​Introduced 1987-89, these models, which were manufactured by Kato and sold by Atlas, have excellent mechanisms and are great candidates for S-CAB battery power and radio control. The cast metal frame is heavy enough for traction, but leaves space above the motor for electronics and battery. With some careful trimming of the body shell, this space can be extended the full length of the loco. The completed installation (photo left) shows no evidence of any modification to the loco.

​This description illustrates use of a circuit board (sometimes called a "motherboard") to simplify installation and complete as much work and testing as possible on the workbench. Wiring within the loco is minimized by mounting front and rear lights on the components circuit board. As a result, there are no wires connected to the body shell, which can be removed and replaced without restriction. The project involves modification of the loco body and frame, assembly and test of two subsystems and finally, installation.

​Traces on the loco interface circuit board are used for rail pickup connections to front and rear trucks. If convenient, motor connections can also be to this board, which makes a total of 6 wires (2 to each truck and 2 to the motor) to be disconnected should it ever be necessary to remove motor or trucks. 

​The component board sits on top of the interface board and is held in place by electrical tape.

Since LED lights are mounted on the components board, there are no connections to the loco body, which simply slips into place to complete the installation.

I occasionally hear from an S-CAB user (Michael) who models On3. Since he's an innovative guy, as well as a skilled modeler, his feedback is always interesting. His latest effort is an S-CAB radio and BPS battery power supply installation for a Climax loco.

Here are Michael's comments:
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Thought you would like to see my latest car (trailing) for the battery and BPS electronics board. The decoder/wireless/speaker are in the Climax but I need a car for the battery etc.

You will note the two pipes (lower left with the chain over the pipes) – these are for power to the loco – there are two small plugs on the loco on the same side, so thin wires will do the connection.

Also, on the top rear of the tank are two small pipes – one higher than the other – these are the recharge points.  Just plug in the power supply and the recharge will start.  The tank is not firmly secured on the flat car just sort of held in position with the chains.  The barrels etc are glued down.  The chain (not glued) at the back is part of the chain keeping the tank in position.

I have two magnetic reed switches (the ones you supplied) glued up at the top inside both ends of the tank. So I just wipe with the magnetic wand for start and stop. 

In the background is another battery car – the tank.

This is a complete battery power, radio control, sound installation in a Bachmann On30 Forney. The entire system fits under the coal load with the battery barely visible where it protrudes on the floor of the driver's cab.

Since this model already has a factory-installed non-sound decoder, the hope is that installation can be simplified by use of existing wiring to motor, headlight and driver wheel rail pick-ups. It's also convenient that the fuel bunker is a separate molding attached to the frame by 4 screws.

Begin by clearing the clutter and planning efficient use of available space. Laying the battery flat on the loco frame and using space in the cab accommodates a 500 mAh battery. Obviously, the speaker must be mounted elsewhere. Internal space within the fuel bunker is 40 mm long, 40 mm wide and 22 mm high. Since the battery is approx. 6 mm thick, the challenge is to fit a sound decoder, S-CAB radio receiver, BPS battery power supply and speaker in the remaining 16 mm above the battery. Several arrangements are possible, but I eventually decided on a major rework of the BPS circuit board to make it a "middle layer", with radio receiver and speaker mounted at the top of the assembly. This gives good speaker acoustics and keeps the radio antenna clear of metal surfaces and wire tangles.

BPS has 2 standard arrangements. The long configuration can be cut in half and the 2 halves mounted back to back to form a short configuration.

BPS-L
This is the standard, one-sided BPS circuit board 

​At this point we have an installation plan and a modified BPS circuit board. Let's determine if everything fits.

What to do with a tangle of wires is often considered too late in an installation. For this model, the entire installation must fit a space measuring 1.575" square (40 mm) and 0.79" high (20 mm). The planning process included component placement as well as arranging wires to minimize both quantity and length while still being able to make the required connections. The final arrangement is illustrated below. There are 3 unused decoder function outputs (green, yellow and brown wires) where leads have been shortened, but are still accessible for (unlikely) future use.