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FED 1 shutter not capping
Old 07-10-2011   #1
Nomad Z
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FED 1 shutter not capping

Just as I was about to go out and try my FED 1 after replacing the lens mount and making some other changes, I noticed that the shutter isn't capped while it's being wound on. The gap is 1mm or so wide. I've got the body shell off and have had a good look around, but can't see anything that looks like an adjustment for the gap between the laths. Is there any adjustment? If not, then is this all set up when the curtains and ribbons are glued to their respective drums?

I speculate on the latter because one thing I haven't mentioned in my FED reports so far was that the second curtain seemed to be peeling off the drum - a few millimeters kept trying to lift, revealing what appeared to be a tacky white adhesive on the curtain. I could push it down with my finger, it would stick, but if I left the camera for a while with the shutter uncocked, the end of the curtain would have lifted again. I fixed this with a couple of tiny spots of rubber solution glue (Copydex in the UK), and the lifting hasn't happened since.

What I"m thinking is that the adhesive on the curtain was weak, and if the same adhesive was used on the ribbons that go around the drum, perhaps these have slipped. Thinking back to when I first got the camera, I'm sure the capping was okay - no fogging across the frame on the two rolls I put through it.

Is my thinking correct that the gap/capping is set during assembly of the shutter curtains on the drums? If there is no adjustment, does that mean that my thoery that the ribbons for the first curtain have slipped is on the right track? If it's not adjustable, does the shutter assembly need to be dismantled and the ribbons reglued or replaced?
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Old 07-10-2011   #2
wolves3012
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Unfortunately, I can only confirm what you thought. The gap (actually, NO gap - overlap when winding on) is determined by the positioning of the curtains and ribbons on the drum side of the shutter. In addition, the exposure time is also dependent on it, since the exposure slit-width IS the gap. This becomes increasingly important as the exposure time is shortened (i.e. towards 1/500th).
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Old 07-11-2011   #3
Nomad Z
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I'm a little surprised it isn't adjustable - seems a bit odd for the exposure timing to depend on glueing something correctly when it isn't even in the camera. Maybe they used assembly jigs during manufacture.
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Old 07-11-2011   #4
acheyj
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Thinking about this, occurs to me not only the gap but the speed of travel also controls the exposure time. So spring tension as well as gap width will determine exposure time hence the method for adjustment.
Im no expert so if I got it wrong please correct me .

ron
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Old 07-12-2011   #5
Nomad Z
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It will be dependent on the speed of travel as well, but the critical part is the width of the gap at 1/500. At that end, a small error in the gap width, like 1mm, can constitute a big change in terms of exposure. I don't know what the gap is at 1/500, but if the error resulted in a doubling of exposure at that speed, then the curtains would have to move twice as fast to compensate, and that might cause undue wear, or even be hard to acheive. An error the other way could result in a narrow gap, requiring the tension to be reduced, again, possibly by too much. It seems to me that there's a balance to aim for between gap size and a sensible curtain tension.
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Old 07-12-2011   #6
wolves3012
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Nomad you have it about right. The travel speed and gap determine exposure. BUT...the curtain speed is not adjustable anywhere near as much as you may think.

If the camera is clean and properly lubricated, there is very little change to curtain speed from large changes in tension. The shutter really wants to run at about 1/30th and requires extreme adjustments not to, so much so that it will cause other serious problems, like capping or failing to close.

What this means is that, in a practical sense, the exposure is adjustable only by setting the curtains correctly and hence achieving a certain gap. After I replaced the curtains on my NKVD and did a CLA, I tried to mis-adjust the tensions on purpose to see what it caused. What I found was that the shutter ran properly or had real problems, there really was no in-between.
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Old 07-12-2011   #7
Nomad Z
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Thanks for clarifying, Wolves. I think I'll be having a very close look at the drum mechanism when it comes out - I'm harbouring thoughts of making some new parts for it. Anyway, I think I need to do some research into how the shutter cage comes apart.
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Old 07-16-2011   #8
wolves3012
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Nomad, I'd recommend you to study Jay Javier's excellent site, it should cover all you need to know. Jay is "Zorkikat" on here.

http://jay.fedka.com/
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Old 07-17-2011   #9
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Took the shutter cage off tonight, and took the drums and curtains out. The adhesive does not look very good. It's a white substance with a slightly rubbery consistency, and seems to be the sticky bit of some sort of double-sided tape. The curtain on the drum had peeled away on the 'curtain side', and the adhesive had come clean off its thin plastic substrate for 15-20mm. It seems to me that this adhesive is not doing a very good job.

The ribbons at the drum end look to have migrated around the drums - there is some white ahesive showing on the metal reels. At first, I had thought that this was an applied adhesive, and that it had been applied beyond the positions for the ends of the ribbons. However, there is substrate under the ribbons as well, indicating that this is also the double sided tape. I would have thought the tape would simply be applied and would stay where it was put - no need to brush or spread adhesive past the start point. Since there is exposed adhesive beyond the tape, I'm pretty convinced that the ribbons have migrated. There are also some red marks in ink a few millimeters from the ends of the ribbons. Whether these indicate the positions of a set of ribbons that worked correctly, I can't say, but they do look like they'd be better start points for the current ribbons - setting them to these marks should close the uncapped shutter. I scribed the positions of the ribbon and curtain ends and the red marks onto the drum and the ribbon reels.

I had a general look over the parts, and I have to say that there wasn't much cleaning in the CLA that it was given. There is a fair amount of old adhesive on the drum (hard stuff, like old Araldite). I took the ribbon reels off the drum, and found that all of these parts were rather dirty - a mix of oil and fine detritus. It's the same with the gears and other mechanical parts - they all look wetted with lubricant, but there's muck in amongst it. I also found that the two screws that hold the reels onto the shaft were loose.

I decided to do no more for now. All the bits are carefully stored in a box, and I'll chip away at it as and when I feel like it. Now that I've got the drum out, I can have a good look at this, and the reels for the ribbons, and see if I can come up with a way to make an adjustable version of the reels. Failing that, I might see if I can come up with suitable numbers to make a curtain fitting jig.

One thing I noticed was the shape of the hole in the end of the drum that the coupling pin from the shutter speed mech engages with. On this site...

http://jay.fedka.com/index_files/Page477.htm

...which shows the equivalent parts from a Zorki 1, the hole is round. In my FED, the hole is a slot. I'm not sure what difference that would make, or even if it's supposed to be like that. It does look to have been fabricated as a slot - there is no sign of build up at the ends, as if the pin has been banging into it, and the ends aren't round, but are squarish with small radii at the corners.

Last edited by Nomad Z : 07-17-2011 at 16:13.
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Old 07-20-2011   #10
fidget
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Good luck with the repair. When I replaced curtains for new ready-made versions, I was lucky to have the old curtains in place on their drums (as they had holes). I made a jig (and posted here about it ) from balsa wood based on those that I took off, then glued the new curtains on the drums whilst fitted in the jig. The first set I did still ended a half mm out at one side. This looks obvious when winding on the cam.
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