Bachmann 4-4-0 decode with Train Control Systems M1 decoder

Space

Not only is this a small engine because it is N scale but it is a REALLY small engine because the motor is in the tender.  There is literally NO room on the inside of either the tender or the engine for any size decoder.  I elected then to put it outside, but where?  Well, the coal pile can be any reasonable size you want it right?  So, I elected to put hide it in the coal stack which was just molded on coal anyways.  As I was carving away I thought, hey, wait a minute, this things not a coal burner. The shape of the smoke stack tells us it is designed mostly for wood as its fuel.  This is even better because wood can be piled very high and will look very cool.

Fitting

Placing the decoder in the area where it was going to be mounted, I marked the surface of the coal pile to be ready to cut the shell.  You must remove the face weight that surrounds the shaft, the motor, trucks (watch those springs!) and the bottom conducting plates that pick up from the trucks and distribute to the motor brush contacts. Carefully use hand tools to remove the excess plastic.  You are committed now.

Wiring

I went to bed several nights dreaming of how I was going to solder to the motor brush leads.  It wasn’t as hard as I imagined but it wasn’t as easy as some other things I’ve done either.  We use a very fine tipped soldering iron that has a controlled temperature tip.  Whenever you get in a soldering situation like this it is best to start with the lowest temperature, pre-tin both surfaces or wires and use a liquid flux (like Tix brand) to make the soldering go quicker.  Never hold for longer that it will take to do the job and my rule of thumb is never more than 10 seconds at a time.

Gray and orange wires are connected directly to the motor brushes.  Testing the leads with a bench DC power supply, the orange wire goes on the same brush that will make the engine go forward when it is connected to the positive lead on the supply.

The decoder should be right on top of the motor now and no extra gray or orange wire.  Pull the red and black wires through the holes where the contacts came up through the body to connect to the brushes.  Next we removed about two thirds of the contact that touches the motor brushes.  Then solder the red and black wires to the motor contact plates.  Make sure the wires are no longer than necessary.  There is no room in the tender for excess wire.  There is also no room for shrink tube, so, make sure the connections don’t touch.  This is instant death to the decoder.

Do a short test with a meter if you can.  Put the motor into the tender and try and pack it up.  Put it on the track and do a running test without the lights connected.  This was easier said than done.  When we packed it up the wires didn’t quite fit under the weight.  I bowed the plastic.  So we had to shave the weight to make the wires fit.  
Next we were ready for the lights.

We used an N scale yellow-white micro LED (2mm x 3 mm) from Ngineering.  Soldering wire wrap (.010in. dia.) wire to the two leads.  Instructions say “no more than 260C(500F) for 3 seconds”.  I read this after burning one up!  Don’t know how you would do this without a temperature regulated iron.  Next, drilled about half to two-thirds of the way into the plastic molded front lantern with a drill that matched the lens size.  Then drilled two .025 inch diameter holes in the back (had to allow for the insulation), vertically, to allow the LED to stand upright in the lantern.  There wasn’t room for any wires.  The body was plastic and the body grab rails on the side were metal. They went the length of the body so… We used the rails, one on each side to transfer the electric for the light.  This was wire wrap wire so we wrapped the wire around the front of the rail and were planning to solder to the back, near the cab.  When we finally got it together though, it was too risky and not enough room to solder and then pull back into place. We just used touch or mechanical joints at the cab.  Now we need a resistor.  The LED is a 3.4v, 20ma device.  Doing the calculations: E=IR or R=(13.3volt supply-3.4volts LED)/.020amps we get 495 ohms.  We use a 510 ohm resistor for most of our LED connections so this was almost as good as you can get.  The problem was that our 510 ohm resistor was about as big as our entire decoder.  We could have used a surface mount resistor if we had one.  The closest surface mount was 470 ohms and we felt that this was just too small and would make the LED to be warmer thereby shortening its otherwise almost infinite life.  We decided to put it in the cab but had to machine the weight there to make it fit after visually trying out the possibilities .

Testing

We bench tested the light before we tightened it all up.  Boy was it bright!  We tested just the tender on the rails before putting the package together.  Hint, leave the drive shaft off.  We didn’t and almost tore it up!  Oops!

 

 

Program

Ready to put it on the programming track.  Will be number 82.  Will also put into it some momentum: CV3 and CV4, a value of about 3 to 6 depending on response.  This is a TCS decoder.  We will be putting in a value for the front light to tweak it for steam (dynamic) and LED optimum.  We will also be tweaking the values for the motor to give it great slow speed response.

Finish

Left to do:

1. Repaint the tender to match the cab.  Some of the paint is wearing off from handling.
2. Paint the wires black to resemble hoses and cover up the wiring at the front light.
3. Fill the open spot over the motor in front of the decoder with styrene.
4. Paint some round hardwood toothpicks a brown/black/gray mix to resemble bark and then cut into fourths and approximately 2 scale feet in length and then glue over the decoder area.
5. Left the yellow wire intact, terminating in the cab on the left side for future red LED firebox light (?)
6. Probably before I get to the previous item, paint #82 on the cab sides and “Train Buddy” on the tender sides.  (in gold of course!)