Saturday, 4 July 2020

The Garden Railway: Trouble with Turnouts

The design and construction quality of LGB equipment is astoundingly good. You can leave the trains outside in all weathers with no damage or deterioration, whether from rain, snow, intense heat, or UV radiation. The locomotives will pull heavy, friction infested trains all day long without complaint. If anything does break, even the tiniest moulding is available as a spare part, albeit at a high cost. The track too is tough as anything - you can step on it without damage, and electrically it works far better than you could reasonably expect.

But nothing is perfect. The one place where their attention to quality seems to have lapsed is the pointwork, those necessary but fiddly places where trains get a choice of direction. They're eye-wateringly expensive - roughly $100 for a new, electrically operated turnout. But with LGB you just have to get used to that. The problem is, they just aren't that well designed. There's a sort of pervasive optimism, a feeling of "it'll be alright on the night", that applies to every aspect of the design: electrical, mechanical and trackholding.

My garden railway currently has a total of 17 LGB turnouts, all electrically operated via my NCE DCC controller. All the ones on the main running lines are 16xxx medium radius. There is a yard with the small, 600mm radius 12xxx turnouts, mostly bought new 20 years ago. The others are a mix of new, at various times over the last 10 years, and some eBay bargains, of which the oldest was probably 40 years old.

Keeping them all in good working order, so the trains run over them smoothly without derailing, jerking, or just coming to a halt, requires constant attention.

Electrical Problems

All of the electrical side of LGB stock suffers from a degree of design optimism. There are simple rubbing contacts everywhere, for example between the pickups, motors and other electrical connections. The wires are made of brass, which slowly forms an insulating oxide layer on the surface, so intermittent electrical problems slowly arise as the trains gets older, especially when they live outdoors.

The slider pickups on the locomotives are a case in point. The idea is excellent, but the connection from the slider to the rest of the electrics depends on a fragile spring, wound with wire barely thicker than a human hair. If ever there is a short circuit in the engine, the spring heats up to the point where it loses its temper - which is to say it stops being a spring, so the pickup stops working. It's possible, but very fiddly, to replace the springs, and to make it more complicated a different part is needed depending on the particular locomotive.

This pervasive electrical optimism really strikes hard on the points. The outer running rails are solid brass, connected to the adjacent track by heavy, springy fishplates. No problem there. But the connection to the switch rails - the ones that move - is made by very primitive sliding contacts under the rail. This works way better than it deserves to when the track is new, but as it ages the contacts and the rail itself oxidize, and the force holding it all together weakens. The net result is that trains hesitate or flat-out stop as they are going over the points.

It doesn't help that there is a lot of dead track. The place where the two rails cross - the "crossing" or "frog" depending on your train-speak dialect - would ideally be connected to one rail or the other depending on the point setting. This is difficult to arrange, and LGB didn't try. These sections are made of insulating plastic, meaning that one wheel, at least, stands no chance of picking up power. Four wheel locomotives, like "Shiny", our Wismar railbus, are especially vulnerable - the more wheels the better.

The diverging rails are connected invisibly, under the sleepers, by metal strips that are spot-welded to the running rails. They also are a bit optimistic. On several of my older points these welds have failed, leaving a lengthy piece of rail with no connection.

Underside of turnout showing
soldered connecting wires
The solution to all these problems is to make soldered connections between the various pieces of rail. This is a bit daunting since large-section brass rails conduct heat away from the joint area very effectively, and there is an obvious risk of melting the plastic base. To deal with the second problem first - the plastic used for the bases is pretty resilient to soldering. It softens, but doesn't melt, when you heat the rails up. It will melt and burn instantly if you touch it with the hot iron, though.

I've been pretty successful soldering fine wires to the underside of the rails. My technique is:
  • start by cleaning the metal very thoroughly, with a fibreglass "scratch brush", until it is gleaming
  • then cover the joint area in non-corrosive resin flux
  • I use a 50W temperature controlled iron, set to its highest temperature of 425°C, with a substantial chisel-shaped bit about 7mm across - providing plenty of reserve heat
  • hold the iron flat against the rail, holding it as far as possible from the plastic, and hold the solder against the iron - when melted it acts as a heat transfer fluid
  • now hold the iron in place until the rail is hot enough to form a proper joint with the solder. It's easy to see this because the blob of liquid solder suddenly spreads out on the metal
  • now add the wire, then hold it in place with a screwdriver or similar until the solder solidifies again. This will take a while - up to 30 seconds - because of the heat retained by the rail
  • Don't touch anything! - the rail stays painfully burning hot for a long time afterwards.

Mechanical Problems

In real life, track is held on the sleepers by some kind of spike driven into the wood, which either directly holds the rail, in US practice, or holds a metal plate which in turn presses on the base of the rail, in Europe. (It's different for serious railways, with high speeds and heavy trains, but light and narrow gauge railways work like this). The LGB track provides a good visual impression of this, but it really isn't very strong. The rails are held in place by tiny flaps of soft plastic, less than a millimetre thick. It takes very little to twist and break them.

On normal track this isn't really a problem. The sleepers all support each other, so they aren't subject to high stresses. And even if one does break, the rail is still supported by those around it. Points are a different story though. For example, the very first sleeper, closest to the moving switch rails, is the only one supporting the point motor and the first few inches of rail. It can easily get broken, and when it does, the vertical relation between the fixed rail and the moving one is lost. Trains fall off the track as a result.

It's impossible to repair the track base. What I have found effective is to glue the rail in place on the damaged sleepers, using the remains of the simulated spike. The plastic is something soft and difficult to stick to, but I have found a two-part epoxy that works well, Loctite EA9340. I originally bought it to make some repairs in the kitchen, where prolonged exposure to steam softened regular hardware-store epoxy, but it seems perfect for this too. Another advantage is that it dries to a murky dark green, making it pretty much invisible on the track.

The technique is simple. First get everything as clean as possible. Clean the rail with a fibreglass brush, and swab everything with alcohol. Then mix up some epoxy and make it into a blob around the base of the rail, so it looks like part of the sleeper. If several sleepers are damaged on the same point, do it for all of them.

Sometimes you can't blame LGB. One of my points was hit by a heavy steel ball, from playing French bowls (petanque) in the garden. The rail was badly twisted both horizontally and vertically, and many rail fastenings were broken. After I dismantled it and straightened the rail out, the epoxy worked perfectly to hold the rails in place. The repaired point is back on the layout, and trains pass it without problems.

Trackholding Problems

In Victorian times facing points - ones where the train has a choice of which way it goes - were regarded with horror. Railway designers went to great lengths to avoid them on main lines wherever possible. Where they were unavoidable, they always had facing point locks, which held the switch rails firmly in place while a train passed over them. They were interlocked with the signals, so it was impossible to clear a train to pass over the points unless the locks were in place.

Sadly our LGB points don't have these devices. They are held in place rather feebly by the magnets in the point motors. It's quite common to have a tiny gap between the fixed and moving rails - a fraction of a millimetre, but enough to cause problems. If a flange rides over the sharp end of the rail it can move the rail under it, opening the point and dropping into the gap on the wrong side. The rest of the train inevitably derails when this happens.

I haven't found a really good solution to this. Some point motors work better than others. I had one point that would consistently cause derailments. It was an old one, from eBay, with an older design of point motor. Replacing the latter with a newer motor held the rail in place much more firmly, and solved the problem.

The ideal, in the absence of an actual lock, would be a really firm over-centre spring mechanism, but I can't see an easy way to do this. In any case the force produced by the point motor probably wouldn't be enough to overcome it.

LGB four-wheel carriages and trucks have pivoting axles, to simplify going round the tight 600mm radius curves. Normally these are held at the correct angle by the traction on the coupling, but that doesn't work if the train is being pushed. And sometimes they get stiff. So they will occasionally end up trying to go through a point when the wheels aren't aligned correctly with the track. This makes the above problem a lot worse. It causes another problem, too.

In real life, points have check rails, or guard rails, which ensure the wheels go the right way through the "crossing" or "frog", where the two rails cross. The check rail presses against the back of the wheel and stops it slipping into the wrong, diverging flangeway.

Unfortunately the check rails on LGB points are mostly decorative. They are way too far from the rails to be really effective. Mostly this doesn't seem to matter, but on the three-way point they are not only too far away, but not in the places they need to be. There are so many problems with this item that it deserves an article to itself.

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