a. Forward component unit vectors.
b. Vertical component unit vectors.
c. Resultant forces.
Figure B6. Forces on a rigid rolling wheel.
Two tests were done in fairly deep snow with significantly different wheels.
Figures B3c and d show the results for the CIV wheel (tire width of 26 cm) and the
HEMTT (tire width of 48 cm). For both tests the maximum perpendicular displace-
ment is about 1820 cm. This indicates that the effect of tire width on resistance may
not be linear.
The results of some simple tests to examine the deformation of snow around a
rolling wheel were presented. Although they were primarily qualitative, some
interesting phenomena were observed. Snow deformation caused by a tire is three-
dimensional and, depending on the depth and density, will primarily occur at or
below the wheel rut in shallow snow and in the upper area if the snow is deep.
Increasing wheel width does not seem to increase deformation in the direction
perpendicular to vehicle motion, at least in the one comparison available from these
tests. The ratio of wheel radius to sinkage should be considered to account for
increased deformation in deeper snow covers.