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The Randall Museum in San Francisco hosts a large HO-scale model train layout. 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 de-facto layout 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.

2018-12-15 - Automation Train Changes

Category Randall

The main automated route operates two trains in alternance. We used to have an Amtrak GE engine with one coach car, and a Santa Fe pulling that little freight train.

The Santa Fe engine started acting up the couple last weeks -- for some reason the engine’s decoder would have its direction inverted and it would decide to run backwards when asked to run forward. When I noticed that, I immediately checked the decoder’s direction bit on the DCC programming track and it was correct. So fine, I inverted the direction bit in the decoder. Put the train back on the track and at the first turnout it derails. Grrr. Crawl in there to re-rail it and… it’s back to the normal direction of running. That made no sense.

Then a few days later it acted up the same way, but this time I wasn’t around. One second the train is at the station, and I hear it starting, and the next thing I notice is the train stopped a few feet away… in the wrong direction. And stalled apparently, which was fortunate. Time to change the engine.

The initial goal was to replace the Santa Fe engine by an MTH SP GP35 #6580 that Jim got. After spending some time on it, I just gave up in frustration. The coupler height was not proper and it disconnected pretty much every time I tried to use it. It also managed to derail on the problematic T311 turnout. And the nail in the coffin is that I hate how MTH is doing the sound startup -- the problem is that most DCC functions are toggles, not on/off functions. Instead of having a “turn sound on function” like on most decoder, we have a “toggle sound on/off”. But the computer has no way to know the current state, it can just blindly toggle between whatever is the current state and the other state. That kind of uncertainty doesn’t work in automation.

Instead I used an SP #2468 switcher which ironically Jim got just for that purpose a while ago. Back then I decided to not use it as that engine is painfully slow. BLI made a good job replicating the speed from these EMD SW1500 -- and they did an excellent job at the details, sound and lights. It’s a pleasure to watch it run and visitors will have all the time in world to see it.

One the passenger side, the Amtrak train is replaced by a UP SD70 pulling a single UP coach, which is fairly amusing. That’s a lot of engine for just the one car :-) It runs really well and was actually quite fast so I had to drastically reduce its speed, especially in the return trip crossing the problematic cross-over at T321 followed by the S curve at T311. That said it’s quite eye catchy in yellow like this.


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