leaves it with the dog tightly latched in the ratchet wheel; later when the air has leaked off, the brake shoes will drop away from the wheels and, if on a grade, the car will roll out in the way of traffic. And another thing: if the hand brake at either end of the car is left lightly applied -not enough to bring the shoes against the wheels, but to take up the slack almost completely in the brake gear-then when the air brake is applied the piston travel will have been so shortened that either the piston will not pass the leakage groove in the brake cylinder and the air pressure will at once leak off, or, passing the leakage groove the piston will have such a greatly increased pressure that the wheels may skid. With the "harmony" hand-brake gear now being rapidly installed, the air brake does not pull against the hand brake at either end of the car. The hand brake at either end can be effectively applied while the air brake is set, and afterward when the air has been released the hand brake will remain applied with the same power as was developed by the application of the air brake. And winding up the hand brakes will not shorten or otherwise affect the air-brake piston travel. a This change has provided the opportunity for simplifying the whole system of foundation brake on passenger equipment cars. On all freight cars, and until quite recently on all eight-wheeled passenger equipment cars, the brake-beam levers (sometimes called truck levers) were inclined laterally at an angle of about 50 degrees from the perpendicular. (See Fig. 1). Originally there was good reason for inclining them diagonally, but for a number of years past save in exceptional cases there has been no reason why the brake-beam levers should not have been set in a vertical position: except that custom stood in the way of the change. Brake beams were formerly placed "outside" of the wheels-that is, at the outer ends of the truck, and as shown in Fig. 1-and the main brake pull-rods were connected with the levers on the outer brake beams-the beams at each end of the car, called the live brake-beam levers; now if those levers were placed vertically, the connecting pull-rods would have to follow the (longitudinal) center line of the car, and the center bearing of the trucks that support the body of the car would be directly in the way. So, to carry the pull-rods past the center bearings the live truck lever Fig. 2. Plan View of Brake Gear on Eight-Wheeled Passenger Car was inclined to one side; and to accommodate the straight bottom-rod connection between the two brake-beam levers, the dead, or adjustable brake-beam lever was inclined equally in the same direction as the live lever. The inclination of the brake-beam levers on one truck was opposite in direction to the inclination of the levers of the truck at the other end of the car (See Plan View of Brake Gear, Fig. 2); this provided the standard position lines for top brake-rod connections that would not be affected by changing a truck from one end of the car to the other. On passenger cars with six-wheel trucks, the brake-beam levers have always been placed in vertical position, because the brake pull-rods on these trucks all lay Lelow the axles where they meet with no interference along the center line. truck face in opposite directions the fulcrums must have opposite angles of inclination in order that they will assume a common angle when in place. The top truck-rods at one end of the car lying opposite across the center line from the top rod at the other end of car, required more levers and rods in the body gearing to make the hand-brake and cylinderlever connections, and which are unnecessary when vertical brake-beam levers are used; yet many roads in order to comply with the requirements for a "harmony" hand brake, are merely adding a lot more rods and levers to the old system. The introduction by the Westinghouse Air Brake Company of the long, slotted crosshead for brake pistons in passenger equipment has made the application of an economical design of air-brake gear with harmony hand-brake and vertical Fig. 3. Passenger Car Brake Cylinder. Piston with Slotted Crosshead Some years ago all of the railroads began changing the point of suspension of the brake beams to the inside, on both freight cars and eight-wheeled passenger cars, and now practically all of the latter, and probably ninety-five per cent of freight cars, have their brake beams hung between the wheel pairs of the trucks. With this method of suspension the lever on each inside brake-beam becomes the "live" lever with which the main pullrod is connected, and the bottom rod connecting the live and dead brake-beam levers becomes a push rod; the top rod (main pull-rod) does not extend as far as the center bearing of the truck, so there is no reason in present circumstances why the brake-beam levers might not be placed vertically-one advantage of which is to eliminate "rights" and "lefts" in metallic brake beams, for the fulcrum at center of brake beam has an angular jaw to allow for the inclination of the lever, and as the two beams of a brake-beam levers to passenger equipment cars a very simple matter. Fig. 3 shows a brake cylinder with the piston fitted with the slotted crosshead. The end of the cylinder lever lies in the slot that is shown; but the crosshead is also slotted vertically, to receive the cylinder-lever pin and act as guide for pin and lever; a long link is attached to this pin, and a chain connects the link with an independent hand-brake lever; the handbrake rods from both ends of the car connect oppositely with the ends of this lever. When the air brake is applied the crosshead is pushed out, carrying the end of the cylinder lever with it, dropping the slack of the chain and not disturbing the hand-brake lever. When the hand brake is applied (with air brake released) from either end of the car, the hand-brake lever is turned on its fixed, central fulcrum-pin, the chain connecting it with the cylinder lever is stretched and pulls the cylinder lever out to deliver braking power through the rest of the foundation gear that transmits the pressure to the brake shoes in applications of both the air brake and hand brake. Fig. 4 is a rough sketch in diagram, illustrating in a plan view the brake cylinder and the body gear of the simplified foundation brake with vertical brakebeam levers and the harmony hand-brake arrangement, slotted crosshead, etc.; the truck gear at each end is represented in side elevation. The air brake and general parts of the gear are shown in full black lines, while the independent parts of the hand-brake gear are drawn in narrower lines. It will be noted that the formerly used "Hodge levers" in the body gear are dispensed with, the main pull or top-rods in the presented plan running from the cylinder levers to direct connection with the live brake-beam levers, the whole pulling force of the entire system of brake gear being exerted along the exact center line of the car. On our road we began changing the brake gear of our eight-wheeled passenger equipment cars to the improved style as described, some eighteen months ago. On our twelve-wheeled cars the truck brake gear was not changed, they already having the standard vertical-lever, six-wheel-truck gear, but they were fitted with the slotted crosshead and the connection with the independent hand-brake lever same as used now on the eightwheeled cars, with the main pull-rods running from the cylinder levers along the center line of the car and connecting directly with the main, or long, brakebeam lever, thus eliminating the four body levers formerly used in all twelvewheel brake equipment. And all cars reequipped with the new foundation brake are given a total braking power of 85 per cent. of the weight on braked wheels, based on 50 pounds brake-cylinder pressure a material increase in the actual braking power of our cars. Our passenger cars were formerly braking at 90 per cent. of the car weight, based on a suppositious 60 pounds brakecylinder pressure; and for quite a while before the change to the new style of brake gear we had constant trouble from slid-flat wheels on our eight-wheeled baggage cars and day coaches weighing from 48,500 pounds to 70,000 pounds, hardly a day going by without report coming in of one or more such cases; usually mysterious, too, with no evidence from trainmen, enginemen or inspectors Fig. 4. Diagram of Passenger Car Brake Gear, with Vertical Brake-Beam Levers and Harmony Hand-Brake (Four-Wheeled Trucks) BOTTOM ROD TRUCK GEAR that would show any cause for the skidding-usually of but one or two pairs of wheels-and upon arrival at the terminal the brake would in most cases "prove an alibi," the triple valve testing sound, the piston travel normal, and no evidence apparent except the flat spots. Since the first car came out of the shop with the improved brake gear a year and a half ago, rot one case of slid-flat wheels on the cars equipped with the vertical brake-beam levers and harmony hand-brake has come to my notice-in spite of the fact that these cars are exerting a higher brake-shoe pressure than formerly. The only explanation I can offer is that on a car with brake beams inclined in an angular position, when the brake is applied while the car is running the pull on the live brakebeam lever is on one side of the truck, being so far to one side of the center line of the car there is a stretching or letting out of the entire brake gear-depending upon whether the curve is to the right or left; but as the brake-beam levers of the other truck incline in the opposite direction, if both trucks are on the same curvature the letting out of slack at one truck is about equal to the amount taken up at the other truck, and due to this auto-compensation the undesirable feature suggested is supposed to be neutralized. To permit of the brake-beam levers inclining at opposite angles as between the two trucks, floating, or "Hodge" levers are interposed in the body gear, to throw the main pull-rods on opposite sides of the center line of car. On locomotive tenders, however, to conserve space of which there is little to spare, all body brake-levers are elimi and that this slews the truck around and causes the flanges of two wheels in each truck to bind on the rails, this flange friction providing enough resistance to wheel revolution, that, added to the brake-shoe resistance, the wheels bearing the least weight-due to the slight shifting of the center bearing of the truck at the time-stop turning. When a car with angular brake-beam levers is standing, an emergency application may not slew the trucks the least bit, noticeably; but while running, the side pull may easily roll the wheels around until the flanges bind against the rails. And we expect our vertical brake-beam levers to overcome a large part of the flange wear that has been experienced, for the reason just advanced. When a truck with angular brake-beam levers is rounding a sharp curve while the brake is applied, on account of the pull-rod connection with the live lever nated except the essential cylinder levers; the main pull-rods running from the cylinder levers to direct connection with the live brake-beam levers. This of course necessitates inclining the angular brake-beam levers of both trucks in the same direction-usually toward the left side of the tender; therefore, with the brake applied while rounding a curve to the left the distance between the top ends of the live brake-beam levers is lessened, and there is a relaxation of the brake gear which permits the piston to travel somewhat further out. But when the trucks reach straight track again, the gear is put under a certain strain to readjust itself and the piston must be forced back slightly against the resistance of the already heavily compressed air in the brake cylinder. If the brake is set just before hitting a curve to the right, while rounding the curve the tendency is for the top ends of the live brake-beam levers to pull in opposite directions, away from each other, and this would necessitate forcing the piston a slight distance back in the cylinder, or else something would have to give way under the strain (Note Plan of Tender Brake Gear, Fig. 5). Of course the above is generally considered a rather negligible feature in view of the very slight piston displacement that can be observed as between the brake when set on a right and then on a lefthand curve-noted while the locomotive is standing. But while running at high rates of speed the tender is subjected to many supplementing strains; there is a lurching from one side to the other as the water shifts; the lifting effect off the front tender truck by the pulling bar when the engine bounces up on a rough piece of track; and worst of all, the effect on curves of the rather close coupling together of the rear end of tender with its short overhang, with a baggage or postal car with a long overhang. Anyhow, it is a fact that for several years there has been an epidemic of locomotive tender derailments reported from all over the country, for which there have been no satisfactory explanations proposed, either. Vertical brake-beam levers are therefore specially desirable for locomotive tenders, and on which it would only be necessary to provide new brake-beam fulcrums with vertical jaws, and to arrange that the pin holes in the outer ends of the cylinder levers are on the center line of the tender. The power at emergency application of the modern high-speed brake is so extreme that it should be directed along the exact center line of the car and the center line of the trucks, on every vehicle in the train. |