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2. Automatic in action in the case of an accident, or of a
division of a train, without any interference from engine-driver or guards, so that the break-blocks may -on the separation of the couplings between any
two carriages—be self-applied on every wheel. 3. Adapted to fly on, and not off, so that the blocks may
be applied to and not released from the wheels, on failure of any of the parts, which would prevent the train from being started unless the couplings were
complete and the whole apparatus in working order. 4. Instantaneous in its application-say to full force
within one second of time--when operated by engine.
driver or guard, or when self-applied. 5. Safe and simple in working—which does not necessarily
imply simplicity in construction, as distinguished
from risk and confusion in working. 6. Moderate in cost, as compared with efficient durability
of parts and easy maintenance. 7. Capable of constant employment in the conduct of
traffic, and not merely for employment in tests and
in cases of emergency. 8. Provided with indicators for engine-drivers and guards,
showing at a glance the condition of the break-power
and the continuity of the connections. The above conditions, coupled with those laid down by the Commissioners, that the break should be capable of bringing a train to a stand under any circumstances within a distance of 500 yards, seem sufficient for all practical purposes, and, if capable of being realised, not less than should be demanded in the interests of the safety of the travelling public. These conditions necessarily imply the use of a continuous break; but before considering which of the numerous inventions at present in use mostly fulfils them, it may be interesting to describe briefly the principles attached to each of the best of them respectively.
The several classes of continuous breaks at present in use may be divided according to the kind of power employed to actuate them. They may be classified as follows:-1. The chain break. 2. The hydraulic break. 3. The vacuum break. And 4. The air break. It is not pretended here to give descriptions of every kind of break that might be included under the above headings severally, but only of those which are unquestionably the representatives of each class, in consequence of their undoubted superiority, so far as has been hitherto ascertained by actual experience gained in the constant use of them in general work on lines of railway. The following particulars relative to these breaks are taken from the Appendix to the Report of the Royal Commission, and may therefore be considered as describing those forms of each which are most perfect of their class :
1. The Chain Break.—T'he latest improvement in this form of break is that known as Clark and Webb's continuous break. A chain or, in the newest form, a steel rope-runs the entire length of the train, underneath the carriages, terminating in the guard's van, by means of which the breaks are applied to the wheels of every carriage. In the experiments made for the Royal Commissioners with this break, the train was divided into sections of four or five carriages, which were placed in the following order with reference to the break-vans:- First, there were four carriages together, then a break-van. From this van the breaks of the first four carriages were worked, and also those of the four carriages following the van.
The remaining five carriages were under the control of the van at the tail of the train. Each carriage was provided with its own length of chain and couplings. The chain passed over seven pulleys fixed under the framings of the carriage, and under one pulley carried by levers which were in connection with tension-rods attached to the break-blocks. When the chain throughout a section was coupled up, one end of it was made fast to the end of the extreme carriage of the section, and the other was led to a chain barrel hung under the framirg of the guard's van at the other end of the section, close to the centre axle of the van. On the chain barrel, and also on the van axle, there were friction-wheels, and by releasing a weighted lever in the van the frictionwheels were brought into contact, and, if the van was in motion, the chain barrel was made to rotate. By this means the chain throughout the section to which the barrel belonged was tightened, the pulley carried by levers under each carriage already mentioned was raised by the chain, and the breaks were applied to the wheels. The van from which the breaks of a section, both in front of it and behind it, were actuated, had two chain barrels set in motion by the release of one weighted lever. To release the breaks the guard in each van had to put back the lever into its normal position, and secure it with a catch, at the same time surrounding and releasing the breaks by a weighted lever arranged for the purpose. In order to place the continuous breaks of the whole train at the command of the driver, a cord was passed over the roof of the carriages to the engine. This enabled the driver to release the catch
holding the weighted lever in each guard's van, but the guards could only apply the breaks to their own section. There was, however, separate cord communication throughout the train. The breaks on the wheels of the vans themselves were applied by hand only. The guard could also, by pulling a signal cord attached to a whistle handle, call attention of the driver in case of danger.
However well this break may work under ordinary circumstances, it must be clear to anyone that it labours under several inconveniences, and could scarcely be relied upon in extremely exceptional circumstances. In the first place a chain is no stronger than its weakest link, and an imperfect weld or subsequent injury may remain undetected until the occurrence of an emergency, when the whole break-power of a train might be rendered useless by the breakage of a single link or the failure of a strand of wire-rope. Again, the means of placing the break-power within the control of the driver are complicated, and supplemental to the breakapparatus itself; besides which there is the difficulty of getting this break to act quickly, from the length of the buffer-strokes between the carriages, owing to which it was found, on the North London Railway, that more than 2 feet of chain had to be wound up for every carriage ; and it was explained to the Commissioners that, where long buffers are used, in a train of eight carriages there would probably be sixteen revolutions of the carriage-wheels necessary before the slack chain was wound up sufficiently to put the breaks on to the wheels. This, with wheels 3 feet 6 inches in diameter, implies 168 feet run by the train, after setting the break-power in motion, before it begins to make itself felt in bringing up the train. In experiments on the Midland Railway accidents occurred through the break being applied too powerfully and too strongly, which caused the couplings to break and the train to part in two. The Carriage Superintendent of the Midland Railway further explained that, in working Clark's break it loses power every carriage away from the van, as the power gets less the further it is applied by the chain. Consequently the break bites tighter on some of the wheels than on others, which causes a slack or rebound. While some of the carriages are being very much retarded by the break, others are not so much retarded.
In pointing out the defects in this and other breaks which were brought to the notice of the Royal Commission, it must be understood that the object in view is not in any way to deprecate some and puff up other breaks, but to show in what respects each break requires improvements, so far as the evidence concerning them respectively given before the Royal Commission seems to indicate their weak points.
2. The Hydraulic Break.-Barker's hydraulic break, which is the representative of this class of break, was applied to the engine and the whole of the passenger carriages of an experimental train ; but the tender and two vans were fitted with breaks worked by hand-power. The hydraulic apparatus, as used at the trials, consisted of the following parts :-On the engine there was a double-acting steamaccumulator, consisting of a large-sized cylinder with a piston in it connected with a plunger working in a second cylinder, which was kept filled with water from the tendertank. The piston in the former was actuated by pressure direct from the boiler, without the use of any pump, and in making its stroke the plunger in the smaller cylinder was made to force water, with any degree of pressure, into pipes leading to small hydraulic rams attached to the engine and carriage breaks. These pipes led the whole length of the train, the connections between the carriages being made with india-rubber hose furnished with ordinary unions. Each carriage was fitted with two of the hydraulic cylinders and rams just mentioned, and these were connected directly to the break-blocks in such a manner that on the ram of each cylinder being moved by the pressure of water from the accumulator, the break-blocks on one side of the pair of wheels to which the ram belonged were forced against the wheels, while the pressure of water against the bottom of the same cylinder caused it to recoil, as it were, and draw the tension-rods of the break-blocks on the other side of the pair of wheels, thus clipping each wheel between its two blocks. In this arrangement, of course, the cylinders attached to the break-blocks have to be loosely suspended, and free to move horizontally for a distance nearly equal to the length of the arms. This description answers also for the action of the engine-breaks. By reverse action in the accumulator the pressure in the break cylinders can be relieved, and the blocks taken off from the wheels. The amount of pressure in the pipes can be regulated by a reducing valve; also, in order to keep the power always ready for immediate use, it is an essential part of this system that the pipes and cylinders throughout the train should be always full of water. The breaks were not arranged so that they would be self-acting in case of a train parting asunder.
The testimony given in favour of this break by those who had experience of its working was generally favourable ; but it appears in the evidence that it is in no sense automatic, and it is entirely under the control of the guard, and not of the engine-driver. One necessity of its successful working is that the pipes should always be full of water, and in the event of a leak occurring in any part of the train its efficiency might be seriously interfered with, but when in proper working order it is no doubt a very powerful break.
3. The Vacuum Break.-Smith's vacuum break, which formed one of those experimented with by the Royal Commission, may be thus described :-On the side of the smoke-box of the locomotive there were two steam ejectors for exhausting air, operating conjointly, but acting independently in case one should part. Under each carriage and van throughout the train there was an india-rubber cylinder, of 15 inches diameter and 16 inches extreme stroke, stiffened with internal metal rings, and capable of collapsing and extending lengthwise. Under the tender there were two such cylinders. These cylinders were in communication with the ejectors on the engine by means of a double line of pipes, connected at the tail of the train and forming a complete circuit through it, with hose couplings between the carriages. On steam being admitted to the ejectors by the driver, the air is exhausted from the collapsing cylinders, and the movable end of each being connected with the ordinary break gear of each carriage, the breaks are at once applied. By opening an air-valve the cylinders refill, and the breaks are released. In addition to the above there was in the front and rear guards' van another arrangement for applying the breaks in case of emergency. This consisted of an air-exhauster in each van, nearly over one of the axles. On this axle a grooved friction-wheel was bolted and keyed, and in line with this another grooved friction-wheel of the same dimensions was suspended from the carriage in such a way that it could be thrown into gear with the first wheel or kept clear at pleasure. By means of a belt which passed up through the floor of the van, the second wheel, when set in motion, drove the wheel of a rotary pump-exhauster which was fixed in the van. The exhauster was made to run either way. Near the pump in the van there was a lever held up by a notch in a standard, and when the pump was required to work the lever was pushed out of the notch by a cam lever. By this operation the second friction-wheel under the carriage was thrown into gear with the axle-wheel, and, if the train was in motion, the pump was set to work and the air