As some of you will have read, Fintonagh was misbehaving at the weekend, with four main culprits:
The turnout to the turntable
The turnout at the entrance to the yard
The first two were covered in the Layouts thread, but the turntable has needed a complete rebuild, while the magnets remain work in progress.
The turntable is a Peco N gauge one, with a wider deck to take 21mm track. Its 15cm diameter is just right for the Clogher Valley locos, while to many visitors' surprise, the railcar fits on too. Just. However, its operation is far from prototypical in that all the weight of the loco is born by the centre 'boss'. As this is where the sprung, plunger pick ups are located as well, what happens is that my heavy CVR tanks make the deck drop down about 2mm as they drive on to it and also tend to skew it sideways as they drive off too. Not good then...
I've lived with this for a few shows, but wear and tear has started to cause problems, mainly a very stuttering rotation, especially when it is cold for some reason. The weight of the loco should be born by the single 'rail' in the well. This is simply a raised, moulded line on the model, with four, moulded, none rotating 'wheels' under the deck which rub on the rail and therefore simply hinder progress. A solution came to me from building the new South East Finecast table for Belmullet. Here, four ball bearings act as carrying wheels for the deck, so the weight of the loco is taken on the outside of the well and everything is thus better supported.
You can see what I've done from the two photos, which show the underside of the deck. First, I cut two pieces of 8mm brass strip, to act as carrying arms for the four new outer wheels. At the outer ends of these, I drilled four holes and reamed them out to take Slater's loco axles. Working in 36.75mm gauge, I have plenty of spares of these. What I did, was grind off the squared ends, still leaving enough of the tapped hole for the wheel nut. A section of each axle was then soldered into the holes in the brass strip, leaving about 4mm sticking out, to make stub axles. On to these have been put a Slater's brass wheel bearing, to act as rollers on the deck bearing, with these being held in place with wheel nuts. All that was then needed was to use a junior hacksaw to cut a slot in the underside of each end of the deck, just inside the former dummy wheels. Finally, I bent the brass strips to match the curve of the rail in the well.
Hence the deck is now supported where it should be, at its outer edge and there is no drop when a loco drives on or off. Happily, the plunger pick ups in the centre boss still transmit current to the deck rails! The real test will be at the weekend, when Fintonagh is operating at the Canterbury show, so cross everything, as they say. However, thus far, I'm rather pleased with the result, which owes a little to good engineering practices than my usual bodging techniques, with special thanks to SE Finecast forgiving me the idea in the first place.
The magnets are a different story though. I use [mainly] 5mm diameter, 10mm long rare earth rods, in holes drilled either side of the track centre line. These attract [most of the time] the dropped wires on the Kaydee No 5 couplings I use. However uncoupling can be erratic at times, with in the worst scenario wagons failing to uncouple when place over the magnet, but actually coming undone when pulled across one. Very annoying, and more difficult to solve on Fintonagh, where wagons get turned around after each sequence because I have a turntable fiddle yard. Hence, no matter how much you practice/test, there are a great many combinations of wagons pairings, some of which, for whatever reason, do not work reliably.
Talking to one of the Burnisland crew at Stevenage, it seems there are a few issues I hadn't considered:
Apparently, it can help to have the rare earth magnets slightly staggered, rather than opposite each other, as this helps stop the dropper wires being pulled in the same direction
It is important to make sure that all the magnets are pointing the same way. Not sure which is best [all north or all south], but one way gives a wider magnetic field for some reason. Perhaps somebody out there can enlighten?
It helps if the magnets are as far apart as possible, though even if your track gauge is 21mm, using 5mm diameter magnets doesn't allow that much space.
Interestingly, I put 3mm dia magnets in the train shed and these work fine, as do the 5mm ones in two places further along the platform. The 5mm ones in the end loading dock have thus far foiled all attempts to get them working properly, so am going to replace them with two of the 3mm ones, to see what happens. Otherwise, it has been a case of sticking rigidly to the same wagons on each train and with each train shunting a single siding [exchanging just a single wagon each time], hopefully I can eventually rule out the 'rogues' and put them aside for future fettling. If it sounds like Fintonagh is not running well, fear not - generally derailments only occur through operator error and the couplings are around 80-90% efficient. However, when stuff is working well, it is a real pain when it doesn't as the whole illusion is spoiled. On these occasions, all I can say is that it is a good job any children present don't know what I'm thinking!