Most of the members of the Sundance Central have converted their locomotives to battery power so that multiple trains can be run on our two loops of track. After the NMRA Regional Convention in Ocala, I decided it was time to follow their lead. I contacted Jonathan at Electric Steam and Model Works, and ordered an Airwire system including batteries and charger. He has done a Bachman Connie conversion before, and was very helpful when it came to product selection. The Sierra Soundtraxx, Phoenix 2K2 or P-5 sound systems work well with the Airwire system, and there are detailed instructions and diagrams included with the Airwire system on how to hook them up.
I will start with the tender where all the circuit boards and batteries will be located. The tender shell is held in place with two screws and two tabs, so it is very easy to remove. The first step is to remove all track power pickups from the wheels. I clipped all the wires going to the trucks, and then removed the spring wipers on the tender axels. The screws that hold the wipers in place, also hold the brake shoe assemblies to the truck side frames, so don't lose the screws and replace them after the wipers are removed.
I built a speaker enclosure out of styrene to project all the sound out of the tender shell. As you might remember from previous articles on sound systems, speaker enclosures allow for more sound projection from the front of the speaker. Tender shells are good enclosures, but in this case the possibility of having to drill vent holes in the tender floor would interfere with the shell as being a good sound chamber.
I next wired and installed the switch that Airwire requires to disconnect the throttle from the battery during charging. This switch also disconnects the sound system so that it will not be damaged during charging. Airwire recommends #18 gauge wire from their battery pack to the throttle board. The battery pack built by Airwire fits into the rear of the tender perfectly. It produces 14.4 Volts at 4200 MAH, and consists of 12 NIMH cells. This is plenty of power for the Bachman 2-8-0 with lights and sound.
I built a bracket out of styrene to hold the Airwire board above the tender deck for good air circulation. The instructions say that the transistors can get very hot during operation, and proper air flow is a necessity. I did not drill any vent holes, as there are several under the board from where I removed the power pickup wiring harness for the trucks. The board is held in place with double sided foam tape. There is an antenna on the Airwire board that must remain vertical. Since the 2-8-0 tender is rather low, I had to drill a hole in the coal load next to the tool box so that it could stick up through the tender shell. It is not really noticeable, and its position important for proper performance.
I have a Phoenix P-5 sound card which will be installed next to the Airwire board, but on the tender deck with double sided foam tape. This board is connected to the Airwire board for power and sound function operation. Once again both Phoenix and Airwire provide instructions and diagrams on how to install and hook up everything. The P-5 sound board is designed primarily for DCC operation, and as such has only two inputs for reed switch triggers. One is for primary chuff and the other is for secondary chuff, such as a Mallet. Because the P5 board is so small, Phoenix has put connection plugs on all the wires for speaker, volume switch, computer jack, etc. which makes hookup simple. The Airwire controller has assigned buttons for all sound functions on the P5 board. These functions include Headlight On/Off, Manual Whistle, Crossing Signal, Bell, Clank, Coal Loading, Water Fill, Volume Up, Volume Down, and Blowdown. This provides greater control over these functions than if you were using voltage or reed switch triggering.
There is a four pin plug that connects the locomotive and tender for power, there is also a two pin plug that is connected to the chuff trigger on the locomotive. All the connections were cut in the tender when I removed the wiring from the truck pick ups. The battery power leads were connected to the Airwire board per their instructions. The two leads for the tender backup light were cut from the original wiring harness and connected to the Airwire board which has directional voltage sensors to control the headlight and backup light. With LEDs, the lead with the resistor is the positive lead, and the other wire is the negative lead. If you hook them up in reverse, the LED will not light, so check this before you do any soldering or make permanent connections. I ran a test with the battery turned on, and all sound functions worked perfectly. The motor ran in the proper direction, and reversed when the switch was pressed, so I knew that all my electrical connections to the tender were correct. Since the four pin plug is for power to the motor and firebox flicker, I found that I could not use it to control the headlight. I decided to use the two pin plug from the chuff trigger for headlight power control. This plug was rewired and then connected to the Airwire board. I now faced the problem of opening up the locomotive so that I could rewire the headlight, and at the same time keep the firebox lights flickering.
Based on some e-mails and phone conversations with Dave Goodson on the West Coast, I learned how to open up the locomotive. I was a little bit hesitant about this portion of the project, but it had to be done. The first step is to lay out some packing tape to hold the screws in the order that you have removed them. The deck braces must be removed. They are held in place by four very tiny screws ( thus the tape to hold them). The firebox pan is held in place with four small screws and must also be removed. Remove the lead truck, and take the single screw out that holds the front of the boiler in place. There are four screws in the firebox that hold the rear of the locomotive to the frame, and they must be removed. Now the tricky part: Locate the reverse gear on the engineer's side of the locomotive. There is one screw that holds this part in place which must be removed. It is a shouldered screw which of course is not magnetic. The boiler will now come off the frame. While the firebox bottom is open, remove the plug from the circuit board. This eliminates power pickup from the drivers which you want to eliminate when going to battery power.
I pulled the the smokebox front off and located the two wires (one also has a resistor) that went to the headlight. These were cut from the wiring harness and new longer wires were soldered to them. These wires were then passed through the boiler and dropped out of the hole where the motor fits into the boiler shell. I had to grind out the hole on the back end because the motor is a tight fit, and would not allow the wires to pass through. I then unsoldered the leads from the chuff trigger, and attached the headlight wires to these leads. I once again tested the the polarity of these leads to make sure that the headlight would work. The next step was to reassemble the locomotive and tender hoping that I had not lost any screws and that everything would fit back in place.
The tender was a tight fit due to all the extra wiring, but it finally closed and the two screws were attached to hold the shell in place. The locomotive was placed on a test track, and all functions were tried to make sure that everything worked properly. While the conversion was extremely successful, I can't thank Jonathan from Electric Model Works (Airwire), John from Phoenix, and Dave Goodson from Northwest RCS who patiently helped me with installation and programming of the system.
Note: The Airwire system does not like humidity. I left my tender out on the table of our covered lanai overnight. It was extremely muggy out due to rain in our area. When I turned the system on the next day, I got a loud squeal out of the throttle, and all functions ceased to work. I brought the unit into the house and after several hours in the air conditioning, it worked just fine. Heat does not bother the system, but high humidity does.