PROFESSOR T. A. HE ARSON ON THE KINEMATICS OF MACHINES. 
27 
Group O 3 , Containing 2 Turning Motions—(continued). 
Combination. 
Inversions. 
Notes and examples. 
0 2 o 2 UI 
0 2 o 2 UI 
o 2 UI0 2 
UIOV 
IOVU 
In this combination the deviation of the line of slide is equal 
to the difference in the length of the two finite links. This 
is_the limiting deviation possible compatible with 0 motions. 
OoII. 
Only one link is of finite length. 
The lines of the two slides may be inclined at any angle one to 
the other > zero. In general, the angle is a right angle as 
in the following examples. 
OoII 
Example: The Yoke pump, a compact engine, much used 
for feeding boilers. The relative motion between crank 
and piston is like that due to an infinitely long rod in a 
crank-and-connecting-rod engine. The motion is said to be 
“ Harmonic.” 
oIIO 
This movement occurs in Oldham’s coupling employed to 
connect two shafts which are parallel but not in the same 
straight line. In this case the two shafts have a constant 
angular velocity ratio which is not the case with the drag- 
link coupling oIJUO previously quoted. 
IOoI 
Every point in the link joining Oo moves in an ellipse. The 
mechanism has been used in an instrument for drawing 
ellipses. 
The 4th inversion would produce a movement which would be 
a repetition of the 1st. 
