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BULLETIN *711^ U. S. DEPARTMENT OF AGRICULTURE. 



A roller thrust bearing reduces the friction. Separate oscillating 

 plates are used to increase the compression surface. The opening 

 between the jaws when the screw is fully extended is 7 inches. 



The device complete, including the lever, weighs 166 pounds. 

 However, it is of a take-down design, so that this weight can be 

 divided about equally between the two f allers. Figure 13 shows the 



Fig. 11. — Method of inserting tree 

 fallcr in notch. 



Fig. 12. — Cut opened ahout 7 inches 

 with tree faller. 



special pack boards used in carrying the parts in the woods. The 

 amount of time consumed in taking down or assembling the machine 

 is insignificant. 



Figure 11 shows the method of inserting the jack in place on the 

 oscillating plates, also the jack ready for operation, with the roller 

 on the jaws nearest the fulcrum set in the third cavity of the plate. 



At this point of the opera- 

 tion the strain is greatest. 

 Figure 12 shows the cut 

 opened 7 inches with the 

 end roller (the one farthest 

 away from the fulcrum) set 

 in the third roller cavity of 

 the plate. At this point 

 the strain is least. 



The manufacturers of 

 this device have spent sev- 

 eral years in experimental 

 work, building several dif- 

 ferent types with several different kinds of steel. They now feel 

 that the machine has passed the experimental stage. The principal 

 difficulty has been in finding a steel that would stand the very trjdng 

 service demanded of it. Jacks built of other steels than the kind now 

 used stood the test for a while, and then broke under strains seem- 

 ingly no more severe than those they had successfully withstood. It 

 is to be hoped that the jack as now constructed will measure up to 



Fig. 13. — Method of carrying tree faller in 

 the woods. 



