did the track geometry differ on NYC between the freight mains and the passenger mains ?
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4 track main geometry question
- Discussion relating to the NYC and subsidiaries, up to 1968. Visit the NYCS Historical Society for more information.
Moderator: Otto Vondrak
As an Operating Dept employee can't furnish all differences; do know elevation in curves was different, switch point lengths were different, as were frog angles. At some locations track centers were different and/or speed restrictions were necessary to account for tight clearences. These were a function of the differences in speed allowed on psgr tracks & frt tracks. There were I'm sure many other differences, an interesting topic...let's wait for an Engineering Officer to weigh in on this subject.
The superelevation in curves was different between some freight and some passenger tracks. It was determined by the maximum authorized speed, with a nominal maximum superelevation (at that time) of seven inches with three inches underbalance. If that superelevation in a passenger track couldn't accommodate the zone speed, a curve speed restriction was placed.
The freight tracks, IIRC, had a maximum superelevation of four inches, and generally were limited to 50 mph. Superelevation was limited so that slow freight trains, operating well below the max authorized, would not lean on the low rail and flatten it, and to reduce the chance of a rock-off to the low side at low speed.
Superelevation is the height of the outer rail of a curve above the inner rail. Given the degree of curvature (the measure of the "sharpness" of the curve) there is one level of superelevation for a given speed that will give "equilibrium," where the vector resultant of gravity and centripetal force will intercept the centerline of the track. "Underbalance" is the difference between actual superelevation in a curve and the amount of superelevation that would provide "equilibrium."
The turnouts used on the NYC main tracks generally had frog numbers of 10, 16 and 20. The frog number is the measure of the spread of the gauge lines over a unit length - a No. 10 frog spreads one foot in ten feet, measured perpendicular to the bisector of the frog angle. NYC train speeds through diverging routes of interlockings were defined in the Book of Rules as Slow, Medium, and Limited Speed, which were communicated by the signal indication. In the 1937 Rules, Slow Speed was 10 mph, Medium Speed was 30 mph, and Limited Speed was 45 mph.
The speed permitted through a diverging route depended on the lowest numbered frog in the route - No 10, Slow; No. 16, Medium, and No. 20, Limited Speed. Generally, often-used routes between passenger tracks had No. 20's, and they were also common in some freight routes where the extra speed was needed and there was enough space to use them. Otherwise, were a slower speed route was acceptable, No. 16's were common. The selection of turnouts was usually the result of an economic analysis of the cost of the turnout versus the cost of train delays due to speed restrictions. In short, the size of the turnout was determined by the speed necessary for a route through the interlocking, and not as much by whether or not it was a freight track.
NYC had fairly tight clearances, both lateral and vertical. I think the minimum standard between passenger mains was 12-1/2 feet. I don't recall any locations where permanent speed restrictions were governed by clearances, but they were a major factor in the operation of dimension loads. In some extreme cases, a wide load had to be moved in a special train that could not meet or pass another train on an adjacent track at many locations. When the Mohawk Division was double-tracked, many of the controlled sidings were made from Track 4, the most northern track, so that they could be used for meeting and passing dimension loads.
Gordon Davids
The freight tracks, IIRC, had a maximum superelevation of four inches, and generally were limited to 50 mph. Superelevation was limited so that slow freight trains, operating well below the max authorized, would not lean on the low rail and flatten it, and to reduce the chance of a rock-off to the low side at low speed.
Superelevation is the height of the outer rail of a curve above the inner rail. Given the degree of curvature (the measure of the "sharpness" of the curve) there is one level of superelevation for a given speed that will give "equilibrium," where the vector resultant of gravity and centripetal force will intercept the centerline of the track. "Underbalance" is the difference between actual superelevation in a curve and the amount of superelevation that would provide "equilibrium."
The turnouts used on the NYC main tracks generally had frog numbers of 10, 16 and 20. The frog number is the measure of the spread of the gauge lines over a unit length - a No. 10 frog spreads one foot in ten feet, measured perpendicular to the bisector of the frog angle. NYC train speeds through diverging routes of interlockings were defined in the Book of Rules as Slow, Medium, and Limited Speed, which were communicated by the signal indication. In the 1937 Rules, Slow Speed was 10 mph, Medium Speed was 30 mph, and Limited Speed was 45 mph.
The speed permitted through a diverging route depended on the lowest numbered frog in the route - No 10, Slow; No. 16, Medium, and No. 20, Limited Speed. Generally, often-used routes between passenger tracks had No. 20's, and they were also common in some freight routes where the extra speed was needed and there was enough space to use them. Otherwise, were a slower speed route was acceptable, No. 16's were common. The selection of turnouts was usually the result of an economic analysis of the cost of the turnout versus the cost of train delays due to speed restrictions. In short, the size of the turnout was determined by the speed necessary for a route through the interlocking, and not as much by whether or not it was a freight track.
NYC had fairly tight clearances, both lateral and vertical. I think the minimum standard between passenger mains was 12-1/2 feet. I don't recall any locations where permanent speed restrictions were governed by clearances, but they were a major factor in the operation of dimension loads. In some extreme cases, a wide load had to be moved in a special train that could not meet or pass another train on an adjacent track at many locations. When the Mohawk Division was double-tracked, many of the controlled sidings were made from Track 4, the most northern track, so that they could be used for meeting and passing dimension loads.
Gordon Davids