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About the Model Railroad

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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.

2018-02-24 - Mainline Issues

Category Randall

Running under automation is only one aspect for the train model railroad on the Randall Museum.

The other aspect is supporting people who want to run on Saturdays. There are a few challenges to solve here, such as complying with museum requirements and defining our own screening and approval process. That could be tricky since ex-members might want to run as if they were back in their old club, using their old ways.

One point I have been trying to make is that running on this layout is more tricky than it looks. The panels are confusing, labeled yet hard to understand. Most people have the natural bias of overestimating their own proficiency and that is clearly visible when operating this layout. That is why I want to insist in everyone, including ex-members, in having a training before running again yet at the same time there’s little traction for it from said people -- the typical “how hard can it be”.

But before getting there, one issue to address is the lack of maintenance on the mainline.

5913 approaches turnout T322. The point was stuck and throwing it shorted the mainline.

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2018-02-18 - Automation Toggles

Category Randall

Now that the barrier is up, the automation toggles are hard to reach.

The original design goal was that operators can quickly look whether the toggles are physically up or down, and being able to easily flip with up or down. So having them in a central location made a lot of sense. During the renovation, we used to work in the middle area and have direct access to the mountain panel. Now we don't.

Passenger Automation

Branchline Automation

What would make sense now is to have them in the valley panel area.

Another choice is to have both, e.g 3 state toggles (off, rest, on), repeated on both panels. Push up for on, down for off. The computer keeps the state. By then at that point, we might as well not have physical toggles and move the control to the tablet. The “downside” is that it makes the tablet indispensable for the automation, which is a big no-no.

2018-02-12 - Automation Feedback from the Randall Opening Day

Category Randall

Issues noted during the Randall Opening Day:

  • Passenger:
    • One derailment from 204 going down on B320 between the signal bridge and the turnout.
    • Two derailments from 209 going up right when leaving the station. This is again a very very subtle left turn.
  • Branchline:
    • About 4~5 times, the RDC stopped at a station and never left again. One time it missed the stop at the reverse station.
    • 2 times we couldn’t figure where it was.

To deal with the Passenger train issue leaving the station: this happens where the train accelerates and there’s a very very slightly left curve. ⇒ Delay the acceleration till the train is in the straight line after, which leads to a right curve.

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2018-02-01 - Rapido F40PH

Category Randall

The main passenger automation runs using two new Rapido F40PH engines. They have superb detail and superb sound.

Since we use them for the automation in a back-and-forth route, our initial concern was that some dirty track where the engine stops and reverse would have them lose power. Thus we got two ESU current keeper which I installed.

Many weeks pass and I finally complete the automation of the route. At first everything is fine and then we realize quickly that one engine derails consistently in one of the curves, just before the canyon bridge by the entrance.

Oddly enough we have seen hundreds of engines go through that route, and even though the layout track is not exactly new, it does seem OK.

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2018-01-28 - Randall Repairs: Turnout T130

Category Randall


Turnout T130 (mainline to industrial city, after Sultan).


Trains stop shortly / continue on layout. Some are unaffected.

Cause: Resistance in the frog.

Summary Fix

Bypass the frog polarity contact/inverted.

Description of Issue

Engines often stop / hesitate on the turnout. Some pass unaffected, others totally stop.

Frog issue: Measurement with multimeter shows a DC offset of 3 V on the frog.

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2018-01-13 - Brancheline Power

Category Randall

The power for the Branchline includes a Lenz Digital Plus LK100:

This is a DCC Reverse Loop polarity reverser.

Yes, the branchline is a reverse loop.

An engine going from B321 (mainline) to branchline will come “in the back” in the tunnel in the reverse direction.

2018-01-12 - Sonora Signal Mast

Category Randall

The signal mast on Sonora is a double track signal bridge.

What we want, for trains going up hill:

  • T330 Normal aka “mainline” (block 320). Mainline green, Siding red.
  • T330 Reversed aka “siding” (block 321). Mainline red, Siding green.

First I need to identify wires under the layout, there are likely 6 of them, 3 for each signal.

Apparently most of these use a common anode (e.g.

[Update ⇒ 5, one is a common anode.]

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2018-01-05 - Activation Buttons

Category Randall

Issue: short push on activation buttons are not detected fast enough by the AIU01 polling.

Solution: use a basic RC to make the signal seem longer.

Experiment at home:

  • Use a 1000 µF between GND and the input.
  • Use a 110 Ω R in serie from input to button (to avoid shorting the capacitor).
  • This results in a hold time of about 5-7 seconds when fully charged.
  • When powering up, this also activates the input while the capacitor charges.

Quick drawing:

2017-11-15 - Progress Update

Category Randall

Time for an update on the progress on the layout.

Last time our group of volunteers and I got access to the layout was in May and June 2017. Claudette spent a lot of time carefully dusting all the buildings and the scenery. Greg, Mike, Robert and Jim all helped refresh the scenery, which looks much greener and less dusty.

A lot of time was also spent in cleaning the track and make sure trains could go around properly. There are some areas that need more work, e.g. at least 2 spots were trains hesitate on a turnout (probably frogs that need to be rewired) and I'll need to come back to them. Here are two videos of a train going around the track -- there's nothing like a good cab ride to identify all the problems on the track. I'll spare you the earlier camera recordings with the trains stopping at the most hard to reach location and instead let's focus on the last working version:

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2017-04-14 - Randall Passenger Train Brainstorming

Category Randall

Some brainstorming ideas regarding the issues with the Randall Passenger train.

The core of the issue is having two engines in push-pull configuration. When one loses power due to dirty track, the other engine is either pushing or pulling the whole train and it results in irregular motion that easily derails the whole thing.

Question is: Can this be avoided, yet still having two engines in push-pull.

Note: I am NOT doing any of this. Just thinking aloud about the problem and potential solutions.

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