John's Jottings

157. The Expert on Everything - July 2019

Posted on June 30, 2019 at 2:35 PM

The other week we heard a story about another club. It seems one knowledgeable member examined a newly-constructed control panel. He was disgusted at what he saw.

“You’ve not installed enough point switches,” he commented.

“Which ones are missing?” asked the chap who was fitting the panel to the layout.

“For a start, you’ve missed out one for that cross-over,” the self-appointed club expert-on-everything replied with a certain amount of glee. He always liked to point out the mistakes made others. It was a good thing he was such an assiduous member, otherwise the club’s layouts would be in such an un-prototypical state, they’d become the laughing stock of the exhibition circuit. “And the lack of a point switch will affect the flexibility of operations.”

“Only one switch is required,” the installer assured his questioner.

“It’s essential to have two,” the critic insisted.

“Why two?”

“One for each point,” was the curt reply. “That way you can insolate a loco in the platform by just moving a single set of point blades.” He asked himself how the installer could have failed to realise this. He answered himself: “You might be a competent electrician, but you didn’t understand trackwork or operation needs.”

“In all the signal boxes where I’ve been a guest, every crossover was controlled by a single lever,” the electrician stated. “Having all four blades co-acting has been a safety feature for over one hundred years. It makes sure that if one end of a cross-over is changed, then both ends are changed. That prevents derailments of trains using the cross-over, should the signalman forget there were two separate levers.” The critic was is no way convinced.

“And your double slip: with just two levers, it’s impossible to understand, never mind operate, You’ve tried to be too clever by far this time, my friend. With the ordinary points that lead to it, you really need at six levers.”

“I think it’s time you did some homework,” he was told, firmly but politely. “Go and observe the working of the cross-over at our local station. You’ll see that though each point has its own motor, they work in parallel. That’s what I’ve replicated on our model. Go and study published signal box track diagrams. You’ll see that the points at both ends of a cross-over have the same number. That means they are controlled by a single lever. Study photos of real signal boxes. If you can read the labels, you’ll see crossovers have just the one lever, and double slips have only two.”

“Why mention this now?” the electrician went on. “When the PW team installed the point motors, they connected the wires to those at opposite ends of the crossovers so they were in parallel. They didn’t raise any queries, or raise any objections.”

“Perhaps they didn’t know any better,” was the tart reply.

“The wiring diagram has been available for weeks for members to examine, comment on, and suggest improvements,” Sparky continued. “You’ve had plenty of time to scrutinise it and suggest changes. But you haven’t raised any objections.”

“It’ll never work,” was the damning response. “Just you see.”

Later the evening, the first loco trial was held using the fully-powered-up panel. The loco ran. The points worked as required. The loco went where it was intended. When more locos were added and the isolation section brought into use, all prototypical moves were possible.

“It all goes to show,” our chairman commented.”Some self-proclaimed experts aren’t all that knowledgeable. They only think they are.” And we all agreed with that.

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