Grundner Shutter Repair/Servicing

[Steven Tribe]

Also known as the "Eye lid" or "Silent" Studio shutter.
I have two of these which came built into Studio cameras.
All the Studio cameras I have seen in Denmark and Sweden have either the Grundner or the lokal NORKA (like a double door Guerry - but designed to fit behind the lens board).
One is not working, although the bellows eye-lids are undamaged.
I have no idea of what is inside the activating metal cylinder but it is held together by just two screws. I don't have access to X-ray equipment.
I will be working on this the coming week. If anyone has either a cross section drawing - or better still, real live experience - please post.
In lieu of this, I'll post my discoveries, good or bad as work progresses (or is abandoned)!

[Steven Tribe]

A very easy design.
The Pneumatic and mechanical parts are completely separate.
The two singe screws on either side allow the separation of the container with rubber expansion bellows.
The mechanical unit looks and works like a doll's house kitchen scales!
Finger pressure on the scale reveals that this section is OK. Fortunately, as it partly assembled with solder rather than screws and nuts.
Once more, the problem is a solidified rubber non-expanding and leaky bellows.
The cylinder form means that this requires a similar custom-made rubber part.
There will go some time before the next post!

[Jim C.]

Steven, you have the most awesome collections of shutters !

When you say that the mechanical portion works like a scale I assume that
the disc teeter totters so the 'lids' of the shutter don't open evenly ?

[Steven Tribe]

The platform is held in a central piston type arrangement.
There are obviously a few links and axles that need a touch of oil after 100 years. Each "eye-lid" has its own mechanism and separate axle torsion springs.
The photos show closed, haf open and almost fully open. Sorry about the grimey fingers - have manhandling spruce branches to-day!

[Jim C.]

I see, the lids seem to pen pretty evenly, thanks for posting pictures of how the mechanism work.

[Steven Tribe]

I have been looking at the bellows construction. It is quite obvious that this is not a replicatable item. It is also made from two pieces which have been vulcanised together.
A replacement has to be compressible to 1cm without placing too much strain of the springs and must expand to 2.5cm to fully open the eye-lids.
Last night I experimented with cut bicycle inner tubes, metal washers and forming through oven heat and I think I have found a method that will produce air tight/reliable bellows which will fill the requirements of 1 - 2.5cm movement.
I have also discovered that the rubber bellows on the Grundner is the same as that used on the Norka (that means at least two other LF members!).

[Asher Kelman]

Steven,

This is wonderful and nurturing work! What's the diameter of the aperture of the shutter? Do you have a picture?

Asher

[Steven Tribe]

The Grundner was made in 8, 9, 10, 12, 14 and 16cm opening versions. I have the 14 and the 12cm versions.
The front mounted Guerry covered lens diameters of 53-108cm, 112-130cm and 135-145cm. The earlier range must have more extensive as I have Guerrys that manage 40-50cm and 150-175cm (yes 7"!).

[E. von Hoegh]

McMaster-Carr has a variety of bellows for machines and machine tools.

http://www.mcmaster.com/#universal-j...ellows/=f1ndkk

If you enter "bellows" in the search box, you get the whole listing. Hope this helps.

[Steven Tribe]

They have the right form and dimensions. But I doubt something made of "rigid neoprene" will compress easily to a 1cm length. I have messed around with these when fixing my front wheel drives.