Radio Control and Battery Power for Model Railroads
  • Home
  • News
  • Battery Power
    • Batteries Explained
    • Battery Care
  • Radio Control
  • Price List
    • Contact Form
  • Quick Start
    • Getting Started
  • Documents
    • Hints, Comments, Notes
  • Neil's Blog

Full S-CAB Installation in On30 Forney

8/3/2016

 

Project

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.
Picture

Preparation

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.
Picture
Lifting the lid, we find a relatively large circuit board with a standard 8-pin decoder socket, decoder and speaker. None of this is reusable, but the expected 6 wires are nicely accessible, despite non-standard color coding, which fortunately is labeled on the circuit board.
Picture
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.
Picture

Modified BPS board

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

Because the Forney space is square, 2 halves of the BPS board are arranged side-by-side, wired with a few extra connections, and glued with epoxy, which was never considered in the original design. I remember something about "necessity being the mother of invention". It's not something I expect a user or even an experienced installer to attempt, but having done it for this project, it could be a special-order item.
Picture

Installation

​At this point we have an installation plan and a modified BPS circuit board. Let's determine if everything fits.
​First, add (using super glue) a styrene plastic frame to hold battery (the slot at bottom) and modified BPS board above between the side tabs.
The trail fit looks good, but there's still a third layer of components and some awkward wiring to fit into the remaining space.
Picture
Picture
​Here's a closeup photo of the completed installation.
And yes,  .    .    .
   .    .    .      the lid fits.
​The battery is visible though the open cab door, but there is no externally visible change to the model. 
Picture
Picture

Wiring

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.
Picture
Picture


Comments are closed.

    Author

    I'm a retired electrical engineer, but still spending more time on engineering than on my layout. These days, it's mostly about applying radio control and battery power on smaller scale layouts (HO, On3, On30)

    Categories

    All
    Historical
    Installation Notes
    Loco Projects
    Operation

    The photo above is not my layout. It's a great view of Seattle's King Street station by Ross Fotheringham.

    Archives

    December 2022
    August 2021
    December 2020
    February 2019
    October 2018
    September 2017
    August 2016
    April 2016
    January 2015
    November 2014
    May 2014
    April 2014
    February 2014
    November 2013
    October 2013
    September 2013
    August 2013
    July 2013
    June 2013

    S-CAB Conversions:
    S-scale NW2 Switcher
    On30 D&RG 4-4-0
    HO-scale GP9
    HO-scale GP35
    HO brass 4-8-4
    HO Bachmann 2-6-2

    S-scale EMD F-40PH
    HO-scale ALCO DL-109
    On30 Forney
    HO-scale Atlas-Kato GP-7


Proudly powered by Weebly