UNIQUE FRAME DESIGN

Evening Star, Issue 21993, 1 April 1935, Page 15

UNIQUE FRAME DESIGN

AMERICAN EXPERIMENT Independent springing with leal' springs for all four wheels, and a tubular wislibonc-backbonc type frame, are 1 major features of the latest experimenj tal car developed for the benefit of the I American automobile industry co-opera-tively by members of the Leaf Spring Institute and other manufacturers. 'Hie car, aside from its highly interesting mechanical design, represents 1 (says the ‘ American Automobile’s ’ overseas edition) what probably is the finest piece of co-operative development the industry lias ever seen. Fathered by the Leaf Spring Institute, it represents a further development of the independent springing research programme instituted some time ago by this association. Whereas former cars developed by the Leaf Spring Institute were adaptations to stock cars, the newest car is developed from the ground up. In the work the institute has obtained the ready cooperation of virtually every major parts and accessory manufacturer in the industry, supplying specialised technical advice, and in some cases specially developed parts for, the actual assembly. The suspension itself does not depart materially in principle from that of the original suspension announced several months ago. It consists_ of a double transverse-spring, one behind the other, with the spring eyes double (military) wrapped for maximum road safety. Above the springs, extending from the frame to the knuckle support, are devised rods forming a spring and rod “ parallelogram ” resulting in relatively small track changes in combination with a minimum of camber variation under spring deflections. The leaf springs arc provided with progressive spring seals to shorten Ihe effective length of the spring under heavy deflections. This cut is at about one inch of spring deflection from normal position. For deflection of less than one incli, therefore, the maximum of freedom is permitted with minimum rate, for a good boulevard ride. With larger reflections there is up to approximately 50 per cent, of effective “ shortening ” of the spring. This provides an automatic increase in spring stiffness and spring rate for bad road conditions. The same general suspension conception lias also been applied at the rear in an interesting manner, details of which are not permitted as yet to reveal. It also incorporates the progressive spring seats and double transverse springs. Obviously in development work of tins kind manufacturing and service problems arise in the study of the original engineering design. The availability of virtually all the best brains in the automobile parts plants has therefore proved of real benefit to the. Leaf Spring Institute in the development of this car. A case in point is in connection with the method of attaching spring ends to the knuckle support arms. Obviously tbo use of two parallel springs would on the face require an accuracy of spring length control in manufacture that would increase maim-

factoring costs and also aggravate servicing problems. Co-operative research, however, uncovered an ingenious design of eccentric bushing and pin assembly, the use of which not only permits considerable manufacturing variations in spring lengths (within the usual reasonable limits, of course), but also provides an extremely simple method for the service adjustment of caster and camber angles. „ ~ , . ~, As to the new frame, which is of the tubular backbone plus double wishbone end type, the general idea is not new, of course. It has been in use for some time, but most of the designs have been rather complicated and certainly more expensive to produce than would have been justified to meet popular needs. What has been done for this experimental car is to take the general idea and apply it to latest principles of design and "production methods. The net result is a frame which appears to offer no major difficulties in production, is simple in design, and of decidedly lower weight than frames for comparable weight in present-day cars. . Actual figures on torsional stiffness and weight arc not released as yet, but it can be said that the frame (for a 3,000 to 4,0001 b car) can actually be handled by one man, an interesting sidelight on shipping ami handling costs aside from the over-all reduction in manufacturing costs achieved by a major weight reduction.