PDA

View Full Version : Grundner Shutter Repair/Servicing



Steven Tribe
20-Nov-2011, 15:52
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
21-Nov-2011, 02:51
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.
21-Nov-2011, 06:30
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
21-Nov-2011, 13:44
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.
21-Nov-2011, 18:44
I see, the lids seem to pen pretty evenly, thanks for posting pictures of how the mechanism work.

Steven Tribe
22-Nov-2011, 03:35
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
22-Nov-2011, 06:31
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
22-Nov-2011, 07:31
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
22-Nov-2011, 08:36
McMaster-Carr has a variety of bellows for machines and machine tools.

http://www.mcmaster.com/#universal-joint-bellows/=f1ndkk

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

Steven Tribe
22-Nov-2011, 08:55
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.

Asher Kelman
22-Nov-2011, 09:42
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"!).

That's impressive. So they have one speed? Can that be altered?

Asher

E. von Hoegh
22-Nov-2011, 10:53
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.

There are other bellows available from that source. The U-joint bellows were just an example.

Steven Tribe
22-Nov-2011, 11:23
They open on applied pressure and collapse on release. Best for seconds but can function done to 1/10s of a second.
Will search Mcmaster again.

Jim C.
22-Nov-2011, 14:33
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!).

Unless you've taken the petrified bellows apart, I doubt that it was made in two pieces
I'm 99% sure that it was cast in a 2 piece mold and what you're seeing is the seam line on the outside.
Only way to be positive is to look inside the bellows around the seam area, it's it's smooth
it was cast.

cyberjunkie
23-Nov-2011, 21:07
Will search Mcmaster again.

Keep us informed if you find a viable solution.
I have two of those shutters, and one must be restored.

cheers

CJ

Steven Tribe
24-Nov-2011, 02:53
I did find a more suitable flexible bellows in McMaster. Question is whether these are able to stand up to the pressure and whether the surface will accept bonding. I will procede with the bike inner tube project and report back asap.

Steven Tribe
24-Nov-2011, 09:14
This is the new "expansion unit" placed on top of the mechanism.
The forced streching (and glueing) of the inner tube makes the lateral compression of the rubber tube possible. I have measured the compression required to reduce the length of 3cm down to under 1cm as being around 400grams. This is fortunately not enough to start the opening process.
I have run out of suitable tubing so must wait until tomorrow to finish the job.

Steven Tribe
27-Nov-2011, 03:26
I have completed the drive bellows for the Grundner. I am fairly satisfied with it. The pressure exerted is easily enough to move the 100 years mechanical system everytime. The only doubt question is the glue used to hold the streched inner tube around the end discs. I have used both cycle repair glue (vulcanising fluid) and commercial contact glue. Neither is particular easy to use and with extreme pressure I have been able to break the rubber/zink disk seals. The search is on for a glue (or surface preparation) that can exclude the occasional failure!
Meanwhile I have made another version for a Norka shutter (double barn door type) which has the same basic design. This has thickness of f around 7mm collapsed and nearly 20mm expanded. The photos show the result.
Although it works OK, this is not something I will allow out of the house. I need a more secure bonding - butyl rubber is a notorious surface! If anyone has any good ideas I would be grateful .....?

BrianShaw
3-Dec-2011, 10:43
Steven, I've been intriqued by your FS posting but had no idea what you were talking about until finding this thread of yours. FASCINATING! What are the dimensions of this shutter... and what kind of shutter speed do they deliver?

Also, the type of bellows you describe has been in use by organ builders for centuries, except the material used was thin leather. Two types of bellows are used by organ builders - the hinged kind and these linear-motion bellows.

Steven Tribe
3-Dec-2011, 12:54
The available sizes in 1911 were (diameter) 8, 9, 10, 12, 14 and 16cms.
Speed - perhaps not quite as fast as the Packard. Obviously, most useful in Studio lighting.
I suppose that to compete with Jim Galli and his primitive solution, I will have to make a U Tube demonstration of the Grundner and its silence in operation.
The "commissioned" bellows in post #18 turned out OK after a few days glue hardening and is reported installed and working as it is supposed to do.

cyberjunkie
4-Dec-2011, 12:09
I didn't open mine. I think i'll do it as soon as i'm done with more urgent stuff...
I don't understand if the original bellows inside the "actuator" was linear (i.e. cylinder-shaped) or pleated (like camera bellows). A pleated design would allow for easier extension, but i guess it would take more room when compressed.
BTW, which glue did you use to attach the cycle tube to the metal parts?
I guess that you prepared the parts with little sanding and de-greasing with some solvent, isn't it?
If the cement you used didn't fail under pressure (once completely cured), i think i will copycat your solution :)

well done

have fun

CJ

Steven Tribe
4-Dec-2011, 13:40
You can see the solution in an earlier posting. You have to check the minimum and optimum position of the new bellows to counterbalance the permanent long weak spring (usually in fairly good condition).
Steps are:
1. Cut inner tube to the required length (expanded length plus twice times 1/2" for overlap at the end disks.
2. Cut out two end discs (ca. 30mm in diameter). Drill a hole 1mm wider than the hose you have selected.
3. Make a grove about 5mm from the end of this hose. About 0.5mm deep with a triangular file edge.
4. Mount the two end discs on the cut inner tube. An overlap of a 1/2" should make a stable construction.
5. Heat the rubber/disc assembly in a domestic oven (when you partner is absent as it smells) to about 180 deg C for approximately 15 mins.
6. Allow the turkey - sorry - cylinder to cool before taking it out of the oven.
7. This process collapses and forms the rubber to some extent which allows glueing without the rubber slipping off the discs.
8. Lift the edge and insert contact glue right down to the rim. Place under a 5 kilo weight to maintain pressure for hours. That is, don't rely on the instructions on the tube of glue!
9. Wait 24hours before inserting the rubber hose and testing.