Locomotive Running and Repairs.

Answers by F. P. Roesch.

1994. Draft Arrangements.-"Can you tell

me where I can secure information in regard to the front end of a locomotive and its contents, and what the duties of each are? I am a young fireman and have lots to learn, and I believe this is one of the first things to learn. When an engine does not steam properly I want to be able to locate the reason."L. O. P.

Answer. When a young man admits his ignorance and desires to learn, we like to do all we can to help him. We agree with our correspondent that one of the first things a fireman should learn, after obtaining a knowledge of combustion, is the construction of the draft appliances in the front end, their locations and duties. By referring to "Our Special Study Course," beginning with Article 10 on page 174 of the August, 1911, issue of the Magazine, and reading this carefully, you will be able to obtain nearly all of the information desired. To make the action of the draft more clear, however, we would suggest to our correspondent that he study the action of natural draft in an ordinary heating stove. You will note that the heating stove has the pipe connected to the chimney in order to carry out the smoke, and at the same time create a draft; draft being created by the fact that the heated air being lighter than the same amount of cold air, it naturally rises and cold air rushes in to take its place. After we build our fire in the heating stove, we open the damper at the bottom. Consequently, all air flowing into the stove to take the place of that which is heated and which passes off through the stove pipe, must pass through the grates, and so through the fire, thereby furnishing the oxygen necessary to stimulate the fire. After the fire has attained the temperature desired, in order to reduce the draft it is simply necessary to either wholly or partially close the damper at the bottom of the stove. If we wish to still further reduce the draft, we open the stove door so that the cold

Now,

air can rush in over the fire. while the stove door is open, practically the same amount of air is still passing through the chimney, but as it passes over instead of through the fire the fire does not burn as freely as it did before; and if the stove door is left open long enough the fire will gradually go out, as it is necessary to bring the air through the fire in order to produce perfect combustion. Practically the same thing obtains in the locomotive, the stack of the locomotive being the stove pipe and chimney; the grates, of course, serving the same purpose as the grates in the stove; the ashpan dampers, when used, performing the same function as the stove dampers. Therefore, if natural draft alone were depended upon in a locomotive we would increase the height of the stack and enlarge the dampers in the ashpan in order to obtain more draft, and, consequently, make the fire burn more freely. As it is necessary in the locomotive, however, to burn more coal per square foot of grate area per hour than can be burned by depending on natural draft alone, we are compelled to resort to forced draft. This forced draft is obtained by allowing the exhaust steam, which has performed its functions in the cylinders, to pass out through what is termed the exhaust nozzle, located in the front end and directly under the center of the stack. The current of steam passing out of the exhaust nozzle and up through the stack creates a partial vacuum in the front end. This partial vacuum must' be filled with air from some source. Now, as the front end is practically air tight and as the steam escaping through the stack will not permit air to rush down into the stack and so fill the front end, it is plain that this air must come from the rear of the boiler or through the firebox and flues. With the firebox door closed and the ashpan dampers open, the air will rush in through the ashpan, through the grates and up through the fire on its way to the front end. When passing through the fire it gives up its oxygen, thereby

stimulating combustion. If the fire door is opened, however, the air would naturally flow in through the point of least resistance, which would be the open firebox door, and, consequently, pass over the fire, and instead of stimulating combustion would retard it. It is therefore plain that the less time you keep the firebox door open-except when it is absolutely necessary to throw in additional fuel-the more action the draft can have on the fire and the better the fire will burn.

Referring now to the figures as shown in "Our Special Study Course," on pages 174, 175 and 176 of the August, 1911, Magazine, you will find stated the different types of what are termed the "Master Mechanics' Standard Front End." It will be seen that the front end is provided, first, with a baffle or diaphragm plate, extending at an angle from the front flue sheet; a table plate, through which the exhaust nozzle passes, and an adjusting plate connected with the diaphragm plate. The object of this plate, and especially the adjusting plate, is to distribute the draft equally all over the fire. As a further aid towards the distribution of the draft one or more pipes, termed "petticoat" pipes, are also used. The front end is also provided with netting to prevent the emission of sparks. The distribution of draft is obtained where both petticoat pipes and adjusting plates are used, by moving one or the other, or both, up and down. Lowering the adjusting plate cuts off a portion of the draft through the upper flues, increasing it through the lower flues, thereby increasing the draft at the front end of the firebox. Raising the plate has the opposite effect. Consequently, if your fire burns too hard at the front of the box, raise the adjusting plate; if too hard at the back of the box and not hard enough at the front of the box, lower the adjusting plate. As a further aid towards distributing the draft the petticoat pipe is sometimes used, as previously stated. The regulation of this pipe to control the draft, however, is seldom resorted to, as the distribution can generally be obtained by means of the adjusting plate providing the petticoat pipe has been properly adjusted. This is usually set so that there is twice the distance between the base of the stack to the top of the pipe as between the bottom of the pipe and the top of the nozzle. In adjusting this pipe the action is

practically the same as adjusting the plate, as raising the pipe increases the draft towards the back of the firebox and lowering the pipe has the contrary effect. Where the petticoat pipe is used it should be maintained centrally with the stack, and, as a rule, its position can frequently be determined by watching the smoke coming out of the stack, as if the smoke comes out at one side only it is evident that the pipe has come out of alignment, and in this case will frequently interfere with the steaming of the engine. There are several other features that affect the steaming of a locomotive, but for a full explanation we would refer our correspondent to "Our Special Study Course" previously mentioned.

1995. Movement of Crosshead.-"Does the crosshead move in the guides in both directions or only one? Some enginemen claim that the crosshead never moved back in the guides. Please give your opinion in regard to this question."-N. V. C.

Answer.-When the locomotive is moving forward and you consider the movement of the crosshead in relation to a fixed point on the ground, if, for instance, you place a stick in the ground just opposite the crosshead, you will note when the piston is moving from the back center to the forward center that the crosshead moves in the guides, the crosshead at the same time being carried forward, or ahead, of the point where the stick was placed in the ground. When the crosshead is moving from the forward center to the back center, however, it will be noticed, by means of the stick, that instead of the crosshead moving back the guides are carried forward; that is, the crosshead remains stationary in relation to the ground, while the whole engine moves forward, this, of course, carrying the guides with it. The crosshead will move in both directions when the engine is slipping, as in that case the engine is making but little progress over the ground.

1996. Names of Connections Between Engine and Tender.-"What is the proper name for the casting on the tender where the pulling bar is connected, where the lower end pin passes through it? Also, the name for the connection on the rear of the engine?"-N. V. C.

Answer. The term usually employed for the former is the "tender drawbar casting," and for the latter "rear engine drawbar casting."

1997. Evaporative Power of Heat Units."How many pounds of water will 15,000 heat units cause to be evaporated into steam?"-C. F. R.

A

Answer. This depends altogether upon the temperature of the water before the heat is applied. Water boils, or is converted into steam, at sea level at a temperature of 212 degrees Fahrenheit. heat unit is the name given to the quantity of heat that will raise the temperature of one pound of water one degree Fahrenheit. Therefore, 15,000 heat units would raise as many pounds of water to the temperature of steam, that is, 212 degrees from zero, as 212 is contained in 15,000, which is 70.75 pounds. If the temperature of the water, instead of being down to zero point, however, was 60 degrees Fahrenheit, then it would only be

Name of Road...

necessary to add to it the difference between 60 degrees and 212 degrees, or 152 degrees, to raise its temperature to the boiling point or convert it into steam. In this case the 15,000 heat units would convert 98.68 pounds of water into steam.

1998. Dimensions of Pacific Type Locomotives.-"What are the principal dimensions ing railroads of the country? of Pacific type locomotives on the leadAlso include in the list engine No. 5000, recently built by the American Locomotive Company."-Subscriber.

Answer.-The following comparison compiled by the American Engineer and Railroad Journal, and shown on page 262 of the July, 1911, number, gives a comparison of the principal Pacific type locomotives constructed up to that date:

P. R. R.

N. Y. C. B. & O.

Vandalia.

C. & N. W.