STEERING-GEAR ANALYSES 240014

Lack of scientific research is specified by the author as being the cause of failure to develop steering-systems generaly to meet the present need for better and easier steering-ability. He comments upon the meager data available regarding steering-system faults and factors that influence design and emphasizes the necessity for determining the live stresses in steering-systems while the vehicle is traveling over roads of all kinds, so that designs can be made with greater confidence and greater safety attained. Defining comfort as being inclusive of easy steering, a comfortable sitting position, convenient location of the controls that must be handled frequently and peace of mind relative to steering accuracy and dependability, he analyzes the causes of hard steering, saying that the steering-system includes every part from the steering wheel through the steering-gear and linkage to the front wheels and that the steering-gear itself is simply the reduction mechanism.

Assisted by H. A. Huebotter, he is developing a set of automatic recording instruments that will record not only the physical effort needed to steer an automobile but, simultaneously, the forces and shocks imposed upon the entire steering-system, so that such records will constitute a basis for steering-system design.

It is essential that the steering-gear provide the necessary mechanical advantage or leverage that will enable the driver to handle the ear, and that this be accomplished with a reasonable angular turning-movement of the steering-wheel. Unfortunately, these two fundamental requirements conflict, in that an increase of mechanical advantage causes a greater amount of steering-wheel turn; so, charts are presented to show that the final overall mechanical advantage is made up of factors such as helix ratio, inside ratio and the relationship of the diameter of the steering-wheel to the length of the steering-arm, and as aids to the analyses that follow, to the end that present steering-system faults may be minimized.

Steering-gears are classified as bevel-gear-and-segment, worm-and-wheel, screw-and-nut, split-nut and cam-and-lever types, and all but the first depend upon a helix for actuation. A study of helix characteristics follows, a description of the test apparatus being included, and the possibilities of producing a variable-ratio helix that gives great mechanical advantage in the center-driving position with smaller mechanical advantage in the extreme positions are discussed. The author says that a steering-gear must absorb all objectionable road shocks and still retain road sympathy; that is, it must be a gear that permits the front wheels to follow the road more or less naturally, so that somewhat of a self-steering effect is secured.