Abstract
The wealth of information already available on the subject of brakes is indicated by a prolific bibliography. There is little scope for new subject matter, the only novelty being in the approach to the problems. Emphasis is laid on the importance of discriminating between the characteristics of the linkage and of the brake units themselves, and the paper concentrates on the latter. Shoe characteristics are considered separately from those of the complete brake assembly, and a standard “three-to-one” shoe is evolved as a common basis on which to compare the different types of brake. Formulae are given for both shoe and brake factors and it is shown that, by using their reciprocals, the form of the equations becomes remarkably simple, and that, when thus plotted, the significant values are more easily read. The features considered most desirable in a brake are listed and a preference is shown for the two-leading-shoe brake using sliding shoes and hydraulic or pneumatic operation.
Some outstanding problems, such as improved cooling of the brake path, are raised. Wear, squeal, and fade are discussed, further developments in automatic adjustment are indicated, and a plea is made for improved oil and grease retention for hubs and axles to prevent contamination of brake linings. Brake testing is considered from first principles, and a routine for road testing is suggested. It is recommended that the investigation of temperature effects be confined to the laboratory.
The paper concludes with a reminder that it is not the characteristics of the lining as a whole, but those of the surface finishes prevailing at the moment, which are being observed, and that the basis of further progress is the study of surface phenomena and the search for better cooling.
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