The Randall Museum in San Francisco hosts a large HO-scale 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 Museum Model Railroad and I maintain a separate tech blog for all my electronics & software not directly related to Randall.
2025-11-30 - Zephyrette on the Branchline Automation
Category RandallThe RDC SP 10 failed again on the Branchine automation. Courtesy of Orion and the Willcox estate trains, we are now running the Western Pacific Zephyrette on the Branchine automation:
The Zephyrette on the Branchline Canyon Bridge.
Note the tunnel portal on the image above.
This engine is a great Proto 2000 with a LokSound decoder and a great rich sound.
After a few runs, the engine oddly stopped in an unusual place… That’s where we learned that the Branchline at Randall has some “interesting” curve tolerances involving that tunnel portal -- here’s a close up of the tunnel portal seen on the image above:
Interestingly we had been running the Rapido RDC engines (both SP10 and ATSF) there for years, so how come? Well it turns out they are just narrower by half a millimeter. No kidding -- doesn’t take much. They were actually rubbing a very very tiny bit against the tunnel pillar.
The problem was easily solved by taking the pillar off (it’s just lightly glued in place) and we’re going to reglue it a couple millimeters in the curve.
If you want to know more about the Western Pacific Zephyrette, I suggest this fascinating read, especially all the insane technical details on page 4: https://www.wplives.com/passenger-operations/self-propelled/zephyrette-01.php