It is needless, in this period of railroad history, to argue the value of air-brakes in the operation of trains. According to the report of the Interstate Commerce Commission for the year 1910, out of 47,095 passenger-cars all but 178 were fitted with train-brakes. It is conceivable that even these 178 are merely old cars, which are wearing out their last years of service on lines which are being operated so cheaply that even such an improvement is financially impossible.

Of 2,135,121 freight-cars all but 27,809 (a little over 1.3%) have been equipped with train-brakes. Even this proportion of cars which are not equipped with train-brakes is far smaller than it was a few years ago. In 1889 less than 12% of the total number of cars and locomotives were equipped with train-brakes. In twenty-one years the proportion has been increased from 12 to over 98%. It is probably safe to say that no new regular equipment is now being built without train-brakes.

The operation of passenger-trains at high speed, and the operation of very heavy freight-trains at almost any speed, but especially at high speed, would be absolutely unsafe without the use of air-brakes. Their use is now so universal and their advantages so well recognized that no further comment is necessary.

95. Use Of Automatic Couplers

The use of automatic couplers to replace the old-fashioned link-and-pin coupler was ordered by Congress on all cars used in interstate traffic. In 1889 the percentage of equipments fitted with automatic couplers was less than 8%. In 1910 it had increased to 99.3%. As in the case of the air-brakes it is needless to point out the advantages. The old link-and-pin coupler was not only inadequate for the heavy rolling-stock as used at present, but was always a fruitful source of injuries and death to railroad employees, chiefly brakemen. With the demand for something to replace the old link-and-pin coupler, a multitude of inventors came forward with various plans. The Patent Office was besieged with claims for patents on every conceivable method. The interchange of freight-cars among various roads and the combinations of such cars into trains imperatively demanded that some standard should be adopted, so that whatever the details of the coupler all couplers should be capable of being used with each other. The Master Car-builders' Association therefore adopted a standard outline. All the automatic couplers now in use have the same essential outline as is shown in Fig. 7. The variations of the different designs have to do entirely with the details of their method of operation or the manner of their fastening to the car-body.

96. Draft-Gear

The demand for heavier locomotives and heavier cars has entailed with it the requirement that the draft-gear of cars must be improved. The frictional resistance which must be overcome in starting a train, as well as the inertia, is very great. But the figures which have been determined experimentally as the starting resistance are much less than they would be if it were not for the slack which always exists to a greater or less extent between cars. In the old days of link-couplers, especially when the links were fastened to a coupler which was rigidly attached to the car-body without the intervention of spring draft-gear, although the links made some slack, the inevitable result was a jerk on the coupler which would frequently tear it loose from the car-body, even if the car-frame was not badly wrenched or torn apart. The adoption of close couplers removed all the slack which had formerly existed in the links, and was only made practicable by the use of spring draft-gear, which permits a yielding either in compression or tension.