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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.

2021-11-10 - Maintenance: Automation Stopping on Mainline

Category Randall

Recently a dead spot has developed on the mainline track #1 just in front of Stockton Station.

And last week we had another one: the automation trains are stopping on the mainline between the Branchline Interchange and the Sonora turnout.

As with (the one) previous short we had on the mainline, this one is intermittent, which makes it so fun to find and debug. It works for a while and then suddenly stops. That’s the typical sign of a cold / broken solder joint that moves during the day as the rail expands or shrinks with humidity or temperature. So now I have to look for a solder joint. Could be a track feeder, or it could be a rail joiner, who knows.

The “nice” thing is that I can temporarily fix the dead short just by pressing on the outer rail. So that gives me a clue...

See the “old shack” on the left? On the mainline track #2, there’s a solder on the side of the rail. I can’t see it, yet I can feel it when I slide a nail on the side of the rail.

And here’s a picture of it -- I even placed a car next to it to remember where it is...

Can you see it now? Don’t worry, me neither. It’s that tiny dark speck on the side of the rail. I need to go crawl under the layout to verify there’s a feeder there. The one thing I know is that on that spot I can flex the rail inwards and that outer solder does not move… which is definitely not what it should be doing.

So at least now I know what to fix. It’s going to be interesting because it’s just at arm’s length so I’ll get to work and barely see what I’m doing.

In the meantime, my workaround to get the automation continue has been… to double-header the UP train:

It looks overkill and I totally love it. I’m guessing the extra added weight just flexes the track enough “differently” to keep the solder joint in contact.

Now I need to fix the mainline by the station the same way. Figure which solder joint had broken and fix it.


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