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Topic: Fumeo 9119 problem, help needed
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted February 24, 2017 07:34 PM
From Andrew:[/QUOTE] It contains a fair amount of initial inertia given its mass and takes a while to stabilize its running speed on anything other than a capstan driven mechanism, whereby the smoothing section is already at stabilized full running speed well in advance of the film getting there.
Typically, all other mechanisms rely on the thickness of the film itself to drive the capstan and flywheel properly. This again, doesn't help as thicknesses vary and ideally you want the flywheel already turning at the matched speed of the rest of the transport system, well before the film and stripe pass over the magnetic head section or optical sound photocell [QUOTE]
On the Elmo GS1220, the flywheel is driven up to speed by a worm gear on the fan axle, even with the projector in standby mode. Unfortunately this does not eliminate start up WOW, which can be pretty awful on these machines with lubricated films. The problem is the small diameter capstan and pinch roller which does not have sufficient area and contact pressure to avoid film slippage. On the other hand, I have had zero start up WOW problems on all my Eumig 800's and 900's, none of which idle the flywheel in stand-by mode, but do have large diameter capstans and pinch rollers, clamped together with plenty of pressure. And the flywheels on these machines are so free and well balanced that they will keep spinning for several minutes after the machine is stopped.
-------------------- The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection, Elmo GS1200 f1.0 2-blade Eumig S938 Stereo f1.0 Ektar Panasonic PT-AE4000U digital pj
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted February 25, 2017 10:42 PM
You've got it right Phil. The GS1200 fan has a brass worm gear at the end of its shaft, which drives a little rubber roller attached to a lever arm. When the projector is in standby mode(powered up but not moving film) the little roller rests against the outer diameter of the flywheel and keeps it spinning at a speed corresponding to about 21 frames per second of film projection (i.e. mid way between 18 and 24fps). When the projector button is pushed to forward (play) a solenoid lifts the lever and the rubber roller away from the flywheel and so only the motion of the film over the capstan drives the flywheel. Very clever, but unfortunately it does not compensate for the bad design of the small capstan and pinch roller, and start up WOW is usually significant. That's no problem at all in projecting film prints, but how these projectors were ever used for serious sound editing, where a full speed start up is required, is beyond me.
-------------------- The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection, Elmo GS1200 f1.0 2-blade Eumig S938 Stereo f1.0 Ektar Panasonic PT-AE4000U digital pj
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