I have a Bachmann 4-4-0 that I want to switch to battery. Can someone show me photos or instructions on how to take apart the engine an a wiring diagram.
There are four screws in the firebox. Two towards the rear of the firebox, just forward of the rear driver, and two near the front, just behind the front driver. (One on each side.) That, and a screw that goes up from underneath the cylinders into the smokebox are the main screws that hold the boiler onto the chassis. You’re also going to want to remove the smokebox boiler supports on the front (really tiny screws into the pilot), and also disconnect the reach rod that goes from the cab to the reverse gear on the engineer’s side.
As for wiring, the locomotive is pretty basic. I don’t know that I’ve seen a wiring diagram like Bachmann has for other more complex locos. Basically, there’s a central board just inside the front of the boiler which takes the power from the rails and sends it to the motor, headlight and tender light (if equipped), as well as the smoke unit and firebox light. (I don’t think the loco has a cab light.)
Wiring for battery power, you have some options. Most folks just gut the factory electronics and wire everything directly to the decoder. That’s usually what I do. You can also opt to leave the central control board to control the lights if you want to.
As the loco comes from the factory, there are 6 wires running between the loco and tender. There’s a 2-pin plug that’s used for the chuff cam on the rear axle, and a 4-pin plug that carries track power forward from the tender, and (if equipped) power back to the tender light from the control board in the smokebox. If the tender has no light, then these two pins are not used.
What I’ve done on mine is to put all the control electronics in the tender. (Batteries, power, and sound.) It’s a bit tight in that tender, and you will probably want to remove the stock coal load and open the top of the tender up to give you just a bit more room (not to mention access to the battery). I use the 6 existing wires, and don’t need any extras. The chuff contact wires go to the sound board.
The two unused pins on the 4-pin connector (or the two wires that go to the tender light if it’s there) get used to bring power to the motor. Remove the noise-reduction board from the back of the motor, and just solder new leads direct to the motor terminals, hooking them to the wires going to the 4-pin connector. (If there’s a back-up light in the tender, you’ll power that from the electronics in the tender, so there’s no need to worry.)
The two wires that originally carry power from the rails get connected instead to the battery power going forward. I run this forward to control the lights in the loco. You can just run this to the stock board in the smokebox and you’ll be fine. (You will want to disconnect the wires going down to the track pick-ups in the loco and tender.) That will give you power to the firebox lights and headlight. I believe the headlight is directional, so if you’re keeping the stock board and you don’t get lights, flip the “NMRA/Large Scale” switch in the smokebox. This reverses the polarity of power going to the PC board. Or, you can gut that board and just wire the headlight directly to the power coming from the decoder. The headlight is an LED (typically yellow or orange), so I’d first replace that with a more suitable warm-white LED. If you’re keeping the PC board, I think the current-limiting resistor is on that board, so you can just swap out the LED and be happy. If you’re chucking the PC board, you’ll want to wire in a current-limiting resistor in series with the headlight. I use a 1K-ohm resistor.
That should get you started, at least.
Later,
K
(Edit - I forgot two screws behind the front driver towards the front of the firebox, so a total of 5 screws holding the boiler and cab to the frame.)
Welcome, we like pictures of.progress
Thank you Kevin for your fast response it is just what I need. I will start later today and will upload photos of my work.
Well I finally finished the installation of battery, rc and sound into the tender of my 4-4-0. I had to modify the tender deck and build a new load of wood. Thank you Kevin for furnishing directions on how to disassemble the engine.