Sunday, 22 June 2014

The Garden Railway

One summer when I lived in France, I started building a simple garden railway. It was just a large oval of LGB track with some loop sidings, and a couple of trains. With my son, we automated it using the LGB train detectors and some creative wiring. It was fun to build, and watch the trains going round while drinking the first Pernod on the terrace. But soon after that it got packed up with everything else when we moved to California.

Soon after we moved to our present house, I noticed that one of our neighbours had some LGB track in their garden. Talking with him inspired me to build a very small layout in the enclosed atrium of our Eichler, which is about 15 feet square. This time I automated it using a computer, with the JMRI control system. I had three trains that took turns to go round, but in the tiny space (for LGB) it wasn't all that interesting, and it was in the way too. It didn't last long.

Our garden is big enough for a decent sized railway, but I could never figure out how to make it compatible with having an actual garden. Then my daughter decided to visit, with her son. At three years old, he's completely obsessed with Thomas the Tank Engine and anything and everything to do with trains - for a while his favourite video was a documentary about the construction of the French TGV network, though he surely understood none of it.

He won't actually be here until nearly a year from now, but it was a good excuse to get started. We suddenly realised that if we used the concrete pool surround, I could create a permanent layout. As a bonus, it is relatively flat which would make it much easier to keep the trains on the rails.

I took stock of the LGB track sections which had been gathering dust in the garage for over a decade. I had enough to build along two sides of the pool - a total of about 60 feet - with a reversing loop at each end, making a kind of dogbone suitable for continuous running. On one side of the pool there's enough space to put several parallel sidings, so different trains can be run at the same time.

I also bought a Bachmann Thomas set, with Thomas and his two coaches, Annie and Clarabel, while on eBay I found the coal truck labelled "S. C. Ruffey" (geddit? - he was quite a card, that Reverend Awdry).

The first attempt had one of the loops on a corner of the lawn. I quickly realised this was a bad idea. The LGB trains could just about cope, but Thomas his coaches certainly couldn't. A quick extension along the third side of the pool gave access to a big concrete area, solving that problem.

When I was a lad and used to drool over Hornby-Dublo layouts in the Meccano Magazine, they always had reverse loops in them. There was a reason for that: because they could. On a three-rail system, like Hornby-Dublo or Marklin, there is no electrical problem. But in a two-rail system, like LGB, the two rails are the positive and negative sides of the power supply to the trains. A quick sketch will show that a reverse loop inevitably connects them together, creating a short circuit. Many and varied are the ingenious solutions to this problem. After several false starts, I eventually built a little control box for each end of the layout, using the LGB train detectors to operate some relays that switch things around as required.

In the process, I discovered some limitations of the LGB system. The trains are superb, and the track is indestructible. But the control system for points has some odd idiosyncrasies. The detectors can in theory operate the points directly, but they contain wimpy little magnetic reed switches, rated at just half an amp. It doesn't take much to toast them. They get red hot, which fuses the contacts together - guaranteeing instant destruction. Luckily it isn't hard to replace the failed switches (just as well, because like all LGB parts, they're eye-wateringly expensive).

The real answer is to use them to drive only very light loads, like relays or computer inputs. Another problem is the electrical switches that you can arrange to be changed as the points move. I was relying on these to change the polarity of my reverse loops - until I found that often one would switch and not the other, creating a short circuit across the power supply. More relays were the answer, and the LGB switches are back in the parts box.

The electrical control of the trains themselves uses the DCC system. In the old days, the rails carried the actual electric voltage for the motor in the locomotive. This was very restrictive, and made it very complex to be able to run more than one train at a time, or even have more than one train on the track. DCC avoids this by providing a permanent voltage, overlaid with a control signal that tells each train individually what to do. As a bonus, it's easy to interface to a computer.

The ultimate goal of all this is to make it run completely automatically. In parallel with building the railway itself, I've been experimenting with using an Arduino to run the control system. It's coming along nicely, more on that soon I hope.

Today was the first day that I've run the full layout, with several trains. I have a Bachmann Shay which I added sound to and converted to DCC back in France - very painfully. It pulls a train of eight or so log and other freight wagons. There are a couple of LGB European locomotives, and of course Thomas with Annie, Clarabel and Mr Scruffey. Control for the moment is still manual, using a virtual control panel built with JMRI. There are still hours of endless fun to be had - and quite a few minutes of frustration, no doubt.