Point actuator
New control panel
Just two this week, as Laurence had a car failure and spent the morning with a very nice man from the AA.
Stephen removed the first actuator we had fitted (with the separate slider-unit), modified it with the extra operating arm and refitted it. Point actuators were finished! Hopefully.
Geoff started to strip out the wiring from the temporary control panel. A print of the old panel layout allowed the wire numbers to be recorded. The ringed point, formed part of the engine shed cross-over, was the only one that needed extra wires.
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| The ringed point needed two wires not available from the solenoid wiring scheme. |
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| Careful labelling and recording of each removed wire. |
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| Quite a birds nest. |
We were also keen to find out if there would be sufficient wires in the existing loom for the new actuators. These would require two wires per servo (polarity reversal by DPDT switch). The old system had one wire to each of two coils on the H&M motors and a single, common return. However, a few of the points were operated together, requiring only one wire to two points. In the end, we were lucky, and only the engine shed point needed two extra wires (circled above). We were able to use the point motor common return as one, but a new wire would have to be fitted into the loom. A quick check revealed that there was one spare pin in the connectors.
Geoff then raised the question of ancillary items such as lighting, the gas engine motor and probably others. Whist the end boards had spare wiring capacity, the middle board was now full. We could gain two wires (enough to provide auxiliary power to the board) if the two crossover points above, used just two wires. However, this would create a unique situation on the new control panel - one switch to operate two points. Furthermore, both would move at the same time, something Geoff had been very keen to avoid, as a signal man would operate each in turn. There were three options:
a) Use a single switch to control two points simultaneously and accept the operational 'anomaly'.
b) Use separate switches (one extra wire required). Lighting etc. would require a different solution.
c) Use a single switch, but design a system to delay the second point moving until the first had stopped.
The latter really put the cat among the pigeons! Both S&G recognised the potential of the challenge and the final part of the day saw the temperature in the workshop rise as two brains struggled with the problem. On parting, both resolved to solve it!
Stephen initially sought a wire/component solution, but then started investigating electronic delay modules and circuits. It looked promising, but then Geoff came up with a wire/diode only solution. Exquisitely fiendish!
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| Part of the proof that it worked! |
This gave us three working solutions, but which one we adopt will depend on how important saving wires in the loom is. The meeting next week should be interesting!
