The falling off of tractive force of a locomotive as the speed increases is caused by a reduction of the ratio between the mean effective pressure in the cylinders and the boiler pressure. This ratio plotted against piston speed is used to calculate the tractive force at various speeds and is usually termed "speed factor". This factor has been universally used in determining the tractive force and the maximum cylinder horsepower, which was determined some years ago by F. J. Cole, and is plotted as curve No. 1 in Fig. 1.

Developments of the most recent locomotives, however, have shown that it is possible by the use of high superheat and correct proportioning of the boilers and cylinders to raise this ratio considerably. On the same figure have been shown curves No. 2 and No. 3 which illustrate this ratio of speed factor obtained on carefully conducted tests on two recently constructed locomotives. It will be noticed that a remarkable improvement has been made on these and other similar locomotives and these curves present the best picture that can be painted to illustrate the improvements in locomotive design of today. The speed factor shown in curve No. 2 can safely be used for freight locomotives with wheel diameters up to 70 in. and curve No. 3 for high speed passenger locomotives when a Type E superheater and a feedwater heater is used.

With the above suggestion for determining the maximum tractive force for starting and at speeds, we can now calculate the maximum cylinder horsepower that

can be developed with a locomotive using highly superheated steam.

Steam Consumption

The next step is steam consumption per indicated horsepower. In the calculations for the steam demand of a superheated locomotive, a figure of 20.8 lb. per horsepower-hour has been used universally. This was also proposed and used by Mr. Cole and was based on steam around 200 lb. pressure and 200 deg. superheat.

Since the introduction and use of 300 deg. or more of superheat obtained with the Type E superheater, coupled with a somewhat higher pressure and better steam distribution in the cylinders, this steam rate has been materially reduced.

Numerous tests have been made showing a steam rate as low as 15 to 16 lb. per indicated horsepower-hour at maximum capacity. It is, therefore, suggested that when a locomotive is designed to use steam superheated to 300 deg. F., a pressure of from 225 to 275 lb., a feedwater heater and large grates, a steam rate of 171⁄2 lb. per indicated horsepower including auxiliaries, can be safely used. General Boiler Design

With these important points in mind, we now come to the question of the design of the boiler, superheater, feedwater heater, etc. Experience shows that some locomotives are better steamers than others and some are not very good. It is evident, therefore, that there are some features in the design of a poor boiler that impose a limit on the development of higher power or reduce the efficiency as compared with others. Our efforts should, therefore, be directed toward finding out where the weak link is in a particular design and discover the ratios or proportions that would show improvement.

My first intention was to discuss the high pressure water tube firebox boiler only, this being the problem that is today most intensely studied. By high pressure is meant boilers carrying upwards of 300 lb. pressure. When reviewing the accomplishments, however, that have been made in the design of the most recently constructed standard type of locomotive having a Type E superheater and a feedwater heater with a pressure around 225 to 250 lb., it appeared that the most valuable

weight per engine of 80 lb. per i. hp. when pulling a train of 26 steel passenger coaches at 67 m.p.h. When you find that this has been done with a boiler and superheater efficiency of 78.6 per cent, an average steam consumption of 17.14 lb. per hp.-hr. and a coal consumption of 2.09 per i. hp.-hr., including all auxiliaries, then you must sit up and take notice. These figures are average results of many tests, and the best average results on any single run with this train were an average boiler and superheater efficiency of 84.2 per cent, a steam consumption per i. hp.-hr., 15.04 lb. and 1.89 lb. of coal fired per i. hp.-hr. This included all auxiliaries. The coal per drawbar hp.-hr. was 2.68 lb. and the maximum temperature of steam was 750 deg. F.

Fig. 2 shows the comparison between tractive force and cylinder horsepower calculated from Cole's formula and the tractive force and power actually obtained from test.

A recent large freight locomotive of the 4-12-2 type has developed a maximum of 4,917 i. hp. with a weight on the drivers of 72.3 lb. per i. hp. and total weight of 101 lb. per i. hp. This is very remarkable for a heavy freight locomotive and represents, as far as I know, the heaviest power output recorded.

Another locomotive of the 4-8-2 type having a total engine weight of 95.8 lb. per i. hp. pulled a freight train of 122 cars of 9,315 tons at a maximum speed of 34.8 m.p.h. and an average speed of 18.25 m.p.h. with a coal consumption of 2.59 lb. per drawbar hp.-hr., including all auxiliaries. This performance was equalled by another locomotive of the 2-8-4 type hauling 9,324 tons at 18.3 m.p.h. average speed on 2.50 lb. of coal, per i. hp.-hr. The drawbar pull-speed for this 4-8-2 type is shown in Fig. 3.

There have been several reciprocating steam locomotives built in the last few years carrying over 300 lb. boiler pressure. All are constructed with water tube fireboxes and compound cylinders as follows: One with 350 lb. and one with 400 lb. boiler pressure by the Delaware & Hudson, the Baldwin No. 60,000 with 350 lb. pressure, and the Schmidt-Henschel locomotive carrying 880 lb. and 200 ib. The performance of the D. & H. locomotive is not known, but that of the Baldwin

able efficiency now obtained with a 225-lb. pressure locomotive with a Type E superheater and a feedwater heater, it seems that in order to get a return on the in

vestment and maintenance cost of water tube fireboxes and compound cylinders, a seam consumption of from 10 to 12 lb. of steam per i. hp.-hr. should be obtained and a coal consumption well below two pounds per drawbar hp.-hr.

The Water Tube Firebox

It was a courageous step when the steam pressure for the staybolt boiler was jumped from 200 to 250 lb. Thousands of these are now operating successfully. Recently 265 lb., 275 lb. and 300 lb. boiler pressures have been used on a few locomotives. Whether a 300-lb. staybolt boiler will prove satisfactory, only experience will tell. The general opinion among the best authorities now is that above 250 lb. or 275 lb. pressure, a water tube firebox is the safest and most desirable.

The water tube firebox is an old design. It was first designed 30 years ago by the eminent Russian engineer, J. Brotan. Several locomotives were built in 1904. C. Noltein reported on these locomotives to the International Railway Congress in 1910 as being satisfactory.

The reason why the Brotan boiler has not been placed in general use throughout the world is probably due to the great difficulties experienced and the time required to keep the water tubes free from scale. Where good feedwater is available, we know from the experience of the New York, New Haven & Hartford and the Delaware & Hudson, that a water tube firebox can be satisfactorily maintained.

Unfortunately there are only a few places in the world where pure water for locomotive use is available. In localities of bad or even normal water conditions, the loss of time and cost of keeping the water tubes clean might be very high. It appears, therefore, logical that the only water tube firebox that can be satisfactorily used is one where only pure, or preferably, distilled water is used in the water tube end of the boiler.

This paramount requisite for successful operation of the water tube firebox is incorporated in the principle used by the Schmidt-Henschel locomotive referred to, where the steam used by the cylinders is evaporated by means of indirect heat and then condensed in heat interchange coils located in the steam drums, the condensate returning to the bottom of the firebox headers, thus forming a closed cycle.

While this design was particularly evolved for a high pressure locomotive, this form of construction may prove of advantage with lower pressures as well. It would seem, however, that the many apparent advan

The standard of excellence in design should be the locomotive that has given the highest power output per unit of total weight, the weight of the drivers and per 1,000 lb. of theoretical tractive force. These ratios will give you an accurate picture not only of the excellence of the general proportions and over-all efficiency, but also of the refinement in the mechanical design. Only locomotives in approximately the same class of service should be directly compared with each other.

It is to be regretted that actual dynamometer tests are not available for all of these modern locomotives, but it is known that the performance of the others shown has been excellent and probably equalled those for which tests have been published.

It is evident that it is impractical to lay down a definite rule or ratio that would fit any given condition. All rules and ratios must be used with great care and analyzed in the light of actual conditions to be met. There are certain fundamentals, however, that must not be lost sight of and it is the intention to present and tabulate here the facts available to aid in properly designing a locomotive boiler with as little theoretical speculation as possible and at the same time, give assurance that the best possible locomotive will result.

Boiler Efficiency

When the performance of a locomotive boiler is analyzed, one immediately notices that the efficiency decreases rapidly as the rate of firing increases, or from about 75 to 80 per cent with a coal rate below 40 lb. of coal per square foot of grate per hour to about 40 to 45 per cent efficiency with a coal rate of around 200 lb. per sq. ft.

A number of curves are plotted in Fig. 44, showing the boiler efficiency vs. the rate of firing. It will be noticed that some curves are considerably higher than others while other curves show a different slope. It is thus clear that there must be some factors entering into the proportion of the boilers that have a great influence upon the efficiency for any given rate of firing, as well as upon the rate of decrease as the rate of firing increases. The principal factors that are responsible for the great heat loss, as the output increases, are as follows:

First-Imperfect combustion producing carbon monoxide Second-External radiation from the boiler and firebox Third-Loss of heat in the smokebox gases

Fourth-Unburned fuel escaping from the boiler. This heat loss increases very rapidly on the older type of boiler as the rate of firing increases. Numerous tests have shown that this heat loss will run from 15 to 20 per cent at a 60-lb. coal rate, up to as high as 50 per cent when the coal rate is 200 lb. per sq. ft.

This is due to the fact that the grate area and furnace volume are too small to give the carbon and volatile combustible time to to mix intimately with the oxygen and burn before they enter the flues and is also due to the small gas area through the boiler, which causes too high a gas velocity and draft loss through the flues. It is clear, therefore, that a great gain in boiler efficiency will result from any effort that will improve these conditions.

These curves were taken from tests and illustrate the fact that superheat follows the law of increasing return. The production of high superheat on the modern locomotive, however, has been made more and more difficult, due to radical changes in the boiler proportions of very large power. It has become necessary for the superheater designer to meet this condition by enlarging the capacity of the superheater. This has been done by increasing the superheating surface. The necessity of this is evident from the fact that less heat is left in the gases entering the flues, due to the greater

heat absorption in the large fireboxes, which decreases the heat available for superheating. The use of feedwater heaters and exhaust steam injectors also, by reclaiming heat that would otherwise be lost, reduces the rate of firing that is required for the same evaporation. and naturally decreases the amount of heat offered to the superheater flues.

On the extremely large locomotives of today, the steam space in the boiler has been substantially decreased. The steam liberating surface, has also decreased in proportion to the total amount of water delivered by the boiler. Both of these conditions have contributed to a marked increase in the amount of water that is carried by the steam from the boiler to the superheater. As the evaporation of one per cent of moisture requires as much heat as a superheat of 17 deg., it is a difficult task to provide an adequate superheater as steam may carry five per cent, or more, of moisture when it enters the superheater units. This condition. not only points to the necessity for a greater capacity superheater, but to the importance of proper handling of the water level on the road.

The increased demand for operating trains at higher speeds, requiring more steam for a given size of locomotive, requires superheaters of greater capacity, in order that these demands on the boiler may be met without a too serious sacrifice of boiler efficiency and evaporating capacity. The greatest possible total steam area. through the superheater is also very important as it will result in less pressure drop through the superheater

Feedwater Heating

Before closing this paper it could not be considered complete without some reference to the part played by the principle of preheating boiler feed water with waste exhaust steam. No locomotive can be considered efficient without being equipped with some means of doing this. The reasons, therefore, are well known, but will be summarized briefly :

1--It increases the maximum evaporative capacity from 15 to 20 per cent on any boiler, no matter how efficient it be in itself. 2-It decreases the weight of the boiler from 12 to 14 per cent for equal capacities.

3-The first cost, or capital investment, is not any greater for a boiler with a feedwater heater than for a boiler without one and having the same capacity.

4 It increases the cylinder horsepower due to lower back pressure on the locomotive.

5-It increases the capacity of the tender by 20 per cent. 6-It decreases the cost of boiler maintenance, because from 15 to 20 per cent of the feed water is returned in the form of condensed steam or distilled water. It also reduces the ex

pansion strains of the boiler, provided that the feedwater heater is so designed that cold water cannot be pumped into the boiler at any time.

7-It increases the combined efficiency of the boiler and feedwater heater by at least 15 per cent net as it recaptures this amount of heat from the waste steam exhausted from the cylinders.

8--It reduces the total net weight of the engine and tender.

test.

Fig. 7 indicates the boiler efficiency obtainable by the Type E superheater on the same locomotives from which the data shown in Fig. 7 was obtained. Curve 1 in Fig. 7 is the boiler efficiency of a locomotive with a Type A superheater and Curve 2 of the same class of locomotive with a Type E superheater. Both were for tests in which the live steam injector was used.

In the above references to test results and from the figures and curves shown, it will be clear that it is possible with a Type E superheater to increase the sustained capacity at high speeds by at least 20 to 25 per cent over that obtainable with a properly designed Type A superheater. For large locomotives this is also possible without increasing the weight of the locomotive to a great extent wherever the boiler is properly proportioned for the Type E superheater. Where the axle loads on any railroad have reached the permissible limits and it is necessary to have a still more powerful locomotive, the necessity for and the advantages of a Type E superheater are clearly indicated. Most of the recently constructed high capacity locomotives are equipped with the Type E superheater and there are now about 1,500 installed.

T

Through Use of Cup Flats

HE decided advantage of cup flats over the ordinary strawboard flats and excelsior pads in the shipment of cases of eggs is demonstrated in inspections made by the Western Weighing and Inspection Bureau at Chicago and by the Trunk Lines Freight Inspection Bureau at New York recently. When the ordinary flats and excelsior pads were used the damage varied between 3.5 per cent and 4.5 per cent, but when cup flats and excelsior pads were used the percentage was reduced to between 0.9 per cent and 1.4 per cent. In other words, 52 per cent of the cases involved were packed with a plain flat and 4 or 6 pads per case, and 48 per cent were packed with the cup flat while the former class contributed 80 per cent of the total damage and the latter only 20 per cent.

A total of 15,403 cars or 6,281,705 cases were involved. Those packed with 6 pads and ordinary flats totaled 2,054 cars or 819,492 cases, while the damage amounted to 28,431 cases or 3.5 per cent. Those packed with 4 pads and ordinary flats totaled 6,013 cars or 2,337,492 cases, with damage to 105,137 cases or 4.5 per cent. Those packed with 4 pads and cup flats totaled 3,005 cars or 1,227,292 cases, but damage occurred to only 17,244 cases or 1.4 per cent. Those in which cup flats alone were used totaled 4,331 cars or 1,897,427 cases, with damage to 16,887 cases or 0.9 per cent.

Further evidence is found in an incident at Chicago involving 1,343 cars containing 543,771 cases, packed with 8 cup flats and 4 excelsior pads per case where only 2,376 cases or 0.4 per cent were damaged. Again, a total of 1,911 cars or 373,965 cases packed with 14 cup flats resulted in damage to only 2,854 cases or 0.8 per cent. At New York 1,894 cars packed with 14 or 16 cup flats checked out with damage to only 1 per cent of the 873,138 cases in those cars.

A

T the Burnside plant of the Illinois Central in Chicago where the general store and the principal shop of the railroad are located, a study has been made of material handling methods and costs since 1920, following the return of the railroads to their owners by the government, which indicate that the company has saved over $100,000 a year in payrolls and effected various other economies.

In 1920 the Burnside paint was well supplied with such material-handling devices as transfer cars, push cars, warehouse trucks, four-wheel push trucks, baggage trucks, wheelbarrows and barrel and box trucks. It is doubtful if another railroad layout in the country had a better equipment of push cars and material tracks. An average of 31 cars of material, exclusive of scrap, is unloaded and loaded at the general store daily, of which 90 per cent is in box cars. This comprises an aggregate of 1,080 tons of material. In addition an average of 102 tons of material is delivered to the local shops each day. To unload, load, distribute and store this volume of material by means of transfer cars, warehouse trucks, push trucks and push cars required a large number of men, and operations were slowed down by delays at elevators resulting from men passing each other in narrow aisles, also in side-tracking push cars on single tracks and in getting push cars over turntables.

A general plan was developed for the installation of concrete roadways, retiring material tracks, re-arranging store facilities and purchasing necessary equipment before any changes or expenditures were actually made. Also before reaching a decision as to the advisability of any change, counsel was taken of all departments likely to be affected by the plan and careful