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Hollenbj
Tinkerer
Username: Hollenbj
Post Number: 25
Registered: 03-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 22, 2012 - 11:46 am: | 
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I have a Canon IIF with a film advance knob that will turn backward. It should only turn forward (advance film).
I opened the camera and checked the area where there would be a spring actuated dog on a Leica IIIf or a Fed3(top of shaft, under top plate), but there is no dog or place where such a dog would reside. There is only a coil spring surrounding the film advance shaft and a notched collar that spins freely on the shaft.
I'm stumped. I have no idea how this setup would keep the shaft (knob) from turning backward. Does anyone here know how this works? I shouldn't be missing parts, the camera has never been entered before. This camera is supposed to be heavily based on early Leica (IID to IIIa) and I've never been in one of those either (yet).
Some direction would be very much appreciated!
Thanks. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1203
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 22, 2012 - 12:43 pm: |
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I haven't disassembled this particular spot on the Canon, but the device you describe is very common and much cheaper than the dog-and-gear approach: The spring is wrapped tightly around the shaft, and anchored to the chassis at one end. When you rotate the shaft in one direction, the shaft tends to "unwind" the spring, and it turns freely. Try to rotate the shaft the other way and it wraps the spring tighter, and the shaft will not turn.
Here's a pic of a repair on this type of clutch on a Vokar, where the spring had broken off at the anchor and I wasn't equipped to wind a replacement spring for it:
http://www.flickr.com/photos/26262745@N08/4799936709/in/set-72157622552007096/
(cut & paste this URL, the hyperlink didn't take) |
Hollenbj
Tinkerer
Username: Hollenbj
Post Number: 26
Registered: 03-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, April 22, 2012 - 12:58 pm: |
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Thanks Rick,
Well, I figured it must be a clutch-type mechanism, but I still can't seem to get how this particular one should work. My spring is still attached to its anchor, I guess that's good.
I'm going to look at this again tonight, maybe I'll post some pics and someone will recognize the configuration. I have CLAd the remainder of this camera and its working well. I'm ready to run some film though it but first need to fix this advance issue.
Thanks again, Rick, for your help.
j. |
Thepurush
Tinkerer
Username: Thepurush
Post Number: 35
Registered: 01-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 25, 2012 - 08:58 am: |
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What i say might look silly but i hvnt really understood the problem I believe.
The problem posted could be interpreted in two ways. Pressuming by advance knob umean film takeup spool.
1. The spool isnt supposed to move only in one direction but it also rotates in other direction.
2. The spool rotates back ward according to you.
I cant imagine how the takeupspool can rotate in oppoiste direction. But it is worth mentioning here that in some cameras it rotates from left to right and in some the opposite. So it cd be just your interpretation of the right direction.
Loading procedure depends on which direction the spool rotates. There is nothing like standard direction among all cameras.
I believe (may be silly) ther is no problem at all with spool. Please let me know if I am right or if I am wrong too. |
Hollenbj
Tinkerer
Username: Hollenbj
Post Number: 30
Registered: 03-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 25, 2012 - 10:36 am: |
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Thepurush,
Thanks for your help.
I am indeed talking about the film take up. On this particular camera, the knob will wind film on the take up and pull the shutter into cocked position, but I can also turn the knob the opposite direction and "unwind" film and the curtains will go back to their uncocked position. This is not supposed to happen and all my other Leica clones (and more) have a mechanism to prevent that. Rick (on this forum) suggested it was a pawl mechanism, as found in the IIIf (and I see in my Fed3 too), but the Canon IIF was based heavily on the IIIa, which doesn't seem to have a pawl. The mechanism I'm struggling with is a spring wrapped around the film advance shaft that somehow tightens and prevents the knob from turning when it is turned in the wrong direction. That same spring will slacken and allow the knob to turn when turned in the correct direction. It's almost the identical mechanism on my Zorki C. I haven't looked at the other clones to see who has a pawl and who doesn't, but either way, what I need to figure out is the exact way my current set of parts should be installed to achieve the clutch effect. And of course, I have no idea how it was "broken" in the first place. The person I bought this camera from said it "takes great pictures". They all say that, but 9 out of 10 cameras I receive are broken in some way.
If anyone has a photo or drawing or parts diagram of an early Canon rangefinder film advance/take up assembly, I would dearly love to view it. I think I have all the correct pieces, just need to see how that spring and collar are supposed to be positioned.
Thanks again for all your help.
jeff. |
Brcamera
Tinkerer
Username: Brcamera
Post Number: 171
Registered: 08-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 25, 2012 - 12:56 pm: |
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As mentioned in the posts, the early Canon rangefinder cameras have fairly primitive but usable clutches. I have attached a photo showing the spring and spacer installed on a Leica IIIa shaft which is pretty much an identical copy of the Canon with a little different threading for the knob.
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Hollenbj
Tinkerer
Username: Hollenbj
Post Number: 33
Registered: 03-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 25, 2012 - 03:19 pm: |
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Brcamera,
That's it! I can see exactly what I needed to know. Tonight I'll get this gem back together.
Thank you, thank you, thank you!
jeff. |
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