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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.

2018-09-29 - The RDC is back

Category Randall

The Rapido RDC SP-10 is back on the model railroad.

The engine had stopped working a month ago and it took some interesting amount of work to make it functional again.

The motors were replaced, once again. I had been in contact with Rapido’ tech support. This time I found that both motors’ U-joints were cracked, and one of the motors was not running as smoothly as expected. After looking at several options, I decided to convert the RDC from a dual-motor to a single-motor engine. This means I had to disassemble one of the trucks and remove the main gears, making the rear truck a non-powered one. I changed the front motor by a new one provided by Rapido with a non-cracked U-joint. Although technically it makes the RDC a bit less powerful, it is not a problem in our case since it runs on a mostly flat piece of track, and I programmed it to run at a fairly slow speed (speed 10 on 28 in this case) which I think will not stress the motor.

The RDC program runs fully now independent of the mainline program. It has a 10 minute pause in between runs, and start is done solely by the motion sensor. This should even further reduce stress on the engine by giving time to rest and avoiding running for too long within a day.

Since I rebuilt the program from scratch for the RDC, I also made it resilient to power outages -- no matter where the RDC is on its dedicated track when the power goes off, the program should be able to bring it back to the station next time the layout is powered up. Eventually I will apply the same principle to the mainline automation.

Amtrak Passenger train passing by the RDC

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