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Author
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Topic: Eiki Claw Mechanisms etc
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John Whittle
Jedi Master Film Handler
Posts: 791
From: Northridge, CA USA
Registered: Jun 2003
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posted August 21, 2009 02:52 PM
The Eiki pull down (which in the early machines with the fibre cam is almost identical to the Elmo design) is a square operation. There are two cams in the cam tank. A large round plate that has a rise and fall in it moves the claw in and out and the fibre cam (replaced with a cast metal cam in the R series) moves the claw up and down.
If you are observing an arc or lazy pattern, then the cam plate is worn or defective. There were some bad cam plates but these were way back on the "S" series machines which appeared between the MS three sprocket machines and the ST or first self threader machines. The S machine was put on the market a little too early and had problems with threading and picture steadiness. These were almost all replaced with the ST machine so if you have one, it is a rare beast indeed.
The major change in the cam tank design cam with the R series. Prior to that the claw lever has held in place with bearing springs on the top and bottom of an opening in the claw lever--this was identical to the design in the Elmo and the RCA 400 series (which was a pattern for both Elmo and Eiki early machines). With the introduction of the R series, Eiki suffered a loss in personell. The man who cut every cam for the projectors and did it by eye and feel, died. Those early cams are stamped with L M H for variation in lift. What Eiki did is select through the finished cams and pick the best and then used them as a pattern for casting.
The R Series also changed the claw lever, instead of the springs on top and bottom of an opening, a nylon bearing is at the bottom and a spring holds it in contact with the cam the in/out cam follower is also a nylon bearng and can be replaced.
As the projector wears, the amount of claw protrusion actually increases. There are adjustment on the cam tank to handle variation of protrustion and overall position of the claw and the framing relationship to the aperature.
Again if you are having problems with what appears to be a lazy arc, make sure the the cam follower is actually following the cam (there is a flat spring that holds the lever against the cam plate for the in/out motion), the the cam plates are lubricated and everything is turning smoothing.
If instead you are seeing streaking, then check your shutter timing to the claw during pull down. Early or late will result in streaking of white titles on black either up or down. The mounting holes on the shutter are slotted allowing a slight adjustment of shutter timing. This this isn't enough to solve the problem, we should look further for problems that might be causing this issues (such as framing being way off).
John
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