Recontituting a Unicum shutter

[Ole Tjugen]

Now I have a weird problem...

I have this fine old Unicum shutter, which works perfectly. As a shutter.
But the aperture blades seem to have shrunk! does anyone here have any idea about what I can treat them with, to make them swell to their original size so that the aperture can be adjusted without the end pins coming out of their slots?

See attached pictures - the shutter is fine, but picture 2 shows the shrunken aperture blades.

[Ole Tjugen]

I meant Reconstituting, of course...

[Nathan Potter]

Ole, would it be easier to fabricate a new pin capture plate but with a smaller inner diameter that would retain the aperture pins in their maximum inner radial movement? Using sheet shim stock say laser machined on a CNC mill?

Nate Potter, Austin TX.

[Ole Tjugen]

Perhaps it would Nathan - but I don't have a CNC mill at my disposal. ;)

[cowanw]

I made a larger studio shutter blade out of fully exposed 8X10 film using a good one as to trace and mark holes. Maybe with a scalpel and a dremel drill. Maybe you can make a whole set of the right size.

[Ole Tjugen]

I could make new blades - but fitting the pins would be difficult. Making a new pin capture plate seems like a better option, if I can't find a way to make the old blades swell to their original size.

Searching the net for Unicum shutter information I have found reports that the shutter blades are vulcanite - in my shutter they are definitely steel. But it's possible the aperture blades are vulcanite, but I've failed to find any reports of vulcanite shrinking!

[cdholden]

I'm not aware of any steel alloy having the ability to shrink as much as you're talking about in this shutter. Are you sure this wasn't the victim of some parts pillaging frenzy?
Maybe someone swapped parts with another shutter.

[Jim Jones]

Could the shutter be assembled with the pins in the wrong slots?

[Jim C.]

I tend to agree with cdholden, and Jim, it was probably a victim of a frankensteinian
experiment or it was disassembled for a CLA and wasn't assembled properly, or
worst case scenario the aperture mech is missing a part that would prevent the
leaf pins from falling out.

It may be worth the effort to puzzle them back into their original positions.

[Paul Fitzgerald]

" But it's possible the aperture blades are vulcanite, but I've failed to find any reports of vulcanite shrinking!"

Well you can find plenty of large B&L Unars and Tessar sans iris blades for that very reason. Yes, those plastic blades do shrink and warp fairly often.

You could try paste wax with a Q-tip to clean each blade, the Stoddard solvent in the wax may help them relax back into shape. Any other solvent I can think of would be too strong and may warp them. Maybe butcher-block lemon oil could work.

"It may be worth the effort to puzzle them back into their original positions."

from the photo, they are in their correct position, they 'just short of' pull out normally. The blade have not shrunk very much.

Have fun with it.

[Ole Tjugen]

Cd and Jim(s), all the parts are in the correct position and as I stated the steel bladed shutter works perfectly, as such. Only the aperture is affected, and what has happened is that the vulcanite aperture blades have shrunk enough that they now slip out of the pin retaining slots.

So now I need to find a solvent that can soak in - preferably one that can be used at a relatively high temperature over a prolonged time, so that it doesn't evaporate out of the blades again...

[cdholden]

Some people soak shutters in lighter fluid as a lame attempt at cleaning. I am not one of them. While it is a solvent, it is a weak one and may work for this purpose.

Chris

[GPS]

...
Searching the net for Unicum shutter information I have found reports that the shutter blades are vulcanite - in my shutter they are definitely steel. But it's possible the aperture blades are vulcanite, but I've failed to find any reports of vulcanite shrinking!

Yes, vulcanite can shrink, due to high humidity. It is possible that your shutter was exposed to it or even had a bath.
Trying to soak it and then iron it is what I read was attempted by someone without knowing the end of the story... Personally I would think it would be trying to exorcize a demon with a devil...

[Rider]

According to this ad from 1898, the blades are "thin rubber".

http://upload.wikimedia.org/wikipedia/en/c/cd/Unicum_shutter_advertisement_1898.jpg

Do you know what sizes the threads on the Unicum shutters came in? Mine seems to be slightly bigger than a Seiko 0 and Copal 0.

[GPS]

Vulcanite was a name for hardened rubber.

[Steve Smith]

Perhaps it would Nathan - but I don't have a CNC mill at my disposal.

I have the use of a laser cutter and a CNC drill/router at work. If you had suitably detailed dimensions and some suitable material, I could laser cut some new aperture blade parts.

Or it might be easier to make a new plate with a slightly smaller inner diameter and therefore, longer slots so they engage with the pins (as has already been suggested).


Steve.

[GPS]

Now I have a weird problem...

I have this fine old Unicum shutter, which works perfectly. As a shutter.
But the aperture blades seem to have shrunk! does anyone here have any idea about what I can treat them with, to make them swell to their original size so that the aperture can be adjusted without the end pins coming out of their slots?

See attached pictures - the shutter is fine, but picture 2 shows the shrunken aperture blades.

I dare to doubt about the "perfect" shutter function - these shutters have inherent constructional defects that makes their accuracy very approximative. Their history shows that they were dismissed from use after about 10 years by the arrival of more reliable constructions.
But if you really want to make it alive again - why not to glue on the short blade a longer flat section of a blade made of a suitable material?

[Steve Smith]

why not to glue on the short blade a longer flat section of a blade made of a suitable material?

Because that won't solve the problem of the pins not aligning with the slots in the plate.


Steve.

[GPS]

Because that won't solve the problem of the pins not aligning with the slots in the plate.


Steve.

Obviously, you cut off what is not aligned and use the newly glued part for guiding the pins...

[Ole Tjugen]

That would be slightly more difficult than making NEW aperture blades, I believe!

The blades are anchored at one end, the other end is moving as the aperture is changed. To keep the process reversible the free end is guided by the slots cut in the controller plate.

As the blades shrunk, the distance between the fixed end and the free end (guided with inset pins which are limited to staying inside the slots) decreased to the point where the slit no longer traps the pins sufficiently.

To "cut off what is not aligned and use the newly glued part for guiding the pins" means either making a guide plate with a smaller inner diameter by cutting OFF bits of it, or alternatively cutting and splicing very thin hardened rubber blades, ending with a perfectly smooth blade of uniform thickness that is slightly larger than the original.

It seems to me that making a new smaller guide plate is the least impossible solution. ;)

[GPS]

Now I see, it was the other way round - the blades shrunk and the guiding plate is good. My bad, I saw it the other way...

[GPS]

Now I have a weird problem...

I have this fine old Unicum shutter, which works perfectly. As a shutter.
But the aperture blades seem to have shrunk! does anyone here have any idea about what I can treat them with, to make them swell to their original size so that the aperture can be adjusted without the end pins coming out of their slots?

See attached pictures - the shutter is fine, but picture 2 shows the shrunken aperture blades.

Ole, just curious - why don't you get a healthy Unicum shutter to take aperture blades from and put them to your guiding plate in your "perfectly working" shutter? I have a Unicum shutter (not at all perfect in exposure timing) in front of me as a paper weight and it seems there were not many different sizes of it.

[Steven Tribe]

Sometimes old threads become very relevant!

There are many sizes of Unicum shutters.
My guess is (I have the Busch unicum casket set too!) that someone has installed iris leaves from a smaller Unicum shutter, which are more common.
I don't believe in skrinkage of this magnitude!

I have normal sized leaves on mine (after a 100 years). But unfortunately all pins are either loose - or have fallen out. The fixing system is horrible - tiny pins into "plastic" holes.