High Braking Research Articles

Landing Gear Ancillary Equipment

THE major problems concerning aircraft tyre design are the high ground speeds involved, very high braking torques which have to be transmitted, high temperatures which can be generated in the brakes and transferred to the tyres, as well as the stringent weight and space limitations imposed. These problems have all been magnified many times through the years with the great increases of aircraft speed and weight: modern jet airliners having ground speeds of up to 250 m.p.h.

Adhesion and Friction in Rail Traction

For dry rails, a coefficient of adhesion of 0.25 may be assumed for speeds up to 40-50 m.p.h. At higher speeds, however, there is less information to draw on. Above the 40-50 m.p.h. range, the dependence of adhesion on speed introduces a bend into the curve connecting speed and power output. For wet rails, the coefficient of adhesion is reduced to about 0.6 of the value determined for dry rails. Of the many variables encountered in brake-block friction, there is abundant evidence of the dependence of coefficient of friction on speed and brake-block pressure. Substances should be saught for blocks for which the coefficient of friction is less affected by speed than in the case of cast iron; the effect would be to allow acceptable braking distances without having to use high braking ratios, so that a reduction in the weight of brake gear could be contemplated.