The following line of argument, showing the economy in heavy cars, is condensed from an elaborate presentation of the subject by Mr. Rodney Hitt, which was published in the Railroad Gazette, May 19, 1905. The advantages are briefly stated as follows:
1. The smaller number of cars which are required to transport a given amount of freight. The actual investment in equipment is smaller, since the increase in cost is not proportionate to the increase in capacity. There is less work for the car-service department; the empty car movement in the direction of least traffic is decreased.
2. The number of cars, and even the number of trains, required to handle a given traffic is very materially decreased. Economy in this direction might be computed in a manner very similar to the computation of the economy in using heavier locomotives as given in Chapter VII (Motive Power. Economics Of The Locomotive. 74. Total Cost Of Power By The Use Of Locomotives). This economy, of course, involves a saving in the wages of train- and engine-crews, an economy which is independent of the number of tons hauled, and which depends chiefly on the number of trains required to handle the traffic.
3. There is a saving in the cost of car repairs - per ton capacity, if not per car. The amount of this saving is not easy to compute, and under some circumstances it is ap-parently negative. The high capacity cars are necessarily built with steel frames and are sometimes built entirely of steel. Such cars have established an enviable record by their immunity from material damage during train-wrecks, when lighter wooden cars, caught in the same wreck, have been utterly destroyed. Although the early designs of high-capacity cars were not properly designed with respect to draft-gear, wheels, etc., and therefore their records of repair charges were abnormally large, improvements in design have resulted in a reduction of such charges, even below the average figures for the lighter rolling-stock. It has been found that the repair charges on lighter rolling-stock have been materially increased when such cars have been used in the same trains with the heavier steel cars, since the effect of a collision or serious bumping during careless switching almost invariably results in a crushing of the light wooden car, although the heavier steel car usually suffers no damage. The cars of latest design have shown a very considerable economy in the cost of repairs per ton-mile.
4. There is a reduction in the frictional and atmospheric resistance per ton. The frictional resistance per ton decreases with the axle-load. The atmospheric resistance, depends almost entirely on the number of the cars. The lighter and heavier cars are so nearly of the same size that the very slight increase in atmospheric resistance, which is due to an increase in size, is of no importance in this case. "An engine which can haul 1000 tons in 90 cars can haul 1250 tons in 50 cars at 8 miles per hour, and at higher speeds the difference is still greater".
5. There is a saving in track-room in yards and terminals. An 80,000-pound car occupies but little more track-room than a 40,000-pound car, while it permits twice as much freight to be loaded and unloaded in the same time. This consideration is of special importance in the congested terminals of the trunk lines at tide-water, where land is so very valuable. The recent difficulties of railroads in clearing some of their freight-yards would have been very largely augmented if the cars had an average capacity of only 10 or 15 tons rather than 30.
6. There is a saving in switching charges per ton of revenue load. The cost of moving a car through a division or terminal yard varies from 20 to 65 c, as was shown in a recent report from one of the large railroad systems. If a car is passed through four yards on one trip, the cost of switching, etc., may be as high as $2. For a 50-ton car this is at the rate of 4 c. per ton, while for a 20-ton car it is 10 c. per ton, which is an appreciable difference.