Abstract
In the past, when a transport vehicle was moved on soft ground in a horticultural greenhouse and turned to a different direction at an end of a furrowed track, the surface of the track was made uneven by the tires in some cases. There are so called “multi-sheets” present not only over raised areas but also over furrowed areas in strawberry greenhouses, and there were also instances where multi-sheets were broken by tire sidewalls when the vehicle was steered. As a measure to overcome this problem, we developed a three-wheeled transport vehicle which could move along furrows in greenhouses without breaking multisheets. We focused on the shape of the wheel in this development, developed a globular wheel equipped with a special steering mechanism, which changes the steering angle and camber angle together when the vehicle is steered, and adopted it. We analyzed the steering characteristics and moving performance of this transport vehicle, and identified the following:First, in testing the frictional characteristics of the ground contact area of a tire, it was effective to make the COF between the tire and multi-sheet smaller than that between the multi-sheet and weathered granite soil (0.53). Next, the stress acting on a multi-sheet measured 4.3 Mpa when the globular wheels were steered, which was a small value just equivalent to 58% of that of general tires, so that using the globular wheels was effective enough to protect multi-sheets.Finally, the climbing performance of this transport vehicle was 18° when a tire material with a COF of 0.5 was adopted, and this was sufficient for practical use.
