Thursday 24th September

Worklist:
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.

The ringed point needed two wires not available from the solenoid wiring scheme.

Careful labelling and recording of each removed wire.

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!

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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!

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!

Thursday 17th September

Worklist:

Point actuators.

It was 'full steam ahead' this week, with all three of us fitting actuators to both of the main boards. Most needed wires extended, but not the same blade remedials as last week.

After testing, the actuator wires were trimmed to the correct length.

Just one to go. The first actuator we fitted was of the original design, which would have to be replaced in due course.

A brief discussion took place regarding the switching system we'd agreed to use on the new control panel. Many of the components had arrived, but the relays were still winging their way from China.

We confirmed that the relays would be operated by their own 5v supply, switching the 1.5v (min.) supply feeding the servo's. It was acknowledged that as the servo's appeared to operate differently, it might be necessary to increase the base supply voltage and fit local resistors to the more freely-operating units.

The original system had pairs of stud contacts feeding each of the two coils on the H&M point motors, with a common return. The two feed wires are reused for the servo supplies, with the polarity reversed by the relays. A DPDT switch would do the job much simply, but we couldn't find a suitable rotary switch.

Stephen would make a start on the veroboard bases, fitting dil sockets, wires and terminals, allowing the relays to be dropped in later.

Thursday 10th September

Worklist:
Point actuators

Yes, business as usual..... but we are making progress.

Geoff and Stephen fitted the operating wires to the remaining actuators. We discovered we'd bought two thicknesses of spring/piano wire, so decided to try both out.

Meanwhile, Laurence stripped out some existing H&M units and started to fit the new ones. Things didn't go as smoothly as they could have. The assemblies worked, but alignment of the operating wire needed to be more precise. We accepted that we were still developing a method of assembly and soon corrected the issues - a useful exercise.

Stephen fitted another unit and transferred the wiring from old to new units. As found previously, short wire extensions were required.

The other problem that came back to haunt us was John's method of point making. He preferred not to split the blades from the frog rails, which increased the stress on the blade/tie bar joints and obviated copper-clad tie bars. To overcome this, he silver soldered a solid tie bar to the blades. To prevent a short circuit, the tie bars could not come into contact with the stock rails. The old H&M rotating arm held the tie bar down in place, but this would not be retained. The first point to be converted needed something else to hold the tie bar down, and a short section of rail, laid down the centre of the track, was used.

As we are prone to do, we veered off on another, but allied subject. How were we going to operate the points? We were using toggle switches for the sections, so a rotary switch made sense. We had several 'standard' switches, but these only clicked through a small angle where something larger would be preferable. Stephen had sourced a switch, but found it only available as a DPST option (two on-off circuits instead of DPDT where polarity change-over could be achieved). Geoff suddenly remembered that he had TWO stashes of the switches, which were 'played with' and admired. Stephen suggested using them in conjunction with relays, to achieve the change-over. This arrangement was approved. It was agreed that instead of a round knob/pointer, something more demonstrative could be made up.