Chapter 25 of 31 · 772 words · ~4 min read

PART XXIV.

PERFORMANCE AND COST OF OPERATING LOCOMOTIVES.

QUESTION 445. _What is the cost of operating ordinary locomotives per mile run?_

_Answer._ The average cost at the present time (1874) is from 20 to 25 cents per mile.[103]

[103] Deducting 10 per cent. from this amount will give very nearly the gold value of the cost. The figures given above represent the cost in the depreciated promises to pay of the United States Government.

QUESTION 446. _What items of cost are included in this, and what proportion do they each bear to the total cost?_

_Answer._ The items of cost and the percentage of each to the whole expense of operating locomotives, and also to the total of all the expenses of operating locomotives are given in the following table:

From this table it will be seen that the locomotive expenses are 20 per cent. of the whole cost of operating railroads. This cost of course varies under different circumstances. The above is probably somewhat lower than the average cost in this country.

QUESTION 447. _How many miles do locomotives ordinarily run per ton of coal and per cord of wood?_

_Answer._ This also varies greatly under different circumstances. An average taken from the monthly reports of 52 different roads gives 38 miles run per ton of coal, and an average from the reports of 16 roads gives 47¹⁄₂ miles run per cord of wood. No deductions should, however, be made from this of the relative value of wood and coal for fuel, because the trains which are run with wood for fuel are usually lighter than those hauled with coal-burning engines. The above figures are the average results during the month of May, 1871, of all the trains on the roads from whose locomotive reports it has been compiled. The following report of experiments, which were carefully made by the writer, will give the performance of a locomotive when great care is taken to produce good results. It should be stated, however, that the engine with which these experiments were made had been in service eighteen months, without receiving thorough repairs, and that the boiler at times primed badly, so that the rate of evaporation of water per pound of coal is not a fair indication of the performance of the engine in that respect. The coal used was known as Brazil coal, from Indiana, and in order to compare the performance of two engines only lumps of coal were used, so as to leave no room for question regarding the relative amount of fine coal used by each engine. The maximum grades on the road on which the experiments were made were 30 feet per mile, and the total ascent from the lowest to the highest point on the road was 374 feet.

LOCOMOTIVE EXPERIMENTS.

1873. 1873. 1873. Date of experiment July 21. July 28. August 2. Number of miles run 145 145 145 Number of cars hauled 41 31 41 Total weight of cars, lbs. 1,497,240 1,119,650 1,508,860 Total amount of coal burned, lbs. 8,676 5,102 7,221 Total am’nt of water consumed, lbs. 63,531 45,719 52,609 Water evaporated per lb. of coal, lbs. 7.32 8.02 7.04 Miles run per ton (of 2,000 lbs.) of coal 33.4 50.8 38.8 Coal consumed per car per mile, lbs. 1.45 1.13 1.21 Average speed, including stops, miles 11.1 13 13.8

QUESTION 448. _How can we determine the speed at which an engine is running?_

_Answer._ In the absence of any special instruments for the purpose, BY COUNTING THE NUMBER OF REVOLUTIONS OF THE DRIVING-WHEELS PER MINUTE, THEN MULTIPLYING THE LENGTH OF THEIR CIRCUMFERENCE IN INCHES BY THE NUMBER OF THEIR REVOLUTIONS PER MINUTE AND THE PRODUCT BY 60, AND DIVIDING THE LAST PRODUCT BY 63,360. THE QUOTIENT WILL BE THE SPEED IN MILES PER HOUR. Thus, supposing driving-wheels which are 61¹⁄₂ in. in diameter, and whose circumference is therefore 193.2 in., should make 164 revolutions per minute, then 193.2 × 164 × 60 ÷ 63,360 = 30, (nearly) miles per hour.