What is in this article?:
The 1976 release of the motion picture King Kong relied heavily on electrohydraulics. Here is our coverage from the April 1977 issue, which details some major challenges and solutions that are just as relevant today as the were more than 30 years ago.
Proportional valves control motion
Cylinders in Kong's hand varied in size from a ¾-in. bore by 2-in. stroke for his fingers, to those with 4-in. bores and 3-ft strokes to flex his 4½-ft diameter, 20-ft-long arms. Remotely controlling these cylinders was to present an equally serious challenge.
Whatever made Glen Robinson, who is chief of special effects in MGM Studios in Culver City, think that he could do what a high-priced mechanical engineering firm had said would take three times as long and much more money to accomplish?
The first thought was to put a special effects man in an ape suit (to be used for some location shots) and outfit him with potentiometers that would be wired to proportional valves controlling the big ape's cylinders. As the actor would move inside the suit, the big Kong would duplicate his movements exactly.
But suppose that while Jessica Lange was in the big hand, the man in the suit sneezed and flung his hand up toward his nose? "We could just imagine the big ape doing the same," said Robinson, "sending the female star flying over his shoulder and into the rafters of the stage!"
They then decided to use manual remote control boxes, one for each cylinder, manned by carefully rehearsed operators. However, there were still problems.
Applying a variable electrical input signal to a proportional control valve controls only cylinder speed, not its final position. In addition, the 30% deadband in the standard proportional control valves they were using caused a delay before the valve spool shifted far enough to actuate the cylinder. This delay meant that the ape would not respond quickly enough when director John Guillermin called for a certain action, and the scene would be ruined.