The practice of dropping the frame just forward of the rear axle, which has been entered into by a number of the leading automobile manufacturers, with a view to lowering the center of gravity of the car and also of helping to bring the transmission and the power shaft in a direct line with the engine, has been carried still farther in the new Imperial car which we illus- trate, for in this instance the designer has made a double drop in the frame, so that the whole center part is at a lower level than the forward and rear end. The main advantage of this method of forming the frame is claimed to be its great strength, while the secondary advantages are a lower center of gravity and a greater road clearance for the car. This shape of frame, it is claimed, follows the principles embodied in the more recent Pullman car construction, whereby great rigidity and strength are obtained. The motor is mounted upon a sub-frame, and made to line up with the transmission, which is hung from arms that are attached to the members of the main frame. On account of the drop of the frame, the rear shaft of the transmission is made to line perfectly with the propeller shaft when the car is going. The result is that practically all the time the propeller shaft is perfectly in line with the transmission and the crankshaft of the engine. Although two universal joints are fitted to the propeller shaft, these are rarely in operation when the car is running along on the road and power is being transmitted to the rear axle. The claim is made by the builders of the Imperial car, that from 7% to 25 per cent of the engine power which should be delivered to the rear wheels is lost by bad alinement.
This article was originally published with the title "The Imperial Chassis" in Scientific American 97, 19, 325 (November 1907)