44 
BULLETIN" 111, U. S. DEPARTMENT OP 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 fallers. Figure 13 shows the 
K lj I jjB °g^Sj~P 
Fig. 11. — Method of inserting tree 
faller in notch. 
Ejgplj 4 |5 |iHb 
-Cut opened about 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 3^ears 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 trying 
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. 
