35MM Cinch marks

[Richie May]

Hey guys,

I searched but couldn't find anything. We run 6000' reels on Kinoton projectors. Floating hubs for take up and regular hubs for feed. We're getting cinch marks on the film. They are ONLY in the first 15 minutes of the 6000' reel. They gradually lessen in those first 15 minutes until they are gone. Nothing for the rest of the reel. First, I checked take up tension figuring it might be a loose wrap and causing it to cinch during rewind on the Kelmar table, since more pull is needed on rewind as the film gets closer to the hub. Made sense since it's only cinching on the first 15 minutes of the movie. Didn't seem to change anything. Before I start adjusting anything else, I figured I'd ask.

[Brad Miller]

Your theory that it may be the clutch tension on the Kelmar being higher than the takeup tension on the Kinoton is certainly solid. Keep in mind as well if your Kelmar feed side shaft is bent a bit, that will exaggerate the effect. Similarly if the clutch holding the feed reel to be rewound has a tight spot every revolution, that will do it too.

Also make sure your floating hub reels actually have a ROUND hub. I've seen more bad Goldberg reels than good ones when it comes to this. They are often out of center, so every revolution exerts more and less pressure which can cause the film to slip on itself and dirt/dust on the print will turn into cinch scratches when the film slips on itself.

Another favorite Goldberg reel defect is when they have egg-shaped hubs where most of the hub is round, but there is a bump in it. The ones they have made in the last 5 years or so are notorious for this and work nicely if the goal is to create cinch scratches.

A quick and dirty way to check the reel is to get a piece of paper with a Sharpie dot in the middle and lay it on the floor below your rewind table motorized shaft (right side). Now start the reel spinning (empty / no film involved) at a slow to medium speed. Then stand right in front of the reel and look straight downward in between the two flanges with one eye and slowly move your head forward/backward/left/right until you get your head in the ideal position so that you can just barely see the dot centered between the reel flanges, and right next to the hub. Does the hub's surface appear to move in relation to the dot in the distance?

If you're running Odyssey or some other film that was shipped on the black plastic FT 6K reels, give those a try on takeup. That will likely resolve the issue since the injection molded hub will always be perfectly round. You don't need to worry about them not being "floating hub" for takeup because they are so lightweight.

[Ryan Gallagher]

I figured Brad would be the first to respond to this one. Excellent advice.

I think the real clue is the "1st 15min of film" comment. With 6000ft reels this implies something near the start of pulling the head off a heads out reel. I would suggest motor ramp timing or rewinding variac habits, but 15min is too long for that kind of damage... almost a whole shipping reel.

It could be while building up onto the 6000ft reels. The tension difference on the bench between a shipping reel as it approaches the core and an almost fully loaded 6000ft reel, it is going to be pretty massive if not mitigated over the course of the build up with a variable tension feed?

If there is no build up process (showing things shipped to you on 6000ft), then I'd speculate reel condition and relative tension issues on the rewind bench, creating a pack that is too loose compared to takeup tension? Or too loose upon takeup relative to rewind tension as you speculated.

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I wasn't chasing cinch scratches in my booth, but I was trying to systematically classify our reel conditions and do a comprehensive tension review of our common reel sizes and rewind situation. My situation may be unique trying to set appropriate tensions around a non-adjustable kelmar reverse motor at the bench.

With a set of those little spring guages and length of leader, I recorded our existing tension conditions on both a full and empty reels, both at projector and on the bench. Checked for bounce, serviced clutches if there was any bounce present.

Because our kelmar bench is a stupid reverse motor one, with Brad's valuable input, all projector tensions had to be adjusted relative to that non-adjustable rewind feed tension, such that the projector takeup was the highest tension in the room (just above the rewind bench in both full and empty conditions, depending on film guague and reel type/size. I make sure to keep our empty reel projector feed tension below the rewind bench minimum seen with a full reel, etc.

The core roundness and shaft straightness was a separate topic. Brad's method for core roundness is a good one, you can also usually tell just by looking without the paper and target when it's really bad. It will be more obvious on an empty reel than a full reel (the film averages the out-of-round aspect over larger and larger radii making it harder to see).

In my case, I like specialty tools, I used a long shafted micrometer and actually quantified our best house reel cores that way, retired many reels. I did some additional work to re-true and re-condition subtly bent shafts at the re-wind bench and projector spindles, but only cause I wasn't getting any traction for replacement part purchases. We also purchased FT 70mm 24" plastic reels to replace our hodge-podge of smaller core 70mm house reels around the same time.

[Ryan Gallagher]

I would add that if the cinching is happening at the bench, you can usually see/hear/feel it happening. It's like a subtle chatter as the outer winds slip/stop/slip as they tighten on each other rather than pay out smoothly. If it is happening on the projector it might be harder to notice it due to noise etc. It's pretty pronounced when happening on small cores of film, such as a trailer on a tiny trailer core... it may be more subtle if occurring at the start of a full 6000ft reel.

What core size are your house reels?... you didn't mention that in the OP. Bigger is better in avoiding cinch scratching.

[Richie May]

Thanks guys. I should have thought of that. We NEVER run 6000' reels here. Looking at them run now on both projectors. Take up reels are definitely not true. Also, our spindles on the rewind bench are indeed bent a little. I'm going to try the plastic reels on take up to test the take up shafts.

[Ryan Gallagher]

Kelmar still sells their stuff, replacement spindles is much easier than trying to re-true them.

If the rewind spindle bends are not compound it is possible though, I used a dial indicator and a bunch of patience with a rubber mallet and a deep well socket/ratchet that fit over the shaft.

probably not as strong as original though, since they had already been bent beyond their spring return once.

[Richie May]

Running with the 6000' plastic reels now on both Kinoton take ups. WOW! My metal reels are TERRIBLE!!!! That was definitely one of the issues, if not the Whole issue. Can't way to see how it rewinds on the bench.

Rewinding now. Spindles are not as bent as I thought on the bench. Still, I'm going to pick up some new ones. Thanks for the help, guys!!!!