But now we have a design that works pretty good. It mounts on the platter, and slides up when "activated." (It slides up like the take-up regulator on a Potts-type platter, or like one of those vertical interlock accumulators.)

We get two different types of platter-wraps. One is where the film will tangle slowly. This slowly increases tension until a break.

Or (two), the film will wrap on itself and bind. The film payout stops suddenly

We wanted to detect both types, and so needed it to accumulate film, because the flywheel on the Simplex's we have keep the projector pulling on the film for a long time after the power is removed.

We also have a V8, which stops almost immediately.

Also, our feed-out tension switch has two sets of contacts. One goes to the projection automation, and the other shuts off the 110VAC power to the platter itself. That way, if the feed-out is jammed in the "feed" position, you won't have the deck spinning away.

 

My beef is that all they do is shut down the platter system. They then rely on the projector fail safe to notice that the film isn't being picked up, and shut down the projector. Trouble is, the film will continue running through the failsafe and pile on the floor.

I wish that the wrap detector actually interfaced with the automation (I have the Strong CNA-200) and just told the projector to shut down. Does anyone know if this can be wired, I haven't found anything in the manuals showing this.

------------------
Dave Cutler

"Do or do not, there is no try."
 

------------------
Dave Cutler

"Do or do not, there is no try."
 

One problem with this, however occurs when running "yo-yo" or one print through multiple projectors. As the film is feed off on platter, and taken up onto another platter down the hall, a bind on the first platter will not trigger a shut-down on the second, thus no stoppage will occur, often resulting in lost performances while the resultant mass of film is untangled.

The obvious cure for this was to feed the tension fail-safe to the automation so that (when interlocked) both automations would immediately detect a fault and shut down both machines simultaneously.

This simple cure, however, was not without its problems. Many manager/projectionists are in the habit of securing their date-strips (coming soon & feature presentations, ect.) with masking tape when storing them on the shelf. While this provides for quick identification, it leaves a sticky residue on the film that triggers the fail-safe device.

In the cases where the power to the platter is interupted, this proves no problem, as the sudden "jerk" as this film passes through, is not long enough for the platter elevator to reach the bottom causing shut-down. In cases where the fail-safe is fed to the automation, however, the shut-down is instantaneous, often causing the booth personell to wonder what the problem is and putting in emergency calls for automation malfunctions.

We have found that some form of time-delay is required so that these momentary "jerks" (refering to the sticky film here, not the booth personell) do not cause sudden shut-downs.

I agree that good fail-safe design should be coupled directly to the projector automation, so the projector is shut down as soon as tension becomes excessive. Likewise, a well-designed failsafe has enough slack to allow the projector to coast to a complete stop.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
 

Rick, try buying paper tape. It won't leave any residue on the film. Well, I guess it does if left on for months at a time, but this usually doesn't happen. Paper tape is a bit more expensive than normal masking tape, but much better for the film.
 

The problem with this, as I mentioned, is that there is no time-delay and shut down is immediate, even with non-serious temporary binds, as might occur from masking or splicing tape residue.

In the booths where interlock is not possible, we have left the tension sensors wired as shipped, interupting the power to the platter. We find that the short "jerks" caused by residue, do not interupt the performance.

I have been somewhat sucessful in getting the theatres to convert to the use of large elastic bands to hold the roll together, when it is stored on the shelf.

I'm not familiar with the Strong tension fail-safes, but I have purchased fail-safes from Speco and experienced similar problems. The roller that raises during tension was not heavy enough and we had problems with false triggering. I ended up adding a spring to hold down the roller and adjusted the spring tension so the roller would not activate until about ten wraps around the brain. If you notice on the picture of my homemade fail-safe, I installed a spring and screw to adjust for this very problem
 

On another note, I wired the micro switch on the fail-safe payout bracket to the projector motor run circuit, as well as the take-up elevator micro-switch. The switches are wired so that either one will stop the projector motor. Each one will light an individual alarm light on the motor control panel so that the operator can see what caused the stoppage- take-up or pay-out.

------------------