From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The principles of integral or chassisless body construction for improved strength and efficiency.
| Identifier | ExFiles\Box 117\1\ scan0085 | |
| Date | 31th May 1936 guessed | |
| 3. present day automobile body is mounted on rubber pads, elaborate trussing is used to complement the frame stiffness, and yet any conventional design automobile has the radiator "jitters" on a medium to rough road. Certainly this is fair proof that the present design is inadequate for the load carrying and torsional loads imposed upon it. Naturally, in our dire necessity for relief from this trouble, we turned to the other alternative, the integral structure or so-called "chassisless" construction. Looking at the fundamental reasons for this rather drastic change, we referred to the elements of mechanics and found the following pertinent data: 1. Deflection is kept at a minimum by absorbing the load at the greatest possible distance from the neutral axis. 2. Torque reaction is best absorbed by a member having section equidistant radially from the neutral axis. 3. The most efficient section from a weight standpoint is that which utilizes smaller members at a greater distance from the neutral axis. Turning to the first item we see immediately that our true design for minimum deflection is accomplished. By skin stressing the body, the loading is taken at the maximum possible distance from the neutral axis of the vehicle. We have in effect a thin yet rugged shell, upon which is mounted the running gear, within which is mounted the power plant and sit the passengers. This shell is impervious to deflection from any usual loading and the stresses are transferred thru the body in the proper proportion as in any well designed bridge truss or similar structure. The second item, torque reaction, is best met by a hollow tube of the approximate diameter of the vehicle body. Admittedly, our chassisless structure is not of this shape, but does it not seem able enough in comparison to the conventional frame members. The point remains that the shell structure approaches the tube in section and thus very nearly fulfills the ideal conditions. The solid metal roof, inverted saucer style, the curved body sides, and rididly tied bottom structure make for ideal torsional resistant construction. To further eliminate torsional effects due to sudden road shock on one or the other front wheels, we tie diagonally from corner to corner beneath the floor with a structural "X" member which also forms some of the floor support. The third item, efficient section, is best accomplished when the stresses to which a vehicle is subjected are spread over the greatest number of parts in the entire structure. This means that each part must do its proportionate share of work. If the parts are to be light, then they must be located as far as possible from the neutral axis, namely; at the outer extremities on body shell. The chassisless type of construction lends itself to this efficiency most ideally. Weight reduction, especially in connection with economical sections, is always a "red flag" subject at most engineering discussions. In the motor coach industry we have driven home to us day in and day out, "Keep the vehicle weight down". We must, and do constantly, scheme and try to eliminate a pound | ||