Monday, 20 September 2010

September time

As September rapidly disappears we are still keeping busy, although we are into the 'late summer holidays' time when some of us hope to catch some lovely Autumn days somewhere on the Planet !
We welcomed another happy Birthday Party visit last Saturday, followed by a 'Footplate experience' session which was thoroughly enjoyed by all (well done Steven! and Alan of course!).
On the jobs front we have replaced the Shay's handbrake cable, (not easy but our erstwhile engineers like a challenge!), continued with the gardening (bit like painting the Forth bridge), and we have installed six Junction signs (photos to follow), very smart, so our drivers know roughly where they are on the circuit?
So something to look out for when you visit on our next Open Day on SUNDAY OCTOBER 3rd. Hope to see you there!


Tuesday, 7 September 2010

The ALR track detection system

After 18 months development, the ALR Track Detection system is up and running, although there is still some fine tuning to do. The basics are that the track detects when a train is present by a short circuit being detected across the two rails via the metal wheels and axles of the engines and carriages. This triggers a low impedence relay which is housed in the trackside distribution boxes (in batches of four- one relay for each track section - see photo).

We spent some time experimenting with different relays until we found one that had suitable impedence and drop out voltage characteristics. If these were wrong we found it difficult to achieve relay switching in wet weather conditions because the resistance across 200 wood sleepers drops dramatically when wet, and holds the relays on. Also the length of track sections had an effect.
The track is divided into 16 sections. The switched contact of the relay is fed to the input of a 555 electronic timer circuit which is designed to give a 5 second consistent high on its output as soon as it detects a train. The reasoning behind this is to give a constant output even if the track is dirty in places resulting in relay judder. This 5 seconds also allows the next section of track to be detected and displayed in the signal box before the last carriage leaves the previous section.
The output of the timer circuit is then fed via another PO type relay to the display board in the signal box which lights up relevant LED's on the display board. As you can just see in the photograph, there are three sections lit, 'Bamboo', 'Home straight' and the first ''Lake' section which indicate there are 3 trains running.

At this month's Open Day we had 4 trains running simultaneously for the first time and the track detection system enabled the signalman to keep trains evenly spaced ( most of the time!) around the circuit.

2010 Open Day Number Five-excellent !

Lucille makes her way around the Lake

Our latest Open day for this year last Sunday (5th September), was another very enjoyable day for us all, and we hope our visitors too, you all seemed happy, and if you are happy, then so are we!
The weather once again was excellent, with a steady breeze and plenty of lovely warm sunshine......

The stars of the show were, The General, Hotspur, Lucille, The Shay and Sergeant who all performed very well (good driving I say!). Hotspur decided to take its own route rather than the one the signalman had set as it entered the station area on one trip, which resulted in the loco having a rest in the ballast! But we like a challenge, and after a few minutes the loco was on the rails once more, the trackwork checked and we were on our way again! We decided not to use 'Den' section for the remainder of the afternoon just in case there is a problem with the pointwork, and so with a slightly shorter ride we were able to keep the queue moving steadily forward.

It's also good to be able to spend time chatting to our visitors and on Sunday the local railways were well represented with staff from the North Norfolk, the Mid Norfolk, the Fenland Light Railway and the Little Orchard railway visiting us! Particular thanks to Andy P who gave us some invaluable advise on the mysterious art of steam loco firing!

So one more Open Day to go and that's another year almost gone!


P.S. Just been reminded that good 'ole 'Thunderbox' tramped round on Sunday too....ooops !