When we consider that boiler repairs constitute one-third of the cost of loco

motive repairs, fuel one-half of the total cost of locomotive operation, and that one-half of engine failures are directly or indirectly chargeable to boilers, we can not fail to realize the importance of directing a large part of our effort in locomotive design toward the production of a boiler which has the minimum cost of

repairs, maximum efficiency and is the

most reliable. Some of the results to be sought for in good boiler design are:

1. Reliability and economical maintenance, i. e., freedom from cracked sheets, leaky seams, leaky and broken staybolts and leaky flues.

2. Continuous development of maximum horse-power within the capacity and endurance of the average fireman.

3. Efficiency approaching as closely as possible to that of the best stationary

boilers.

Reliability and low cost of maintenance depend chiefly upon freedom of circula

tion around the firebox. Since circulation depends upon the head creating it and the size of the passages through which the water must flow from the bar

rel of the boiler to water legs around firebox, it follows that the greater the depth of firebox and the wider the water legs the more rapid the circulation. This depth should be obtained by maximum depth of throat sheet and not by raising the crown sheet at the expense of steam space.

Experience with smoke consumers and fuel oil has demonstrated the inability of the ordinary locomotive firebox to withstand the heat of perfect combustion, no doubt due to the fact that natural circula

tion is unable to supply the firebox with water rapidly enough to prevent overheating. It is doubtful if it is possible, through natural circulation under the best possible conditions, to construct a boiler

whose firebox will withstand the heat of perfect combustion, but when coal is burned in the ordinary manner the better the circulation the less the firebox troubles. It is probable that there is a point beyond which the speed of natural *Paper by D. Van Alstyne, Mechanical Superintendent N. P. Ry.

where below which is the maximum reliable capacity of the boiler, and so far as the firebox is concerned it would appear that forced circulation is very desirable if it could be made practicable.

The greater the length of the firebox the greater the volume of water required to pass from the barrel of the boiler into the water legs, hence the side sheets and staybolts of a short firebox are less likely to give trouble than a long one. The tendency, therefore, should be toward a de

cided increase in depth of throat and width of water space and as short a firebox as is consistent with necessary grate area. The result will be an exceedingly heavy and bulky boiler at the firebox, necessitating the use of a trailer truck which it is likely will eventually have four wheels instead of two.

With reference to flues considerable observation leads me to believe that a comparatively wide bridge, say one inch, or possibly more, is desirable for large boilers because of the greater stiffness of the flue sheet and probably better circulation between flues. But wide spacing does not cure leaky flues, which are the most difficult boiler trouble to control. I think it can be satisfactorily shown that the rolling of a flue into a sheet is a water-tight job to withstand almost any degree of heat, provided the flue and flue sheet can be made to expand and contract together, and therefore that when flues leak the

conditions are such as to make the flue try to expand more than the sheet, and in so doing it is compressed and made smaller than the flue hole in the sheet. The length of the flue, quality of water and coal, method of firing and working injectors, weather and severe service all have an influence on the leakage of flues, and this influence is, I believe, exerted

The

chiefly through their effect on the size of the nozzle. Whatever causes, therefore, have the greatest tendency toward reducing the nozzle would be the most productive of leaky flues, and these, I believe, to be poor coal and severe service. smaller the nozzle the more severe the blast and the greater the blow pipe action on the end of flues, making them hotter than the sheet which compresses them so that they are smaller than the sheet when they cool down. So far as my investigation goes the great majority of leaky flues

are below the center line of the boiler, indicating that the short flames of highest temperature enter the lower flues. Hence the need for the greatest possible depth of firebox below the flues so that these hottest flames can not reach them.

Any other means of keeping the intensest heat away from the flue ends will have the same good effect on flue leakage, and recent experience with a combustion chamber which sets the flue sheet three feet ahead of the throat sheet has shown a marked decrease in flue leakage. Of utmost importance, however, is the care of boilers. The most poorly designed boiler is made better by more care, while the best designed boiler will not do well if neglected, and some of the important features in good care of boilers are regular and thorough washing out and blowing off, washing out and filling up with hot water, uniform boiler feeding and avoidance of working injectors as far as possible when the engine is not working steam, removal of broken staybolts promptly and intelligent expanding of flues. Water treatment has done much to reduce boiler troubles, but it has its limitations, and in my judgment should not be attempted until the possibilities of design and systematic maintenance have been exhausted.

To sum up, it seems to me that the locomotive firebox in its fullest develop ment will be much larger and heavier in proportion to the barrel than it is now.

It is quite likely that it will be necessary to carry the overhanging weight back of the drivers on a four-wheel trailer truck.

The tendency for road engines, either freight or passenger, will be to make the dead weight due to increased size of boilers a larger percentage of the total weight. This increased dead weight, however, should not be a matter of concern so long as it increases the reliability and efficiency of the boiler. The limiting capacity of the fireman is sufficient reason in itself for striving in every way to increase boiler efficiency, either through better boilers, superheating or compounding.

I think it is not overdrawing it to say that no heavy road engine should be built with weight on drivers more than 70 per cent. of the total weight, and the lower this percentage is the more reliable and efficient the engine will be, it being understood, of course, that as much of the dead weight as possible is put into the boiler.

A cut of a heavy Pacific type locomotive is presented to illustrate the principles set forth in this paper.

The cut shown in the paper I have just read represents an engine that I don't think has ever been built-that is, a passenger engine of that weight. Everything is exaggerated on it in order to show what the possibilities are and what the views set forth in this paper would lead to in locomotive design. You will notice on the cross-section that there is 12 inches of water space at the crown sheet and six inches at the mud ring: that there is eight inches at the throat, and the bottom of the mud ring is about four feet below the lowest flue. The length of those flues, on account of large drivers, would be 22 feet if the combustion chamber were not in. This engine has out of a total of 250,000 pounds only 150,000 pounds on the drivers, which is rather a small percentage, but is not as small as a good many Atlantic type engines now running. You will also notice that the total heating surface, 3,527 square feet, will ordinarily be considered low for an engine of that size; but I don't believe that the greatest possible number of square feet of heating surface is the thing that we are most after. What we want is the greatest possible number of feet of heating surface that will be effective. What seems to me an especially good feature of the combustion chamber, if it is practical, is the fact that it very materially increases the heating surface of the firebox. In this case you will note that it is 334 square feet; and it does not need much argument to prove to you all that the firebox is what does the best work in the steaming of an engine. I don't think that there is a great deal in getting shorter flues: but no doubt there is some advantage. The beauty of the combustion chamber is in getting the flues away from the fire.

MR. FOQUE (Soo Line): Mr. President, I have been away from the office, so I did not receive this paper until today, and had very little time to look it over. I note, however, that Mr. Van Alstyne, as usual, has taken a step a little in advance of the rest of us, and he certainly has opened up here a subject to which we can, perhaps, give considerable thought to advantage.

I note in his paper that he speaks of an engine already built which has the flue sheet three feet ahead of the throat sheet. I assume that that engine, perhaps, so far as the internal design is con

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cerned, is constructed somewhat upon the lines shown in the diagram, and to start this discussion I will ask Mr. Van Alstyne to tell us a little more about that engine, and if it has been in service long enough to make the owners want more of them, and say what results are being obtained, both as regards the lessening of flue trouble and the increase, if any, of trouble with stay bolts or side sheets or the walls of the combustion chamber itself.

MR. VAN ALSTYNE: I can tell why the combustion chamber was put in, but inasmuch as the engine is in Mr. Curry's district I think he had better tell what she is doing.

MR. CURRY: Mr. President and gentlemen-About two months ago I inspected the firebox of this engine in comparison with one that stood in a stall next to it. The difference in the flues of the two engines was more marked than one would have thought conceivable, the engines having been in service the same length of time. The flues in the engine with the combustion chamber were practically free from showing evidence of being overworked, while in the engine with the ordinary firebox, flues were in a condition that as nearly as I could calculate would last about three or four months. The chamber was perfectly free from leakage. There was just one stay bolt which showed signs of having leaked just a little. It was as nice a firebox as I ever looked at, and is in service on one of our heaviest engines. Mr. Van Alstyne on various occasions talked to me about this engine, which takes me back to the time when we had on the Northern Pacific several engines with combustion chambers, and they were not considered a marked success; but in the application of the engine under discussion the sheet is flanged evenly-that is, the bend in it is so gradual that I think the comparison between the old combustion chamber and this one is not a fair one.

MR. VAN ALSTYNE: The great convenience and economy that is derived from this combustion chamber is due to the fact that the flues can be worked without disturbing the brick arch. Is it not true, Mr. Curry, that she has only received the second brick arch since we have had her? (Mr. Curry: I think that is the record of the engine-two or three.) I think it is two, as Mr. Allen told me he had put in the second brick arch.

MR. FOQUE: How long has that engine been running?

MR. VAN ALSTYNE: Since November, 1904.

MR. J. E. GOODMAN (N. P. Ry.): Mr. President, I was not aware that the N. P. had an engine with the combustion chamber before I heard this paper read. I recall years ago when they had several engines with combustion chambers. As I recollect, those engines were economical in the use of fuel and good steamers when combustion chambers were tight, but it was a difficult matter to keep them tight, and the chambers filled up badly with cinders. I suppose modern design has overcome all those difficulties, and I imagine it would be a great saving on flues and increase the heating surface thereby and get an economical engine. The development of the locomotive has brought about conditions in train operation, especially increased tonnage, that it has got to a point on a majority of railroads where the fireman can not stand up against it. It is not altogether due to the fact that firing the engine is so hard, but they are so long in getting over the road. That I think is a very serious difficulty on a majority of the large railways. I figure that our modern locomotives of today would be far more economical if the runs were not over ten or twelve hours. You can take the best kind of a locomotive, and if it takes over 18 hours to get over the road, the service on the last eight hours is going to be very much inferior to the first ten hours-firing, running and everything else. I do not know that I have anything more to say about this.

MR. GOODMAN: I would like to ask Mr. Curry if they have any difficulty with this chamber filling up.

MR. CURRY: No, sir. The current report is that not to exceed two or three inches of fine ash accumulate there-not enough to interfere in any sense whatever. It takes care of itself.

MR. MCCREE (N. P. Ry.): Mr. Van Alstyne, following Mr. Curry's remarks about the circulating tube. Is there not difficulty in repairing it if it is leaking on the top end?

MR. VAN ALSTYNE: It would be altogether easier, but it can be done.

MR. MCCREE: Of course I can understand that as the crown sheet is the most effective heating surface in the boiler, you will increase it by increasing the length of your combustion chamber three feet, making it six feet instead of three. Is there any other reason why this should be done or just carrying out a good idea?

MR. VAN ALSTYNE: The reason we did not go any longer than three feet in the one we have was that it was more or less of an experiment, and we were afraid of two possible difficulties one that if the combustion chamber was too long the water could not get back fast enough to take care of the steam generation, and in consequence the firebox and combustion chamber would burn out, and the other was we would get too little heating surface. As you lengthen the combustion chamber the heating surface decreases very rapidly, and just where the proper point is to stop we do not know.

MR. MCCREE: Of course the crown sheet is the most effective heating surface?

MR. VAN ALSTYNE: Yes, I think it is. MR. LARRISON : Not having had any experience with this engine on the Yellowstone Division (I am on the division adjoining) I can not speak from actual observation, but I have heard a great deal about it. It has always occurred to me that we could derive just as much benefit from using shorter flues as from the present long flue, for the reason that the flame when entering the flues is immediately smudged, and all we get from that point on to the front end is gas, and I firmly believe that this combustion chamber could be extended to even greater length and all that portion added to the firebox and increase the heating surface of the boilers.

a

I also noted the location of the circulating tubes, and would like to ask how the upper end of the tube can be flanged

out the same as the lower end.

MR. VAN ALSTYNE: Well, it can be done with a long stem roller.

MR. LARRISON: The upper end of the tube is in that portion of the side inside of the cab. Would there be sufficient room between the top of the cab and the top of the boiler to get at the tube?

MR. VAN ALSTYNE: You might if you cut a hole in the roof of the cab.

MR. CURRY: I would like to ask Mr. Foque a question. I was over to visit you some time ago, and you stated that in your large passenger engines there was a marked tendency for flue leakage to exist. In your heavy Pacific type engines is there more of a tendency for flues to leak than in lighter engines?

MR. FOQUE: Oh, yes.

MR. CURRY: Why is it that flames should heat flues in large engines to such

an extent as to cause them to leak and not in the smaller engines-the fire is not any hotter in heavy engines than it is in the small ones. How do you account for that?

MR. FOQUE: I don't account for it. In our modern power we have two classes of freight locomotives and one class of passenger locomotives. The smaller engines are moguls weighing about 125,000 pounds on the drivers, built for low grades, and these engines have given the most satisfactory service of any modern engines we have put in service anywhere. They run from one water to another and are going all the time, and the stay bolt trouble is so small that it can be neglected altogether. We have run these engines 17 or 18 months between shoppings, and have not found a broken bolt, and the flue trouble is reduced to a minimum.

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other engine is a consolidation, same type of boiler exactly, but larger. Now, these engines won't begin to give the service in the same districts as the moguls. Flues pull loose and stay bolts give us a great deal of trouble. Our Pacific type of boilers are built on the same general lines, and while these engines are in very severe service the trouble on the road is not so very much. It is after the engines reach terminals that we begin to have our trouble. As you may be aware, we run those engines into St. Paul. They arrive there at night and are housed there, but no work is done on them. We had a great deal of trouble with the engines leaking, hard work firing them up in the morning, and we are keeping them hot, keeping a light fire in them all night. In the morning these engines come over to Minneapolis and from there they go to the roundhouse, and we have noticed a marked improvement since we have adopted that system of caring for them. Why those engines or why the consolidations should give so much more trouble in the same districts and in the same service, you may say, as the moguls, which are built along the same lines, I am unable to say.

MR. CURRY: About what would be the percentage of the difference in the proportion?

MR. FOQUE: I don't recollect now the it quickly. power of those moguls, but you can figure The moguls are 125,000 pounds on drivers, and the consolidations, the last ones, about 170,000. The last ones went up a little bit. Taking the weight per wheel it is pretty much the same. The tractive power of the con