Sidebilder
PDF
ePub

requires about 10,000 pounds of mine screenings per hour to fire it to its maximum rating, possibly a little more under certain conditions. It is fired with a Street stoker and is in daily service, doing the work successfully.

In a published interview regarding this locomotive, Mr. S. M. Vauclain, vice-president of the Baldwin Locomotive Works, makes the following statement:

"This type of locomotive would never have been suggested, however, were it not for the fact that we are now able to feed a locomotive boiler any amount of coal up to its capacity to burn it. Thus the human equation heretofore preventing the use of large power units has been overcome, and it is my belief that we are just beginning to enter the field of large power units for freight service of the trunk lines of this country. If it can be proved that we can operate locomotives of 150,000 pounds tractive effort with the same engine crew as heretofore and with less physical exertion on the part of the fireman than with the locomotive of only 50,000 pounds tractive effort, it would appear reasonable that such units of power will be in demand, not only by the railroad companies but by the employees as well."

The fact that more than 1000 locomotives such as I have shown you are being fired with mechanical stokers ought to prove conclusively that the mechanical stoker is no longer an experiment and that it must have some economic value to warrant its application to so great a number of the largest modern locomotives.

In searching for all answers to the question, "What is to be gained by the use of mechanical stokers on locomotives?" the really important consideration is that a locomotive is the only thing on a railroad that earns money, and if the stoker can and does remove the limit which is set to the capacity of large locomotives by the inability of the fireman to fire them to their maximum capacity, especially for long periods, then something has been done of economic value not heretofore accomplished.

A brief explanation of why it is almost impossible to hand-fire a large locomotive to its absolute maximum capacity may be of interest here.

It is not generally appreciated that the boiler plant of a locomotive differs in many respects from that of a stationary power plant.

The over-all dimensions of a locomotive, which are largely governed by road clearances, centre of gravity, etc., make the firebox of such size, even the largest permissible, that the rate of combustion per square foot of grate area per hour is several times that of a stationary boiler.

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][subsumed][ocr errors][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small]

Diagram illustrating boiler efficiency and dynamometer horse-power at different rates of firing.

This is a diagram illustrating the relation between the efficiency of a locomotive boiler and the dynamometer horse-power developed when burning coal at different rates per hour.

The drop in the efficiency curve is very marked as the horse-power. increases. It will be noted at once that the per cent. of boiler efficiency drops off almost in a straight line as the locomotive is worked harder. This will illustrate why it is more difficult in proportion to fire a locomotive as the engineer opens the throttle and drops the reverse lever "over amongst the oil cans," as the enginemen term it. The average fireman usually is at his limit when the firing rate reaches 75 pounds per square foot of grate area per hour.

The curvature of the dynamometer horse-power line is brought about by the decrease in the amount of water evaporated per pound of coal as the combustion rate increases.

[blocks in formation]

This diagram will illustrate the rates of evaporation as the coal fired per square foot per hour increases.

This will also explain why it is sometimes said that a stoker

fired locomotive burns more coal than hand-fired. It does, usually, because worked harder, and it takes more coal to evaporate a pound of water at the point where stoker-fired locomotives are worked.

[graphic][merged small]

All large locomotives are not now in a service requiring stokers. On the other hand, there are large numbers of rather small locomotives that are in use where larger locomotives, stoker-fired, could do the work more economically from every point of view. This is an illustration of such a condition: Five hand-fired locomotives on one train, worked hard and not well fired, either, if appearances count for anything.

Larger locomotives can and will be designed, two of which could handle this train.

Locomotive capacity then seems to be the real point in the stoker proposition, even at the expense of some economy in the amount of water evaporated per pound of coal, and what this means in increase of earning power of a locomotive as compared with any increase in cost of coal as the consumption increases per square foot of grate area per hour is illustrated on this diagram.

[blocks in formation]

Diagram showing increase in earning power of locomotive as it is worked harder.

It will be seen at once that the increase in earning power is of vast importance as compared with the slight rise in the line showing the coal cost as the locomotive is worked harder.

These curves were plotted from statistics showing freight train earnings when handling such commodities as coal, ore, limestone, etc. -just such lading as is in heavy drag service where stoker-fired engines are used. The coal cost was figured at $1.50 per ton on locomotive tender.

So far as I know, there is not a single case where stokers have been applied by any railroad company that there has not been a material increase in tonnage rating, and in spite of the increase in tonnage there has usually been an improvement in the general' smoothness with which the traffic has been moved on the stoker-fired divisions.

« ForrigeFortsett »