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Camera / Mag issue? Film lets go in the middle


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#1 Jay Young

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Posted 11 October 2016 - 05:20 PM

Twice now over two weeks I have went into the changing bag only to find about an inch of tightly wound film on the core on the takeup side of the mag, and about 300 more feet of floppy mess.  Its as if the core stopped spinning and the camera pushed the rest of the film through into the mag... If the core is locked with the pin, I don't see how that can happen. 

 

When I watch the camera, running an entire roll of 400' through it works every time.  But for some reason, starting and stopping like normal, with takes ranging in the 50 - 90 foot realm I get a floppy pancake.  Has anyone else ever experienced this problem?  

 

It doesn't seem to do it every time, and I'm forced to wind it back onto the core by hand otherwise it wont fit in the black bag.  

 

I'm sure the lab loves me.  HA!

 

 


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#2 Dom Jaeger

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Posted 11 October 2016 - 06:40 PM

Hi Jay,

Well my first thought is either the take-up tension is too loose and the spindle slips way too easily or when you close the door it's somehow fouling on the take-up spindle, core or film itself. Since it seems fine with the door open, maybe it's the latter. Could be a combination. Is it just the one mag?

Is it a CP-16? I'm not very familiar with those, and can't remember what the inside of the mag looks like exactly, but check that nothing is protruding too high, the core is properly seated and locked to the spindle, and the film isn't coning as it winds on. Any scrape marks on the inside of the door?

The take-up tension should be strong enough so that when the camera is running it takes a firm grip on an empty take-up core to stop it spinning. Check that the drive belt hasn't stretched and is slipping too easily.
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#3 Gregg MacPherson

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Posted 11 October 2016 - 06:41 PM

If you tell what camera this is and take a photo of the whole roll on the take up side (use an old scratch test roll) the camera techs can probably see for sure.  Can't be the fixing to the core,  as you have about 100' tight on there.  Take up belt or friction clutch behaving badly..? 


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#4 Gregg MacPherson

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Posted 11 October 2016 - 10:38 PM

sorry,  didn't see Dom's post, sent while I was writing mine...


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#5 Tyler Purcell

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Posted 12 October 2016 - 02:25 AM

Hey Jay, sounds like your take up speed has slowed. This is quite a common issue with the CP-16, I've had it happen before on me. I always checked the magazine take up from the outside by turning the take up cam before shooting. I just found as the stress on the pickup side gets greater, the system starts to slip. I don't recall if it's direct drive (the belt being the only "slip" mechanism) or if there is another slip device in the magazine itself like MOST mags have.

It could also be some of the fabric in the magazine putting a tiny bit of pressure on the spindle and the drive system can't push through it.
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#6 Jay Young

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Posted 12 October 2016 - 05:24 AM

Yes, its the CP-16.  The SR is fine, and it doesn't happen every time. 

 

The take-up belt is new, and when engaged is at least strong enough to keep me from moving the core by hand.

 

The inside of the magazine has a single guide roller and the spindle.  Black velvet (or some have been replaced with corduroy?) lines both sides.  There seems to be at least a 2mm clearance from the back of the core to the actual fabric material however I notice sometimes the film wants to bottom out and wrap itself around the core while touching the side of the mag.

 

The doors don't have any signs of wear, and the back of the mags seem to also not show much sign of wear.  Maybe I should try loading the mag upright instead of laying it down.

 

These magazines are basically the standard Mitchell magazine except with doors instead of screw on covers.  


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#7 Tyler Purcell

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Posted 12 October 2016 - 12:21 PM

When the take up gets more full, there are a lot more stresses on the drive system. The only logical thing is that the drive isn't strong enough to break through any "stiction" that's happening.
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#8 Gregg MacPherson

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Posted 12 October 2016 - 03:39 PM

Jay,

Is the problem with one particular mag?

Is the takeup spindle loose,  with some wear?  Does it feel lubricated and smooth when you push the tip of the spindle to the side while turning it with your fingers?


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