Effects of hull shapes on floating power tiller performance under wetland conditions

Date

1988

Abstract

Two types of hull, of trapezoidal and elliptical shapes, were developed and tested together with the existing pontoon-type hull of hydro-tiller with the upper hull area (corresponding to a sinkage of 10 cm) of the pontoon-type as the basis for the other hulls. The hull shapes were designed with the gross weight roughly the same (98 ± 10 N) and based upon the concept of shallow depth of sinkage, i.e. the sinkage of the hull was limited at less than 10 cm. The effects on drag and sinkage of the weight exerted on the hull, the soil compaction, and the ratio of length-to-width of the upper hull area was studies. The elliptical-shaped hull at length-to-width ratio R1~ less than 2.3 gave lower drag over the trapezoidal and pontoon-type under the medium and particularly at high weight levels (Q = 0.539 and 0.833 kN, respectively) applied on the upper hull area (A=2260 cm^2). A range of ratio R1~ from 1.3 to 2.3 for the elliptical shape gave least drag (25.20-33.78 N), higher stability and low difference in drag at different soil conditions. Under this condition, the elliptical-shaped hull could work in a wider range of soil condition from normal to soft soil condition. The pontoon-type hull gave higher drag resistance in soft soil (soil compaction of about 18-20 kPa); and particularly under high weight level 0.833 kN) its drag was highest, 158.18 N, as compared with 134,88 and 98.37 N for the trapezoidal and elliptical-shaped hulls, respectively. In normal soil (soil compaction of about 50-53 kPa), its drag (46.95 N) was roughly equivalent to the other types under medium weight (0.539 kN). This suggests the suitability of the pontoon-type in normal soil condition more than in soft or in saturated soft soil with deep hardpan. The center of gravity position and velocity also affected drag resistance of the hull. Lower drag resulted when the center of gravity position was at rear-side of the center point of the hull length and when the hull moved at low velocity. Under shallow depth of sinkage (less than 5 cm) and at high weight level (or ground pressure) in soft soil condition, although the drags of all types of hulls reached highest values (98.37, 134.88 and 158.18 N for the elliptical, trapezoidal and pontoon-type, respectively), the drag/weight percentage of these types were rather small: 11.8, 16.2 and 19.0%, for the above-mentioned hull types. This proves the advantage of limiting the working depth of the floating device at shallow level (less than 10 cm) for improving the mobility and utility of the hull in wetland. The static ground pressure of 5.7-6.9 kPa for the hull to operate in regular soft soil (soil compaction of about 18-20 kPa within 1-15 cm depth) and 3.0-3.5 kpa, in saturated soft soil with deep hardpan is suggested as reference in the design of the floating device of a floating power tiller.

Document Type

Master Thesis

Language

English

LC Subject

Farm tractors, Hydro-tiller

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 995 1988 A2 V56

This document is currently not available here.

Share

COinS