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Topic: Basic question about interlocking

Manny Knowles
"What are these things and WHY are they BLUE???"

Posts: 4247
From: Bloomington, IN, USA
Registered: Feb 2002

posted 08-19-2002 12:13 PM

This is one area where video wins.

Video (digital or analog) will always run at the same rate. Videotape syncs up via a control track. I don't know if CD's and DVD's sync to anything like that or if they're just precise because they are (a-hem) digital.

I know that you can sync a CD to a video with no problem because I have done many video recordings of concerts and live theatre shows where the audio was burned out to CD from the mixing board. There's never a problem maintaining sync.

Two videos of the same program -- once synchronized -- will remain in sync.

With film, there are real-world variables that interfere with tidy theories.

~Manny (operators are standing by)

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Josh Jones
Redhat

Posts: 1207
From: Plano, TX
Registered: Apr 2000

posted 08-19-2002 11:49 PM

Also, a cd player uses a crystal reference for the sampling rate, so it will, in theory, not drift.

Josh

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Ken McFall
Jedi Master Film Handler

Posts: 615
From: Haringey, London.
Registered: Apr 2001

posted 01-14-2003 03:09 PM

It's worth mentioning that if you use inverters to run your motors then there is no 'slippage' when you start and stop the projectors.

The inverters will be set to the same run up and slow down delays and the projectors will therefore start and stop at exactly the same rate.

With inverters you don't just turn the power on or off .... you start and power down the projectors in a controlled fashion. It's a very elegant solution and works remarkably well.

The loop absorber placed mid way is there to allow for the unexpected and the fact that the drag of the film will cause slight movement of the absorber. However, I've never had more than an inch or so, which was the film tensioning as it ran due to the drag over such a long distance.

You do need to use timing belts to eliminate any slippage on the projector drive itself. Apart from that you can use any combination of projector types. The inverters will power up the projector in such a fashion that there will be no slippage etc. Trust me it works and its very reliable.

The hardest part is hammering home good practice to your staff to ensure they don't 'create' problems. Also enforcing a minimum turnaround of at least 30 minutes when the manager does the time sheet so there is no rushing during lacing up and accidents happening.

I've run many shows now and have had no problems.

I should add that the last interlock, 'LORT Two Towers', was the first time I'd used Film Guard at the same time. The result was exceptional. With the film running over such a long distance there is going to be more abrashion and dust. Film Guard eliminated that and the print looked as good after three weeks running as it did on its first run.

Regards Ken.

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