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| Boston Transit 21/10/2023 at 23:00 #153761 | |
9pN1SEAp
1102 posts 
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An interesting article about an extension to the transit system in Boston which was somehow built out of gauge and the right people didn’t know. https://www.trains.com/trn/news-reviews/news-wire/mbta-green-line-extension-was-built-with-track-out-of-gauge-faces-significant-repairs/ Jamie S (JAMS) Log in to reply |
| Boston Transit 22/10/2023 at 00:38 #153762 | |
GeoffM
6282 posts
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Even living in the US for many years, I still can't get my head around measurements like "4 feet, 8 7/16 inches" (it's 1433.5mm instead of 1435.1mm... I think)
SimSig Boss Log in to reply The following user said thank you: KCRCRailway |
| Boston Transit 22/10/2023 at 17:38 #153768 | |
bill_gensheet
1317 posts |
A discussion elsewhere. https://districtdavesforum.co.uk/thread/31893/lul-track-gauge More like sack whoever wrote the spec / signed it off ! NR has varied +/-3mm by intent. Log in to reply |
| Boston Transit 22/10/2023 at 22:40 #153773 | |
dmaze
87 posts |
...this is a project that started construction, then was cancelled and re-bid when actual costs came in much much higher than expected. Meanwhile, the entire MBTA rapid transit system has come under increased scrutiny from the US Federal Transit Administration for major safety issues. Large parts of the Red Line heavy-rail rapid transit, normally 40-50 mph, are still running at 10 mph after the T lost documentation on track work. On the Green Line Extension work discussed in the Trains article, most of the 3 mph slow zones have gotten fixed. But it's still an embarrassment for a brand-new rail line. (The Somerville Community Path adjacent to this is a pretty good spot for train watching: it is not just the Green Line, but also the MBTA Lowell commuter rail line, the route of the Amtrak Downeaster, and even gets some CSX freight.) Log in to reply |
| Boston Transit 23/10/2023 at 07:59 #153777 | |
Giantray
330 posts |
GeoffM in post 153762 said:Even living in the US for many years, I still can't get my head around measurements like "4 feet, 8 7/16 inches" (it's 1433.5mm instead of 1435.1mm... I think) Yes track gauge measurement is intriguing. Just a millimetre sounds like nothing. In the 1980s here in the UK, British Rail was having issues with newer trains hunting, rocking side to side, on newly installed Continuosly Welded Rail. So the Research Department looked into this and came up with a solution. The standard gauge was always 1435mm (4' 8 1/2"). The solution was to install CWR at 1432mm (4' 8 3/8"). This stopped the hunting of vehicles on CWR. However during the period 1980 -1999, there were several freight train derailments on CWR which they attributed to the smaller gauge. Eventually it was decided that the National standard would be made 1435mm and a change was made to wheel/tyre profiles to prevent the hunting. There are many instancies of the Standard gauge being wider on tight curves, to allow wheel sets to take the curve. One location was between Borough Market Junction and Cannon Street Bridge before the relaying and layout changes of 1991. Retired Professional Railwayman (1981-2023); Pway & S&T (1981-88); Former Signalman/Signaller/ Signalling Trainer (1989-2023) [AB, TCB, Mechanical, NX, WestCad, Hitachi SARS]; Railway Historian (esp.SER, LCDR); Member of The Permanent Way Institution.. Log in to reply |
| Boston Transit 23/10/2023 at 08:51 #153778 | |
postal
5190 posts |
Giantray in post 153777 said:GeoffM in post 153762 said:You've been posting some fascinating stuff in this and other threads over the last few days. Thank you.Even living in the US for many years, I still can't get my head around measurements like "4 feet, 8 7/16 inches" (it's 1433.5mm instead of 1435.1mm... I think) “In life, there is always someone out there, who won’t like you, for whatever reason, don’t let the insecurities in their lives affect yours.” – Rashida Rowe Log in to reply |
| Boston Transit 23/10/2023 at 10:12 #153779 | |
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Jan
889 posts |
Giantray in post 153777 said:In the 1980s here in the UK, British Rail was having issues with newer trains hunting, rocking side to side, on newly installed Continuosly Welded Rail. So the Research Department looked into this and came up with a solution. The standard gauge was always 1435mm (4' 8 1/2"). The solution was to install CWR at 1432mm (4' 8 3/8"). This stopped the hunting of vehicles on CWR. However during the period 1980 -1999, there were several freight train derailments on CWR which they attributed to the smaller gauge. Eventually it was decided that the National standard would be made 1435mm and a change was made to wheel/tyre profiles to prevent the hunting. There are many instancies of the Standard gauge being wider on tight curves, to allow wheel sets to take the curve. One location was between Borough Market Junction and Cannon Street Bridge before the relaying and layout changes of 1991. Funnily enough I've come across a relatively recent engineering handbook suggesting precisely the opposite – gauge widening on straight track is supposed to increase the critical speed for hunting oscillations, whereas now that steam locomotives with their relatively enormous wheelbases are no longer a thing, some slight gauge tightening on tight curves is supposed to improve the self-steering of the wheelsets through the curve. While I don't know how much the gauge tightening on curves to improve self-steering has been taken up on any mainline, because most everybody that I'm aware of still does the traditional gauge widening on tight curves, general gauge widening even on straight track to reduce hunting at high speeds definitively seems to be a thing. As far as I know, DB in Germany uses 1436 mm, Austria and Switzerland are using or at least experimenting with 1437 mm, and isn't it the case that the UK has actually been using 1438 mm for some time now? Circling back to Boston, supposedly even on light rail infrastructure with the associated extremely tight curve radii (where the self-steering of conical wheelsets will never work), gauge tightening can supposedly be beneficial, although of course only on those tight curves, not on the whole line. Germany gives the same recommendation in its official light rail track gauge guideline, and I do know that my local tram network does indeed use a slight amount of gauge tightening on curves below 50 m radius. Two million people attempt to use Birmingham's magnificent rail network every year, with just over a million of them managing to get further than Smethwick. Last edited: 23/10/2023 at 15:13 by Jan Reason: wording Log in to reply |