2000
1000
800
600
Eq 4
400
Eq 3
200
Eq 2
100
80
60
2
4
6
8
10
20
Density . Arc Length . Width (kg /m)
Figure 3. Leading tire motion resistance.
eq 3. Further analysis of this data set (old and new
pendix B. Snow density (i.e., snow characteristics
CIV data) using a stepwise regression procedure
other than depth) may have been too similar be-
showed that an equation including only snow
tween tests to develop a clear effect.
depth and the ratio of arc length a to 1/4 the
perimeter of the wheel provided a slightly better
Trailing tire resistance
The initial analysis consisted of examining scat-
correlation to the data. This equation
ter plots of the independent variables (snow depth,
4a
Rs = 66.148 + 51.915h 490.26
density, tire width, sinkage and velocity) and sev-
(6)
rπ
eral different combinations of these parameters vs.
has an r2 of 0.68. It is interesting that neither the
several forms of the dependent variable: rear
wheel width nor snow density is included in the
equation, even though wheel width varied from
of the trailing wheel motion resistance were con-
0.156 to 0.274 m (albeit there are only a few data
points at the narrowest width). The lack of a wheel
width effect was also suggested by the analysis of
(coefficient form), ratio of rear tire motion resis-
snow deformation by a wheel presented in Ap-
w
Undisturbed
r
a
z
Snow
h
Compacted Snow
Figure 4. Snow and tire characteristic dimensions.
7
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