"An ideal case is the one in which the coal is fed into the furnace constantly and at a uniform rate, as is done with some mechanical stokers. The coal supply is then as uniform as the air supply."

Slack was never used extensively for locomotive fuel until the advent of the Street stoker, and now something over 1000 locomotives are being fired with coal that will pass through a screen having twoand-a-half or three-inch round holes.

If, by chance, a hand-fired locomotive should get a tank of this kind of fuel, the fireman would usually complain of "bad coal."

With the main points of the stoker story in our minds, as related thus far, that is, the aims of the different inventors in the early state of the art, the findings of the stoker committees to the effect that not much of real value had been accomplished up to the end of the year 1911, and the descriptions given of the machines sold commercially since that time and now in service,-some information about the principal stoker-fired locomotives will be the best way of illustrating the progress made in the last three years.

In connection with the description of the locomotives, I shall also try to give information about the work the stokers are doing which will enable you to judge of their present economic value and draw conclusions as to the possibilities for the future.

This is a photograph of a Norfolk and Western Z-1 and Z-1-A road Mallet locomotive having 72,800 pounds tractive effort and 62.2 square feet grate area. Not a remarkably large locomotive, but well within what we have come to term the stoker class. There are 120 of them in service, all stoker-fired, and, from the stoker point of view, these locomotives are of somewhat unusual interest. They were practically the first locomotives to be bought new with mechanical stokers in the original specifications and the first ones to be commercially equipped. Forty of them were ordered to be fur

nished by the builders, complete with stokers, during the summer of 1912; forty during the summer of 1913, and forty during 1914. Of the 120, 105 have the Street stoker and 15 the Hanna.

Each of these locomotives hauls from one and one-half times to twice the tonnage of the consolidation locomotives displaced by them. The fuel used is mine screenings or slack secured from the mines direct or screened by the railroad company from the coal used for hand-firing. Practically none of it could be used for hand-firing.

This locomotive was also built to be stoker-fired, is much larger than the one just shown, and, if size alone has anything to do with the need for mechanical stokers, this would be a shining example. The tractive power is 105,000 pounds and grate area 99.9 square feet. Thirty of this class are in pusher service on the Baltimore and Ohio, all having Street stokers.

The fuel used is mine screenings secured by passing run-of-mine coal over bar screens with bars placed one and five-eighths inches apart. Some of the thirty have been in service three years and all of them over eighteen months.

Using 100 pounds of coal per square foot of grate area per hour

as a conservative figure for the amount of good quality coal required to fire these locomotives to their rated capacity, it will be admitted at once that this, then, would be a place for stokers, even if there were no other considerations.

This locomotive represents another phase of the stoker proposition. The locomotives just shown are unquestionably of the stoker class from their size alone, requiring more coal to fire them to their maximum capacity than could be put in manually, especially for any extended period. This locomotive has but 54,000 pounds tractive effort and 70 square feet of grate area, and can be fired by hand very satisfactorily in regular service. There are 320 of these locomotives on the Baltimore and Ohio, 160 of them stoker-fired with the Street stoker, 160 hand-fired. There are both saturated and superheated engines stoker and hand-fired, so that ready comparisons can be made of the advantages, if any, of the use of the stoker on an engine of this size under various conditions of operation. Fifty of the stokers were applied during the summer of 1912, and the other 110 during the year 1913, so that all of the stokers have been in service long enough to permit these comparisons. There are two things which have been accomplished on the 160 stoker-fired engines which are of interest.

First, each locomotive stoker-fired is given more tonnage per train as its rating than the same engine hand-fired, and this increase in tonnage can be safely stated to be 500 tons for a superheated stokerfired engine over a superheated hand-fired, and at least the same amount for a saturated stoker-fired over a saturated hand-fired, and this work is done on a stoker-fired locomotive with fuel that could not successfully be used for hand-firing in regular service. This fuel is secured by screening run-of-mine coal over bar screens with the bars one and five-eighths inches apart, or is purchased direct from the mines, this latter being the case when gas coal mine screenings are used.

A careful record kept for a considerable period of the hand-firing done on stoker-fired engines showed that at least 90 per cent of the total fuel was fired with the stoker, counting everything, and in many cases no hand firing whatever was needed. This would illustrate the reduction in physical labor of the firemen, and, as the fire door is open very little, the heat in the cab is so reduced that the fireman can follow the locomotive trip after trip, almost, if not quite, as regu

larly as the engineer. Another rather interesting advantage came with the use of the stokers on these engines, in that since the tonnage rating had been raised for those that are stoker-fired there is great rivalry as between hand-fired and stoker-fired engines of the same class, and within the past year or eighteen months the rating of the hand-fired engines has been materially increased, but, as this has been raised, the tonnage rating on the stoker-fired has also been still further increased until on some divisions it is now one thousand tons per train more than was given the hand-fired engines before any stoker engines were received, and is still at least 500 tons higher than any hand-fired engine.

It was also found not practicable to run shovel-fired and stokerfired locomotives on the same division, even with the less tonnage, as the speed of the hand-fired was so much less that they could not keep out of the way, and now all trains on the different divisions are generally either stoker-fired or hand-fired. In one case, on three divisions adjoining making a total distance of something like 450 miles, all of the freight power is stoker-fired.

This is one of the largest Mikado locomotives in service today, having a tractive effort of 60,000 pounds and a grate area of 66.7 square feet.

In answer to the question, "What size or class of locomotives. should have stokers?" it can be said, first, that under average conditions any locomotive, freight or passenger, which has a maximum tractive effort of 50,000 pounds or burns 4000 pounds or over of coal per hour for an extended period, one hour or over, should be fired with the stoker.

This locomotive was designed on the basis of requiring approximately 120 pounds of coal per square foot per hour for its maximum

capacity, or about 8000 pounds per hour. This, with a tractive effort. of 60,000 pounds, would then theoretically bring this locomotive well within the stoker class. In practice this also proves correct, as on a certain division equipped with these locomotives the stoker-fired rating is 6000 tons, and if, for any reason, the stoker should be inoperative, the official rating is 4800 tons. Fifty of these locomotives were equipped with Street stokers during the summer of 1912, and they therefore have been in service long enough to secure records of mileage per mechanical failure, cost of maintenance, kind of coal suitable or available for stoker firing, and dynamometer car tests have been made which confirm the above statements as to comparative rating possible between stoker and hand-firing.

This photograph is of interest as showing one of the smallest locomotives to which stokers have been applied. The tractive effort is 52,400 pounds and there are but 44.7 square feet of grate area. This is one of the locomotives on the Norfolk and Western that was used before the arrival of the Z-1 and Z-1-A. Mallets, which are now hauling nearly twice the tonnage this locomotive was able to handle. The grate area of this locomotive is rather small for the boiler plant, and therefore it is a hard locomotive to fire as compared with others of similar size, and stokers have been applied to some fifteen or twenty of them-four or five Street stokers and twelve or thirteen Standard stokers. In this particular case the necessity for the application of the stokers might be questioned, although the engines can undoubtedly be worked harder and much relief is afforded the fireman from labor and heat.