A journal following the history, design, construction and operation of Bernard Kempinski's O Scale model railroad depicting the U. S. Military Railroad (USMRR) Aquia-Falmouth line in 1863, and other model railroad projects.
©Bernard Kempinski All text and images, except as noted, on this blog are copyrighted by the author and may not be used without permission.

October 18, 2010

Wiring Completed...

The wipers are clearly seen in this view.
 Well not totally, but it is completed in the main layout room.  With the additional of the auto-reverse control unit for the turntable, and laying and wiring the final tracks in the Falmouth engine terminal, all track and wiring is done in the main room. I still have to lay track and wire the Aquia Landing area, but the rest of the layout is operational.
The auto-reverse unit and its bracket.
The first two photos at left show the auto-reverse unit and the wiper mechanism I used to power the turntable. The auto-reverse unit is an On Guard auto-reverser unit from Tony's Train Exchange. I bought several years ago.  Unlike the Frog Juicers, this unit will reverse polarity for both rails. Like the Frog Juicer, this unit does not require a separate power supply. Just connect the DCC bus lines to one terminal and the track feeders to the other. It has provisions for a LED output, but I opted to not connect it as the unit is under the bench work and the whole idea is to make the operation transparent to the user.

The On Guard unit is now obsolete as it can't handle the current demands of numerous simultaneous sound decoders. For now it is working as I only have one non-sound decoder on the layout. We'll have to see if multiple sound decoders cause it to malfunction.  My layout even at its peak will be a light density operation with at most 5 locos running at the same time. According to information at Tony's Train Exchange web page, this unit should be OK under these conditions, but I won't know for sure until I actually test it.

If I run into problems I can add additional boosters. Having more than one booster is a good idea in general because it isolates the layout into electrical sections. These sections are not like the traditional electrical blocks where you have to manually control the throttle connected to each block. The booster sections are transparent to the operator. All they do is help limit current flow in each booster by spreading the load across multiple boosters. More importantly, they prevent a single short from taking down the whole layout. So for example, if an operator at Aquia Landing causes a short, an operator at Falmouth on a different booster would not be affected.

I have wired my layout into three separate power districts. So typically I will see a max of perhaps three locos operating in any one district.  But for now I am running the whole layout on a single booster.  I will need to purchase additional boosters at a later point.
The bracket is scrap wood, so please ignore the black
writing as it doesn't pertain to this application.

The third photo shows how the electrical wipers rub against the metal bands on the turntable shaft creating a home-made commutator. The design will allow the turntable to be removed for maintenance or scenery installation.  The wipers are twin sections of 0.032 inch phosphor bronze soldered to a brass plate.

The two white wires are frog feeders for the double slip switch at Falmouth. Those feeders must run the full length of the room to reach the Frog Juicer circuits.

I decided to add wipers to the tender of the Haupt to improve its pickup. It was running pretty well without them, but I want to see how much of a difference all wheel pick-up on the tender would make.

First I installed an insulating tab on the bolster beam of the tender trucks. The tender trucks are hot, so without insulation the new pickups would short.

Then I fabricated electrical wipers. At first I tried using 0.010 inch flat brass stock. But these did not work well as the wheels have a fair amount of lateral play, and the brass did not have enough flexibility to maintain contact with the backs of the wheels. So I modified the tabs by cutting off the brass extensions, and soldering on 0.010 inch phosphor bronze wire wipers. I arranged these to wipe on the surface of the wheel. They are flexible enough to track the wheels as they move laterally. I applied a liberal amount of 5 minute epoxy to hold the tabs and wipers in place.

I had to drill two holes in the tender frame to run the wires from the new wipers to the motor lead. I cut the existing red wire to the decoder and soldered in the new feeders, covering the joint it with heat-shrink insulation. I actually did this before adding the wipers.

I tested the connections and they worked. The tender will now run without the engine attached.
With the engine attached it runs nearly flawlessly. It takes a fair amount of dirty track to stall it.

So with the engine reassembled. I did some test running. I ran a train from Aquia to Falmouth, reversed on the turntable and then back to Potomac Run to drop off a flat car of lumber. Everything worked, so I can declare the layout operational.

Overall view of the tracks at the engine terminal at Falmouth


  1. This era is so not my cup of tea, but you do such a great job at it that this is becoming one of my favourite blogs that I'm following at present.

    Keep up the great work!

  2. Thanks. I'm glad you are enjoying the blog.