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rigid pontoon flexible track with separate bogies 
ca A {aw 
considerable stress concentration 
vertical . by Wee ee 
uniform pressure distribution beneath each bogie wheel 
stress 
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flexible track around 
large-diameter wheels 
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stiff, all-steel girderized track 
‘ely ersten fetal 
Pressure distribution 
close to uniform 
i) 
slack track io track 
severe stress concentrations 
beneath the wheels 
D 
Figure 31. Stress distributions of three track systems. 
Most of the heavy prime movers and large overland vehicles used in 
the Antarctic and other cold areas have one pair of tracks. The Low Ground 
Pressure Caterpillar Tractors, Models D-8, D-6, and D-4, manufactured by the 
Caterpillar Company, Peoria, Illinois, and the Russian Kharkovchanka, manu- 
factured by the Kharkova Tractor Works, U.S.S.R., are examples of these units. 
Although they are called oversnow vehicles, they all have a ground bearing 
pressure of about 4 psi and must operate on hard surfaces or where there is 
a shallow, hard subsurface. 
Besides the tracked vehicles, there are many other concepts for 
providing support and traction on soft surfaces that have been tried with 
various degrees of success. Some of them are discussed below. 
Endless Belt. The endless belt is similar to a segmented track but 
has a rubber belt instead of the linked track. The belt supports the vehicle 
weight on bogie wheels, but in order to minimize heavy stress concentrations 
at their points of contact with the soft flexible belt, the bogie wheels are 
usually more numerous and smaller than bogie wheels on the more rigid 
segmented tracks. 
40 
