A Simple AirWire G3/Phoenix P8 Battery Conversion

Comments added 2/26/13:  It has been brought to my attention by several readers that there are errors in this article.  Specifically:

  1. The circuit boards should not be painted with primer.  Doing so may void the warranty and can adversely affect the ability of the circuit to radiate heat.  A better solution would be to encapsulate the boards with pieces of heat shrink tubing to hide them.
  2. Although speakers were not included with the Phoenix Sound Kit that I purchased, some vendors offer various options with the kit including speakers of your choice.

CHANGE LOG:  Added PROTOTYPE INFORMATION paragraph on 2/27/2013


The Bachmann Rail Truck provides a convenient platform for doing a simple radio-control, battery-power conversion.  It is a great starter project for a “sparkie” who may be contemplating coming over to join the dark side but is hesitant to tear into an expensive steam or diesel locomotive.  The large cargo area behind the cab provides plenty of room to place the electronic components.


The Rio Grande Southern Railroad, a 3-foot narrow gauge line in southwestern Colorado, always referred to their rail trucks as “motors.”  Motor #1 was built from a Buick “Master Six” four-door sedan in 1931.  This first motor in the line that eventually led to the larger motors (the Galloping Geese) weighed just 5300 lbs, and was only 20′-0″ long. Its engine developed 28 hp, and top speed was 30 mph (although 20 mph was more typical.)  Cost was $828.55.  It had a cab capable of carrying 2 passengers and a stake body in back for mail and other cargo.  The stake body was soon replaced with an enclosed cargo area and the passenger seating capability was increased to seven.  The original color was dark green or black – it is hard to tell from the old B&W photos.  All of the Motors (#1 through #7) were eventually painted silver.  Motors #2 through #7 survived to the end of operations in the early 50’s.  The Bachmann Rail truck is a fairly faithful representation of Motor #1 in its original stake bed configuation and is available in a variety of colors. 


I started by removing the simulated wood railings from the rear chassis.  I also took off the large black tool box containing the internal circuit board and switch.  I removed the yellow leads from the front truck and the red/black leads from the rear truck.  I also removed the electrical contacts from the front and rear trucks to reduce drag.  I used a rotary tool and cut-off wheel to remove the two metal posts on the chassis where the tool box had been attached.  This left me with a large flat space to install the required components.

Stripped Deck

I left only the two red leads going to the motor, and the three pairs of green/black leads going to the two headlamp LEDs and the single tail lamp LED.  Check the factory wiring on the Rail Truck before you start clipping wires – the actual wire colors and connections on different production runs of Bachmann motive power often differ from what is shown on the Bachmann furnished documentation.

For some excellent tips and tricks on optimizing the performance of the Rail Truck and other great information, see Greg Elmassian’s and George Schreyer’s Rail Truck  pages at




I used an AirWire G3 DCC Decoder Board and a Phoenix P8 Sound Kit.  Since the Rail truck has a low stall current you could go with a less powerful DCC motor/lighting controller and smaller sound controller to save a few bucks.  However, I wanted to experiment with the new G3 and utilize the impressive Phoenix sound library.


The G3 is at the bottom of the photo.  The P8 is above it on the right.  I also used a 14.8 volt battery and a couple of QSI large oval speakers.  The two black boxes are enclosures for the two speakers.

The G3 receives the radio commands from a hand-held wireless throttle and processes the motion, lighting, and accessory commands.  It passes the DCC packets on to the P8 which processes the sound commands.

The external antenna on the G3 will be hidden under a tarp covering the electronics.  If extra range reception is needed, the antenna can be routed through a hole in the tarp and extended vertically above it.  I didn’t find it necessary to expose the antenna and it responds well at distances of over 100 feet on my layout.  Your mileage may vary depending upon your electrical interference environment and the transmit power settings of your wireless throttle.  (I used an AirWire T-5000 throttle at the factory default power setting of 5.  I also tested the reception using an NCE G-Wire ProCab throttle at its default factory transmit power setting with equally good results.)


Here are the items I purchased for this conversion.  These items are generally available from multiple sources.  The Rail Truck is often available at deep discounts on some of the auction sites.  The suppliers listed are the ones I used and highly recommend.  Prices shown were current at the time of posting.

  • Bachmann Rail Truck, Silver, Reindeer Pass, P/N BCH83295, $119.89, http://www.reindeerpass.com/
  • AirWire G3X DCC Command Control Decoder, external antenna with terminal blocks, Reindeer Pass, P/N G3X, $139.89
  • Phoenix P8 Sound Board Kit, no Speaker, with programming jack and volume switch, Reindeer Pass, P/N P8SOUND, $167.89
  • Cordless Renovations Lithium-ion battery pack, 14.8 Volt @ 2800maH, Reindeer Pass, P/N CR1600B, $54.89
  • Fuseholder, In-line, 20AWGx6 inch, 5mmx20mm Fuse,Jameco, P/N 109330, $0.69, http://www.jameco.com/
  • Fuse, 250V, 5×20, 3.15 Amp (GMC), Slow Blow,Jameco, P/N 197482; $0.39
  • Toggle Switch, DPDT Center off,Jameco, P/N 21952, $1.95
  • Toggle Switch, SPST,Jameco, P/N 72161, $1.49
  • Battery charging jack,All Electronics P/N DCJ-21, $2.20, http://allelectronics.com/index.html
  • Resistor, 680 Ohm, ¼ Watt, 3 required, available from multiple sources, approx. $0.10 each
  • Speaker, QSI, 8 Ohm, TDS Large Oval, 2 required, Tony’s Train Exchange, P/N TDLGOVAL, $9.95 each, http://www.tonystrains.com/
  • Speaker Enclosure, for TDS Large Oval Speakers, 2 required,Tony’s Train Exchange, P/N TDS, $6.95 each


I drilled a 7/32” and a 15/64” hole for the two toggle switches and two 5/16” holes for the jacks in the rear chassis.  I installed the switches and jacks as shown.  Exact placement is not critical.

Switches and Jacks Mounted

Deck Underside

I peeled the paper label off of the battery pack and spray painted it with brown primer.  I also used the same primer to paint the nylon fuse holder and circuit boards.  I covered the connectors on the boards with masking tape before painting.

Painted Components


I positioned the battery pack immediately behind the cab with 3-M double-stick tape.  The tape also holds the wires coming from the headlamp LEDs and the motor to the deck.

I attached pair of 6” long wires to each oval speaker.  I drilled a 1/16” hole in the bottom rear of each enclosure for the speaker wires.  I inserted a speaker into each enclosure and covered the enclosures with black fabric.   I mounted the enclosures on the chassis as shown with a dab of silicone.

The P8 board is mounted flat on the chassis aft of the battery with double-stick tape.  I made sure that the tape completely insulated the underside of the P8 from the deck.

I glued a small wood block to the chassis deck and attached the G3 board to the top of the spacer block with double stick tape.

Components Mounted on Deck


Normally, I like to color-code my wiring for easier maintenance.  Since much of the added wiring is exposed, I used black wire to make it less noticeable.  The exceptions are the existing Bachmann wires from the motor and LEDs, the Phoenix wire harnesses that came with the P8 sound kit, the battery leads, and the fuse holder leads.

Since the current draw is low on this model, I used AWG #24 and AWG #26 wires for the added wiring.  These wires have a rated ampacity of 3.5 Amps and 2.2 Amps, respectively, when used for chassis wiring.

Here is a schematic to show how I wired the components.  The black dots represent solder connections.  The circles with an “S” represent screw terminals.  The circles with numbers represent terminals on the Phoenix sound kit connectors and wiring harnesses. The white circles are existing connections where the wires were already attached to the component.  I covered the soldered wire connections and resistors with black heat shrink tubing.


The GRAY wire on the C1 wiring harness that comes with the P8 sound kit is not used.  I clipped the wire off as close as possible to the connector.

I decided not to use C2 wiring harness that comes with the P8 sound kit.  This harness has three wires attached to a SPDT momentary toggle switch which can be used to raise or lower the volume of the sound system.  The harness has additional wires that can be routed to reed switches for sound triggers if you use track magnets.  I control the volume and trigger all sounds with DCC commands from the wireless throttle.


I turned the RUN/OFF/CHARGE switch to the RUN position and turned on the P8 power switch.  I programmed the G3 decoder board from a wireless hand-held throttle (AirWire T5000 or equivalent) per the G3 User Manual.  I selected one of the lower 8 frequencies from the 16 available on the G3 to allow me to run it with either my AirWire T-5000 or my NCE G-Wire ProCab wireless throttle.

I set both the G3 and the P8 decoders to the same loco address.  On the G3, I set CV 60 to a value of 6 so that the headlamps and tail lamp were always on whenever power was applied.  The lights are turned on and off with Function 0.

I connected the P8 programming jack to a USB port on my PC and downloaded the Galloping Goose sound set and the “ahh-ooga” horn (PC and Phoenix Sound Computer Interface required.)

The G3 and the P8 share CV numbers 49 through 53.  Sending programming commands, OPS or SERVICE, to one decoder will program both.  I did not use these CVs so there was not an issue.  If you need to program these CVs, program them on the P8 first.  Then turn off the power to the P8 and program the same CVs on the G3.

The G3 User Manual has a page of Operation Tips for using the G3 and P8 together.  I used the Phoenix computer interface to set the P8 effects and function key assignments per these tips.


I made a simulated canvas tarp to cover the cargo area from a piece of cloth painted with acrylics.  I added simulated tie-down ropes made from thick thread.   I repainted the Bachmann driver figure with acrylics and used an India ink/alcohol wash to bring out the details.  I attached him to the seat with a dab of silicone.  It is much easier to position the figure on the seat if you remove the cab (two screws under the frame.)  Removing the cab also gives you a chance to detail and weather the interior if desired.

Painted Driver

I brushed over the shiny aluminum body portions and roof of the Rail Truck with Slate Gray acrylic and let it dry overnight.  The next day, I scrubbed off most of the gray paint with a stiff bristled nylon brush dipped in a mixture of India ink and isopropyl alcohol.  This gave the body a well-used and faded appearance.

I weathered the underside of the frame, the running gear, and the engine compartment with dirt and grime using acrylics.  I added “rust” to the exhaust pipe, muffler, fuel tank, air ballast tanks, radiator, wheels, and front bumper.  I gave the exterior a final weathering using powdered pigments applied with a soft brush.  I gave the entire vehicle an over-spray of clear flat acrylic to seal the finish and the Rail Truck was ready to go to work earning its keep.  Here is the completed model.

Completed Model


This conversion was relatively easy, although perhaps a bit more expensive on the electronics side than some other conversions I have done in the past.  This is probably due to (1) using two separate DCC decoders, and (2) using strictly “off-the-shelf” components rather than making some of my own from scratch.

However, I wanted to do a simple conversion that most folks could follow without requiring any special electronics skills.  Also, since I have used QSI Magnum and Titan decoders with G-wire receivers for all previous battery conversions, I wanted to try something different.  This project allowed me to get some “hands-on” experience with the AirWire G3 and the Phoenix P8 decoders.

Total time to build was about four hours.  The model runs great and I am very pleased with how it turned out.  The dual speakers sound really nice. The available Phoenix “Goose” sounds are fantastic.  I especially enjoy listening to the motor cranking sequence that replicates starting a motor with an old six volt auto battery.  The transmission gear changes are perfect.  The ahh-ooga horn is a true delight.

Run time with the 2800maH battery is far more than I need for a typical operating session, so I don’t have to charge the battery as often.  Since I have plenty of power available, I am contemplating installing a smoke generator to simulate how prototype rail trucks often overheated.  Besides, the output from smoke generators looks more like steam than smoke anyway.  The G3 has a dedicated smoke driver output – I might as well put it to use.

I’m also toying with the idea of using some of the G3’s auxiliary lighting function outputs to power some figure animations using muscle wire or servos – perhaps having the driver wave or turn his head as he drives by.  We’ll see.  There is some unused space under the seat just begging to be used.  If I make changes, I’ll post a follow-up.

I might do another similar Rail Truck conversion using the AirWire CONVTR module, a SoundTrax Tsunami TSU-1000 decoder, and a smaller amp hour battery pack.  This would lower the total cost and reduce the size of the electronics package in the cargo area.

All-in-all, this conversion was a good chance to play around with an AirWire/Phoenix lash-up (a first for me), and to get a feel for the G3 and P8 capabilities.  I was extremely impressed with both and plan on using them for additional conversions in the future.  It was fun – hope you enjoy the results.

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