AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

Some Interesting Braking Problems

15th November 1946
Page 20
Page 20, 15th November 1946 — Some Interesting Braking Problems
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

INCLUDED in this issue is an abbreviated version 1 of an interesting paper dealing with problems in the design of braking systems. Some of the difficulties encountered are not such as would ordinarily occur to the mind of anyone except technicians. They therefore deserve emphasis.

The author points out that a brake is merely a device for converting energy into heat, and the greatest problem of all is to remove this heat rapidly or, at least, to make certain that its effects are not such as to render the braking power excessively variable between the extremes of heat and cold experienced.

Above 400 degrees F., braking materials arc apt to produce vapours. which condense on the internal faces of the drums and reduce the coefficient of friction. This remains lower than normal, even at lower temperatures, until the deposit is removed during subsequent use. Often the braking is good at 500-700 degrees F., because. then, the vapours have not condensed. On the other hand, if the heat be so increased that oil burns on to the faces, the coefficient may rise to such an extent as to cause " spraggini." When this happens, the brakes cease to act as such and the tyres do the work, which, of course, is most undesirable, for it promotes skidding and causes excessive wear.

Public-service vehicles present far more difficulties than goods types. They stop more frequently and, normally, the brakes cannot be so well ventilated.

Another point raised by the author was that, in his view, there is no great gain in employing two-leading-shoe brakes except in vehicles weighing around 7 tons. Below this figure the pedal pressure required is not excessive with the normal type, whilst above it a servo becomes essential. and then there is no need to embody the system. He also does not favour very light pedal pressures, as they constitute a temptation to drive on the brakes.

Reference was made in the discussion to a certain American device in which the special riedal increases the braking effect on the front wheels as. deceleration occurs.

Tags


comments powered by Disqus