1578. Young Valve Gear.-"Could you give me a diagram of the Young valve for a locomotive, illustrating valve, its ports and seat, also wrist plate to which valve rods are connected, bell crank and union rod connections to reversing shaft?"C. W. Answer. This valve and gear was fully described and illustrated on page 27 of the January, 1909, issue of the Magazine. 1579. Cause of Flues Leaking.-"As I am having trouble with an engine I am firing regular, I thought I would appeal to you for a little help. The engine is or was a Kingston cross-over compound consolidated engine, which has recently been converted into a simple engine using superheated steam. The flue sheet and tubes are both new, and I have tried all manner of ways which my four years of experience has suggested to me, but I am unable to keep the tubes from leaking. The mechanical officials appear to think that my method of firing is responsible, which I deny, having fired other superheated engines successfully. The boiler of this particular engine is of the long firebox type, and what I would like to know is, what mechanical defects, if any, could cause the trouble? I have had the engine for about six weeks now, and with the exception of a couple of trips have brought her in leaking. The engine is in way freight service and does 190 miles per round trip with an average of eight hours terminal switching. Please say in your reply why each defect named will cause the trouble, as, for instance, the expansion and contraction of the tubes and the effect on the flue sheet, etc. I expect to be called in before the master mechanic on account of it, and would like to be able to explain all these things." J. W. W. Answer. There is no reason why an engine fitted with a superheater should leak any more than one not so fitted, and the very fact that, as you state, you have brought the engine in twice in six weeks without leaking would indicate that there might be something wrong either in the way the engine was fired or in the way the engine was handled, as if the leakage was due to any mechanical defect this defect would necessarily exist every trip and not occasionally. The only mechanical defects which might cause leakage would be due to the fact that as the superheater smoke tubes (we are taking it for granted that the engine is equipped with a smoke tube superheater, that is, a superheater of the Vaughan-Horsey type, wherein the superheater elements are contained in large smoke tubes running from the front to the back flue sheets) are made of heavier material than the other tubes, commonly called flues, that these flues expand more than the other tubes or flues. This would have a pushing action on the flue sheets and might set up a strain in the other flues sufficient to cause a pull on the beads, and as the tubes cooled off, by letting the fire get low or leaving the firebox door open too long, the contraction of the superheater smoke tubes being greater than the contraction of the other tubes (as the expansion is greater, the contraction would also be greater) might have the effect of pulling the sheet back to its original position and so leave the beads of the other tubes away from the sheet, causing same to leak. Repeated experiments have proven that when an engine is first fired up the tubes, on account of being exposed to a greater heat, will expand before the shell of the boiler begins to expand, thus producing a bulging action on the flue sheets. After the temperature of the water in the boiler begins to rise, the boiler begins to expand, until its expansion is practically equal to that of the tubes; this would have a tendency to straighten the sheet again. It has been further proven that if the door has been left open or the fire becomes low, the tubes will begin to contract before the shell of the boiler contracts. This produces a pulling action on the flue sheet, and it is this constant pushing and pulling that pulls the beads away from the flue sheet and finally causes the flues to leak. This action on the part of the tubes can not be termed a mechanical defect in a strict sense of the word, as the same action practically obtains in all locomotive boilers. Good flue setting will, of course, go far toward preventing leakage, and it may be possible in the present instance that the flues are not properly prossored, in which case, the flues having begun to expand would have a tendency to push through the sheet instead of bulging the sheet or allowing the flues to spring up or down, as generally occurs with long flues. Before criticizing the mechanical work, however, it might be well for you to see if the trouble does not lie in the way in which the engine is fired, or possibly in the way the engine is handled by the engineer. We would therefore suggest that you try keeping a bright fire under the flues at all times, whether working steam or drifting, swing the door after every scoopful of coal put into the firebox, and pump the engine so as to maintain a regular and even supply of water; as it would not look well if, after you have criticized the mechanical work on the boiler, another fireman went out on the engine and brought it in dry every trip. a 1580. Young Valve Gear.-"I enclose sketch of a cylinder on passenger locomotives Nos. 391 and 394 of the C. & N. W. Ry., and would like to learn through the Magazine what kind of cylinder arrangement it is. As I tried to show in the sketch, the cylinders on the top appear to run crosswise and the valve gear operates from the top of same. I would like to know what kind of valve gear is used on these engines and to see a photograph of same in the Magazine. If you can not furnish the information on these particulars, could you let me know where I might procure same, as I am very much interested?"-V. G. Answer. The gear in question is what is known as the "Young" valves and valve gear. The two cylinders mentioned by our correspondent as being crosswise of the main cylinder are the valve chambers, and contain rotary valves which are operated by the valve mechanism on the outside, as mentioned. These valves differ from the ordinary valves used in locomotives in that they do not slide forward and back over the seats, but rock or rotate same as Corliss valves used in connection with stationary engines. The operation and construction of these valves and valve gear is fully described and illustrated on page 27 of the January, 1909, issue of the Magazine, and as our correspondent states that he has been a subscriber to the Magazine since April, 1908, he has doubtless retained all previous copies and is therefore in a position to refer to the copy of the Magazine mentioned. 1581. Unequal Cut-Off.-"While looking over the valve setting rules in McShanes' book called 'One Thousand Pointers for Machinists and Engineers,' I found a rule number 19, which reads as follows: 'When trying the length of reach rod, by trying the cut-off in each extreme notch of quadrant, remember most engines carry their steam 21 inches in forward motion and 20 inches in back motion.' Please explain why this is if engine valves are set when engines are cold, which most of them are?" H. T. T. Answer-We are at a loss as to what is referred to in the rule quoted, as, with the valves correctly set, steam should be carried the same distance in the forward as in the back motion, unless the rule quoted refers to the fact that on most engines the correct adjustment of the valve gear in the back motion is sacrificed in order to obtain a better adjustment in the forward motion, as, for instance, on most passenger engines, and also in the case of some freight engines, in order to obtain the proper steam distribution in the forward motion the valves are set line and line in forward gear but with from 1-16inch to -inch lead in back gear. This gives an earlier admission, earlier expansion and earlier exhaust in the back motion than in the forward motion, and consequently steam would not be carried as far in the back motion as in the forward motion. Unless the valves are so set, the cut-off should be the same in both motions. 1582. Ash Pits in Roundhouse.-"Sometime ago the Northern Pacific Railroad erected a roundhouse at Delworth, Minn., and placed the ash pits inside of the house. Will you advise me what success they obtained with this arrangement and what is the probable saving?"-C. D. Answer. We regret to advise that we have no data showing exactly what saying was effected by means of this arrangement. There is no question but what the intention was to avoid the necessity of running engines from the cinder pit, where located outside of the roundhouse, into the roundhouse without any fire in them, thereby in extremely cold weather having the effect of chilling the flues, side sheets, etc., and causing contraction and leakage. The saving, if any, was therefore simply the saving in boiler repairs, ble to effect a saving of any extent in the as we can not see where it would be possi-. cleaning of fires or handling of ashes. 1583. Feed Water Heater.-"In 1908 the Georgia Central Railroad placed in oper ation on one of their locomotives a feed water heater. Can you advise if it was a success, and give the saving in boiler repairs, coal, etc.?"-C. D. Answer. The feed water heater referred to was placed on engine 1223, an engine having cylinders 20 x 28 inches, 34,000 pounds tractive power, 44 square feet grate area and a total heating surface of 2,458 square feet. This engine was tested against engine 1081 of the same power and practically the same design, except that the 1223 was equipped with Walschaert gear, while the 1081 had the Stephenson link motion. The 1081 also differed from the 1223 in that the 1081 had a narrow firebox and was equipped with a solid brick arch; the grate area of the 1081 being 30 square feet as against 44 square feet of the 1223, and the total heating surface, including arch bar pipe, 2,220 square feet as against 2,458 square feet in the 1223. The feed water heater used in connection with the 1223 may be briefly described as follows: "The water is taken from the tank by a duplex steam pump located between the frames behind the cylinder saddle and about on the level with the floor of the tank. The water is delivered into the heater drum under the left running board, where it is heated by the exhaust from the steam pump and the exhaust from the 'left hand air pump, From the left hand drum the water goes under pressure into a similar drum located on the right side. From this latter drum the water is forced through the heater in the smokebox, which consists essentially of a set of Baldwin superheater coils, and from this again through an ordinary boiler check into the boiler, the check being located in the usual place on the left side of the boiler. The heater drums mentioned are 15 inches in diameter and six feet long, each containing 19 tubes 11 inches in diameter through which the air pump and feed water pump exhausts pass. The condensed water from the exhaust steam of the feed water and air pumps is carried back into the tank through suitable connections where it heats the tank water from normal up to 170 degrees, according to the temperature of the atmosphere and the service in which the engine is engaged. In conducting the tests, the same grade of coal was used on all engines and each engine handled by the same engine crew. The coal was accurately weighed and sacked to 150 pounds to the sack. The water was carefully measured and taken from the same supply for each engine. Although but one round trip was made with each engine, the conditions were made as nearly identical as it was possible to have them. The results of the tests show that engine number 1223, with the feed water heater, burned 98 pounds of coal per 1,000 ton miles, with a ratio of evaporation of one pound of coal to 7.13 pounds of water. Engine 1081, which was not equipped with a feed water heater, consumed 110 pounds of coal per 1,000 ton miles, with a ratio of evaporation of one pound of coal to 6.9 pounds of water. Another engine, namely the 1224, practically a similar engine to 1223, except that it was fitted with a Baldwin superheater, had cylinders 22x28 inches and carried 160 pounds of steam as against 200 pounds for the 1223, was also run in a comparative test with the latter engine. This engine proved to be the least efficient of the three engines tested, its coal consumption being 118 pounds per 1,000 ton miles, and its ratio of evaporation 6.98 pounds of water per pound of coal. Therefore, judging from the above results, and the fact that the Central of Georgia is equipping more of its locomotives with this type of feed water heater, it is evident that the heater is a pronounced success, not only in fuel economy but boiler repairs. 1584. Calculating Strength of Beam.-"I know it is somewhat out of line to ask questions of this nature, but would like for you to answer the following question: On page number 160 of the Cambria Steel hand book can be found the following: The section number of a steel channel, Depth. Weight per foot. Moment of inertia, axis 1-1. Will you please work out an example showing how each of these terms is used have always been very explicit in your in figuring the strength of beams? You explanations, and I hope you can make this one plain to me."-C. D. Answer. We believe that the trouble of our correspondent is that he does not understand the terms used in connection with this problem, hence is at a loss as to how to apply them. In the words sections, etc., as given by the Cambria steel hand book, the object in specifying same is simply to save the intending purchaser the trouble of working out the different factors, as in all beams of irregular sections, regardless of whether they are channels, tees, angles, etc., considerable calculation is necessary in order to obtain the area of section, moment of inertia, radius of gyration, etc. The term or factor once given, however, the remainder of the calculation is easy. The term at the right of moment of inertia, namely, axis 1-1 and 2-2, and at the right of radius of gyration and section modulus, axis 1-1 and 2-2, indicate the part of the beam to which these terms apply, and where referring to section modulus indicates the resisting inches of the section, that is, moment of inertia divided by greatest distance of neutral axis from outside fibers of the section. In order to know the correct application of the terms used it is first necessary to understand the meaning of the terms. Take, for instance, the moment of inertia; this, in connection with an example of this nature, is simply a multiplier or co-efficient indicating by what number the ultimate strength of the material under consideration is to be multiplied in order to determine the load it will carry. The moment of inertia, as used in connection with this example, means the average value of all the fibers composing the section, and is obtained by adding together the products resulting from multiplying each particle of the body or area of the figure by the square of its distance from the neutral axis, which is the point in a beam where the fibers are neither under compression or tension. Thus, for instance, if, instead of a channel, the beam were of square section, the neutral axis would pass practically through the center, so that if the beam were supported at the ends and the weight applied in the middle its resistance to bending would be practically the same in both directions, that is, with either side up. Were it, instead of square section, of a rectangular section, however, say a bar of iron two inches thick by eight inches wide, the support as before, it is plain that it could not support the same load if placed in the center between the two supports with the bar laid flatways as if laid edgeways, as if the bar were laid flatways its moment of inertia would be much less, as the distance from the edge of the section to the neutral exis, the point where the fibers are neither in compression or tension, would be less than if the bar was laid edgeways. The calculation for finding the moment of inertia is rather long and intricate and much more so when applied to irregular shapes, as in case of channels, tee irons, etc. It is found by dividing the body or section into many small parts and multiplying the weight or area of each part by the square of its distance from the neutral axis of the section; the sum of these products will be the moment of inertia, or the resistance of the beam to bending, and it is to avoid such calculations that the moments are given, as has been stated above. like the moment of inertia, simply a constant or multiplier by which the ultimate strength of any beam is to be multiplied, but is to show its resistance to bending when the load is applied to the end, and differs from the moment of inertia in that the moment of inertia is taken into consideration or used as a multiplier when a beam is supported at its ends and the weight applied in the middle or supported in the middle, or the weight applied to either end. Perhaps the best illustration that could be given is to consider the use to which the channels in question are to be put; say, for instance, that the channels are to be used as the center sills of a locomotive tender or car; when used in that connection the sills are subjected to the strain of the load imposed on them which would cause them to bend downward (the supports to the sills are of course the points indicated by the body bolsters), and it is to find the safe load that can be carried on top of the sills that the factor, moment of inertia, is used. The sills are also subjected to another strain, namely, that of pulling when the engine is pulling its train (which need not be considered in this instance, as this limit is determined simply by the tensile strength) and the pushing strain, as when the engine is backing up a train; this pushing strain has a tendency to bend the beam in the direction of its greatest weakness or least resistance, and it is to determine how much of a strain can be imposed on the channels in this direction that the factor "radius of gyration" is used, as, for instance, taking the previous example, where instead of a channel, a bar of iron were used of a rectangular section, say 2x8 inches; if the bars were set up edgeways we know that they would carry a greater load than if laid flat. If now the load was applied at the end, as when pushing, we know that the bars would have a tendency to bend out sideways, while if laid flat they would bend up or down. The radius of gyration is, therefore, simply a relative term to indicate the resistance to bending of the beam under consideration when subjected to pressure applied at its ends, and the factor "radius of gyration" depends altogether upon the shape of the beam in question, a channel having a higher factor or higher radius of gyration than a flat bar of equal area, and a beam or "I" section having a higher factor or radius of gyration than a channel. The term The next term, radius of gyration, is, "section modulus" is, like the term "mo ment of inertia" or "radius of gyration," simply a term to serve as a basis of comparison, same as a constant or a co-efficient, and in this instance simply indicates the resistance of the section in relation to the axis 1-1 or 2-2. It would hardly serve any good purpose to work out a hypothetical example (in order to determine the weight that a beam or channel used, for instance, as the center sill for a tender or car, will carry, such as a load imposed on it, or the pressure it will stand before bending when applied at the ends, as in backing up a train, or resisting buffing shocks, as when the slack of a train runs up against the engine), as there are so many other things to take into consideration, all of which involve long and intricate calculations, that the example after being worked out would probably be of little value as applying to the question under consideration. These calculations would be especially intricate if the channels under consideration were to be used as sills for a tender or car, as in this case the body bolsters would form the supports for the channels, and the load imposed upon the channels would be ahead of the front body bolster and behind the back body bolster, and also between the two body bolsters, and consequently each distance from the point of support would necessarily have to be taken into consideration. 1585. Reheater.-"Describe the reheater as applied to the locomotive?"-C. D. Answer. The reheater is a device used in connection with compound locomotives for the purpose of reheating the exhaust steam from the high-pressure cylinders before it is admitted to the low-pressure cylinders. The forms of reheaters differ on various railroads in accordance with the ideas of the heads of the mechanical department; thus on some railroads the Baldwin type of superheater, which consists of a series of tubes taking the place of the ordinary steam pipes, is used, while on other railroads as, for instance, the Santa Fe, the reheater consists of a large drum placed directly in front of the front flue sheet and back of the exhaust nozzle, that is, between the exhaust nozzle and the front flue sheet. This drum is filled with a series of tubes through which the hot gases pass on their way to the exhaust. The exhaust steam from the highpressure cylinder passes into one end of this drum where, by means of a series of baffle plates, it is forced to circulate around all of the tubes before it can pass out through another steam pipe to the low-pressure steam chests. In that way this exhaust steam becomes reheated or, as has sometimes been termed, superheated. On the Canadian Pacific, a reheater was employed which was somewhat different from either of the two above mentioned; its purpose, however, same as the others, was simply to increase the temperature of the exhaust steam from the high-pressure cylinders before it was admitted to the low-pressure cylinders. 1586. Adjusting Walschaert Valve Gear."I am running a Baldwin ten-wheel, 20x 28-inch cylinders, outside admission valves, Walchaert valve gear. Engine is lame. Heavy exhaust forward end of right cylinder. Also light exhaust in opposite end of same cylinder. Left side appears to be equally divided. What I want to know is, what changes should be made to get an equal distribution of steam; that is, to get the engine square? Explain fully how to adjust this valve gear, as it is the first Walschaert gear I have ever ran."-D W. G. Answer. If the engine has a heavy exhaust when exhausting from the forward end of the right cylinder and a light exhaust at the opposite end, it indicates that the engine is getting too much steam at the forward end. In other words, that the valve is pulled back too far (if the heavy exhaust appears when the piston is at the forward end of the cylinder, it would be the back end that was getting too much steam); it is therefore evident that the valve stem, or radius rod, is too short. All parts of the Walschaert gear are correctly designed at the locomotive works when engines are built, and as a rule can not get out of adjustment, except such as is due to wear. In this instance it may be possible that a new valve yoke has been applied which is not the same length as the one original to the engine. Ordinarily, the dimensions of any of the parts should not be altered, as there is little possibility of their becoming out of adjustment. In the case cited, however, it is evident that some change has been made, and to locate it, or, in other words, to adjust a Walschaert gear, proceed as follows: Make your port marks of port openings on the valve stem. Now place the back end of the radius rod so it will be exactly in the center of the link; have your engine on either the top or bottom |