this?

Instructor.-Yes, the air pressure certainly does press the leather against the walls of the cylinder, or rather it has a tendency to do so, and does whenever the pressure is sufficient. When the pressure is admitted slowly to the cylinder, however, it will escape by the leather, when it is not held out by the expander. good illustration of this may frequently be seen with a driver brake on a freight engine, which, when coupled to a train, will not apply, but with lone engine applies all right and is tight.

A

in place properly, and nuts screwed up as they should be, there is very little trouble from this source.

Student. The driver brake cylinders on the engine I have been firing are not like the one shown in the cut. They have a stuffing box on the rod.

Instructor. The cylinder shown in the cut is a tender cylinder. There are two types of cylinders, known as the "pull," and "push." The "pull type" is so constructed that air is admitted at the piston rod end and, as it moves the piston, the rod is drawn in. This construction requires a rod stuffing box to prevent the escape of air around the rod, and as it is very difficult to keep this joint tight this

of use. This is the type the engine you refer to is. equipped with. The cut illustrates the "push type." With this con

cylinder air tight, but is leather air tight? Instructor.-Leather is not naturally air tight, that is, air under pressure will escape through it, unless it has been treated so as to fill up the pores. The leathers used in brake cylinders have been so treated, and are perfectly air tight, but after being in service some time they are apt to become porous again. In order to keep the packing leather in cylinders in good condition so that they will make a tight joint between the piston and walls of the cylinder, and also prevent air passing through them, it is necessary that the cylinder be so located that it will not be affected by the heat from the locomotive, and the leather must be kept pliable by oiling it.

Student.-Is there any other way by which air may escape from the brake cylinder?

Instructor.-It may escape by the gas

struction the air is admitted to the opposite end of the cylinder from the rod and, therefore, no stuffing box is required. The piston rod in this case is pushed out when the piston is moved by the air pressure.

Student.-There are different styles, or patterns of this "push type" of cylinder, are there not?

Instructor.-Yes, several.

Student.-About how much air pressure does it require to move the piston and compress the release spring?

Instructor. With an 8-inch cylinder it requires about 3 pounds to move the piston about 6 inches, without levers being attached to the rod. Three pounds pressure of air acting on a piston 8 inches in diameter exerts a force of about 150 pounds. Most of this is due to the resistance of the release spring, but some of it is due to the friction of the packing leather against the walls of the cylinder.

travel?

Instructor. It is the distance the piston moves in the cylinder to apply the brake, and may be measured with a "pull" brake by marking the rod at the stuffing box, when the brake is applied, and then measuring from the stuffing box to the mark when it is released. With a "push" brake mark the rod at the cylinder head and, then, when the brake is applied measure from the head to the mark.

Student. What is the shortest travel that can be had and have any pressure on the piston?

Instructor. The space between the piston and front head, or pressure head as it is generally called, has nothing to do with the pressure on the piston, that is, the shortest travel that can be had and have the piston cover the leakage groove is about 4 inches (leakage grooves vary somewhat in length) and, if the groove is not covered, the air will escape through it by the piston and thence to the atmosphere. However, assuming the leakage groove to be stopped up, or take a driver brake cylinder without a leakage groove, there will be the same force exerted on the piston in release position as when at 8-inch travel, with the same air pressure acting on it. The volume, or quantity of air, back of a piston does not affect its force. The area, or square inches, on the face of the piston multplied by the pressure of air gives the value of the cylinder, or force exerted at the outer end of the piston rod.

Student. I always supposed that it was necessary to have a quantity, or depth, of air in the cylinder to obtain any power.

Instructor.-No, the space between the piston and the head may be no more than the thickness of a sheet of paper.

Student.-Do all brake cylinders have a leakage groove?

Instructor. All except driver brake cylinders have them, and within the past few years the manufacturers have been putting them in driver brake cylinders for such roads as desire them. There is no leakage groove in the driver brake cylinders on this road.

Student. I have noticed that the driver brake piston travel is never so much as the tender brake, and I wish that you would please explain why this is so. Instructor.-All cylinders except driver brake cylinders are of such length that the piston may travel 12 inches without striking the head. Driver brake cylinders are made of different lengths, some permitting a travel of only 7 inches, others 8, 10 and 12 inches. Both driver brake cylinders are operated from the same triple valve and the pressure that may be developed in either will be the same, and will depend on the total travel of both pistons, therefore it is necessary in order to obtain the proper pressure that each one have about half the travel of the tender piston, where there is but one cylinder operated by a triple.

Student. I have always understood that the piston travel had something to do with the pressure that may be developed in the cylinder and, if I remember rightly, you said you would explain it to me when we have a lesson on the brake cylinder.

Instructor.-Yes, you are right, I did say so and I will now endeavor to make it plain to you. Auxiliary reservoirs and brake cylinders are made of such proportional sizes that an auxiliary reservoir with 70 pounds pressure will equalize into a cylinder with exactly an 8-inch piston travel at 50 pounds by a service application of 20 pounds reduction. Should the piston travel be less than 8 inches, then there will be less space to fill and they will equalize at a higher pressure than 50 pounds. On the other hand, should it travel more than 8 inches the space to fill will be greater and they will equalize at a lower pressure than 50 pounds. For illustration, with 4 inches travel they will equalize at about 56 pounds, and require an application of about 14 pounds reduction, whereas with 12 inches travel they will equalize at about 43 pounds pressure, and require an application of about 27 pounds reduction. With the same piston travel the pressure developed with a 10-pound reduction will be about 40 pounds and 6 pounds respec

Instructor. It is to offset slight leakage in the train line, that is, when the leakage is only sufficient to cause the triple piston to be moved and admit a very little air to the brake cylinder it will escape through the groove by the piston before it has moved far enough to

ton travel, or the space that the air in the auxiliary reservoir must fill, is a very important factor in the developing of pressure in the cylinder.

Student. I understand that the auxiliary reservoir remaining the same size, and the space in the cylinder to be filled with air being changed by the piston

travel on a tender with the brake beams hung above the springs?

Student. I do not know, I am sure. Instructor.-With the beams hung above the springs the relative position of the shoe to the wheel is changed by the load varying, they being at their lowest point when the tender is loaded with coal and the tank filled with water, and at the highest point with no coal or water. Should the connections be taken up on a loaded tender so that the shoes just cleared the wheel they would be forced hard against the wheel when the tender became nearly empty. Therefore, when adjusting the piston travel on a tender the load on the springs must be taken in consideration, with beams hung above the springs.

Student. I understand from your explanation that with beams hung below the springs the load will not change the relative position of the shoe to the wheel and, therefore, it is not to be considered when adjusting the travel with beams so hung.

Instructor. That is right. How can the piston travel be maintained at exactly 8 inches?

Student. I do not know.

Instructor. This can only be accomplished by the use of a slack adjuster, which will automatically adjust the connections as the shoes wear.

Train Rules and Train Practice.

Answers by H. A. Dalby.

77. Form F. Under American Railway Association Rules, No. 28, eastbound, superior direction, is released at A as 'No. 28,' Division extends from A to J. At C receives order No. 1 as follows: 'Engs. 70, 71 and 72 will run as 1st, 2d and 3d No. 28, C to G.' Engine 72 was on regular 28 out of A. At G engines 70 and 71 are run as extras G to J, but engine 73 is at G loading a train of stock. This train gets ready to go and order 2 is put out: "To C and E Eng. 73 and No 28. Eng. 73 will display signals and run as first No. 28 G to J.' Is this proper or should it have read otherwiise?"-C. W. F., Chadron, Neb.

Answer. From a ruling of the American Railway Association in reply to a similar question, we understand that engine 72, having left the terminal as "regular" No. 28, would be authorized, in the

Answers

absence of further orders, to proceed from G as No. 28. The second order was ad

dressed to engine 73 and No. 28 and is according to the first example under Form F. The explanation to this form states that "Each section affected by the order must have copies, and must arrange signals accordingly," so our understanding would be that the order is all right.

We have mentioned before that the rules governing Form F are not explicit, the intention being, we suppose, to allow each road to provide the details by additional rules or by instructions to those concerned. We think, however, that our understanding of this case is warranted by the ruling to which we refer.

78. Whose Fault?" There is a rule on this road that when a train overtakes another, that if the leading train has rights or or

ders to proceed and the following train has not such rights or orders, that the following train can take the orders or assume the rights and go ahead of the first train. There was a case here where No. 24, a second class train, had orders to meet extra 64 west at F and meet extra 66 west at G. There is a yard at G and extra 64 had some work there and while they were there extra 66 came along behind them. They had no work and could go right along, so they arranged with the conductor of extra 64 and took his orders and went to F to meet No. 24. This happened west of the station and a little later the engine of the first extra (64) had to go back to the station for water. The operator reported to the dispatcher that extra 64 was still there, and then the dispatcher changed the meeting point between No. 24 and extra 64 from F to G. The engineer signed the order and of course the operator and the dispatcher thought that was all right. But extra 66 went along to F and came near colliding with No. 24. Everybody seemed to be acting according to rules and yet an accident was possible."-W. B. J., Pittsburg, Pa.

Answer. Perhaps every one thought that he was complying with the rules, but the fact that an accident was possible makes it evident that either some one failed to adhere to rules or else the rules were defective. The trouble evidently lay in the fact that the conductor of extra 64 made the arrangement with extra 66 and allowed it to precede him to F while his engineer did not know anything about it. The question might also be asked if the dispatcher was justified in accepting the signature of the engineer as a hold on the train, but it would appear that this was sufficient, especially if it were the rule for the engineer as well as the conductor to sign for orders. We should think that a rule of this kind would require that the train passing the leading one should either exchange orders with both conductor and engineer or else know that both understood the situation.

79. Combination Order." Please give me your opinion on the following orders. Bass Creek is west of Edgemoor: "Order No. 35.

C. & E. Eng. 86.

Eng. 86 will run extra Edgemoor to Bass Creek until 6 p. m. and has right of track over No. 50 eng. 47 and return to Edgemoor ahead of No. 50 eng. 47. "Bass Creek is a blind siding where

there is a water tank.

"On this order could No. 50, a first class train, leave Bass Creek at 6 p. m. if extra 86 had not arrived? Should extra 86 leave a man at Bass Creek to notify No. 50 that they had arrived and left, or could No. 50 leave Bass Creek until

they knew the extra had left ahead of them? Bass Creek is not a telegraph station. Suppose extra 86 gets another order as follows: "Order No. 36.

C. & E. Extra 86.

Eng. 86 will run extra Edgemoor to Bass Creek until 8 p. m. instead of 6 p. m.

"Would they still have right of track over No. 50 from Edgemoor to Bass Creek?"-W. C. H., Ottawa, Kas.

Answer. These orders each contain a clause which is not authorized by the Standard Code in the sense in which it is We used. We refer to the time limit. suppose this limit refers to the run from Edgemoor to Bass Creek and that after 6 p. m. (according to the first order) the order to run extra in that direction is dead. If the men on the road from which the question came understood it that way, we should say that No. 50 could leave Bass Creek at 6 p. m. whether the extra had arrived or not, so far as that part of the order is concerned. There is another part, however, which says that the extra will run ahead of No. 50 Bass Creek to Edgemoor, and a strict compliance with this clause would require that No. 50 should know that the extra had preceded it from Bass Creek. Unless the extra was there and could be seen by No. 50, the only way that this information could be obtained would be to leave a man to notify the latter train. It is probable that on most roads this point would not be considered of the highest importance, and perhaps on some, No. 50 would proceed from Bass Creek regardless of whether the extra had gone ahead or not, only looking out for them in case they had.

On receiving the second order, as the time limit clause is not "Standard" we are unable to say whether the extra would still have right over No. 50 from Edgemoor to Bass Creek or not. The officers of the road would have to decide that. In the absence of special instructions we should not assume that such right was conferred.

This is another instance of a poorly worded order and shows how complications are more than likely to arise. If the extra reached Bass Creek for No. 50 and No. 50 saw it leave there, it might be all right, but if it failed to do this, we have seen the possible result. We suggest that the order be put in this form:

Eng. 86 will run extra Edgemoor to Bass Creek and from Bass Creek to Edgemoor ahead of No. 50 until overtaken. No. 50 will wait at Bass Creek until 6 p. m. for extra 86 west.