I was idly looking at the track as a steam loco went over a joint and wondered why the joints in the track are not supported in some way by a sleeper (and chair) arrangement. The cantilevered unsupported ends place an incredible load on the strips of metal and bolts. I realise the problem has gone away now - but has anyone any observations?
I guess it simply wasn't found necessary and avoided the need for specialised chairs. The join also allowed for expansion, which would have been an additional complication.
Not quite as much load as you might think. Remember that the loco weight is distributed over several pairs of wheels so that once the joint "flexes" the load is redistributed over the other wheels. Different for carriages where there is suspension on the bogies.
But isn't the load spread well to either side of the actual joint? Even a Stirling Single loco, with just two massive driving wheels (that is, one on each side) has leading and trailing wheels to take some of the weight.
In the days when they still used fishplates and bolts, as well as wooden chair keys, each joint and key was checked at least once a day by the lengthsman, and you could see the wear at the joints on old rails in sidings and suchlike places. The welded rail, as you say, doesn't suffer from this problem.
However, as has been said, you'd need a special chair to support the weight at the joint, which adds greatly to track maintenance complexity, and given regular maintenance, there wasn't a problem. The old system is still used at junctions, and they are still checked at least daily for loose bolts. Modern rail expansion joints are every half mile or so, and use overlapping horizontally tapered sections of rail which need regular greasing. The keys on the chairs which hold the rail steady still need regular checking with a hammer, too.
Fishplates?
I guess as it worked nobody cared much. Brian
They can't be supported normally as they have things called Fishplates lumps of flat metal quite thick and are what holds the lengths of rail together..
Course thats on olde world sections of line, most all the time elsewhere its long lumps of rail that get welded together...
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