The lifting paddlewheel, (LPW), is a non-buoyant, bladed wheel similar to the paddlewheels used on riverboats, but is arranged to produce both propulsive and lift forces. Four suitable LPW's used on a high powered, amphibious vehicle would enable it to drive on land as well as water, where it could lift itself up to drive over the water surface at speed, supported only on its blade tips. Experimental testing tank work with over 40 LPW forms was undertaken, covering force measurements, power measurements and flow visualisation. A wake regime was identified, comprising displacement, transition and planing type wakes, as exhibited by other water craft. A stall-like phenomenon, denoted cavity intrusion, was found to occur when each descending blade begins to encounter the cavity left by the previous blade. A theory was developed to describe the lift and propulsive forces in the relatively simple case of a flat-bladed LPW in the planing condition. These forces were shown to be predominantly impulsive in nature and to occur at blade entry. A semi-empirical scheme, based on the above theory, was developed for designing LPW craft. A 4 kg four-wheel-drive, radio controlled model LPW vehicle successfully demonstrated the LPW concept, and speeds of 32 kph were attained. Practical experience with this type of craft was gained while using this model as a testbed for over 25 different LPW types. Outline design for a full-sized prototype craft indicated that a performance, in terms of power requirements and speed capability, equalling that of high powered hydrojet boats could be expected. It was concluded that with the development of combination road and water LPW's from the present successful designs, the LPW craft could be a unique amphibian with its high water speed and all-terrain capabilities.
展开▼
