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"Track Materials Specially Designed for New York City Subways" (1929)

ELECTRIC RAILWAY JOURNAL · Vol. 73, No. 8 · February 23, 1929 · pp 325-328.

Track Materials Specially Designed for New York City Subways

By Robert H. Jacobs, Division Engineer, Board of Transportation, New York

Double housed switches, as used on the B.M.T. and new subway lines.

High carbon rails are used on tangent track, with manganese rail for parts of special work. Most convenient length for handling found to be 33 ft. Accurate manufacture of screw spikes essential. A 150-lb. section is used for third rail.

Due to the large number of sharp curves on the lines of the new city-built subways in New York, it has been necessary to provide a large amount of guarded construction. This condition has made it necessary for us to provide many special parts to meet the unusual requirements encountered in this situation. The solution of the problems presented has many points of interest. When the track standards for the existing dual system of subways operated in New York by the I.R.T. and the B.M.T. were determined upon, the 100-lb. section had already been adopted for the existing subway. At that time the A.R.A.-B rail section was becoming very popular, and while the Interborough was inclined to favor the extension of the use of the modified A.S.C.E. section for the new lines, the representatives of the city and the B.M.T. favored the new section. After considerable discussion the latter was adopted. The outstanding differences between the two sections are less slope of the head and a narrower and thicker base for the A.R.A.-B rail. While a somewhat lighter rail would, of course, carry the traffic satisfactorily, the use of a larger section is amply justified by the saving in maintenance and renewals.

On account of special conditions, a higher carbon rail than ordinarily used on steam railroads has been found to be practicable. Our specifications call for a carbon content of 0.73 per cent to 0.86 per cent, instead of 0.62 to 0.77 per cent commonly used on steam railroads for this weight of rail. These harder rails, of course, give us longer service.

In general, rolled manganese rail was used on tracks for the dual system on curves of 700 ft. radius and under. The initial purchase of manganese rail for the greater part of the tracks of the dual system was made at a price of about $85 a ton. Since that time the rail was practically doubled in price, whereas the increase in price of the open-hearth rail has been only about 43 per cent. Records of the service on our lines of manganese rail and of high carbon open-hearth rail are not very consistent. Without any question the manganese rail has a much longer life under traffic than open-hearth rail, but it is liable to corrugation. It also has a considerable disadvantage due to the impracticability of cutting and drilling this rail in the field. This affects both original installation and renewals, as well as bonding. On account of these considerations, including its high price, there is a tendency to limit its use. Our standards for the new city subways do not call for the use of manganese rail except for parts of special work most subject to wear.

We are continuing the use of 33-ft. rails, although longer rails are now being used by many railroads. While a reduction in the number of joints is desirable, our determination was based on the difficulties of handling rails longer than 33 ft. in the restricted space in the subway.

The joint bars adopted for the new city subways are similar to those now in use by the operating companies. The "head free" feature providing contact at the top of this bar with the web, instead of supporting the head of the rail near its outer edge, is interesting. Two advantages claimed for this bar are, first, that the joint assumes its final position when applied, assuring the maintenance of perfect alignment through the joint from the time of first application, and second, that the so-called "anvil action" of the wheels on the joints is eliminated, because the underside of the railhead is left entirely free, permitting the railhead to act at the joints the same as throughout other parts of the rail. Another advantage claimed for this "head free" feature is that metal may be omitted from the under faces of the railhead, where it is of no use, and an equivalent amount of metal added to the top of the head, thereby increasing the life of the rail.

The standard "E" bar with alternate round and oval holes is used for all joints except those on the low side of guarded curves and in special work. On guarded curves a so-called "G" bar is used between the running rail and the guard rail. This bar is identical with the standard "E" bar, except that the lower flange is omitted, due to the limited space in which it is to be placed. These bars have round holes only. Bars of standard section are provided with oval holes only for use on the outside of the guard rail, and of the running rail on the low side of curves. The use of bars with all round holes or all oval holes on the low side of guarded curves is due to the necessity of placing the track bolts with their heads on the outside of the rails to facilitate removal.

Welding of rails as an alternative to the use of splice bars has received some consideration, but has not been adopted, largely due to the difficulties of making renewals under traffic.

Contrary to the usual railroad practice, a special type of bolt was adopted for the tracks of the dual system. This bolt has a round neck and a large head, the latter being flattened on two sides so as to fit under a rib at the top of the splice bar in order to prevent turning. This made it possible in the dual system to use splice bars with round holes only. On tangent track and unguarded curves the bolts are placed with the heads on alternate sides of the rail, in accordance with the general practice. As previously stated, on guarded curves it is necessary, in order to be able to back out the bolts, to place all the nuts between the guard rail and the running rail. It was found, after years of use, that this type of bolt, in spite of its advantages, had disadvantages which have led us to abandon it and adopt an oval-neck track bolt with a ratchet or Harvey Grip thread, notwithstanding the fact that it has required the furnishing of bars with special punching for use in guarded construction.

Tie plates for ballasted track are designed for use with cut spikes. The standard "A" plates for use on tangent track and unguarded rails on curves present no special features, but correspond to those in general use. However, special plates are required for use at joints, in guarded construction and in special work. A careful study of manufacturing tolerances was required in order to determine the proper dimensions of the special plates. Tie plates for concreted track are designed for use with screw spikes and require bosses for the support of the screw spike heads in a position to allow a 1/14-in. space between the bottom of the head and the flange of the rail. It was the early practice on some other railroads to turn down the screw spikes tight on the rail, but this resulted in a movement of the spike in the tie affecting the serviceability of the construction. The 1/16-in. space between the head of the screw spike and the flange of the rail has overcome this difficulty.

Only two types of screw spikes are used in our work. Screw spike "A" is the standard track spike for concrete track, while screw spike "E" is used principally for rail braces in curved track and in special work. The accuracy of the manufacture of the screw spike is of the greatest importance ; first, in order that the space between the head of the screw spike and the flange of the rail may be maintained, and second, that the groove formed in the wood of the tie block with the first thread of the screw may be followed by the remaining threads in such a way as not to injure the fiber of the wood. In replacing screw spikes, the groove in the wood should be followed by the threads of the new spike. These conditions are not met in the so-called "commercial" screw spikes.

Service requirements necessitate a substantial form of guarded construction consisting of rail braces on the outside of the high rail, and rail braces on the inside of the guarded rail on the low side. Guard rails are secured to the running rails by bolts passing through separators, separators being needed to provide the necessary flangeway. Although the separator bolts have been placed at frequent intervals, there has been a large amount of breakage under traffic. Several special designs have been developed to obviate this difficulty, but to date none has been tested on our rapid transit lines. The operating companies have been experimenting with the use of guard rail clamps similar to those commonly used opposite frogs on steam railroads. However, these are expensive and clumsy and not well suited for use on concreted track, as they require the omission of a large amount of concrete between the tie blocks.

In our new design we are seeking to minimize this difficulty by providing bolts manufactured to a special specification which will have greater elasticity and will be less liable to breakage. We are also modifying the design of the separator, providing a larger hole for the bolt, and have adopted a headlock washer which has shown good results.

Rail creepage has in the past been the cause of a great deal of difficulty in maintaining tracks, and the use of anti-creepers to overcome this trouble has been the development of comparatively recent years. On the first subways no anti-creepers were used, but when work was started on the tracks for the dual system three anticreepers to the rail length of 33 ft. were adopted as standard. Under actual operating conditions, this number of anti-creepers was found to be insufficient to hold the rail, necessitating a considerable amount of maintenance work which often required bucking of rail for a long distance. As the result of this experience, for the last few years we have used five anti-creepers to the rail length, which has proved satisfactory. In general, experience indicates that rail creepage occurs in the direction of traffic, more or less regardless of grades. Determinations in this matter are the result of intensive surveys which we have made of tracks under operation. On account of the high cost and great difficulties involved in making renewals it has been the uniform practice to provide ties manufactured from a very high class of material. For the ballasted track, including the special work, our specifications call for first growth, long-leaf. Southern yellow pine. No tie is acceptable with less than three heart corners, or with more than 1 in. of sap on the fourth corner or with more than 2-1/2 in. of sap, measured across the face anywhere in the length of the tie. Variations up to 1/4 in. in width and depth and up to 1/2 in. in length are accepted. These ties are delivered cut to the correct dimensions. Standard 6x8-in. ties 8 ft. long, and ties 9 ft. long for the support of the third rail, are used, with ties of various lengths as required for special work, which in some cases run up to 27-1/2 ft. in length.

For the concreted track, as described in an article published in this paper Feb. 2, creosoted timber is used of the same quality as for ballasted track. These ties are furnished to exact dimensions 10 in. wide and 6 in. high, with holes drilled for screw spikes, for anchor bolts where used, and for lag screws used for fastening the third rail insulator cups and brackets. The holes are exactly spaced by template prior to creosoting.

Long life is expected for these ties, based upon the present condition of similar ties which have been in service for about twelve years. A recent inspection shows little deterioration, and practically no tie cutting or failure in the screw spike holes. Because the ties are protected from extreme weather conditions it may be expected that deterioration from decay will be slow, and on account of the use of practically all heart timber, comparatively light wheel loads and the use of tie plates, there has been practically no deterioration from tie cutting.

On tangent and long radius curves, unused holes in the tie plates make it possible to drill new holes in the tie blocks after the first holes are unserviceable. In the case of sharp radius curves, where due to double spiking and other reasons it is impossible to provide spare holes, this cannot be done. However, the use of ties 10 in wide with tie plates 7-1/2 in. wide renders it possible in future to plug old holes, shift the tie plates, and drill new holes.

Standard frogs and switches are used wherever possible in our special trackwork. However, the many limiting conditions of the alignment necessitate the designing of numerous non-standard layouts. The greater part of our special work is of much sharper curvature than on steam roads and consists of No. 6 and No. 8, with some No 10 and No. 12 turnouts of radii from 350 ft. to 1,350 ft., whereas in the case of high-speed crossovers on steam railroads the numbers run anywhere from No. 12 to No. 20 and even No. 30, with very few under No 12. As a result we provide a large amount of guarding through the special work, which is not required ordinarily in steam railroad practice. Our switches are double housed for facing switches and single housed for trailing switches, with guards in front of the housings. Switch points up to a No. 8 are guarded on the turnout side. The wing rails of frogs are extended by guard rails. For the dual system, lapped switches have been used on the Interborough lines, with guards opposite the extended points, whereas on the Brooklyn-Manhattan lines housed switches have been used. We are following the Brooklyn-Manhattan practice in this regard for the new city subways. The use of the lapped switches for the Interborough lines was based on the contention that the rolling stock is so designed that with extreme rail and wheel wear the equipment on the under side of their cars would not clear the housing, which extends 1/4 in. above the top of new rail. Our new cars are similar to the Brooklyn-Manhattan Transit cars in having clearance between the equipment and the rail.

Rail built-up frogs are standard for our work. After years of service these frogs have proved entirely satisfactory and are particularly advantageous from the point of view of repairs under service. We have in a few instances installed solid cast manganese frogs. These have been in track for three years and are being watched in service. However, they are open to the objection of difficulty in repairs under operation in case of breakage. The advantage of the use of housed switches, especially for subway tracks, consists principally of more guarding at the extreme points of the switches. In this form of construction there is an offset in the stock rail, which makes it possible to thicken up the switch point, thereby adding to its stability and life.

Rolled manganese rail is used in special work for parts that are subjected to hard service, especially frogs for main line. Where it is necessary to provide for very frequent train movements, switch points and curved lead rails of rolled manganese are also provided.

For the dual system the third rail, bonding and insulated joints, as well as signal interlocking, etc., were installed by the operating companies as equipment, while for the new city subway all this work is being done by the city. The installation of the third rail, bonding of the third rail and installation of the insulated joints and of conduits in the trackways are all included in the track contracts. The track contractor's equipment for handling materials is suitable and available for handling the third rail, and the work can be carried on to advantage by him in connection with his track work. The necessity of providing for positive and negative cables, lighting, escalators and circuit breaker connections require that a large number of conduits be placed in the trackways. These conduits must, of course, all be placed in advance of the concreting. Delays and interference are reduced to a minimum, due to having all of this work executed by one contractor.

In general, the standard section of the third rail is 150 lb per yard of special section, with the third rail protection boards supported by brackets from the tie blocks extended for that purpose. The insulated joints are installed in the tracks at the time of track-laying.

[Top] Joints at unguarded rail showing B bars. [Bottom] Joints at guarded rail showing F and G bars.	[Top] Separator and tie plate H for screw spikes. [Bottom] 150-lb. third rail with bracket and insulator.

Lapped switches, as used on the Interborough Rapid Transit Lines.

Sources: Electric Railway Journal, McGraw Hill Company, Digitized by Microsoft, Americana Collection, archive.org.