Film-Tech Forum ARCHIVE: HELP! Vertical Unsteadiness

This is topic HELP! Vertical Unsteadiness in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=002294

Posted by Mike Jones (Member # 522) on 05-20-2001, 07:42 PM:

Ok, got a bit of a problem with 3 out of our 8 projectors. Now this has happened with other prints, so I'm led to believe its something projector related. At certain points in the film, if the gate tension is not cranked significantly, there will be a dramatic bobbing, to the point where you wouldn't be able to read the credits for example.

Here are the specs:
-Strong X-90 projector
-Gate tension cranked to anywhere from 3 to 5 o'clock position
-Rails were just replaced in all gates not more than a couple months ago.
-No deposits on the rails
-No burrs or nicks on the sprockets
-Rails have been cleaned with rubbing alcohol
-No perf damage on any of the prints

So I'm left baffled here. Anyone have any guesses as to what this may be? I can't think of anything else...is something out of whack? Our tech is coming Thursday, but I can't wait til then.
Thanks for any help.

Posted by Gordon McLeod (Member # 33) on 05-20-2001, 07:44 PM:

There is no such thing as a strong x90 projector that is the console
check the projector head and also what style of trap it has and does it do it every pass of the print in the same spot.

Posted by Mike Jones (Member # 522) on 05-20-2001, 07:58 PM:

Sorry, wrong info came out of my head.
We have a Strong/Century projector SA/TA.

I'm not 100% sure but I think the trap is by Ballantyne.

Posted by Randy Stankey (Member # 64) on 05-20-2001, 09:15 PM:

Are you using FilmGuard?

If so, vertical jitter can be caused by using too much FG. It will jitter for a second and then stop. A few minutes later it will repeat, at seemingly random places throughout the film.

If this is a the case, then the solution would be to stop using FG on that print. The problem will subside after a while when the layer of liquid on the film evens out. If the problem is bad then you can load up a set of DRY media pads on your film cleaner and run the film through that. This will sop up any extra liquid from the film.

This is the main caveat when using FilmGuard... A little goes a hell of a long way!

Posted by Brad Miller (Member # 2) on 05-20-2001, 10:15 PM:

Yup, it sounds like either way too much oversaturation of FilmGuard or your gate tension spring may have broken, leaving virtually no tension in the gate. (One ounce is enough for a full week's cleaning on a film!) Since you say it only happens to 3 out of the 8, I would check the gate spring over first. Try swapping a "bad" gate with a known good one and see if the problems remains or moves with the gate.

Posted by Darryl Spicer (Member # 711) on 05-20-2001, 10:30 PM:

Check lateral guides and make sure they are turning as the film passes thru. Check intermittent shoe and make sure it is not loose. these things can also cause picture unsteadiness.

Posted by John Pytlak (Member # 331) on 05-21-2001, 07:20 AM:

Does the sound of the film running through the projector change when you get to the unsteady sections? If so, I suspect a change in the lubrication, such as excessive application of FilmGuard. If the film is too slippery, the tension of the gate will not be able to hold it steady.

------------------
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 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by Pat Moore (Member # 380) on 05-21-2001, 08:01 AM:

Mike; I'm wondering if the replacement of rails you mentioned has anything to do with the problem. Are you talking about the runners in the film trap assembly? Were the Intermittent Pressure Pads or other parts replaced at the same time?

Take a close look at the runners (sometimes called "straps") in the Trap. Make sure the surfaces are parallel. I've seen them installed where they are canted and it does nasty things to the picture.

Otherwise, this sounds like lubrication or something that's film related rather than projector.

Posted by Rick Long Jr (Member # 541) on 05-21-2001, 03:25 PM:

Here's a shot in the dark. A loose turret or lens mount can also cause picture instability. I have run into this many times with Simplex projectors. However,since you describe it as a "dramatic bobbing", it could be something as simple as a dirty splicer not completely removing all of the perf cut-outs, which get stuck to the intermittent sprocket and cause vertical jumping. It is usually accompanied by a ticking sound that goes away after a splice or something comes along and takes the offending piece away, only to show up again somewhere else in the film on the next run. This could be why the sprocket appears O.K. after inspection.

Posted by Mike Jones (Member # 522) on 05-21-2001, 11:18 PM:

Thanks guys, I'll check it out.

We don't run cleaners with FilmGuard on them like many people here do, we simply wipe it on the top of the film. Lately, we've been having insane amounts of looping, causing three brain wraps in a weeks time...when we haven't had any incident since September. So that means the Film Guard has been used more than normal.

I just thought it odd that it would happen in certain parts of the film. And yes, there is a very loud rattle when this happens.

The skis/traps/shoepads/straps (call em what you will) were replaced with great care. I even checked that twice before coming here.

But I'm led to believe that FilmGuard is the culprit since the projectors its been happening to have been the ones with significant looping problems.

Thanks

Posted by Brad Miller (Member # 2) on 05-22-2001, 03:37 AM:

Simple answer then, you're overdoing the application. It doesn't take much at all to do the job right. How often are you applying the FG to the edges of the print? How "wet" is the cloth you are using to do it?

Remember, one ounce is enough to run a film for about 3 dozen cleanings.

Posted by John Pytlak (Member # 331) on 05-22-2001, 08:12 AM:

It's very difficult to apply FilmGuard or any film lubricant to the edge of the wound roll evenly --- it's likely some sections of the roll "sucked up" much more lubricant and are too slippery. Look at the surface of the print in the "jumpy" areas --- is there excessive oily deposit there?

Posted by Mike Jones (Member # 522) on 05-22-2001, 11:22 AM:

Yes, there are deposits on the section of film that jump. We'll clean it and get it taken care of.

We apply FilmGuard with a lint free cloth on the top of the print. We have been using more than the recommended ounce because of brain wraps at the worst times. We had one on a sold out Friday show and one on a sold out Saturday show. What we ended up doing was just having a projectionist/floor person come up and watch the prints while the other one threaded. (We're an 8 screen). Something we've never had to do before but a neccesity.

Our humidity levels have been hovering between 20 and 40%. But all winter, no matter what the humidifiers kicked out, we had on average a 20% reading with absolutely no looping problems.

I hear the recommended level is between 40-60%, but can this be right? Thoughts anyone?

Posted by John Pytlak (Member # 331) on 05-22-2001, 12:05 PM:

Kodak recommends relative humidity be kept ideally between 50 and 60 percent RH.

You said earlier: "Lately, we've been having insane amounts of looping (interlocking?), causing three brain wraps in a weeks time...when we haven't had any incident since September."

Could it be that running the same print through several projectors is drying it out to the extent it is more prone to "static cling"? As the film exits the last projector, does it lie nearly flat, or is there significant "curl" or cupping from excessive dryness?

Look at the factors that influence "static cling": proper humidity, conductive platter and roller surfaces, winding orientation, winding tension, platter timing, restraining the roll to prevent "fling", etc.:
Platter Patter article

In severe cases of static cling, treatment of the full width of the film with an antistat is more effective than just the edges (i.e., use a slightly dampened media cleaner rather than wiping it on the edge of the film).