Short Circuits = Short Fuses

Digital Command Control - or DCC as we have all come to call it - is a wonderful thing, but let's not pretend it doesn't have a lot a downsides.

Many might regard the cost of the chips as the biggest drawback, which is especially the case when you're going for sound as well, because it can sometimes double the price of a new locomotive.

Then there's the complexity of the control handsets themselves.  

A couple of times during the Glasgow show I looked across at some of my fellow operators and saw only furious button pressing and furrowed brows, and no trains moving.....

And at exhibitions I would argue that perhaps the biggest issue is the way that everything on the layout comes to a stop as soon as anything creates a short circuit.

Mostly this is because of simple human error - a failure to check the route has been set before moving off and the loco runs towards point which are set against it.

The problem is affects everything on the system, not just the single train involved.

But as the weekend in Glasgow wore on we began noticing an increasing number of mysterious occasions where a train made up of our set of 'Barn' carriages would come to a stop in the middle of plain track for no apparent reason.

The instinctive reaction each time would be to assume a short had occurred somewhere else on the narrow gauge side of the layout.

(Minffordd is divided into two separate circuits for 009 and 00)

The fiddle yard operators, and the person on shunting duty on the remote controller at the front, would face increasingly irritable accusations and interrogation.  "Was that you, again??!"

By the Sunday afternoon it had happened so often - and there had been so many false accusations bandied about - that the finger of blame started to be pointed at the train itself.

But how?

It was Himself who did the detective work and found the culprit.

It was carriage 14 what did it!

Here's the explanation.

The wheelsets we're using on these carriages are insulated on one side only, which means that on a bogie you need to have both orientated the same way if you are not going to risk creating a short circuit,

This is especially the case when the bogie frames are brass, and the axles fit into brass bearings, because the whole bogie becomes live.

We'd taken care to ensure each bogie on the set had the wheelsets matching.   

What we hadn't done was check that every bogie on every carriage matched.

On carriage 14 we had the wheelsets in the bogies the opposite way round to the rest of the rake.

With us also using brass couplings soldered to a brass bogie, the last line of insulation defence is the paint on the couplings.

As that begins to wear and chip after 3 days of intense running at a show, snaking over crossings and into fiddle yard sidings hundreds of times, it opens up the potential for the different polarities of bogies on adjoining carriages to briefly come into contact with each other, creating the short circuit.

It's simple fix to rotate the wheelsets on the bogies on 14 to they all match now, but it shows how careful you have to be.