Tunnel Technology

"Tunnel collision is the worst to be feared, Sir".

So explained the title character in Charles Dickens' famous short ghost story 'The Signalman',  and everyone with a model railway knows that's just as true in miniature form!

The real Minffordd doesn't have a tunnel, of course, but we had to bend reality - in all senses - to make the Cambrian section of our layout into a complete circuit.

In the Porthmadog direction the line goes under a bridge, which is thereabouts in real life, but our train doesn't emerge on the other side.

Instead it sneaks beneath the narrow gauge ramp down into the exchange yard.

What adds to the complication is that while they are under cover the trains pass over the first of the points where the storage loops begin, indicated by the arrow on the photo below.

Now, modern RTR rolling stock runs pretty reliably and these days you don't get trains derailing routinely on turnouts.  

Except, of course, where there's human error and one of the operators changes a point while a train is going over it..........and then you're in a whole world of pain and embarrassment while you attempt to retrieve it in public.

So Himself has included a neat little piece of technology to try to prevent this as much as we can.

In the tunnel, opposite the point blades, is a light beam sensor which detects when a train is passing over the point, wired to an indicator on the control panel.

When there is a train passing in front of the sensor it breaks the beam and a corresponding LED on the control panel warns the operator not to move the switch.

I suppose it would be possible to also lash up a fail-safe so that when a train is detected power to the point motor is cut, but we haven't taken it that far.

Should all that fail, and we still somehow end up with a derailment under there, Himself has built-in an emergency access flap.

We've never had to use it.   

Yet.........