I finally decided to try the 15V AC supply using a power diode to give half-wave rectification. In theory this should deliver about 7.5V average, well within the capacity of the coil. This proved very successful on all fronts: the magnets successfully and reliably uncouple locos, and the average current drawn is only about 0.5A - well within the capability of my transformer, and the coil itself. The main point here is that although the average voltage and current (and hence wattage) are fairly low, the peak voltage should be about 21V (momentarily) and this is enough to uncouple the most stubborn of couplings.
The only downside is that the AJ’s ‘chatter’ because of the half-wave power, and make a bit of a noise. I can hear this in my workroom, but I doubt that it could be heard at all in an exhibition environment. With a bit more experimentation, I found that a 4R7 power resistor in series with the coil reduces the voltage and current drawn a bit further, (and hence make the uncoupling a little quieter), but doesn’t materially affect the reliability of the uncoupling.
My mechanism for operating ground signals for Brighton Road has proved reasonably ok, but is not 100% reliable. A couple of the motors have failed completely, and a couple of others are rather noisy. For Plumpton I think I will revert to more conventional motors - probably some Fulgarex point motors left over from another project.
Brighton Road is 3ft wide and is operated from both front and back of the layout. Whilst we were at the Bluebell MRS recently, it occurred to me that Plumpton could be operated very successfully from the front of the layout. Having spent a long time building the interlocked lever frame, it seems a bit of a shame to hide it behind the layout where nobody can see it. An obvious solution is therefore to simply turn the layout round, so that what was the back of the layout, becomes the front, spectators’ side. The only material difference is which side the back scene has to be fitted to. Plumpton is due to be shown at the Bluebell MRS next June for its first outing, so it will be operated from the front as an experiment.
August and September 2013. Things have slowed up a bit during the summer for the usual reasons - including a week in Grosmont, close to the North York Moors Railway. A very pleasant week, and their Pullman diner has a lot to recommend it - excellent food while steaming through the countryside.
I had hoped to get all four baseboards laid and wired by the end of September, but have not been able to get this far unfortunately. We have however built the four baseboards, and laid/ballasted the track on the third. This baseboard incorporates an accommodation crossing for the Green Lane which crosses the line west of the station. The photographs show the real thing, and as can be seen it’s quite complex - wrought iron beams bridging the gap, with baulk timber trackwork on top. The real thing only has two lines over it, but because I’ve adjusted the track plan a bit, my crossing has four tracks.
Once the track is laid there will be no access underneath the bridge, so we’ve had to finish the scenic work under the bridge before laying the track. The photos on the left show the basic structure of the baseboard, with the wingwalls temporarily in place before painting. The photo on the right shows the beams and baulk timbers in place, with all the track laid on top. and basic scenic work underneath. There is still a lot.of work to do on top of the bridge.
The next task is to wire up this board - all the Tortoise motors are in place and ready to go.
As described last month, I’m having a rethink about ground signals. I’ve made all ten signals needed for the layout, and devised what I hope is an improved method of operation, going back to the Fulgarex motors we used for Pulborough, but (I hope) in a rather better configuration. More on this when I’ve sorted things out a bit more.
The main difficulty with the final baseboard will be the level crossing. I’ve started looking at various ways of motorising the gates, but haven’t yet hit on anything that I’m convinced by. The gates are still in place and operated from a capstan in the adjacent box. (Network Rail intend to replace them next year with barriers, much against the wishes of the village).
When the gates are opened or closed, they start to move at slightly different times, move at different speeds, and reach the end of their travel at slightly different times - presumably as a result of wear and slop in the mechanism, and no doubt by how much effort the signalman applies. I would quite like to replicate this rather quirky motion if I can. One option which I haven’t yet looked at is servos, and the accompanying electronics. Do these servos travel through more than 90deg? (The crossing is heavily skewed so that one half of each pair of gates moves through move than 90deg, and the other half less). Can the speed of operation of the servos be tuned to replicate the different closing time for each gate? More research needed........
October 2013. A handful of major milestones have been reach in October. All the track has now been laid, and has all been wired up. All the turnout motors have been fitted and are operational from the lever frame. All the ground signals have been fitted, and seven of the ten are functional. All the AJ magnets have been fitted, and are functional.