26 PROFESSOR T, A. HE ARSON ON THE KINEMATICS OF MACHINES. 
Group O 2 , Containing 2 Turning Motions. 
Combination. 
Inversions. 
Notes and examples. 
OoUU 
The link between Oo must be such tbat when added to either 
one of the other three the sum must be less than the sum of 
the two remaining links. 
OoUU 
In a beam-engine the portion consisting of the half-beam, con¬ 
necting-rod, crank shaft, and frame of engine, affords an 
example. 
oUUO 
Example: The drag-link coupling used for connecting two 
shafts which are parallel, but not in the same straight line. 
UOoU 
In this case both primary pieces swing. The 4th inversion will 
give a repetition of the movement of the 1st. 
OoUI 
The line of slide must be at a less distance from the axis of the 
0 motion than the difference in the length of the two finite 
links. In most practical examples of the use of this move¬ 
ment the deviation of the line of slide from the axis of 0 is 
zero, as in the following examples. 
OoUI 
Example : The much used crank-and-connecting-rod engine. 
oUIO 
Example : Rigg’s high-speed engine. 
UIOo 
Example : The oscillating engine much used in paddle wheel 
steamers. 
IOoU 
Example : Stannah’s pendulum pump. 
Four different machine movements are derivable by inversion 
from this combination, and each has been adopted in the 
design of a steam engine. 
OVUU 
The link between Oo added to one other link must equal the 
sum of the two remaining links; but when added to the 
others the sum must be less. 
OVUU 
o 3 UU0 2 
uovu 
Two complete rotations occur at two joints, whilst one complete 
to-and-fro swing occurs at the other two. 
The 4th fixing gives a movement which is a repetition of the 1st. 
