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Title: Performance of Towed Wheels Operating in Turned Mode on Soft Soils : a Pilot Study
Authors: Melzer, Klaus-Jurgen
Mobility and Environmental Systems Laboratory (U.S.)
Keywords: Clay
One-pass performance
Pneumatic tires
Towed wheels
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Miscellaneous Paper (U.S. Army Engineer Waterways Experiment Station);no. M-76-17
Abstract: The performance of single, pneumatic-tired, towed wheels operating in turned mode was investigated in a pilot study. Ninety-nine one-pass tests were conducted in the laboratory on one clay and two air-dry sands with 8.50-10, 7.00-6, and 6.00-9 tires. Turn angles were O, 5, 10, 15, and 20 deg; wheel loads were varied from about 1000 to 7000 N; and tire deflections were 0.15, 0.25, 0.35, and o.40 of the undeflected tire section heights. Clay consistencies ranged from soft to medium stiff, with corresponding cone penetration resistances between 255 and 543 kPa. Relative densities of the sands ranged from medium dense to very dense, with corresponding cone penetration resistance gradients ranging from 0.7 to 4.6 MPa/m. Performance expressed in terms of towed force coefficient, side force coefficient, resultant coefficient, lateral force/drag, sinkage coefficient, and slip is influenced by the following independent variables: turn angle, soil strength, tire deflection, wheel load; and the product of tire width and diameter. Trail moment and eccentricity of the resultant are influenced more or less similarly. For the ranges of the variables tested, the U. S. Army Engineer Waterways Experiment Station system of dimensionless parameters for predicting performance of towed wheels operating at zero turn angle on clay and on sand is extended to treat turn angles larger than zero. For this purpose, turn angle and mobility numbers for sand and clay, combined with additional independent dimensionless variables, are correlated with the aforementioned six performance parameters. For clay, towed force coefficient (PT/W) decreases with increasing clay mobility number (Ne), but does not show a very well defined dependency on turn angle (a). In sand, PT/W decreases with increasing sand mobility number (Ns); but for a given Ns , PT/W increases with increasing as Side force coefficient (S/W) for clay and sand increases with increasing mobility number for a given a and also with a if the mobility number is constant. Resultant coefficient (R/W) and lateral force/drag (s'/PT) follow either the trend of PT/W or of S/W , depending on which of the two latter parameters has the dominant influence. Sinkage coefficient (zT/d) and slip for clay and for sand follow the same trend as for PT/W in sand.
Description: Miscellaneous Paper
Gov't Doc #: Miscellaneous Paper M-76-17
Rights: Approved for public release; distribution is unlimited
Size: 100 pages / 7.213Mb
Types of Materials: PDF/A
Appears in Collections:Miscellaneous Paper

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