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Edwin_m

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    Modelling N gauge contemporary NW England.

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  1. How much current actually flows depends on the resistance of the can and of its contacts with the rails. Fires from this cause are reported quite regularly so clearly it does happen sometimes.
  2. Something like a drinks can wedged between the 750V third rail and the running rail could well conduct enough current to get pretty hot but not enough to melt (thereby removing the problem) or even to trip out the circuit breakers. There are reports of fires on the third rail a few times a year from this or similar causes. An object of the same electrical resistance shorting out a 25kV overhead would carry about 30 times more current and create 900 times more heating, so would most likely be vapourised instantly. And because the fault current is that much more than the normal current the breakers would almost certainly trip out when that happened, but the ECO would normally re-close them within a few seconds and because the offending item was no longer there it's likely that normal operation would be restored.
  3. Has the failure bit ever actually happened? I'd have thought the current would go through the metal body not through any internal wiring, rather like a plane can survive a lightning strike.
  4. It would have been 1500V not 25kV for a start. The arcing distance is a lot less but because the normal operating currents are higher on DC it's more difficult to detect a fault so it may have taken longer to shut off the power.
  5. And presumably if the train stop failed to prove down, both aspects would be lit indefinitely.
  6. No problem, I just thought that some people might conclude otherwise as it sounds quite alarming!
  7. I don't see that flashover from the OLE is a serious a safety issue provided the protection devices on the overhead line work as designed, to cut the power quickly before damage results that could bring the line down. A train is very definitely earthed by virtue of sitting on the rails, so anybody touching it isn't in danger. It's more of an operational inconvenience and if steam operation causes one every few years then that ought to be tolerable. They happen reasonably often from things like pigeons landing in places where they can short the OLE to an earthed structure, vapourising themselves in the process.
  8. Was there absolute block east of Wareham in those days? If so then the train would surely have been pulled up for lack of "tail lamp".
  9. Just to clarify, there's one there for each direction I think.
  10. These coaches are the same basic design as the new Caledonian Sleeper. Have there been any complaints about noise and rough riding on that?
  11. However in the last few decades the UK electricity supply industry has shifted from heavy dependence on coal to gas and on to renewables which now make up a large proportion of the mix. Both these steps have reduced emissions of carbon dioxide, which causes global climate change wherever it is emitted, and of other pollutants such as sulphur dioxide which are more of a problem in the vicinity of wherever they are produced.
  12. I remember that 31 smoking the place out when it was started up in the RTC yard at Derby back in the 90s sometime.
  13. You could work out the maximum superelevation but not necessary the superelevation that was actually used [aside: from here I'll use "cant" instead as it means the same but is easier to type]. There is an "equilibrium speed" where a train going round a canted curve experiences no net lateral force and the wear on both rails will be equal. But trains may be going slower than that, and therefore wearing the inner rail more, or faster and wearing the outer rail more. So the choice of cant at a particular location depends on the mix of train speeds arising from stopping versus non-stop and also passenger versus freight, with tonnage also taken into account because a heavy train causes a lot of wear on the lower rail if it is going a lot slower than equilibrium speed.
  14. Cant on a model is purely for cosmetic effect, it doesn't help the trains go round curves (and it can hinder if the stock is uncompensated and the cant gradients are too abrupt). Because gravity doesn't scale, model trains can go happily round curves at speeds where the prototype would overturn. Generally speaking modern curves will be canted independently - that is that the lower rails of each track will be level with each other, rather than being in a common plane so the outer track is higher than the lower. This may not be so if there is a crossover or other pointwork on the curve between the two tracks in question, but that sort of layout is avoided where possible as it's difficult to maintain and may cause a lower speed restriction for trains on the principal route. If a junction on a curve is optimised for trains on one route, then those on the other route may encounter reduced or even negative cant, which will lead to a severe speed restriction (Sheet Stores Junction springs to mind).
  15. Best exhibition I have been to for some time - good selection of layouts and the local/secondhand traders and some specialist traders and demos without being swamped by the box shifters. I assume SVMRC have upped the size of this in response to the demise of the big event in Nottingham.
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