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Re: Heatwaves and Drawbridges, Etc
Railroads are sensitive to temperature change. Back when you had 39’ sections of “stick” rail bolted together they each had a wee bit of expansion. But even back then a heat wave would cause the rail to buckle (famous derailment in PA killed quite a few) or a cold snap would cause the rail to “pull apart”. Continuously welded rail eliminates the joints and makes the rail more susceptible to temperature change. For this reason welded is heated when it is laid to get it to a specific temperature before it is finally spiked down. Some other measures are also taken but not being a rail engineer and not paying sufficient attention I forget. I recall expansion joints every mile or so.
Lift and swing bridges are a PITA. There are various safety measures, The but joints have “point detectors” to assure the rail aligns correctly, as donswitches. There is additional (guard) rail between the running rails so that if the damn thing jumps the track it will stay near the track.
Electrified railroad has one of two types of overhead wire systems. The newer is “constant tension” where the wire has weights on one end which raise and lower with temperature change. This is great till the wire breaks and you dump a mile of wire. Then there is the fixed placement type which most of the NEC uses. The wire is fixed at each pole, tension goes up and down with temperature. Cold snaps make the wire brittle and it can snap with high tension. Excessive heat is worse, the wire sags and the locomotive contact can rip the wire down. During excessive heat trains were issued “slow orders” to avoid this mess. Bridges typically fail during heat as they are an obvious place for the elongation of rail or wire to manifest alignment problems.
I once worked on a proposed people mover using ski lift technology. The wire mechanisms have a gismo, a weight on a wire, that pulls on a bull wheel, so as to keep a constant tension on the traction wire. So if the temperature gets too hot the skin-lifts won’t operate, but I guess by then it’s moot anyway.
33' Brewer, Murray 33, steel cutter
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Last edited by hpeer; 07-12-2018 at 08:28 PM.