THE CRUSADE AGAINST INEFFICIENT BRAKES.
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Why Brakes on Heavy--Vehicles Sometimes Give Trouble and Fail on Emergency. The Factors of Neglect and Ignorance in Adjustment or Replacement.
[HE ARTICLE by Mr. L. A. Legros and the editorial comment upon the question of the new police crusade on brakes, which appeared in the issue of The Commercial Motor for July 29th last, dealt with the position that has arisen, or, at any rate, is likely to arise, out of the sudden, but perfectly justifiable, interest now being shown by the police authorities in the application of the section of the Motor Cars (Use and Co_nstruction) Order, 1904, relating to the condition an'd effectiveness of motor vehicle brakes.
The trouble about brake inefficiency may be expected to °coiir more frequently in connection with goods-carrying commercial vehicles and with motor coaches than with private cars, or with buses which form part of an established fleet. Where one or two buses are run from a garage the tendency again will be for brake trouble to occur, because the vehicles will probably be on the road from one week's end to the other, and for most of the hours of every day, thus leaving little or no time for efficient and careful inspection and adjustment.
Our argument, however, is against the method of test which is being adopted by the police. It seems, So far, simply to consist of the holding out of the hand of a policeman, whose intention and even, perhaps, presence had not been suspected by the driver, the constable then noting the distance within which the vehicle is brought to a standstill. This, of course, is an absurd test, because the driver will pull up unwillingly and without. any effort to make brief the interval between seeing the signal and effectively acting upon it. Nor is it at all easy to see how any ordinary police officer can carry out a brake test which would be of any real value, as so much would depend on the gradient of the hill on which the test was made, the speed at which the vehicle was travelling when the brake was first applied,'the distance run with the brake on before the vehicle was brought to a standstill, the surface of the road, the weight of the load carried and the strength of the driver who applied the brake. Even if all these circumstances are taken into consideration, there is the question as to whether the engine should be used as a brake by having a gear in mesh, At the present time, everything is being done to encourage a good feeling between the police and the public, and, if irregular and uncertain tests are to be carried out at the ea-price of any busybody who is invested with the power, it will, as has already been stressed in the editorial columns of this journal, undoubtedly, cause friction between the police and those who own or drive commercial motors. •
Whether such tests are to continue or not, there is no excuse for a vehicle being on the road with its brakes in an unsatisfactory state. All commercial motors, made by firms of repute, are provided with brakes -which, when new, will fulfil all reasonable requirements, and if properly attended to they can be kept in this condition during the whole lift of the vehicle. We will endeavour, in the course of these remarks, to point out the various things which can happen to brakes which will cause them to lose
their retarding power, so that owners and drivers can, if they will take the trouble, keep their brakes in as good order as when new. On the principle of Cr Be just and fear not " if one's brakes are in good order there is nothing to fear from an inspection by a competent authority.
Let us now examine the things that may happen, and see how to remedy them. First of all there is the possibility of grease being on the brake drums. An undue amount of grease or oil escaping from a hub bearing on to the drum will reduce the retarding power of a brake, especially when fibre linings are
used. With metal-to-metal brakes, 11"-;2°1711an undue amonnt of lubrication will delay the brake from acting for a time, but the lubrication will eventually be pushed away, cif en, however, not until it is too late and an accident has happened.
The remedy for this is obvious,, either a neiv felt washer is req•uired, or, if this will not stop the escape of lubricant, it is a sign that the bearing is badly worn and requires a new bush.
Then we must consider wear on linings, drums, etc. All parts or a brake which comeinto contact must, of course, wear away, and in many cases to this fact sufficient attention is often not given.. It is true that adjustments are provided;but these do not serve to replace the wear, and if adjustment alone, without the renewal of worn parts, is all the attention that the brakes receive, the levers will be found to be in the position shown in full lines in Fig. 1, instead of as shown in dotted lines, which represent the positions of these levers when the vehicle left the makers.
The spindles of the cams which expand the shoes in rear-wheel brakes, owing to the difficulty of getting at them, are often neglected, as also are the surfaces of the expander cams where they bear against the shoe, as shown in Fig. 2; these require lubrication occasionally.
The cross-shafts of both hand and foot brake shoUld be properly lubricated and be working freely, as should all compensating links and joints, for it is obvious that the power exerted by the driver in applying the brake is very much reduced by rusty bearings and joints before it can be transmitted to the brake shoes.
These small details of brake work do not, as a rule, receive sufficient attention. To test the efficiency of all working parts, it is best, if possible, to jack up both wheels and to see that both ;brakes are acting equally. It must be remembered, however, that when a wheel is jacked up the position of it in relation to its axle is exactly the reverse to that when standing. on the ground.
When on the ground, any slackness between the hub and the axle will result in a space being formed between the upper surface of the axle and the bush, but, when jacked up, the atxle is supporting the. wheel, consequently the wheel will rest on the upper surface of the axle. In cases where a; very appreciable amount of wear has taken
place this will Olow the wheel to drop in relation to the axle, az -shown in an exaggerated form in Fig. 3. This may deceive the person who is adjusting the , brake, as, owing to the wheel dropping as shown, the brake drum will bear hard on the upper
Part of the shoe and appear to be acting well when, in reality, when the axle is resting on the ground, the position will be as shown in the left-hand view. The only remedy for the fault which the test would disclose would, obviously, be to have a new bush fitted.
In some cases the turnbuckles, or adjusting screws, will have rusted up to such an extent that they can no longer be turned to adjust the brakes. In such a case, the turnbuckle and its rods should be soaked with paraffin until adjustment becomes possible again. It is sound practice, when taking over a vehicle, second-hand, and even when new, to.go over every nut and screw and to grease the threads so that when adjustments or alterations are required they can be made without unnecessary trouble and waste of time.
Brake linings should be riveted to their shoes by means of the proper aluminium rivets made for the purpose, but, in some cases, careless persons will use any rivet that is handy. Aluminium, being a soft metal, will wear away quickly and allow the fibre to come into contact with the drum, whereas hard-metal rivets will prevent the brakes from acting properly. We will now look into a few causes of sudden brake failures.
A practice, which should be made criminal, has lately crept into use among drivers and others who have the charge of commercial motors, of bending the brake rods to shorten them, instead of tightening
up the turnbuckles, or using the proper adjustment provided by the makers. It is obvious that a rod so treated may, under severe strain, become straight again, and the brake becomeuseless. In our opinion any police officer should have the power to summon anyone found driving a lorry with the rods in this condition. .
In cases where a drum has become very muchworn it is "not uncommon for new linings to be fitted, and adjusted up so that all seems to be working well, yet, in half an hour's running, the brake is found to be out of action. This may be due to the fact that, owing to wear of the drum, the new lining is only acting at the tip, as shown in the left-hand view of Fig. 4. In some eases, too thick a lining is used, which 'results in the lining only making contact with the, drum at the heel, as shown in the right-hand view. In either of these cases, the lining will soon crush up and the brake will fail. ' In fitting new
linings, care should be taken to see that the lining is making contact near its centre or all along its surface with the drum.
In some cases a link has been taken out of a driving chain, which has resulted in bringing the rear axle forward, and this is done without readjusting the brake reds. This oversight is often not discovered until the vehicle has been out on the road. Tinkering with brakes cannot be too strongly condemned, spare shoes or linings from the makers of the vehicle should always be kept in stock, and no attempts should be made to improvise means whereby worn parts connected with brakes can be faked up to prolong their life, nor should makeshifts be improvised by drivers and others.
In a case in which fourteen persons were kilted and many others injured for life it was found that the driver, who, like many others, was relying on one brake only, had a pair of brake shoes, for a transmission brake, cast in brass at a Local foundry the day before the accident. He was unaware that brass became brittle when heated. When he was negotiating a long and steep declivity, these shoes crumbled to pieces, and the char-a-banes ran away and finally hit a tree.
After nearly every accident, one reads in the papers the familiar words:• " The. brakes failsai." The real wording should be : " The only brake which was in good condition failed." It is extremely enlikely that both brakes should fail simultaneously, It is only right that owners of commercial motors should clearly understand this, and should take such steps as shall ensure proper supervision of and thorough attention to brakes. if this is done there can be no trouble arising from a practical and fair test by the police, and thought can then be given to the question of devising a test and a method of testing which shall have useful results in putting a cheek
upon carelessness and neglect.