High speed cross over switches

[northeaster]

Some years ago, I read an article about the engineering history of the Pennsylvania Railroad describing some experimental high speed cross over switches for maintaining up to 100 mph track switching. The switch was incredably long in order that the curve could be gentle. I have no idea where I read this but have been trying to find reference to it for several years now with zero results. Obviously, this experiment was many years ago when track pans, etc. were used in an effort to maximize passenger train speeds. I think the Amtrak switches are meant for max 40 mph use. Anyone know about this?

[timz]

#20 crossovers are usually 45 mph; I'm guessing PRR never tried anything longer than that. If you're asking about the long crossovers that have appeared here and there since the 1990s, they're supposed to be 80 mph.

[RME]

northeaster

Some years ago, I read an article about the engineering history of the Pennsylvania Railroad describing some experimental high speed cross over switches for maintaining up to 100 mph track switching.

One example of these was almost certainly the crossovers at Princeton Junction, as revised for the Metroliner project.  These if I recall correctly introduced a nominal 85mph speed restriction on what was otherwise the speedway between New Brunswick and Trenton, which was relatively recently 'relieved'.  A track chart from 1967 on might show the specific technical details PRR (and PC) used.

My understanding at the time was that a good high-speed crossover should involve nearly constant lateral acceleration/deceleration, rather than a long gentle angle alone (to minimize the problem at fixed frogs), so you had the equivalent of a spiraled curve either side of the 'inflection point' at the center of the crossover.  See also for example Klauder's patent on k-spiral, bend, jog & wiggle

Laying this out and then maintaining its geometry in the era before laser guidance and accurate pointcloud alignment might have been interesting - a demonstration of both surveying skill and tracklaying knowledge and experience.

[daveklepper]

Before my departure in 1996, Metro North installed some long high-speed crossoversI on the Harlem Div. line,  I think near Crestwood and at Scarsdale or Hartsdale.  This was at the same time that wayside signals were replaced by cab signals and some form of ATC was implemented.

[BaltACD]

While not a crossover switch, this is a 200 KPH switch.  Eight switch machines operate the switch points and three switch machines operate the movable point frog.

[northeaster]

Wow, I am really impressed at the information out there regarding this question. I would assume that the article I had read was referring to PRR back in the 1930's -40's and their engineers would have face lots of physical plant problems to maintain or even keep such a cross over operational. Thank you all who have contributed to my knowledge about this piece of railroad equipment.

[timz]

RME

One example of these was almost certainly the crossovers at Princeton Junction, as revised for the Metroliner project. These if I recall correctly introduced a nominal 85mph speed restriction

Maybe they would have, if they had existed. I'm guessing in 1969 no crossovers faster than 45 mph betw NY and Washington. The only change to Nassau interlocking's layout was its elimination in the 1980s.

Next question: when/where did the NEC get a more-than-45-mph crossover? I thought Rwy Age said Grove interlocking's x-overs were 60 mph anyway, and they date from the early 1980s, but now I can't find any evidence they were more than 45 mph.