Braking system

“ On a slight and straight hill it is all right to go234 down on high speed, simply shutting off the ignition so that the engine will act as a brake, the foot brake being used if necessary; but on a steep hill it is far wiser to shift into second-speed or even first-speed gear before attempting to descend. The engine will exert a powerful braking force in low-speed gear. Besides, the running and emergency brakes are to be used alternately, so that on a long hill the brake linings will not be burned up. Of course the clutch must be left engaged to secure the braking effect of the engine. ”

“ Bracing links connect these track shoes with brake shoes on the wheel rims, and the drag of the track shoes thus applies pressure also to the wheel shoes. The downward pull of the track shoes gives a greater pressure of the wheels against the track than that due to the weight of the car, and the sliding or "skidding" of wheels, with the consequent reduction of flats, is avoided. A further braking effect comes from the use of the motors as dynamos, driven by the motion of the car, to supply current to the brake magnetizing coils. ”

“ Steering and braking should go together.
On some of the steep mountain roads, which, because of their length and relative grade with the bottom of the canyon, appear to be nearly level, it is impossible to hold the car with the brake alone. It is customary in such cases to assist the brake with the engine; unless the driver is very expert at changing gears the engine should be put in low, or intermediate, depending on the steepness, at the top of the hill, then with brakes and clutch the car may be controlled and kept to a safe speed. ”

“ On back pedaling the square shoulders of the cam inclines engage, the clutch ring is moved backward with the sprocket wheel, and cam inclines on the inner side of the ring force a brake ring inward into a hollow conical brake shoe connected with the frame of the machine, and having no rotary movement. The brake shoe thus is forced inwardly into a brake cup and effects the braking by its friction. In this case, as in the former, a general indication of the nature of the device is sufficient on the question whether the latter embodies the former in the sense of the contract. ”

“ In this connection it is well to keep in mind that on long grades considerable braking may be done by cutting off the ignition and allowing the car to turn the engine over in high or intermediate gear. Keeping the car down to a rather low speed in this manner will also be found to save burning up the brake linings. ”

“ Every motorcycle shall be equipped with two brakes, one of which acts at least on the rear wheel or wheels and the other at least on the front wheel or wheels; if a side-car is attached to a motorcycle, braking of the side-car wheel shall not be required. These braking devices shall be capable of slowing down the motorcycle and of stopping it safely, rapidly and effectively, whatever its conditions of loading and whatever the upward or downward gradient of the road on which it is moving ”

“ The ignition may be switched off or on as the occasion requires. Switching it off gives greater braking power. The clutch must be left engaged, and the brakes may be used to help. It is well to use first one brake and then the other in descending long grades, as too long an application of one will cause it to heat and burn the friction material. ”

“ The braking surfaces shall always be connected with the wheels of the vehicle in such a way that it is not possible to disconnect them otherwise than momentarily by means of a clutch, gear box or free wheel. ”

“ A. The air brakes should be released and a sufficient number of hand brakes applied to hold the [Pg 242] train. Never rely on the air brake to hold the train for any length of time.
200. Q. Why is it dangerous to repeatedly apply and release the brakes without giving time for the auxiliaries to fully recharge?
A. As time is required to charge the auxiliaries, the feed groove in the triple valve being small, if the brakes are repeatedly applied and released without giving time to recharge, the braking power will be lost. ”

“ When the wheels are skidded the retardation of the train is always reduced; therefore, for the greatest braking effect, the pressures on the brake-shoes should never be sufficient to cause the wheels to slide on the rails. The Burlington brake tests were undertaken to determine the practicability of using power brakes on long and heavy freight trains. In the 1886 tests there were five competitors—three buffer-brakes, one compressed-air brake, and one vacuum-brake. The tests comprised stops with trains of twenty-five and fifty vehicles, at 20 and 40 m. ”

“ The braking ability of all types of motor vehicles is an essential factor in the safe and efficient movement of traffic on our highways. The sight distance needed for stopping is one of the important geometric design elements.
In 1941, the Public Roads Administration started a broad program of brake performance studies of motor vehicles in everyday traffic. The Advisory Committee on Motor Vehicle Brake Research was formed to direct and guide the program. ”

“ It then becomes impossible for a driver to run his train in ignorance of any defect in his brake apparatus because such defect at once discloses itself by applying the brakes and stopping the train. Thirdly, that each vehicle shall carry its own brake power in such a manner that the destruction of the brake apparatus on one or more of the carriages shall not affect the efficiency of the brakes upon any of the others. No continuous brake which does not comply with such conditions can ever be satisfactory.--The Engineer. ”

“ Initiating the service reductions sufficiently in advance of the stopping point is absolutely necessary to allow enough time to adjust the speed. Stopping a train from about 100 mph using the power braking method requires about 3,000 feet more than braking the train using automatic airbrakes with locomotive independent brakes or blended dynamic brakes. ”

“ Every car carries at least two brakes of band pattern—one, usually worked by a side hand-lever, acting on the axle or hubs of the driving-wheel; the other, operated by the foot, acting on the transmission gear (see Fig. 48) . The latter brake is generally arranged to withdraw the clutch simultaneously. Tests have proved that even heavy cars can be pulled up in astonishingly short distances, considering their rate of travel. ”

“ In 1891 a so-called high-speed air brake was perfected, this brake being really a modified quick-action automatic brake. This modification consists of the addition of an automatic pressure-reducing valve connected with each brake cylinder. In the high-speed air brake as applied when the train is running rapidly, the highest possible pressure is applied at once to the wheels, but this pressure is lessened by the automatic pressure-reducing valves as the speed diminishes. This method of applying the brakes is the most effective way of getting the full benefit of their stopping power. ”

“ In one type of electric brake the active braking force is taken from an axle of each car. A small friction-drum is made fast to the axle. Another friction-drum hung from the body of the car swings near the axle. If, when the car is in motion, these drums are brought in contact, that one which hangs from the car takes motion from the other, and may be made to wind a chain on its shaft. Winding in this chain pulls on the brake-levers precisely as if it had been wound on the shaft of the hand-brake. The sole function of electricity in this form of brake is to bring the friction-drums together. ”

“ The simplest way of applying a brake is by muscular force, exerted through a hand or foot lever or through a screw, by which the brake block is pressed against the rim of the wheel or the band brake tightened on its drum. This method is sufficient in the case of most road vehicles, and is largely used on railway vehicles. But the power thus available is limited, and becomes inadequate for heavy vehicles moving at high speeds. ”

“ Helper locomotives entrained may not use dynamic brake unless road engine has operative dynamic brake.
The number of axles of dynamic brakes of the helper engine (s) will be added to axles of dynamic braking of the road engine to determine the tonnage that may be handles in accordance with applicable Air Brake Rules.
Dynamic brake on head end of freight trains must not exceed 24 axles. Each helper entrained must not exceed 36 axles. ”

“ As the speeds result from the tightening of brake bands on the drums, there is no danger of damaging the gears by mishandling, for the brakes will slip before the teeth will give way. The brakes, which are leather-lined strips of steel, require attention from the wearing of the leather, and the slipping that results from oil working in between them and their drums. No foot clutch is necessary, for the tightening and loosening of the brake bands is controlled by a lever; in some designs, the reverse is applied by means of a foot pedal, and this may be used in braking the car.
[Pg 139]
Fig. ”

“ Perfect brakes are also indisputably promotive of safety in working traffic and in compensating for unavoidable irregularities. With the usual amount of braking power, a train at 50 miles per hour may not be stopped within 900 or 1200 yards. An instantaneous brake is not of course what is wanted; on the contrary, a length of 200 yards appears to be the shortest desirable space within which a train at 50 or 60 miles per hour should be stopped, so that the process of retardation should not be accompanied by risk of carriages riding over each other, or of violence to the passengers. ”

“ Some automotive engineers think it best not to lock the wheels completely in braking. That the best plan is to apply the pressure only until incipient locking has been reached but the wheels are still rolling. The driver has little control of a skidding car, and certainly would have none whatever with all four wheels locked. While the wheels are still moving there is a chance to guide the car so as to avoid an obstruction even though it can not be stopped in time. ”

“ Non-automatic brakes can be applied only by the person (usually the engine-driver) to whom the management of them is given; they may become inoperative on all the coaches, and always on those which have become detached, if a coupling or other important and generally essential part is broken. Many mechanical and several hydraulic and electrical continuous brakes have been invented and tried; but experience has shown them so inadequate in practice that they have all practically disappeared, leaving the field to the air and the vacuum brakes. ”

“ It has been demonstrated also that the cars can be easily handled in the street; run at any desired speed, and reversed with far more safety to the armature of the motor than in the direct system. The increased weight requires simply more brake leverage. ”

“ Don’t, then, subject your bearings to an unnecessary strain by forcing your motor to labor as it must, if too steep a hill is taken on too high a gear. See that your hand brake can lock your wheels. On a five-mile grade one brake may burn out, and on most cars in this country the hand brake is next to worthless from lack of use and care. Letting the engine act as a brake is a good practice on long descents.
On going through sand or mud that looks as if it might stop you, change into a lower gear and don’t lose your forward momentum. It is easier to keep a car going than to start it again. ”

“ When from any cause it is desirable to have the brake inoperative on any particular car, the four-way cock is turned to an intermediate position, which shuts off the brake-cylinder and reservoir, leaving the main brake-pipe unobstructed to supply air to the remaining vehicles. ”

“ The brake is of course of a totally different kind from that in ordinary use, which would be of no service whatever on such inclines, as the wheels, even if the brake were so powerful as to stop their revolution, would slide down the hill by the mere force of gravity. Here, however, the brake consists in an ingenious adaptation of the means which are employed in driving the engine. ”

“ During a stop something may happen to the brakes so as to make them quite ineffective, or a portion of the brake mechanism may have broken. The driver who perhaps before luncheon has ascertained that his brakes are acting perfectly, after luncheon may start off in the same supposition, and perhaps not discover his error until, relying on his pedal brake to stop him in traffic, he finds that it has no effect, with the result that he probably goes through the back of a brougham. ”

“ It is the opinion of many competent men that the above accident would not have been so disastrous if the train had been fitted with an automatic brake. It had what is called a continuous vacuum brake, which is effective enough so long as the coaches do not become separated. When such separation occurs, the wheels are no longer held in check. With the automatic brake, on the other hand, which is adopted by many of the leading railway Companies, the wheels are immediately acted upon, if by any means the coupling between the carriages should be broken. ”

“ Do not wait until you are half way down the hill before finding out that it is too steep for the brakes to hold the car. Make up your mind before starting to descend and shift to first gear if necessary. Do not allow the brakes to get in such condition that they will not hold to the best of their ability. Never descend the hill at a high rate of speed no matter how safe it looks. Brakes do not hold as well when the car is going fast as they do when it is moving slowly, nor will they stop a car as quickly going down a grade as they will going up. ”