Wednesday 24th October

Worklist:
Point rodding and 'signalling'.
Review sound module.

Fortunately a full house this week, with some serious discussion required to decide what we are going to do.

Geoff and Stephen had circulated emails regarding point rodding and 'signalling'. Geoff had proposed using Wills SS89 4mm point rodding and parts kits. 2 packs would be required to obtain 4 facing lock units and enough rodding, which Stephen estimated to be 1.8m. (This included the 4 locking mechanisms which Geoff had previously thought could be wire operated, but subsequently solid linkages were favoured). The lever frame would be handmade to 7mm scale.

Stephen had reviewed the Wills packs and queried the rod support centres, which he'd calculated at 10ft (40mm); confirmed by Geoff. To maintain 10ft in 7mm, we would need to remove a support from every piece of rodding, which seemed wrong. Stephen had previously floated the idea of making our own kit-of-parts, and this now sounded quite plausible. We considered square rodding, but this would be prohibitively expensive, so round/tubular rodding was agreed. Geoff proposed straightening coiled wire, but Stephen argued for rigid wire to overcome the likelihood of in-situ damage, which would look unsightly and be difficult to rectify. Geoff pulled out an ancient box of piano wire pieces which were mic'd-up - 0.8mm looked perfect. Sketches of the supports, rationalised for our situation and modelling capabilities, were created and a design quickly firmed-up. Laser-cut cardboard seemed obvious, but would it be solid enough? Would the card delaminate? Maybe a coat of dilute PVA or even shellac would help? One way to find out was to make some, so Geoff drew up the pencil design and cut some out of 1mm card. With a piece of plastic rod for the top retainer, the 'plates' and packers were difficult to keep aligned, so another hole, where the pulley spindle would be, was added, which worked well (if incredibly fiddly). After more trials to get the hole size right for easy assembly, we had a kit of parts. About 80-90 pieces were cut for Stephen to have a go at, at home.

An initial rodding scheme and embryonic support design.

The support design transferred to CAD.

The first batch!

Original support with single hole and the final double-hole supports and packers.

A three-rod support unit (without the top retainer). These will be glued onto card baseplates.

We were very pleased with the speedy progress and the components we had created. We will need to see how they behave once assembled, and try some rodding mock-ups. And then there's the cranks and lever frame that need to be considered, but it's a good start.


The rodding and lock units also form part of the system to prevent 'incidents' on the approach to the station and the proposed sequence is:

1) A train arrives from Cottesmore or the quarry and stops at the appropriate 'holding' sign, at which point a treadle triggers the bell and a light on the lever frame. The bell rings for (say) 10 seconds, but the light remains on.

2) The pointwork is set by the controller, the light on the 'holding' sign is illuminated and the train advances into the station.

3) The lights on the lever frame and the sign are turned off.

This could all be achieved with manually operated switches for each element, but automating part or all of the routine had been briefly discussed. With this in mind, Stephen had been experimenting at home with some IR detectors that could be used to automatically trigger the bell and lights scenario. Never having used them before, some research was required and the simplest option had been to employ an Arduino Nano micro-controller. This would also have the ability to be programmed for further parts of the sequence. Once it had been successfully rigged-up, a sound unit was added, as used for the generator engine, and a bell audio track recorded. Stephen now successfully demonstrated the unit, albeit that the bell sound was very poor. This was not improved by substituting a better speaker, so further investigation is required. This will be developed in parallel to the manually operated switch option.

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Homework!

Based on the discussions, Stephen updated his drawing to calculate the number of each type of support. Some questions about rod-end connections and crank orientation came to light, which have to be investigated.

He then assembled several 3-rod and 2-rod support units. The two plastic rods certainly helped assembly, and the dilute PVA that was brushed over the completed units firmed the card nicely. They'll be cleaned up and painted before next week.