8mm Forum: GS1200 PUZZLE

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Topic: GS1200 PUZZLE

Paul Adsett
Film God

Posts: 5003
From: USA
Registered: Jun 2003

posted August 03, 2005 06:45 PM

Here's one for Kev. The question is " How exactly does the GS1200 (version 1) automatically form its bottom loop to the correct size"? I have looked and looked at my machine during threading and start up, and I can't for the life of me figure out how it forms that bottom loop. It seems when you press the forward button, that bottom loop always pops out to the correct size, but there are no mechanical loop formers. How does it do it?

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The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
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Douglas Meltzer
Moderator

Posts: 4554
From: New York, NY, USA
Registered: Jun 2003

posted August 03, 2005 09:07 PM

Here would be a good point for Kevin to talk about the little people who live in all Elmos (except for the 180 series and the HiVision SC-30) that actually perform the functions once the buttons are pressed and the switches are switched. Relay-controlled motors? Not a chance. These highly trained, specialized teams drive the film advance and claw mechanisms. They are responsible for bulb cooling and initiating the motion of the 1.3 lb. flywheel. They can also rewind 400 feet of film in a mere 63 seconds. To answer Paul's question, The highly regarded LRU (Loop Restorer Unit) is a tight knit group of five that works breathtakingly fast to reestablish the necessary counterpoise needed to maintain proper projection.
The wee Elmo folks are getting a bit long in the tooth however. In some models, projector security has been breached and residence has been taken up by rogue groups such as the notorious FSS (Film Scratching Squad) and the League of WWTTSIF (Why Won't This Thing Stay In Focus)?

Doug

[ August 03, 2005, 10:38 PM: Message edited by: Douglas Meltzer ]

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I think there's room for just one more film.....

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Jan Bister
Darth 8mm

Posts: 2629
From: Ohio, USA
Registered: Jan 2005

posted August 03, 2005 11:16 PM

LOL @ Dan.... very funny [Big Grin]

Paul, would you be talking about the loop between the film gate and the sound heads? I found that when I thread film in my ST-1200HD, it sort of runs loosely through the film path until the bottom sprocket starts taking it up - and once the threading is released and the rubber roller and sound head pressure pads engage, they cause the film between the sound drum and the bottom sprocket to tense up. So, during a split second, while everything else is in motion, the piece of film sitting on the sound heads is held still (until tension is achieved further down the film path) which causes the loop underneath the film gate to form! Quite clever if you ask me. [Smile]

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Call me Phoenix. *dusts off the ashes*

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted August 04, 2005 01:27 AM

Doug, That was rather funny I have to say it gave me a chuckle or 2! [Big Grin]

Jan is right, the correct size of loop is controlled by the shape of the bottom guide. Not only is it that shape to guide the film to the second sprocket but also that length to give the correct loop size. Its not quite down to the pinch roller Jan because on the GS is driven at speed to cut down any wow effects so that you get a nice clean start up.
At that point when the solenoids pull on and the pinch roller engages and the head presser assay comes down, the green guide which is over the head presser assay pushes a little lever at the rear of the small black roller. The roller is the one at the input to the soundhead. This little lever in turn pushes the loop former momentarily so that the film is given a slight jerk forward. This action causes the film to jump forward and form the loop. This has to happen due to the fact that the flywheel is driven in the GS. If it wasnt, like on the st600 etc then the action of the pichroller coming down onto the staionary capstan would mean that the momentary stop of the film would cause the film to jump forward at that point to form the loop as it has nowhere else to go. Dont forget its still being driven forward by the claw and the bottom guide is a fixed distance etc. All very clever stuff.
Hope that helps [Smile]

Kev.

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GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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