-shell stack conversion, regauging the wheels, and DCC will be the next steps on this engine.