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Topic: What causes a print to be loose or tight?

Dave Cutler
Master Film Handler

Posts: 277
From: Centennial, CO
Registered: Jun 2000

posted 08-14-2000 05:16 PM

I have Strong DMC Platter systems and some of them leave prints nice a tight and some leave them extremly loose. Does anyone know why this is?

Oh, I have tried to recalibrate the trolley, but it didn't seem to make any difference.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 08-15-2000 02:33 AM

Does it vary from deck to deck on the same platter system, or from system to system?

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Dave Cutler
Master Film Handler

Posts: 277
From: Centennial, CO
Registered: Jun 2000

posted 08-15-2000 09:22 AM

Good question, and I am not sure of the answer. I will check that out tonight when I go in.

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Mike Blakesley
Film God

Posts: 12767
From: Forsyth, Montana
Registered: Jun 99

posted 08-15-2000 05:37 PM

Are the platters properly grounded? Problem could be static electricity.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 08-16-2000 05:17 AM

Mike:

How can buildup of static charge cause a loose roll? "Winding integrity" is usually only a function of winding tension and the frictional coefficient and microscopic surface roughness (matte) of the film. Since Dave's concern seems to vary with the platter, I suspect it is mostly due to winding tension.

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

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Dave Cutler
Master Film Handler

Posts: 277
From: Centennial, CO
Registered: Jun 2000

posted 08-16-2000 09:17 AM

Ok, the problem seems to be consistant on a given platter system. ie all platters on one tree seem to rewind loose, or they all rewind tight. Any suggestions?

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Mike Blakesley
Film God

Posts: 12767
From: Forsyth, Montana
Registered: Jun 99

posted 08-16-2000 01:00 PM

John:

That was just a guess... I've had a number of prints wrap loose over the years, and it just seems like every time it happens, the print is fairly static-y. I didn't know about the "matte" characteristic you mentioned (or more likely, I did know but didn't think of it.) The things one learns on this forum!

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 08-16-2000 02:21 PM

Check your takeup elevator. Generally if the up and down movement is nice and smooth, the print will wind tighter. If there is a little bit of resistance, they will wind loose. I'd try cleaning the rods and coating them very lightly with projector oil and see what happens. Many times it's just gunk built up on them from time and usage that is the cause of the problem. Otherwise, it's generally something mechanical in the elevator out of alignment.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 08-16-2000 02:50 PM

Check for perf damage to see if the sound head is slightly punching perfs
Also i have had problems with both the linkage to the variac and the brushes in some variacs binding just enough to give problems
A fish scale can be used to measure the amount of pull each platter is exerting on the film

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 08-16-2000 03:17 PM

SMPTE Recommended Practice RP 106, "Film Tension in 35-mm Motion-Picture Systems Operating Under 0.9 m/s (180 ft/min)" specifies that "Film tension under normal operating conditions shall be 1.7 to 4.4 N (6 to 16 ozf)."

Tension that is too low gives a loose wind. Tension that is too high risks perforation wear from the sprocket teeth.

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

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

posted 03-07-2002 09:14 PM

I'm having a loose-wind situation with a Christie AW3 system.

There are no elevators with the Christie system...and each platter deck has its own rewind tension arm. And, yet, they are all winding loose.

I calibrated according to the Christie spec's (as I do on all of my Christie platters) and this one just doesn't wrap right.

I have seen two sets of calibration instructions from Christie manuals...the directions from my manual are provided below...

With the feed plate arm at 70, the resistance across pins 12 & 14 is 70KOHM.

With the feed plate arm at maximum, resistance is less than 60KOHM.

Platter speed at 70 = 20rpm

Platter speed at 100 => 25rpm

Platter "creeps" when the feed plate arm is at 20

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And, hey! Let's be careful out there.

~Manny.

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Steven Gorsky
Expert Film Handler

Posts: 146
From: Frederick, MD, USA
Registered: Sep 2000

posted 03-07-2002 09:51 PM

Manny,
Try calibrating your AW3s using Brad's instructions on the Tips page - "Christie AW3 Platter Tweeking". I've not tried this personally, but others here have with great success.

Steven Gorsky

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 03-07-2002 11:18 PM

Manny,

Your AW3s have "U" shaped legs, not "V" shaped legs, don't they?

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

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

posted 03-08-2002 01:18 AM

I just saw those tips and I'll try that method tomorrow (Friday).

Actually, Brad...the legs on these units are V-shaped.

I'm curious about the difference...did they change on the inside, too?

...And, while we're at it, how do I replace the lower nutsert on the slide bar? I have a couple where they've gone missing or snapped loose due to overtightening (there's been a LOT of overtightening here). The problem is access to the interior of the tree...am I going to have to break the rivets on that panel near the bottom motor?

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And, hey! Let's be careful out there.

~Manny.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 03-08-2002 03:51 AM

Interesting. I asked because I've never seen the older platters with the U shaped legs takeup tight to any degree, but have not had a problem with any of the later production units with the V legs. You can remove the entire takeup arm assembly with 4 bolts on the side of each arm and install a new spring from Christie, or play with some springs from your local hardware store. Just remember there is such a thing as "too tight". Don't go overboard. Just tight enough to take up smoothly and snug.

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