CHECKING BRAKE ADJUSTMENT.
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Details of a Simple and Effective Device for Testing Individual Wheels.
MLLE servicing of brakes, and particularly those on high-speed commercial vehicles such as coaches and
buses, demands the utmost care if the maximum efficiency is to be obtained; and it is questionable whether the
average mechanic can, by rule-of-thumb methods, determine the correct adjustment for the brakes on the four, or possibly six, wheels of a vehicle. Without some form of brake-tester the problem becomes one of trial and error, and we are afraid that the " error " often predominates. With a -view to removing this difficulty, Harvey Frost and Co., Ltd., 148-150, Great Portland Street, London, W.1, a company already well known for the many useful items of garage service and breakdown vehicle equipment which it markets, has developed a device known as the H.F. Standard Brake Tester.
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This is a well-constructed instrument of simple design which is so arranged that each wheel can be weighed before the actual braking power is ascertained. Recording, both of the weight and the braking power, takes place through the medium of a diaphragm, which, in turn, exerts pressure upon a gauge. The principle employed is to adjust the brakes on each wheel so that the wheel will lock at about the same figure as the ascertained weight upon it. If the brakes be ineffective the needle indicates less than the weight; if too fierce, the wheel will lock and the figure recorded will exceed that obtained for the weight, there will also be a tendency for the wheel to be forced off the rollers. The actual rotation of the wheel is effected by turning a handle at the upper part of the tester, and it may be turned clockwise, or anticlockwise, according to the
location of the wheels of the vehicle.
During the test the wheel is carried on fluted rollers, the corresponding wheel at the other side being jacked up to maintain the vehicle on an even keel. To perform the weighing a small jacking screw is rotated by means of a tommy-bar, a few turns raising the rollers and bringing the weighing device into operation. Note is made of the weight recorded on the dial and, after weighing, the special mechanism is released, the pointer then reverting to zero. Pressure is now applied to the brake pedal, or lever as the case may be, and the handle of the tester turned.
It will be readily understood that as the braking power cdepends, to a great extent, upon pressure, it is necessary that the pressure on the pedal or lever should be uniform during the testing cf the various wheels ; and to ensure this a special device is used which can be adjusted to give the normal pressure exerted by the driver. This device makes the work of testing a one-man job.
The instrument not only gives an indication of the efficiency of the braking, but it also serves as h tell-tale for the faults to which a brake is liable. For instance, it will indicate if a drum be out of truth, or, if the brakes be binding in what should be the " off " position.
Arrangements are being made for
garages which have An installed the R.F. brake tester to form a chain of brake
service stations throughout the country. The official testing staff will be provided with certificates, of recognized form and convenient size, for attaching to the dashboard or some other convenient place on a vehicle, the certificate showing that the brakes have been tested and found efficient and giving the date.
The lighter model is suitable for all vehicles up to a gross weight of two and a half tons, and this is marketed at the trade price of 127 10s. For heavy commercial vehicles, however, a special model is in course of production. Arrangements are being made to sell the tester on the Mr. extended'credit plan.