Blog & News

About the Model Railroad

RTAC Software


The Randall Museum in San Francisco hosts a large HO-scale model model railroad. Created by the Golden Gate Model Railroad Club starting in 1961, the layout was donated to the Museum in 2015. Since then I have started automatizing trains running on the layout. I am also the model railroad maintainer. This blog describes various updates on the Randall project and I maintain a separate blog for all my electronics not directly related to Randall.

2021-01-02 - Front Yard toggles on Mountain and Valley Panel

Category Randall

The Mountain Turnout Panel has this little mysterious “Front Yard” toggle at the bottom, and for a long while I could not understand what it was connected to nor what is purpose was:

Now I understand that flipping it right or left connect its output to the Mountain 1 or Mountain 2 panels power:

Click here to continue reading...

2021-01-01 - Happy New Year

Category Randall

Happy New Year 2021 from the Randall Museum Model Railroad team.

The museum has been closed to the public for a good portion of 2020. However we kept doing maintenance on the model railroad. After nearly four years off service, the Napa and Bridgeport yards are back at being fully operational for Saturday operators to take advantage of. The lights & bell are back on the Fairfield grade crossing. Other maintenance and improvement has happened which is not directly visible to the public yet will help long term.

Looking forward to a reopening of the museum to the public in 2021!

2020-12-31 - Cleanup & Mystery: Junior Engineer DC Console, part deux

Category Randall

Update: Finally traced the one white + two red wires that were the output of the obsolete “Normal / Children’s” plug for the DC Junior Engineering Day, and which I removed. I found this:

This exposed crappy-looking connection is key to all DCC power for the Mountain 1 panel. Seriously.

The white wire converts to a black wire that then connects to the main terminal under the Mountain panel:

Once again here we can see all “common grounds” are connected together at the terminal. This also bridges the “common” from both boosters used for Mountain 1 vs 2 directly.

Click here to continue reading...

2020-12-31 - Cleanup & Mystery: Junior Engineer DC Console

Category Randall

The amusing thing working on a mostly-undocumented quinquagenarian layout is that most electrical circuits work in layers. Clearly stuff has been added later, then sometimes retrofit and upgraded, etc. As I found out, trying to remove any innocent-looking obviously unused old piece of equipment can result in a lot of fun. As in “mystery puzzle kind of fun”.

Task of the day: Removing the old plug for the Junior Engineer DC console. This little plate & connector on the left side of the Stockton Passenger station. I’m updating the station panel for a circuit breaker to later add more automation block detection and turnout control. I could use the space. That obsolete plug can go away, since it hasn’t been used in 5 years and it will not be used ever again. How hard can that be?

Doing so totally broke power to Mountain Panel 1. Why?

Click here to continue reading...

2020-12-29 - Power Districts for Fairfield and Stockton Station

Category Randall

Time to deal with installing the two new circuit breakers. One for the Fairfield industrial city, and one for the Stockton Station. The former is not powered at all. The latter is powered in a convoluted way from other parts of the layout, and I need it separated to both solve issues and make it suitable for automation. This all needs careful planning to investigate all the possible options.

Location for the breakers. One philosophy is to place the breakers near their usage panel, which makes sense for a walk-around layout design -- the EB1 makes it easy to have a LED on the panel indicating when there’s a short.

The other philosophy is to place all the breakers together, which makes it easy to glance which one is shorting. Since this layout already uses the latter design with all the current breakers together, I’ll stick with it.

Boosters which I have selected for these:

Click here to continue reading...

2020-12-27 - Grade Crossing Installed at Fairfield

Category Randall

After about 3-4 hours of work, the main two-lane cantilever grade crossing is now installed at Fairfield:

First run, before adjusting sensor sensitivity or timings -- works really nicely out of the box.

And it’s functional, with the Grade Crossing Pro/2 module, the sound module, and speaker!

The control module is installed under the layout:

The speaker is installed next to the Fairfield control panel, with a toggle to cut off the sound as needed:

Click here to continue reading...

2020-12-26 - Grade Crossing Pro/2

Category Randall

Today on the bench we have a Logic Rail Technologies Grade Crossing Pro/2:

That is going to replace the module that I had previously installed on the layout back in 2015.

Experiment on the bench first, to check everything out:

This is a newer version of the previous Grade Crossing Pro. For comparison, here’s a picture I took back in March 2015 of the brand new one I had installed back then (that’s the module that was unceremoniously removed):

Click here to continue reading...

2020-12-23 - Bridgeport Auto-Reverser for Second Balloon Track

Category Randall

I recently installed an auto-reverser on one of the two balloon tracks at Bridgeport, as indicated in the previous Bridgeport post. In between I ordered a second one and today I was going to install it.

Two engines led by Walthers Mainline UP 8823 enter the outer balloon track at Bridgeport.

For the auto-reversers, I settled on using the Tam Valley Depot Frog Juicer Auto-reverser; I really like them, they work very nicely.

Unfortunately when the order arrived, I had a little surprise:

Click here to continue reading...

2020-12-22 - A Convention for Wiring Tortoise Switch Machines

Category Randall

How are Tortoise wired on the layout? A lot of the existing mainline turnouts use a terminal block. This makes it easier to prepare the turnout machine at a bench, and then install it in place without soldering. So let’s replicate this. What is the current wiring pattern?

Some examples:

Tortoise at Mainline T110:

Terminal block = 8 positions (1 == right most).

  • Terminal 1 / Green Turnout Control ⇒ Tortoise 8.
  • Terminal 2 / White Turnout Control ⇒ Tortoise 1.
  • Terminal 3 / Yellow = not connected.
  • Terminal 4 / empty.
  • Terminal 5 / empty.
  • Terminal 6 / Red = DCC bus red or from rail A ⇒ Tortoise 3.
  • Terminal 7 / Orange = to frog ⇐ Tortoise 4.
  • Terminal 8 / Black = DCC bus black or rail B ⇒ Tortoise 2.

To reverse the switch, it’s possible to invert the green/white either on the bus side or the tortoise side. An 8-position terminal block makes sense to be able to use both switch contacts. In practice, I rarely see that being used.

On the Fulgurex at T450 Bridgeport, the conventions are different.

Click here to continue reading...

2020-12-21 - An Update on the Lodi Maintenance

Category Randall

The last couple visits at the museum were to deal with Lodi. The original premise was extremely simple as elaborated in the previous post about Lodi: provide access to the block B905 leading from Lodi to Fairfield for switching purposes. Jim indicated he tried to use it only to find it had no power. Since this block is powered off Fairfield, which is currently powered off, the trivial fix was to cut the block in two by creating a gap and then power it from the Lodi side.

Lodi on the left, mainline (the dark rails in the middle), and the Fairfield B905 block on the right.

That did not go smoothly. In fact so far it has gone absolutely nowhere except to create more work for what was supposed to be a trivial thing. Oh well. C’est la vie.

Click here to continue reading...

 Generated on 2021-01-20 by Rig4j 0.1-Exp-91c1dac