Secret Panels

Himself was thinking ahead and anticipating worst-case scenarios when he designed Minffordd, and he was careful to allow access in the event of a major failure or track relaying being required.

That's why there is a six-inch-long section of the narrow gauge lines at the Porthmadog end which can be lifted out to get at the Cambrian fiddle yard points hidden underneath.

At the moment he's investigating a curious fault with the route-setting function.

At each end of the Cambrian yard control panel is a rotary switch where the operator selects which road they require, press a single button, and a matrix of diodes and relays set the points accordingly.

During the Glasgow show we noticed when you had Road 1 selected, and wanted to change to Road 4 the 'king point'  - where roads 1-2 and 3-4 d split - would not move.

However, if you select Road 3 instead, the point will switch as it should, and you can then make a follow-up request for Road 4.

This explains a number of strange head-on collisions in the fiddle yard during the show which baffled the operators who were quite sure they had changed the points, and the LED indictor on the panel backed them up!

So one of the items on the snagging list to be tackled before the next appearance in Porthmadog is to find out what is causing this.

Removing this 'secret panel' makes it much easier to see what's going on under there and whether the point is being switched when it should be.

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.........

What’s The Point?

Some running repairs have been required to the fiddle yards following our exhibition outing.

A couple of the points became a bit iffy over the weekend, needing repeated presses of the push buttons - and a burst from the CPU - to throw.

Another one had a freak failure of the shaft connecting the motor and the point.

All those dodgy units have now been replaced.

It’s remarkable that we should have so many fail in one weekend given how those installed on Dduallt have done nearly 30 years.

One of the rotary switches to select the roads has been changed - a big job with so many connections to be unsoldered and replaced - and there were a number of failed LEDS to be renewed.

Components are not what they used to be, it seems..

The Matrix

I'm not the only one who has been given a headache by this layout in recent weeks.

This time it's been Himself's turn.

He's been trying to remember how he made the point routing system for the fiddle yards on Dduallt more than 20 years ago.

Eventually he managed to find two Railway Modeller articles on a 'Push Button Routing System' which were in the October and November 1974 editions and the spidery circuit diagrams that he used.

Nothing but cutting edge technology on this layout!

If you're looking to make these for yourself the main components are some copper clad strip board and diodes.

He tells me there's 1 board for the 6 routes and the other for the output to the 5 point motors (2 coils each)

The diodes are wired between them to form a matrix logic system which fires the points for a set route.

Here is one of the units made up.

The red wires are from the rotary switch for the 6 roads, the yellow and white go to the point coils.

What they will control is this:

A couple of the points will have have to be switch operated - the furthest kick-back siding point and the loco release points at the ends of the sidings.

Now he's got to finish wiring it all up and see if it works!

Connecting It Up

The point motors have been fitted to the upper end fiddle yard and are in the process of being wired up

The five points controlling access to the 6 main storage roads will be operated by rotary switch and button via a CDU unit and diode matrix board.

Himself built some of these over 20 or so years ago for Dduallt.

They're still working perfectly and on the basis of 'if it ain't broke, don't fix it' he's intending to use the same circuitry again.