The Westinghouse Air Brake.

Answers by F. B. Farmer.

1033. Driver Brake Value.-"What is the value of a good driver brake on an engine weighing 150,000 pounds on the drivers, as compared to a car weighing 30,000 pounds light?"-C. G. P.

Answer.-Omitting consideration of the tender brake the value of a good-order driver brake on such an engine, based on the relative braking powers of it and the car specified, is four to five times as great as that of the car brake. The car would be braked at about 60 per cent. of its empty weight or 18,000 pounds, and the drivers at not less than 50 per cent. of their loaded weight or 75,000 pounds, both based on 50 pounds in their brake cylinders. Some drivers are braked at 60 per cent., which would make 90,000 pounds braking force.

1034. Compressor Stops if Dry.-"If a pump requires more than the ordinary amount of oil to prevent it from stopping, what remedy would you suggest?"Member.

head. This shows that the feed valve pipe pressure must be acting downward on the diaphragm of this head to aid the would not follow. It is assumed in this spring, as otherwise the result mentioned that the high-pressure governor head is regulated above the amount that the feed valve pipe pressure and excess spring combined would amount to.

Another simple test is to bring the brake valve handle from release to running position right after commencing to charge a long train and while the main reservoir pressure is yet reasonably high. If 20 pounds excess pressure is normally carried and the amount shown on the gauge exceeds this right after the brake valve handle is brought to running position the compressor will stop until the excess pressure reduces to or a little below 20 pounds. As brake pipe and feed valve pipe pressures are equal in running position and as the compressor starts when the feed valve pipe pressure plus the 20-pound excess spring exceeds the main reservoir pressure, admitted to the under side of the governor diaphragm at this time, it demonstrates that the feed valve pipe pressure is the variable one above the diaphragm that controls the governor action at this time.

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Another possible cause for increased lubrication being required to prevent stopping is working water. The compressor dry pipe may not be as high as the locomotive throttle, thus causing water to enter the compressor, while it does not get to the locomotive cylinders, or the dry pipe may be leaking. Once a leak starts it will increase with time.

1035. SF Governor Experiment.-"By what simple experiment can you show that feed valve air is carried above the diaphragm of the excess pressure head, ET brake and SF pump governor?"Member.

Answer. By raising or lowering the adjustment of the feed valve and noting that the same excess pressure is carried without changing the tension of the spring in the excess pressure governor

While these are interesting experiments and useful in a way, yet to prove that feed valve pipe pressure is above the diaphragm of the excess pressure governor head requires nothing more than following the upper pipe connection from this head to where it joins the feed valve pipe, which may be the pipe itself or the alternate connection for this pipe in the brake valve pipe bracket, the result being the

1036. Undesired Quick Action Remedy. —“I am running an engine on an eastern railroad. Most of our engines have the latest Westinghouse air brake equipment. Would like to know why I am able to ing method on any train, say, of sixty overcome a 'kicker' by using the followcars or less and not making below twelve miles per hour. As soon as I am aware that I have a 'kicker' in the train when it becomes necessary to use the brakes I bring the handle of the brake valve to service position and make a train pipe reduction of about three to five pounds. In making the reduction I do not wait until the train pipe exhaust has stopped, but throw the brake valve handle to full release and then quickly to running position. Then I at once make a 10-pound reduction, followed by another reduction of, say, five pounds. In this way I do not have any more trouble with the kicker' that gave me trouble by making an initial 10-pound reduction.

"Why does making a slight reduction in pressure cover up the 'kicker'? I have used this method successfully for a num ber of years. Some would say that I would be manufacturing a ‘kicker', but as

soon as I find I have one I use this method and have no more trouble with it. An explanation of the foregoing will be greatly appreciated."-G. L.

Answer. You have evidently been fortunate with "kickers" or "dynamiters," as triple valves that cause undesired quick action are variously termed, as there have been many instances where this faulty operation could not be avoided by any method of operation. First, let us consider the various causes of undesired quick action. While with all kinds and lengths of trains one authority has listed a large number of possible causes, yet for the ordinary freight train and omitting rare causes we have really but one worth mentioning with the car brakes and that is a triple valve slide valve that it too hard to start from release position. The main cause for this is now known to be the use of an oil or grease lubricant on the slide valve and its seat. Making the slide valve spring tension strong and carrying higher brake pipe and auxiliary reservoir pressures increase the slide valve resistance to application. It is plain that if the triple piston cannot start the slide valve until the brake pipe pressure has reduced six or seven pounds the following movement will be so rapid as to compress the graduating spring, cause quick action and thereby so apply the balance of the brakes.

to movement which they cause is greatest after the brake has been charged for some time without any movement of the slide valve.

The foregoing afford the only plausible reasons for such possible prevention of undesired quick action as the plan described might at times afford, those cases where the "kicker" was not too far from the locomotive. The first light reduction would start more or less of the triple valve pistons toward application; how many would depend largely on how nearly this reduction was completed before moving the brake valve to release. This reduction would cause the triple pistons to tap the slide valves, start any that were easy to move and tending somewhat to loosen others. The release movement would drive the triple pistons back and give the slide valves more or less of a bunt in the opposite direction. The immediate reapplication would cause the piston spiders to again strike the slide valves a more or less sharp blow, tending farther to make them start easier as this reduction was continued.

Where the faulty triple valve is well back in the train, say, beyond 25 or 30 cars, it is believed little or no benefit could accrue from the method described. However, where the air is insufficiently cooled before it leaves the last main reservoir, as will occur with inadequate cooling pipes on the locomotive, sufficient moisture will often reach the triple valve slide valves of head brakes to cause a tendency to "dynamite," and in such instances the described method might reduce the liability of undesired quick action.

would alone occasionally result in a very bad shock from slack action, one that would damage draft rigging.

Some of the presumed "kickers" are not faulty-operating triple valves, but instead the jerk that is presumed to indicate the presence of the "kicker" is merely slack action due to the make-up of the train or a change in grade or both, and to the handling of the steam and of the air brakes not being such as to prevent this slack action. Limiting the use of the method described in the question to a minimum of twelve miles per hour recognizes the danger of employing it at lesser speeds. The writer would fear it even at fifteen miles per hour or some higher speed with certain trains. With the growing practice of thoroughly cleaning all oil, grease and gum from the triple valve slide valve and seat and lubricating them with nothing but a high-grade, fine, dry graphite undesired quick action is steadily reducing. In fact, on a few roads where this is done on cars that are used in special service, never leaving the home line, it is practicaly unknown, yet where it was epidemic when oil or grease lubricants were used for the slide valves.

1037. Freight Train Stopping Distance. "In order to help settle a dispute can you tell us about how far it would take to stop a train of 30 average loaded cars running about 10, 12 or 15 miles per hour on level track under average conditions if brakes are set in emergency and no sand is used; also, whether there is any rule to calculate such things?"-C. H. M. Answer. The answer to this question is safe to argue over as with "the average loaded freight train" actual tests with one and another that might properly be so termed would produce results that would vary sufficiently to suit both of the contending parties. This means that for determining a stopping distance no "average train" of any character, and particularly a loaded freight train, can be assumed and expect to arrive within 100 per cent. of a correct answer. Assuming that we know the actual speed, number of cars and the grade and that emergency was used, without sand, all of the data given in the question, we still need to know the brake pipe pressure carried, the weight and lading of each car, the condition of its brake, the brake leverage of each car, the weight of engine and tender, type of brakes on them, condition and leverage of their brakes, number of wheels braked on the engine and weight on these wheels, coal and water in the tender and the character and condition of all brake shoes in the train. With all of this known it is possible to calculate the stopping distance with fair accuracy, but it

any "average" train. In fact, even the one requisite, the actual condition of the car brakes, is not determined in daily practice with a single freight train.

To ilustrate, consider the terminal brake test as best made in practice. The train is fully charged to, say, 70 pounds, a reduction of 20 pounds is made and an inspector starts at once from each end, inspects quickly to the other and then the two confer as to the number of brakes found that had seriously incorrect piston travel or did not hold. If the train were short and they worked quickly they could get over it before some brakes with serious cylinder leakage could release. If it were long the greater time required would disclose some of the same brakes as faulty. All at the ends of the train would get a more severe test than those near the center because it would be longer from the time all were set until the final inspection of those at the ends. Again, there could be brakes with cylinder leakage that when first set would have ten or eleven inches piston travel and which had leaked back to about eight inches at the time they were inspected. Thus with two serious defects such could be passed as good brakes. Where the inspection is made one way only, a customary method, no brake cylinder leakage would be found on the cars first inspected if the brakes applied, but those brakes toward the other end would be given a far more severe test. Also, the chances of overlooking both cylinder leakage and long piston travel would be increased.

Hard metal in brake shoes or a poor contact between shoes and wheels reduce the holding power obtained from the same shoe pressure. New shoes provide both of these features as the outer surface or the "skin" of the casting is harder than the interior and shoes must wear some before a good contact with the wheels is obtained. Again, if the entire shoe is of harder metal than ordinary this will cause a lower holding power even after a full bearing is obtained.

Even the knowledge that the air gauge showed some certain brake pipe pressure is no assurance of this amount unless the gauge has been tested recently. In stops from low speeds even the position of the train slack at the time of brake application can affect the stopping distance appreciably.

How a "loaded train" will vary in load per car is well shown by the difference in the number of loads with one train and another where the same total tonnage is had. The braking power of a car is the same whether empty, lightly loaded or

heavily loaded, but the stopping power of the brake is less the heavier the load. Finally, although it is recommended that all ordinary freight cars be braked at the same percentage of their empty weight, this is not done, part through intent and some by error.

The foregoing will show why it is impossible to give a satisfactory answer to this question and that "all bets are off" unless a test can be made with some particular train. Even then the results will

not indicate what the brakes on a similar train, as ordinarily judged, would do under like conditions.

occur in warm weather, nor in cold weather when engine is alone, but when coupled to a train engine brake applies and we have to keep releasing with the the run. This occurs on the same engine independent brake valve all the time on every trip. I test brakes in shop and everything works correctly."—H: F.

Answer. As we know that the trouble would not occur if all were in good condition and if manipulation were correct it follows that one or both must be wrong, so let us reason the matter out, commencing with the brake equipment. For an ET brake to apply there must be pressure in the application cylinder of the distributing valve, this forcing the application piston to, by moving the application valve and the exhaust valve, admit and maintain a like pressure in the engine and tender brake cylinders. When

Assuming a loaded train of 30 cars with which the per cent. of braking power is 17, that the brake rigging delivered to the brake shoes 90 per cent. of the theoretical pressure obtained by multiplying the brake cylinder pressure by the leverage, that the mean or average resistance offered by the brake shoes throughout an emergency stop was 17 per cent. of the actual pressure delivered to them, that it required one second from the time the brake valve handle was moved to emergency position before the brakes were effective, that brake pipe pressure was 70 pounds and that all brakes were in good order, factors which could obtain in practice and all of which must be considered, then on level track the theoretical stopping distances would be about 125 feet for 10 miles per hour, 200 feet for 12 miles per hour and 315 feet for 15 miles per hour. But as almost all of these conditions vary with one train and another, as explained previously, these distances which would be quite accurate for the conditions stated, cannot be applied to the "average loaded freight train" as this definition is too elastic for determining stopping distances.

brake valve there is supposed to be a direct and free opening from the distributing valve application cylinder to the atmosphere, and so long as there is the ET brakes cannot apply as even if some part were defective and leaked air into the application cylinder it would escape to the atmosphere.

However, there are three places where the opening from the application cylinder to the atmosphere can be cut off. Two are the brake valves, and if each is in running position we can be sure that the opening is free so far as they are concerned, assuming the pipes between them and the distributing valve are properly connected. The third place is the "joker," as we cannot see whether or not it has the passage open. It is the equalizing slide valve in the distributing valve. It is controlled by the equalizing piston and the latter operates the same as a triple valve piston, being governed by brake pipe and pressure chamber air. The latter corresponds with auxiliary reservoir pressure. When the brake pipe pressure is raised above that in the pressure chamber the equalizing piston moves the equalizing valve to release position, where it opens the application cylinder to the independent brake valve. As these parts operate horizontally they stay in release until the brake pipe pressure is reduced below that in the pressure chamber, the latter having previously charged through the feed groove to an equal pressure.