28 PROFESSOR T. A. HEARSON ON THE KINEMATICS OF MACHINES. 
Group U, Containing no Turning Motions. 
Combination. 
Inversions. 
- 
Notes and examples. 
UUUU 
UUUU 
Whichever link is fixed both primary pieces will swing, there 
will therefore be no change in the movement by inversion. 
Watt’s rectilinear motion is an example of the use of this 
mechanism. 
UUUI 
UUUI 
UU1U 
Only two movements by inversion, the other two inversions 
produce repetitions of the previous movements. 
UUII 
UUII 
UIIU 
IUUI 
Three movements by inversion, the 4th being a repetition. 
There is no difference between the four links required for this 
combination and those required for OoII. 
UIUI 
UIUI 
Whichever link is fixed, one primary piece will swing’ and the 
other slide, so that no new movement will be obtainable by 
inversion. 
Two of the infinite links adjacent to an I may be conceived to 
be equal, causing the line of that slide to be parallel to the 
line joining the axes of the two U’s, as employed in Rapson's 
slide for steering large vessels, also in the compensating 
mechanism used in the Worthington steam pump, as pointed 
out, page 111, ‘ Cottekill’s Applied Mechanics,’ edition 1892. 
Both lines of slide may deviate from the line joining the axes 
of the U’s. If the deviation of each is the same the 
mechanism has the remarkable property that in one position 
it may be locked. It appears to be quite new. 
III 
III 
No change in the movement will occur on inversion. 
This is known as the wedge mechanism. It is employed in the 
cotter method of adjusting the brasses at the ends of a 
locomotive connecting rod when worn. 
Although the OUI motions constitute the large majority of the relative motions of 
consecutive directly connected parts of machines, yet there are others, frequently 
found in use, in which the relative motion is of a more complicated character, for 
example the relative motion of the teeth of a pair of spur wheels. The relationship 
of machines in which there are such motions to the foregoing can be best explained 
by a reference to the series of machines shown in the adjoining five figures. 
It has been previously shown that in the mechanism of fig. 2, p. 20, the same relative 
motions occur as in fig. 1, p.,16, though the construction is different. Suppose now 
the pin tv to be enlarged sufficiently to fit the slotway in the link Z, as in fig. 3, p. 29. 
The block X may then be suppressed, and the same relative motion of the links T, V, 
and Z will be retained exactly as before. 
The block X being omitted, it will no longer be necessary for the slotway to be 
curved to the arc of a circle. The radius of curvature may vary from point to point 
of its length ; but, for definiteness of motion, it will be necessary for the width of the 
