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4. Doin' the Run Around


GWL

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Copper vs Steel

 

One of the point control wires I installed last week has broken where it bends 90º through the point bar, which I think tells me all I need to know about my copper vs steel wire conundrum...  Oh well, no going back now. So I‘ve reinforced it with an L pin made from 1.2mm wire through the point bar and soldered it back onto the existing control wire for now.

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Meanwhile, new 0.4mm stainless steel wire has arrived, (thank you Wires.co.uk)  which means I can crack on with the final two points at the far right of the layout, the platform runaround.  As it's a crossover, I want to use one switch to throw both points. Here's how I've done it:

 

...Oh and forgive the jaunty angle of some photos...!

 

 

  • First, cork is cut away for the tubes and slide switch. Three 8mm holes are drilled in the top of the board and then filed into one rectangle for the slide switch to sit in. A 5mm hole is drilled through the bottom of the board (in my case an ikea Linnmon table top) for the cabling to drop through.
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  • The switch is a double pole on-on slide switch from CPC. The travel of the switch is pretty much an exact match for the travel of the points.
    The switch has to change the polarity of the frogs (the V section of rail) of both points, so everything is marked as to what supplies what. The white cables are already soldered to the point frogs and threaded up through the hole I drilled for the switch. The red and black wires are 15cm droppers which will poke down through the hole and crimp to the main DC bus wires.
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  • The switch is soldered up and everything is insulated with electrical tape - sadly my heat shrink kit is trapped at work in an empty theatre!
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  • With the switch in place, two 0.8mm holes are drilled through the head, one with the direction of travel and one across it.
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  • PTFE Tube (0.5mm ID / 1mm OD PTFE Tube from Amazon) is laid into the slots and held in place using hot glue.
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  • The tube is trimmed to length at the points and switch ends. Next, 0.4mm steel wire is threaded through the head of the switch and into the tube, and pushed through until there is about 5cm of excess is protruding past point no.1. The wire is then bent up through the hole in the point tie bar, folded over and cut so it cannot slip back through the bar. A small L shaped pin made from 1mm wire is pushed in with a drop of super glue to fill the hole completely, preventing the 0.4mm wire from rattling about in the hole. The top of the pin and the end of steel wire are joined with a drop of solder. Once the glue has dried, the control wire is now connected securely to the point tie bar.
    This is repeated for point no.2.
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  • The points can then be secured in place, with any adjustment in position facilitated by pulling or pushing more wire through the hole in the switch head. Once everything is fixed down,  the wires are then bent around the switch head and pushed through the hole running through the side of the switch, then trimmed to length. A drop of solder and/or superglue can be used to keep the wires in place around the switch head.
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  • Everything is filled in with hot glue, with any spillage or excess glue trimmed away using flush cutters or a Stanley knife. Once the glue has set, there should be no movement in the switch chassis, PTFE tube, or points. The switch should slide easily and change both points with a nice positive click!
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And thats it! I’m sure there are more elegant ways of doing it, but it cost me less than £30 for the parts to control 10 points, including switches, wire, PTFE tube and wiring. I have 8 points on this layout, so have spares left over for $@%& ups. Of course this does not include glue gun, soldering kit, hand tools, etc. and we shall see how reliable they are over time, but I’m confident!


Next task is wiring up the main DC bus...!

 

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Edited by GWL

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