Friday, 1 August 2014

Churnet catch-up

Here's an update of a few things that have been going on at the Churnet Valley Railway recently:

Last Sunday I was Consall signalman again, for the railway's Sci-Fi weekend. Here's a Wookie by Consall signal box steps. 

Daleks at Consall. Very true to Dr Who authenticity they were too, as they glided effortlessly around the station and yard talking to people in electronically-produced dalek voices. They are based on electric wheel chairs under the skin, and the operator sits inside talking into a microphone and operating the probes, one of which can squirt water (usually accompanied by the command "exterr-minate!").

Darth Vader flashing his weapon (ooh err!) in the guard's compartment in Leekbrook tunnel. We were also visited by Cybermen, Storm Troopers, and many other Sci Fi characters from film and TV, with regular competitions at Consall for the best costume (especially for the children who really got into the event big time!).

The previous day the signal box had suffered a failure of the instrument into which the key on the Froghall staff is inserted to clear the section (to tell the interlocking that the train is out of section), and that fault was still present when I took over the box first thing Sunday morning. The fault prevented me from clearing the Consall to Froghall section so the interlocking would not let me pull off either the up main or up loop starter signals as it 'thought' there was a train in the section. Any train leaving the Consall loop platform for Froghall has to pass the loop up starter so I had to authorise the driver of every such train, before it left and after I'd given him the Froghall section staff (sometimes called the token), to pass that signal at danger but to visually check the up loop point as he approached it. This point is normally protected from being wrongly set by the up starter signal being interlocked to it, so the signal can only be cleared to 'off' (safe to proceed) if the point is correctly set. Although I had correctly 'set the road' for the up departure, by authorising the passing of the up starter at danger I was circumventing the interlocking and the protection against mistakes that it gives, hence my asking for the visual check that that point was set correctly.

Coincidentally, on arriving at the box on Sunday morning I discovered we now had a second fault in addition to that described above; track circuit 5 was showing 'line occupied' when it wasn't. This didn't actually make any difference as that failure produced exactly the same effect as had the inability to clear the Froghall section - it was telling the interlocking that there was a train in that section and therefore I couldn't clear either of the up starter signals. 

My previous stint in Consall box had been 12th July, as reported earlier in the blog, for the Real Ale Weekend. That day I'd had a different track circuit failure; track circuit 2. This meant the interlocking wouldn't allow me to change the motorised point at the down end of the loop near the Black Lion pub, so Howard (my main mentor during training in the box) had to trek down to the point to hand-crank, lock, and scotch it (the latter two actions ensuring it couldn't move under a passing train thus derailing it), coordinating with me in the box using the line side telephone. The fault self-cleared later in the afternoon, but Signal & Telegraph (S&T) staff have now renewed the insulated track joint, so hopefully that fault won't recur.

 S&T fitting a new track circuit insulator into a track joint at Consall. The track circuit works by detecting the presence of a train when its wheels provide an electrical connection between the two running rails of a section of track electrically insulated from track adjoining the track-circuited section. This electrical connection shorts out a current that is holding the needle of the signal box instrument to 'Track Clear'. This (or any failure of the electrical supply, the wiring, or the track insulation) allows the needle to swing under the influence of a spring to the 'Track Occupied' indication. Thus the track circuit instrument 'fails safe'; any fault leads to a 'Track Occupied' indication and the system never allows a train to be present in the section with a 'Track Clear' indication showing.

The finished repair. Note the electrical insulation between the fish plate and the rail, and between the fishplate and the securing bolts to ensure their is no electrical connection between the joined rails. 

The frames of Greg Wilson's first S160, 5197, have moved from the yard into the workshop at Cheddleton indicating that work on getting it back into traffic has been stepped up a gear   

The railway has purchased the water tank from the Thomas Bolton works at Froghall. This will be installed at Cheddleton for watering engines, especially useful during preparation for the day's running.


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