Inquiry into Amphibious Screw Traction

The paper describes an inquiry into the potentialities of the Archimedean screw as a device for amphibious travel and traction. The proposal is that a hulled machine should be supported by two such screws aligned beneath the port and starboard sides; the screws being oppositely handed and contra-rotating, so as to propel the machine either aground or afloat. A major attraction of the scheme lies in the positive action to be expected of the screws when working in difficult grounds of a loose granular, or semi-fluid, nature. The scheme is obviously unsuited to hard and paved surfaces, however, and is not proposed for these conditions. Comparisons are drawn between this and existing types of amphibious machine, with particular regard to the development of useful tractive effort. Theoretical examination of the rotor properties, for both aground and afloat conditions of duty, is supported by model-scale experimental work; and design recommendations are made. Favourable conclusions are reached; though it is necessary to add that the work has been in the nature of a pilot investigation only, and that full-scale tests would be necessary to reach a final verdict.