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Post by Deleted on Mar 15, 2006 1:02:48 GMT
Back on topic, I'm not sure where steel sleepers ARE the best option. They were tried on NR as far back as 1948 (or possibly even earlier) but were never widely adopted, so there must have been problems. They must have ironed out the problems, as they were laid all the way from Wembley to Northwick Park on the Chiltern line about 5 years ago.
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Post by Deleted on Mar 15, 2006 10:06:05 GMT
Back on topic, I'm not sure where steel sleepers ARE the best option. They were tried on NR as far back as 1948 (or possibly even earlier) but were never widely adopted, so there must have been problems. The GWR (and possibly the other 3 companies) used steel sleepers during WW2 because of the difficulties in importing suitable timber. They worked fine, but were significantly more expensive than timber. Concrete sleepers were also tried but, with the technology of the time, there were problems with cracking at the rail chairs. When timber supplies improved after the war, the GWR went back to using the material used by Brunel.
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Post by Deleted on Mar 15, 2006 13:41:12 GMT
adw,post # 21- "Does anyone give a - - - - " I try not to use those expressions when the children are around Er... it wasn't me who said that.
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Post by stanmorek on Mar 15, 2006 16:32:42 GMT
Why did the PWay mob re-lay the up main down the Hammersmith bank from Ravenscourt Park to the bottom of the viaduct with wooden sleepers? The down main is laid with concrete sleepers throughout... P-Way (Asset Maintain) do maintenance work and usually carry out like for like replacement and to existing track geometry (top and line). The capital works or ballast track renewals are carried out by Balfour Beatty for Metronet. Renewal works are a bit more involved and lay FB rail on concrete sleepers (continuously welded and stressed in open sections) to redesigned geometry. Timber sleepers in open sections are normally treated softwood though hardwood is also used around P&Cs and signal equipment. Concrete sleepers will have some flexibility as they have prestressed steel inside to prevent cracking though they're not intended to carry load through flexure. Also even with sections of track with concrete sleepers they'll always be timber sleepers around drainage catchpits.
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Post by Deleted on Mar 15, 2006 17:15:06 GMT
Why did the PWay mob re-lay the up main down the Hammersmith bank from Ravenscourt Park to the bottom of the viaduct with wooden sleepers? The down main is laid with concrete sleepers throughout... P-Way (Asset Maintain) do maintenance work and usually carry out like for like replacement and to existing track geometry (top and line). The capital works or ballast track renewals are carried out by Balfour Beatty for Metronet. Renewal works are a bit more involved and lay FB rail on concrete sleepers (continuously welded and stressed in open sections) to redesigned geometry. Interesting. I always thought it was all the same people responsible for track, both maintenance and renewal (and new build). Timber sleepers in open sections are normally treated softwood though hardwood is also used around P&Cs and signal equipment. Concrete sleepers will have some flexibility as they have prestressed steel inside to prevent cracking though they're not intended to carry load through flexure. Also even with sections of track with concrete sleepers they'll always be timber sleepers around drainage catchpits. Thanks for the info. But it still doesn't answer my question - why is this line using wooden sleepers when the line next to it is using concrete sleepers? [/quote]
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Post by stanmorek on Mar 15, 2006 22:06:21 GMT
I assume the section you mentioned won't be changed over until a later date. The next BTR works in that area are not until June. No offense to P-Way but they don't have the expertise or the equipment to carry out a complete renewal but it still pays to remove things like TSRs.
I believe its the same arrangement with the mainline where Network Rail have taken maintenance back in house but the likes of Balfour Beatty still do the big track renewals. That's where all the money is to be made and they publicise that too much.
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Post by markextube on Mar 27, 2006 15:51:26 GMT
Does anybody seriously answer questions without wondering off the beaten track or trying to be funny. If somebody asks a question its because they want an answer not a load of stupid comments.
The possible answer to the original question is that wooden sleepers are normally used in areas where the trackbed may be weaker i'e over drainage. In this case i assume because the tracks are over various weak brick structures and possible drains, wood has been chosen. Maybe because they are lighter or they might absorb vibrations a bit better i'm not sure. But i've noticed wood is also used around drainage areas within a new section of track with mostly concrete sleepers. And wooden sleepers are alsways used on expansion joints.
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Post by stanmorek on Mar 27, 2006 20:50:20 GMT
The condition of all structures and drainage are assessed and are strengthened if necessary before BTR work can take place so there's not many areas that can't have concrete sleepers. LUL standards demand it. Just because a bit of track has never had concrete sleepers laid it doesn't mean it can't.
And strengthening is usually done for the temporary situation when the track ballast is dug out and there is a risk that foundations can slide or the exposed 6 foot drainage getting hit by machines.
True greater dead loads from heavier sleepers would have a greater dynamic effect on the track bed but they are quite small compared to the actual load of a train whether on concrete or wooden sleepers.
Drainage catchpits have wooden sleepers because they can be cut to size to avoid clashing. Concrete sleepers can't be cut on site because they would loose their prestress if a tendon is cut.
Expansion switches require special rail chairs which clamp the rail ends in the switch. For the same reason as P&C equipment is fixed to timber sleepers it is cheaper to use timber rather than cast a few special concrete sleepers.
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Post by agoodcuppa on Mar 27, 2006 20:55:34 GMT
I'm guessing that the track is still on a viaduct just there, might that have something to do with it?
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