Contax I ribbons

[Dralowid]

My first boss told me that trying to teach me was like talking to a brick wall....

Many thanks to you both. I reckon I understand...ish.

In order:
1) Sew ribbons on to rollers
2) Accurately measure ribbons from roller to the attachement point on the upper or second curtain and mark. (This measurement taken from old ribbon)
3) Roll slack onto rollers
4) Feed up through 'sliding buckles'
5) Sew onto upper or second curtain

Michael

 

[Erik van Straten]

Yes, that is the theory. Now the practice.

Erik.

 

[Dralowid]

Nothing can possibly go wrong...ever!

 

[Erik van Straten]

We will see ...

Erik.

 

[Dralowid]

Ribbon arrived very quickly. Seems thin but I am no judge of ribbon. Shame it is black, makes it difficult to see what you are doing but no matter.

First pic, threaded through a roller. If you can find a stainless steel cable tie that is 3mm wide to help push it through life becomes a lot easier.

IMG_2805 by dralowid, on Flickr

Second pic, both rollers

IMG_2806 by dralowid, on Flickr

Third pic, ribbon sewn and wound round both rollers, fed through sliding buckle with no roller tension. Grey dots mark the 100mm length to match previous ribbons. Next job is to fold over at the mark and sew (with a tiny drop of glue).

IMG_2807 by dralowid, on Flickr

Problems? Apart from threading the ribbon through the rollers the other problem is that my sewing at the rollers has left a bump. Hoping it will be OK.

 

[Erik van Straten]

the other problem is that my sewing at the rollers has left a bump. Hoping it will be OK.

It is better to have the bump on the back of the curtain (towards the front of the camera) and press it flat with pliers. There they do less harm.

Great work, Michael! Looks fine.

Erik.

 

[Erik van Straten]

the other problem is that my sewing at the rollers has left a bump. Hoping it will be OK.

At re-reading I understand that your problem is the bumps at the rollers. I was thinking you ment the bumps from the sewing at the second curtain. At the rollers too it helps when you press the bump with pliers to make it as small and flat as possible.

Erik.

 

[Highway 61]

Apart from threading the ribbon through the rollers the other problem is that my sewing at the rollers has left a bump. Hoping it will be OK.

If the rollers caps are the same as the Contax II ones, they can be removed (too very small screws), so that fitting the ribbon ends through the rollers clutches is a breeze... and it makes things easier not to leave a bump at the sewing point.

I'm afraid you'll have to re-do the sewing - the bump will be a major problem.

Getting a sewing bump or not getting any depends on at which distance of the roller edge you are doing the sewing. If the sewing is too close to the roller edge : sewing bump.

If you leave a few millimeters between the sewing point and the roller edge, so that the ribbon can "naturally" make a loop : no sewing bump.

This is of course my own experience on several Contax II shutters.

 

[Erik van Straten]

If the rollers caps are the same as the Contax II ones, they can be removed (too very small screws), so that fitting the ribbon ends through the rollers clutches is a breeze...

Yes, they have these small screws, but I did not know they could be removed. So you can tension them separate from the first curtain? Makes things very complicated!

Erik.

 

[Highway 61]

Yes, they have these small screws, but I did not know they could be removed. So you can tension them separate from the first curtain? Makes things very complicated!

Erik.

You remove the rollers caps to very easily fit the folded ribbons ends around what then becomes a basic open lip, you sew, you put the rollers caps back on with the ribbons in place, and you're done. You haven't to do anything to the rollers springs !

Doing this, you don't have to hardly fit the ribbons ends through the tiny gap between the rollers caps and the rollers springs at the risk of making the ribbons ends fray or damaging the rollers springs.

And it makes things much much much easier to get ribbons being of the perfect length, because you sew at the rollers while easily maintaining the ribbons folded when they ought to be, without seeing your sewing job alterating the ribbons length.

 

[Erik van Straten]

Oh, I see. Well, I did not have much difficulty in getting the Aki Asahi ribbon in the slit (beginning from the big gap, other ribbons can be harder to get them in). When you remove these tiny screws, there is a risk of loosing them.

Erik.

 

[Highway 61]

"Zero risk" isn't any human thing... 😉

Here is a pic of how looks some rollers sewings which I did using some acetate 3mm ribbon having the same thickness as the original Zeiss ribbon.

Not wanting to damage the shutter curtains blades while sewing I even slided the whole first curtain off the main drum (very easy, you just have to unglue the leather brake pad, which is a good opportunity to replace it if the leather is deteriorated, which is quite frequent).

 

[Erik van Straten]

I even slided the whole first curtain off the main drum (very easy, you just have to unglue the leather brake pad, which is a good opportunity to replace it if the leather is deteriorated, which is quite frequent).

Yes, on one of my cameras the curtain came loose; I could push it back into the slit. Now is seems to be OK (for how long I don't know).

In any case, the high speeds (the "sports group" in Zeiss speak) I can not get to work, but the other speeds work fine.

Erik.

 

[Dralowid]

Well we've got to this stage now. The sewing will win no prizes!

IMG_2811 by dralowid, on Flickr

The sewing at this end is clear of the 'sliding buckles'

IMG_2810 by dralowid, on Flickr

I've flattened the bumps at the roller ends and moved them over the larger slots in the roller so we live in hope!

 

[Erik van Straten]

Looks fine, Michael. Good luck.

Erik.

 

[Sarcophilus Harrisii]

Interesting stuff, well done. I had a thought yesterday that had not previously occurred regarding the Aki ribbon thickness and curtain speed. Given that the curtain velocity is going to be the product of the spring tension and drum diameter, presumably the latter will be slightly smaller with the thinner Aki ribbons spooled around them. Trying to get my head around the significance (or lack of) this will have on the faster speeds. Anyone have any thoughts to share?

 

[Erik van Straten]

Given that the curtain velocity is going to be the product of the spring tension and drum diameter, presumably the latter will be slightly smaller with the thinner Aki ribbons spooled around them. Trying to get my head around the significance (or lack of) this will have on the faster speeds. Anyone have any thoughts to share?

When the ribbons are too short, there is the problem that you cannot get the dial on "B". When they are too long, it will be compensated by the tension of the small rollers. In any case I saw no difference between a little too long and far too long, but it is a German camera -"Wir in Deutschland machen alles genau" - so I don't know.

Erik.

 

[oftheherd]

Thanks for the thread. Very informative.

 

[Dralowid]

So now we arrive at the next stage which may take a while.

The shutter is reassembled

B (or in this case Z) can be selected.

When fired both blinds run down without the shutter opening.
The same applies to the other slow 'red' speeds.

The mid range 'white' speeds allow the shutter to move more quickly however the blinds do not open. The escapement can still be heard.

The fast range of speeds are only selectable occasionally and the shutter does not open.

The advance/speed knob may need to be wound past its setting and back when winding on.

Not very easy to describe but it is as if something is 'out'. So I guess I must look for whatever holds back the second blind from moving?

 

[Erik van Straten]

Maybe the curtain gets stuck against the cover. First try to get the shutter running without the cover. Mind you, the shutter will only work well with the cover in place.

Another possibility is that the two curtains are stuck to one another. The second curtain must get in and out the first very easily.

Study everything very close. Don't give up, the problem can be a very small thing that you've overlooked.

How much tension did you put on the spring?

Are you sure the gear is not out of synch? Unlikely when you did not remove the top roller.

Erik.