grip failure 
occurring along ae RON Ya 
this surface y — ground failure 
NN pe a occurring along 
/ 
Sue) - this surface 
Si sy gud eee 
Figure 36. Tractive behavior of oblate wheel. 
Gree 
Move 
Figure 37. Archimedean screw pontoon. 
This concept has been used with a fair degree of success on a small 
snow “‘scooter’’ but, inspite of extensive developmental work, has not proved 
practical for a passenger or cargo vehicle on land (Beck, 1957). For the ocean 
bottom application, however, it may be worthy of consideration. Tests at 
the Waterways Experiment Station (WES), Vicksburg, Mississippi (Knight, 
Rush, and Stinson, 1965), revealed that the Marsh Screw, and Archimedean 
Screw vehicle, could operate on extremely wet, soft soils where other vehicles 
of equal size and weight could not. If the soil had free water on its surface or 
46 
