Lever-Spring Suspension.
Page 19
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In our issue of the ist August of last year, we were enabled to give the first publication, together with an original drawing, of a combination of levers and helical springs which had been invented by Mr. Stuart D. Marr, of 4414, Clapham Road, London, S.W. The device,
at that time, impressed us as offering a ready means of salving many of the objections which are attendant on the use of plate springs for the supporting of the varying loads which may be imposed on a commercial vehicle. The inventor has had his device fitted on to a four-ton Wolseley lorry chassis which is owned by the Queen's Park Depository, Limited, of 2, Carlisle Street, Soho Square, W. This lorry is chiefly employed for the conveyance of loose box-bodies containing furniture, and the behaviour of the lever-spring device has prompted one of the directors of that company to write to Mr. Marc in the following terms " We have much pleasure in testifying to the easy running of our motorvan that is fitted with your lever-spring suspension. We recently sent the van to Godmanchester with a valuable load of furniture, accompanied by our M. Sanger, who went to observe what difference there was between your system and the ordinary laminated springs. lie noted the complete absence of vihraLan or road shocks while running, and this resulted in the furniture's arriving without the least sign of damage. Our client has written us to that effect.
" hove no hesitation in recommending users of heavy motor vehicles to adopt your system of spring suspension, and we shall certainly have it fitted to all our heavy vehicles.—Yours faithfully, J. Sanger (director)."
The arrangement of the device was clearly shown in the issue to which we have referred, and its principal dimensions, as fitted to the Wolseley vehicle, were : Total length of levers, Ai inches; distance from the fulcrum pin. to the centres of the slippers, 34 inches; ratio of leverage, 4 to r; outside diameter of spring coil (top), 54 inches. ditto (bottom), 34 inches ; section of spring, m inch in diameter ; free length of the six coils, 74 inches; and the diameter of bearing pin, Li inches. The device was made to fit in place of a pair of 6o-inch laminated springs, which it has so successfully replaced. The accompanying illustrations supplement the drawing which we prepared at the outset.
When the top leaf of a plate spring breaks, the whole spring is disabled ; whereas, with Marr's device, the body and its load remain suspended, even if all the springs become broken.. Another of its advantages is that the " gearing up," by long levers, between the frame and the springs, prevents the sudden recoil of the springs after the wheels have passed over any obstacle on the surface of the road.