If, now, when the center of axle 60 is at 65 and therefore the 
center of axle 70 is at 73, a suitably situated solenoid clamp or 
other means is used to suddenly clamp axle 70 relative to the pro- 
jector housing while simultaneously the clamp on axle 90 is released, 
then as rotor 10 continues to turn the center of axle 60 is con- 
strained to follow the new arcuate line of action 63 centered on 
the point 73. As axle 60 oscillates along 63 between the turning 
points 64 and 65, the center of axle 90 will be constrained to 
oscillate along the arcuate line of action 91 centered on point 
121, wherefore the cross arm 110 must then oscillate about its axle 
120 and so the piston linkages 150 and 160 must drive their respec- 
tive pistons in the desired oscillating manner. 
It is important to note, now, that the sudden switching change from 
a condition wnerein axle 90 is clamped at location 93 to one where- 
in axle 70 is clamped at location 73, does not impose any signifi- 
cant impulsive loads on any of the machinery of the projector, be- 
cause all linkages and pistons are then at or very near their zero- 
velocity points both before and also after the sudden switching 
action occurs; this is true despite the fact that the pistons are 
Switched at that time from a condition of zero amplitude to a con- 
dition of full amplitude oscillation. 
If and when it is desired to switch the projector back to a condi- 
tion wherein the pistons are not oscillating, this can be accomp- 
lished, again without imposing any significantly large impulsive 
loads on any of the machinery of the projector, by suddenly clamp- 
ing axle 90 while simultaneously releasing ‘the clamp on axle 70 
whenever the center of axle 60 reaches its turning point 65. 
If it is desired to switch on the piston oscillation at a reduced 
amplitude of such oscillation, means are provided to bodily trans- 
port, without rotation, the axle 70 together with its guiding slot 
and clamping means, along a line from point 73 towards point 93. 
As 73 moves toward 93 it can readily be seen from fig. Cl that the 
amplitude of oscillation of axle 90 diminishes; in fact, if 73 is 
made coincident with 93, the amplitude of oscillation of axle 90 
must vanish altogether, whence the piston motions must also 
vanish (i.e., the amplitude of their motion must vanish). 
3. As a further invention, consider: the system shown in fig. C2. 
Here the elements are all the same as in fig. Cl except that (1) 
the interaxle length of link 80 is made significantly shorter than 
the interaxle length of link 100, and (2) the above-mentioned means 
for bodily transporting axle 70 along with its clamp and its guid- 
ing slot (the "transport means") is designed to be able to move the 
center of axle 70 along the arcuate line 74 which is centered on 
point 65, for example. If, now, axle 90 is clamped with qt center 
at point 93,the center of axle 60 must move along the line of action 
61 and the center of axle 70 is forced to move along the line of 
action 71. However, if axle 70 is clamped with its center at point 
73, then axle 60 is forced to move along the arcuate line of action 
