Inflation pressure 103 kPa

left front

6800

30.5

36.5

27.2

right front

30.0

36.5

27.2

left rear

5510

31.5

37.0

27.2

right rear

32.5

37.0

27.2

Inflation pressure 179 kPa

left front

6800

33.0

36.7

25.6

right front

32.4

37.5

26.3

left rear

5510

33.5

37.5

25.5

right rear

34.2

38.0

25.5

where *h *is the snow depth, and ρf is the theoretical

following in the ruts made by the tow vehicle.

After each test run, the undisturbed snow depths

final density, which is determined from the fol-

along both the left and right wheel ruts were

lowing with *p*max the maximum contact pressure:

measured at 1-m intervals. These data were later

ρf = 0.50 Mg/m3

for *p*max ≤ 210 kPa

averaged to obtain an undisturbed snow depth

ρf = 0.55 Mg/m3

for *p*max > 210 kPa

value for each side of the vehicle. At the conclusion

ρf = 0.60 Mg/m3

for *p*max > 350 kPa

of a series of tests, several snow pits were used to

ρf = 0.65 Mg/m3

for *p*max > 700 kPa.

characterize the snow and to determine an aver-

age density for each test.

A value of 0.50 Mg/m3 is used for the CIV with the

inflation pressure and tires used in these tests.

Three equations are plotted on Figure 3. These

are

Table 3 contains a summary of the data col-

lected. The data are separated into sets based on

(2)

the day of the test and the tire inflation pressure.

Initial snow depths ranged between 10 and 37 cm

which is a fit of the data collected during the CIV

and average initial snow densities ranged from

tests reported herein

0.11 to 0.25 Mg/m3. All of the snow data collected

are given in Appendix A.

(3)

which was obtained for the CIV alone in 1988 and

The leading tire data from Table 3 are plotted in

1989 (Richmond et al. 1990) and

kilograms per meter, developed by Richmond et

(4)

al. (1990). The variables in this parameter are illus-

trated in Figure 4; ρ0 is the average initial undis-

which is the currently used shallow snow resis-

turbed density of the snow, *a *is the arc length of the

tance equation (Richmond et al. 1990). *R*s is the

tire in contact with the snow, and *w *is the maxi-

resistance per wheel (in Newtons) for a vehicle

mum tire width in meters. The arc length *a *is

traveling through primarily undisturbed snow.

determined from the sinkage *z *and the tire radius,

Combining the old and new CIV data yields the

where the sinkage is determined from

following equation

(5)

ρ

(1)

ρf

which has an *r*2 value of 0.58 compared to 0.76 for

4

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