Contax II (1939) – Film Winder Fork Slipping / Clutch Issue?

[desmo]

Hi everyone,

I’ve got a 1939 Contax II that just came back from a CLA. Mechanically it feels smooth, but I’m having trouble with the film winding mechanism. Specifically, the forked drive that engages with the take-up spool seems to slip. When I turn the film wind knob, the fork doesn’t always rotate—it’s like there's no solid connection between the knob and the fork. I can hold the fork with light pressure and it won't move even when the winder knob is turned.

From what I understand, there’s a clutch mechanism between the winding knob and the fork drive shaft. On my camera, it seems like that clutch is slipping or not engaging properly. Sometimes it catches and moves the fork, but often it doesn’t. As a result, the film won’t advance reliably.

Has anyone run into this before? Is this a known issue with the Contax II, and is there a way to re-seat or adjust the clutch? I’d love to hear from anyone who's dealt with this or has experience opening up this part of the camera.

Thanks in advance!

Mark

 

[Coldkennels]

I don't have an answer/solution, but I do know my Contax II does exactly the same thing. I've had so many issues with film transport on it that I've not used it now for almost three years. I think at its worst I shot 30 exposures on the same 10cm length of film!

 

[popavvakum]

According to the repair manual for Kiev which is an exact copy of this Contax model, the friction moment (torque) turning the fork should be 215 plus or minus 25 g.cm. If you wind the film while holding the fork you should be able to stop it from turning if you apply this torque. Interframe spacing depends on it and your repairman should have adjusted it to this specific value. I would suggest that you check that there are fiber friction washers between the spring and the fork and between the fork and the slotted screw holding it.

 

[boojum]

Sounds like another trip to the repair shop. Oleg. He did a great job on mine which did not work at all when I got it.

 

[Valkir1987]

The friction can be increased by adding shimms underneath the screw of the fork. The spool is there to take up film, transport is done by the gear with the sprockets. Test the transport first with a dummy film. I’ve had cameras with a very low friction on the take up spool (Yashica) and their transport was just fine.

 

[Valkir1987]

(Just a second note: the post war take up spools for the Contax S and Pentacon F do not work in the Contax. The height of the spool does not match the alignment of the film gate. )

 

[Coldkennels]

Frustratingly, I've dry-fired entire rolls of film through this Contax successfully (holding the shutter open at B and marking the extent of the frame with a sharpie to check film positioning with each advance). Just when I think it's working properly, I load it up and take it out, and it never gets through a full roll without the sprockets tearing through the sprocket holes (or just letting the film slip off the sprockets somehow), resulting in the film getting stuck and never advancing.

I actually bought two original Zeiss cassettes, thinking the reduction in friction at the cassette side (which is very noticeable - labyrinthine FILCA or IXMOO cassettes even make a Leica feel a lot smoother!) would help. Sadly not. Maybe I'll add a couple more shims under that fork - what's the recommended material to increase the friction? Felt?

I do question the sanity of the entire Contax/Kiev film transport mechanism. It seems like it's nothing but problems; the only camera I can think of with a film transport mechanism that's even more problematic is the Pentacon Six.

 

[TenEleven]

I never had problems on my Contax II's some of which I completely stripped down. I did not do anything special to the wind/rewind section and yet the spacing is perfect and even - just like on my M2. The Contax II metes out the film like every other 35mm camera on earth, via the sprocket drum, which turns the same amounts of revolutions for each wind. The one thing that is user adjustable and could have an effect is the wind stop and the shutter release have to be timed to coincide perfectly and the swing arm should not be sticky so that it clears the rotating drum perfectly.

That all said I am almost 100% certain that adding more friction to the take-up side will not solve your problems. If anything you will make matters worse, also the camera will feel terrible to use. The take-up fork on my Contax II's stops very easily - my pinky is enough to arrest it. And still my frame-spacing is perfect and has been for close to a 1000 of roll through various Contax II.

There are however a couple of things, some are not unique to the Contax II that could foul up the spacing:

• The film has to sit at the correct height. This is the big one.
  Pre-war film cartridges ones were 1-2mm taller. This happens on a pre-war Barnack, too. Modern cartridges are shorter, this causes the film to run at a slight angle when using a pre-war take-up spool. At best this means the picture is slanting downwards but depending on factors such as the humidity and angle of the slant the wind can also foul up completely, if it's not running straight through. It makes the wind feel heavy and grindy because you are twisting the film against sprocket drum as you wind.
  
  The answer to this is to add home-made shims underneath both the take-up spool and cartrige until they sit at the correct height. This has the benefit of also making the wind feel lighter because you are no longer twisting the film.If you look through the front of the camera at "B" you should NOT be able to see even the slightest sliver of the sprockets. If you do the film is sitting much too low.
• The rewind knob has to be smooth running with minimal friction. If there's grit or anything under the rewind knob this can cause irregularities but it should (normally!) not be enough to cause overlap or other sever issues.
• The sprocket drum has to be screwed down tight. During repair there is a screw (accessible through a hole through which the rewind button of the back cover pokes) that you need to slacken to allow the sprocket drum to move up and down in order to remove the backplate of the shutter. If one forgot to tighten that screw after reassembly I reckon that it would cause issues akin to the film sitting too low as the teeth will no longer engage with the sprocket holes properly.
• This was not even on a Contax II but a Nikon F - with very curly film I got lazy and did not wind the film back to be tight during loading. Apparently the coiled up film pushed against the sprocket drum causing irregular frame spacing. Partway through the roll as part of investigating the grindy noises I wound the film back and from that point on the noises disppeared and spacing became regular.

 

[popavvakum]

Frustratingly, I've dry-fired entire rolls of film through this Contax successfully (holding the shutter open at B and marking the extent of the frame with a sharpie to check film positioning with each advance). Just when I think it's working properly, I load it up and take it out, and it never gets through a full roll without the sprockets tearing through the sprocket holes (or just letting the film slip off the sprockets somehow), resulting in the film getting stuck and never advancing.

I actually bought two original Zeiss cassettes, thinking the reduction in friction at the cassette side (which is very noticeable - labyrinthine FILCA or IXMOO cassettes even make a Leica feel a lot smoother!) would help. Sadly not. Maybe I'll add a couple more shims under that fork - what's the recommended material to increase the friction? Felt?

I do question the sanity of the entire Contax/Kiev film transport mechanism. It seems like it's nothing but problems; the only camera I can think of with a film transport mechanism that's even more problematic is the Pentacon Six.

The spacing depends on friction in both take-up and film spools. If the latter is too large the spacing will be too large; if it is too large and the former is too small then the sprocket will tear the film perforation. The screws on both (or take-up fork screw and film spool fork on the non-metered cameras) should be tight but not too over-tight. The washers/shims were originally made of some fibery stuff but I found that ( I cannot recall correctly) M2 or M3 washers could do. A couple of them with a vanishing (not visible!) amount of lubricant. The thing to look for is that on the take-up spool the spring enters into the flange tube completely - it is fiddly to push it in and fix the screw at the same time. Curved fine tweezers and a fine screwdriver help but do not overtighten. The torque on the film spool should be 85 plus or minus 15 g.cm according to the same Kiev repair manual. Once these are set correctly, winding is a bit smoother and the spacing is perfect.

 

[Coldkennels]

There are however a couple of things, some are not unique to the Contax II that could foul up the spacing:

• The film has to sit at the correct height. This is the big one. Pre-war film cartridges ones were 1-2mm taller. This happens on a pre-war Barnack, too.

This is another reason I picked up some original Zeiss cassettes; I was familiar with this issue on early Barnacks, so bought loads of FILCAs and a couple of IXMOOs to use with them, and it's a much better arrangement than trying to shim a regular cassette to fit. Still, it doesn't matter if I use the Zeiss cassettes or carefully-shimmed modern ones - same problem.

• The rewind knob has to be smooth running with minimal friction. If there's grit or anything under the rewind knob this can cause irregularities but it should (normally!) not be enough to cause overlap or other sever issues.

This was my first port of call. I had frame spacing issues on a Kiev years back and remembered that both ends of the film transport can cause problems, so I made sure this was running as smoothly as possible. No fix.

• The sprocket drum has to be screwed down tight. During repair there is a screw (accessible through a hole through which the rewind button of the back cover pokes) that you need to slacken to allow the sprocket drum to move up and down in order to remove the backplate of the shutter. If one forgot to tighten that screw after reassembly I reckon that it would cause issues akin to the film sitting too low as the teeth will no longer engage with the sprocket holes properly.

This is the one thing I didn't consider. However, I've just checked it and it's nice and tight.

• This was not even on a Contax II but a Nikon F - with very curly film I got lazy and did not wind the film back to be tight during loading. Apparently the coiled up film pushed against the sprocket drum causing irregular frame spacing.

I've tried this one, too. I've tried keeping it as slack as possible and as tight as possible, and neither seem to do the trick.

Incidentally, I always suspected that part of the problem was how limply the take up spool is held by the fork - hence why I picked up two Zeiss cassettes. I thought a more solid setup on the take up end would help with tension, but apparently not.

The torque on the film spool should be 85 plus or minus 15 g.cm according to the same Kiev repair manual. Once these are set correctly, winding is a bit smoother and the spacing is perfect.

How are you measuring that torque? This isn't something I'm familiar with.

 

[popavvakum]

This is another reason I picked up some original Zeiss cassettes; I was familiar with this issue on early Barnacks, so bought loads of FILCAs and a couple of IXMOOs to use with them, and it's a much better arrangement than trying to shim a regular cassette to fit. Still, it doesn't matter if I use the Zeiss cassettes or carefully-shimmed modern ones - same problem.


This was my first port of call. I had frame spacing issues on a Kiev years back and remembered that both ends of the film transport can cause problems, so I made sure this was running as smoothly as possible. No fix.


This is the one thing I didn't consider. However, I've just checked it and it's nice and tight.


I've tried this one, too. I've tried keeping it as slack as possible and as tight as possible, and neither seem to do the trick.

Incidentally, I always suspected that part of the problem was how limply the take up spool is held by the fork - hence why I picked up two Zeiss cassettes. I thought a more solid setup on the take up end would help with tension, but apparently not.



How are you measuring that torque? This isn't something I'm familiar with.

85 g.cm is basically 8.5g weight sat on one end of 10cm lever (stick) turning the other end of that stick. Being a peasant, I use two 2p coins on a 10 cm cut of a bamboo small stick - and adjust the friction so that it just turns the film fork - it is a slightly larger torque but roughly does the trick. For the take-up spool I use 4 coins on another small stick of the same length. The sticks should be horizontal so all the weight tries to turn the forks. I hope this does make sense....

 

[Coldkennels]

I kinda get the idea @popavvakum, but how are you actually applying that force? Surely it'd require gravity alone to make sure you were getting a semi-accurate amount of torque - are you resting the camera on its front and positioning the fork so you can just rest the stick into it, with the small stack of coins hanging in the air?

 

[Valkir1987]

When I turn the film wind knob, the fork doesn’t always rotate—it’s like there's no solid connection between the knob and the fork.

I was reading too quick and missed this sentence. The fork should always turn when you turn the advance knob.
If the fork is not screwed on properly or the shutter is not positioned properly in the housing, the winding mechanism will not work. I mentioned the Contax S and Pentacon F take up spools, the same applies to the Contax IIa and IIIa spools. They also don't fit properly in the II and III. Post war Exakta spools however, do fit.

 

[popavvakum]

I kinda get the idea @popavvakum, but how are you actually applying that force? Surely it'd require gravity alone to make sure you were getting a semi-accurate amount of torque - are you resting the camera on its front and positioning the fork so you can just rest the stick into it, with the small stack of coins hanging in the air?

This is correct - with the camera flat on its front (I take the lens out obviously just in case....), just putting one end of the stick between the two prongs of the fork and leave dangling the coins attached with scotch to the other end to turn the fork. Actually, you need about a centimeter to hold between the prongs and the coins are not exactly at the end so with two coins you have larger weight but smaller lever, so it comes just under 100g.cm. With four it is about 200g.cm. With this method I got the interframe spacing about 1mm. Notice that, ideally, in the take-up spool there are two shims/washers between the spring and the fork and between the spring and the flange tube. Tightening the screw should still leave those sliding against each other so a minute amount of lubricant decrease the friction. If you have only one shim then it has to turn rubbing both surfaces and the friction is increased. In that case you rely on how tight is your screw; and in my experience it will try and loosen itself with use. When it will become loose, then the sprockets will tear the perforation at the end of film. I shall try and scan the diagram explaining all this.

Actually, the Contax inventor mastered the friction to a superhuman degree: not only the film advance depends on it but so do the slow speeds and the correct movement of the two curtains relative to each other. It is amazing.

 

[popavvakum]

This is a schematics of take-up spool. The pairs of washers/shims are shown as 10/9 and 7/6. Notice that the fork is 3 and the spring is 11.