Tolcarne Junction

This is (or rather was) a seldom-photographed corner of my layout.  Scenery was rudimentary as it simply existed to bring the St Petrock branch line around my desk at the end of the railway room. Bourdon Mill is on the right and the rotating storage sidings in the foreground. 

Trains from St Petrock station are imagined to take three different routes.  Most go up the North Cornwall 'main' line to Halwill Junction and Okehampton, whilst the branch trains go either to Tregarrick North (Southern region) or Tregarrick General (Western region).  In truth, they all followed the same line into the storage sidings. But not any more... 

Trains for Tregarrick North now diverge at Tolcarne Junction.  The only service on this line is this Auto Train, which doesn't need to be turned before returning to St Petock, so a simple storage line on the other side of the backscene suffices.

Tolcarne Junction only has three signals.  The rest are 'off scene', but even if the junction was fully signalled, the signal box would only need 9 or 10 levers. The signal box is consequently rather too large for the job, but its a beautiful model that I found hard to resist buying.  I justify its existence by postulating that the junction was once more complex, with a passing loop on the 'main' line, but that the layout was simplified in the 1930s. 

The photos above show the Peco Smartswitch control board and its associated bank of switches. Together they control the three signals at Tolcarne Junction and the turnout.  On the left is an auto/manual switch that, in the 'auto' position, transfers control to the Automatic Crispin (Raspberry Pi computer).  

I was determined that Tolcarne Junction would operate automatically. When I run the railway, I am the signalman at St Petrock; I can't be the signalman up the line as well, or I would be sending trains to myself!

The 'Train Detect' button at Tolcarne Junction duplicates the action of a Block Signalling BOD-2 RLY infra-red train detector. I suppose I could have made one myself, but this little fellow does the job faultlessly, is very neat and cost £17.  It tells the Automatic Crispin, after a suitable time delay, to ring either 2-1 (train out of section) for an up train, or 2 (train entering section) for a down train. 

This bank of relays is controlled by the Raspberry Pi.  Four of the relay outputs duplicate the Tolcarne Junction signal and turnout switches, and a fifth switches power to the rotating storage sidings.

Finally, just to assure my loyal reader that Tolcarne Junction really does connect with something, here's a photo of the rest of the railway, with the lid removed from the storage sidings.