| Forum Home | ||||
| PC World Chat | ||||
| Thread ID: 60402 | 2005-07-31 08:40:00 | Continuous Railway Lines | Winston001 (3612) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 377092 | 2005-07-31 08:40:00 | The discussion on materials science reminded me of a puzzle. When I were a lad, steel had a coefficent of expansion of about 112 (Imperial). Or something like that. Anyway, we were told that railway lines were laid with gaps to allow for expansion and contraction of the steel as temperatures varied summer to winter. Sounded right. Then I recall in the late 1980s that a wonderful new idea had arrived - continuous rails. All welded into one loooong length. Funnily enough a few years later, quite recently in fact, rails have been buckling in summer heat and trains have been given an unexpected right to roam. Trains are conservative beasts and generally don't like this radical change to their ordered lives. So can anyone explain why rails, in the face of 300 years of knowledge, suddenly were deemed a non-expanding metal? |
Winston001 (3612) | ||
| 377093 | 2005-07-31 08:52:00 | Progress!! | Dusty (3931) | ||
| 377094 | 2005-07-31 09:01:00 | if remember right...... the deal was to weld most but not all gaps. the gaps need checking every once in a while to make sure they are not full of crap, less gaps make for less checking, less checking = less $$ spent. |
robsonde (120) | ||
| 377095 | 2005-07-31 09:20:00 | To avoid the effects of expansion welded rails are nearly always laid on concrete sleepers, which are so heavy they hold the rails firmly in place, and with plenty of ballast to stop the sleepers moving. After new segments of rail are laid, or defective rails replaced (welded in), the rails are artificially stretched so they expand (this is called stressing), they are then fastened (clipped) to the sleepers in their expanded form. This ensures that the rail will not expand much further in subsequent hot weather. However if temperatures reach outside normal ranges (i.e. a hotter than usual summer), it can cause problems with welded rails. | tutaenui (1724) | ||
| 377096 | 2005-07-31 09:23:00 | sounds like a whole lotta work to save pennies :( | tweak'e (69) | ||
| 377097 | 2005-07-31 10:10:00 | The other problem with welded rails is that no longer do you have the diddley-dum diddley-dee noises any more, so beloved of my generation :) Click here for a treat Trains (www.andmas.co.uk), of course things were a bit different in the days of steam :thumbs: |
Terry Porritt (14) | ||
| 377098 | 2005-07-31 10:17:00 | I believe the welded rails were a maintenance cost saving brainwave by Toll, as they thought that the lesser temperatures in NZ, compared to Aussie, would be ok . They have been proved wrong . I guess most of the welding was carried out on existing rails, with non of the treatment described by tutaenui . Not that I believe that extra ballast and heavier sleepers will have much effect, the physical properties of material will not be denied . All that will do is concentrate the movement to an area where it will give (the weakest point) which, unless it can escape, will cause the metal to buckle . It's much better to allow expansion and contraction to take place in small increments spread over a distance . In that way the related stress is also spread with any buckling in any one place being minor . |
Murray P (44) | ||
| 377099 | 2005-07-31 10:49:00 | I believe the welded rails were a maintenance cost saving brainwave by Toll, as they thought that the lesser temperatures in NZ, compared to Aussie, would be ok. Happened before Toll. The problem in NZ was that some genius picked the wrong temperature as an average for the prestressing. Terry may miss the "diddley-dum diddley-dee" but modern European trains do very nicely without it and on welded rail you can't really pick whether you're doing 60kph or 300kph. |
PaulD (232) | ||
| 377100 | 2005-07-31 10:58:00 | Happened before Toll. The problem in NZ was that some genius picked the wrong temperature as an average for the prestressing. Terry may miss the "diddley-dum diddley-dee" but modern European trains do very nicely without it and on welded rail you can't really pick whether you're doing 60kph or 300kph. :) And, wheel wear is reduced, and shock loading on the bearings is very much less. Roller 'traction' bearings as they were called didn't like all this diddley-dee, diddley-dum nonsense. If anyone listened to 'Trains' by Reginald Gardiner and you come from Brum, then indeed going into and out of Snowhill Station (GWR line) there used to be that sound of striking a piece of tin, and there were often shadowy figures standing there in the tunnel. |
Terry Porritt (14) | ||
| 377101 | 2005-07-31 11:51:00 | Terry - I'd love to listen to Trains because I suspect it is an echo from my childhood when radio ruled supreme. But it is a .ram file which my PC doesn't recognise. Incidentally I introduced my 10 year old son to Wayne and Schusters "Rinse the Blood Off My Toga" this afternoon. Who says humour belongs to its own generation, he thought it was hilarious. You know, children are barely exposed to any humour these days outside of television. :dogeye: |
Winston001 (3612) | ||
| 1 2 | |||||