New Design Features Applauded
Page 28
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THE success, or otherwise, of a conference depends to a considerable extent upon the quality of the papers presented, and the two read and discussed at the Blackpool meeting of the Public Transport Association were both practical and useful. That by Mr. S. C. Vince, chief engineer of the Birmingham and Midland Motor Omnibus Co., Ltd., was particularly valuable from the technical aspect. It proved also what excellent work in the way of experimentation and design, or assistance to designers, can be carried out by a well-organized bus company through the medium of the road transport engineers responsible for the fleet.
Mr. Vince, for example, makes out a strong case for the employment of suitable transmission brakes on -public service vehicles. He gives these as the one answer in the direction of improving handbrake efficiency and suggests that if a brake were designed in disc form and mounted on the rearaxle casing, with the disc carried behind the rear propeller shaft coupling, excellent results would be obtained without the risk of overstressing shafts or couplings.
Such a brake, coupled to the existing hand lever without modifying the linkage so as to reduce the overall leverage, has proved almost too efficient, 0.5 g. stops being obtainable on some road surfaces. By detuning this brake, it has proved pos sible to return a figure Of 0.35 g. and yet substan tially to lighten levers and linkage. The author almost scoffs at the misgivings of timid individua:s who fear an enhanced risk of failure with a brake of this type on passenger vehicles, although they have no hesitation in fitting a transmission brake on goods vehicles. Indeed the Ministry of Transport did not even specify where such a brake should be fitted in the latter, and goods vehicles are not subject to such regular or rigorous inspection.
The only thing which would make the transm:ssion brake, as described, inoperative is the failure of an axle shaft or of the worm or bevel final drive, and the reliability of these components had been greatly improved during the past few years.
The dislike of the transmission brake for public service vehicles is confined to this country, because in the U.S.A. and Europe, practically all vehicles in this class are equipped with such brakes. Their buses often travel at much higher speeds and are usually heavier than ours.
Disc brakes, it is pointed out, are, quite apart from their use in transmissions, likely to make great progress because of their manifold advantages, including much improved heat dissipation and, consequently, reduced fade, whilst brake squeal is never experienced with them.