Nicholas.Spies@H.CS.CMU.EDU (09/19/85)
The interesting messages about rail technology prompts me to ask whether any of you know what has happened to the idea of using pre-stressed concrete for RR ties. Also, what is the service life of rails, ties, and the track bed? As the three are a integral unit it would be interesting to know what the ideal qualities of each would be, which may suggest new ways to build tracks requiring less maintenance, give longer service life, etc. For instance, would simple heat pipes driven into the ground dissipate heat and relieve thermal stress on rails or is it not important enough to justify the expense? Would rails (and wheels) benefit from laser annealing to reduce deformation? Or is this not cost-effective? Would magnetized "sleds" using a generator driven by wheels during breaking be more effective than breaking only with wheels?
mangoe@umcp-cs.UUCP (Charley Wingate) (09/19/85)
In article <1591@brl-tgr.ARPA> Nicholas.Spies@H.CS.CMU.EDU writes: > The interesting messages about rail technology prompts me to > ask whether any of you know what has happened to the idea of > using pre-stressed concrete for RR ties. Also, what is the > service life of rails, ties, and the track bed? As the three > are a integral unit it would be interesting to know what the > ideal qualities of each would be, which may suggest new ways > to build tracks requiring less maintenance, give longer > service life, etc. The AMTRAK line from DC to NY is all laid with concrete ties. It's the most massive-looking right-of-way I've ever seen. Charley Wingate
drockwel@CSNET-SH.ARPA (Dennis Rockwell) (09/19/85)
From: Nicholas.Spies@h.cs.cmu.edu Date: 18 Sep 1985 19:18-EST Subject: Ties The interesting messages about rail technology prompts me to ask whether any of you know what has happened to the idea of using pre-stressed concrete for RR ties. I can report on what I've seen recently. AMTRAK is apparently using concrete ties in the Washington area (specifically in the NE Corridor near New Carrolton), but not in other places (like around DC Union Station). The MBTA is using concrete base plates (each taking the place of about four ties) in new tunnels (esp. in new areas of the Red Line subway), but is still using wooden ties for new track outdoors, and in the reconstructed areas of the Green Line (LRVs and PCCs). The DC Metro follows the Red Line scheme. B&M, while laying all this new welded rail, is still using wooden ties, at least in the places I've seen.
jar@siemens.UUCP (09/23/85)
Would magnetized "sleds" using a generator driven by wheels during breaking be more effective than breaking only with wheels? It seems to be effective because in Germany every passenger car which may run 125 mph has magnetic brakes. There are 4 sleds per car and they are powered by the locomotive (as far as I know). This breaking system is in addition to the regular system (with air pressure). I do not know which system is used in which case although I used such a train because the regular system has now discs just like the cars have and it doesn't make the awfully noise. There is also a third system only on the locomotive where the motors are used as generators. This system is the most effective one because the energie feeds the powersupply and is not converted to heat. This system is in use as long as it provides a sufficient reduction of speed, if necessary another system is used in addition. Just another detail I read in a railroad magazine in Germany: If you use the magnetic brakes in an emergency to reduce the speed from 125 mph to zero, the force will be as strong as a DC-10 during take-off and you must repair the tracks thereafter because in this case the slids are nearly clued to the tracks.
Dan_Bower%RPI-MTS.Mailnet@MIT-MULTICS.ARPA (09/23/85)
Concrete ties have a number of advantages. They mass 3 to 4 times that of a wood tie, giving the track far greater inertia. This makes it harder for a train to knock it out of alignment. With the quality of concrete used today, life estimates range from 40 to 50 years. (This compares to 30 years for a wood tie. Both figures are for ideal conditions. Poor drainage, extremely heavy traffic, etc. can cut the life of any tie in half or less.) Also, because of the way a concrete tie deteriorates (it's either broken or it ain't) you can use a wider spacing between them than with wood ties. With wood, you expect a gradual deterioration and compensate by putting in more than is needed if they performed like new for their entire lives. 19 1/2" to 22" is typical on mainlines for wood ties. With concrete, 30" is common, as a 30" inch spacing is adequate for support and gauge, IF all the ties are up to snuff. There are some disadvantages with concrete ties. One, you can't mix them with wood. Because of concrete's greater rigidity, the concrete ties in mixed track would quickly end up supporting all the load of the train. If you want to use concrete, you have to replace all the ties all at once. Concrete is a lot harder to handle. Two guys can't just grab one and walk away with it like they can with wood. Concrete ties make for more ridgid track, giving a noiser, rougher ride than wood ties. (There are special cushion pads to go between the rail and tie, at an extra cost, of course.) Finally, going with concrete requires a very large capital expendature. As you may know, new capital is scarce on most railroads these days. Also, most concrete ties are not adjustable for gauge. On curves, rail will wear allowing a widened gauge. With wood ties, you pull the spikes, plug the holes, move the rail into gauge and spike it back down. With concrete, you only have the choice of transposing the rail or swapping it with the low side of the curve. Both alternatives require immediate rail grinding to undo the high side wear and low side deformation. Re: rail life It depends on where the rail is, what steel it's made of, and what runs on it. On lightly used branch lines, rail lasts (practically) forever. On heavy mains, rail on tangents may last as long as 35 to 45 years if the track is kept in good surface. On curves, the faster the trains go the more they will abrade the high side rail. They heavier they are, the more they deform the low side. In the worst cases, rail gets worn faster than the traffic can work harden the surface, and it wears out in 3 or 4 years. If the rail was heat treated or of a special alloy, you might get 50% to 100% more life out of it. There are also some asymetrical grinding tricks that can prolong rail life on moderate curves. These involve grinding the high rail so that the wheel is in contact close to the flange (where the radius of the wheel is greatest) and grinding the low rail so the wheel rides on the outside of the tread. This has a slight self steering effect which can double rail life on curves up to 2 to 3 degrees. Curve lubrication has been used for some time. This does reduce abrasive wear, but it reduces traction and has been observed to increase deformation. (The problem with reducing traction is that if the engine slips, the engineer drops sand. The grease holds the sand to the rail, greatly increasing abrasive wear. Some railroads with double track lines only put curve greasers on the track where traffic is mostly downgrade.)
msb@lsuc.UUCP (Mark Brader) (09/25/85)
> The interesting messages about rail technology prompts me to > ask whether any of you know what has happened to the idea of > using pre-stressed concrete for RR ties. > British Railways has been using concrete ties* for all new track on fast lines for years. I don't know if they still have any wooden ties left. In a few places they have experimented with a continuous concrete trackbed. *Called "sleepers" in Britain, of course. The French TGV line has concrete ties that disappear below the ballast in the center, giving the appearance of those antique British lines that had no cross-ties at all, only stone blocks under the rails. Speaking of antique British lines, I think it might be of interest to remind people of the original track construction on the Great Western Railway (of Britain). This track was 7 feet 1/4 inch in gauge (so that the wheel flanges were 7 feet apart exactly). The load-bearing sleepers were laid longitudinally, so that the rails were continuously supported. Cross-ties were placed at intervals of about 10 feet, I think, to maintain the gauge. Originally the cross-ties ran continuously across both tracks (I don't know how they were fastened to the sleepers), and were supported on vertical piles. All of this was in wood, of course. The piles were removed early on when it was realized that they only impeded resilience, but the longitudinal-sleeper system survived for many years. When the GWR was finally regauged to standard gauge* in 1892, the cross-ties had to be sawed to the proper length and the rail and longitudinal sleeper moved in. There is still longitudinal-sleeper track in Paddington Station, London. *Standard gauge means whatever your 4 feet 8 1/4 inch wheel flanges will fit. Traditionally this has been 4 feet 8 1/2 inches, but lines with stricter tolerance use 4 feet 8 3/8 inches. Here in Toronto, some of the newer above-ground parts of the subway system (which, incidentally, is 4 feet 10 7/8 inches gauge) use concrete ties and Pandrol clips. Mark Brader