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Post by ducatisti on Dec 1, 2008 10:15:04 GMT
Whilst lurking about Paddington Bakelerloo southbound platform on Sunday early evening, I saw an unusual fishplate.
Halfway down the platform, the line changes from flatbottom to bullhead. At the end of the bullhead there is a piece of rail that does the transition in profile. After that, between it and and the end of the flatbottom proper, there was a four-bolt fishplate with no bolts in it, but two clamps going round underneath. Judging by the profile the main flatbottom looked fairly new. Would this clipped fishplate be a temporary measure before some new flatbottom was installed in the next engineering possession? Why was it clipped not bolted? I don't see how clamps would be any easier to undo than bolts...
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mrfs42
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Big Hair Day
Posts: 5,922
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Post by mrfs42 on Dec 1, 2008 12:59:42 GMT
The joggle plate may well be a temporary measure - either to move along with the head-of-flatbottom-steel or could have the clamps in for cardiuming [1]. Clamps can be undone by hand and don't require spanners.
[1] I'm not sure if cardium is used in tube, mind.
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Post by stanmorek on Dec 4, 2008 12:31:51 GMT
Sounds like a temporary C-clamp. There are complications with welding rail ends with bolt holes. If I recall there is a 7 day limit for welding of rails with holes 30mm within the end.
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Post by ducatisti on Dec 5, 2008 9:50:09 GMT
Ahhh, that would seem likely. Is that to stop it heat-cycling too much? Presumably they are replacing the rail too, so maybe they don't want to weld the transition bit as it'll be somewhere else the next evening?
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Post by stanmorek on Dec 5, 2008 19:43:12 GMT
Obviously a zone in the rail ends will be affected by heating from the welding process. Holes can be distorted and initiate a defect and eventual rail break.
Its been a while but to my knowledge the forged transition rail is permanent such as flat bottom rail abutting bullhead junction work. Clamping is meant to be temporary. But with all the track taking place now who knows?
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Post by stanmorek on Dec 5, 2008 19:53:23 GMT
Trivia: I'm no carpenter but I assume that a fish plate joint was named after a fished joint. I recall that the angle the surface of the rail head or foot makes with the web is known as the "fishing angle". Then there is also a "scarf joint" at expansion joints.
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