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reddesert
26-Apr-2019, 14:34
Hello, By way of introduction I have lurked here for a while (and all the way back to Usenet once upon a time). I have some experience with photography and optics but not as much practical experience with LF, especially "antique" equipment.

Many years ago I got this old 210mm Goerz Dagor in a barrel mount. The attached photos should show that it's labeled: Goerz Berlin Dagor Dopp. Anastigmat Serie III, 210mm. The SN is shadowed in the photo but it's near 293,000, which if the SN table on the web applies, is about 1910. It is labeled in US aperture numbers.

The barrel mount is unusual to me. The entire front turns to adjust the aperture, including the outer ring and all of the black-painted part of the front barrel, visible in the side view second photo. Clearly, to mount it something has to hold the rear part of the barrel, the brass-colored part with some old black goop on it in the side view. There are two tiny set screw poking out of the barrel side and a hole for a third. There's no flange or other seating surface.

How would this have been mounted originally? My best guess is that it was in a tube of matching diameter, perhaps felt-lined, and the set screws matched the tube somehow to keep it from rotating.

And of course the question, how should I mount it for use? I poked it through this cardboard lensboard just to try out, but it doesn't hold against rotation and leaks light around the lens, of course. I could make a sturdier lensboard and put black tape all over the lens/board joint, but it would be nice to have something more reliable. I thought about trying to work up some kind of clamping arrangement with semicircular conduit hangers, and maybe putting a O-ring over the lens/board joint as part of the light seal. Opinions and discussion are welcome.

190567190568

Steven Tribe
27-Apr-2019, 00:33
The focal length suggests it was made for a format large than 13x18cm - which usually used the 180mm DAGOR. This sunken mount usually had a simple helical focussing arm for "spring-out" cameras like the Goerz Ango with focal plane shutters. This was probably mounted on the more bulky " boxey" type focal plane cameras - where there was a moveable front standard for focussing. The best known was the Goltz & Breutmann Mentor cameras, but there were lots of others made (Germany and the UK). It is tempting to suggest this is from a UK camera, as 210mm would be perfect for 1/1 plate size. Someone with a blowlamp could have removed the flange screw ring. Another posibility is that this was a lens with a helical mount and that the helical section (complete with mounting thread and flange) has been removed for other "photographic activities".

I enclose a photo from an auction which shows both the central part you have and the "missing" focussing mount and the flange. This is a 180mm DAGOR on a 13x18 Goerz ANGO.

reddesert
30-Apr-2019, 14:57
Thanks, Steven, this was very helpful. Some of the missing clues were to look for strut or reflex cameras (makes sense that a barrel lens might have been on a reflex camera). That gave me some more terms to plug into searches.

I found this blogpost showing a 150mm Dagor that is very similar to mine, including the US stops, but still has its focusing mount (unfortunately some of the mechanical details are obscured by the adapters the blogger has fitted): http://lensbeam.com/obektivy/obektiv-c-p-goerz-berlin-dopp

And this post showing a Goerz folding strut camera with a similar lens in a helical focusing mount: http://papayaspoint.blogspot.com/2013/12/goerz-ango-10x15-polaroid-conversion.html This one shows the mount better. The details of how the lens is fastened to the helical are only a little visible. It's possible that on my lens, the setscrews are the means - they could have ridden in helical tracks in an inner cylinder. I'm not going to attempt to re-create that, but understanding that the forward facing aperture ring would have sat in a recess to form part of the light trap, helps me think about how to mount it. Thanks!

reddesert
30-Apr-2019, 16:39
In particular, "Goerz Anschutz Klapp" (a strut camera with focal plane shutter) yields a lot of similar-looking lenses.

Dan Dozer
11-May-2019, 15:40
So - I have one of these in the 180 MM version. I think it is a pretty early one. It doesn't say Dagor - it just says Dopple Anastigmat D. R. P. and serial #74437. At sometime in it's life, someone made an aluminum flange and attached it to the back of the lens so mounting it to a lens board is easy. I've tried to get the flange off, but there is no apparent way to do it. Perhaps they glued it on.

191239

reddesert
11-May-2019, 23:13
So - I have one of these in the 180 MM version. I think it is a pretty early one. It doesn't say Dagor - it just says Dopple Anastigmat D. R. P. and serial #74437. At sometime in it's life, someone made an aluminum flange and attached it to the back of the lens so mounting it to a lens board is easy. I've tried to get the flange off, but there is no apparent way to do it. Perhaps they glued it on.


It could very well be a press fit that cannot be removed without heating the flange. Upthread, Steven mentioned that someone might have used a blowlamp (blowtorch in US) to remove the original mounting flange. Some more speculation:

I took a machinist's class in college (physics department shop) and we made a practice dingus using a press fit. An aluminum cylinder was fit into an aluminum disc similar to your flange. We machined the hole in the disc to have close to zero clearance, that is the hole was the same size as the cylinder. With zero clearance, you can't push the cylinder into the hole. We then cooled the cylinder and heated the disc - I forget how hot, but not red hot. Aluminum has a relatively high coefficient of thermal expansion for a metal, so this makes the hole just big enough for the cylinder. We then quickly set the two pieces together and slammed them home with a hand press. You only have a few seconds to do this, because once they are in contact they come into thermal equilibrium pretty quickly, and then they're stuck for good. Apparently press fits are pretty stressful even for experienced machinists. https://en.wikipedia.org/wiki/Interference_fit

Because your flange is aluminum and the lens barrel is likely brass, and aluminum has a slightly higher coefficient of thermal expansion than brass, you might be able to heat the flange enough to expand it and press it off the lens. I would be super careful with this because I think getting the cemented glass elements hot would be bad. (It's the cement, black paint, etc that would worry me; the glass itself can probably take a pretty high temperature).

Dan Dozer
13-May-2019, 08:25
It could very well be a press fit that cannot be removed without heating the flange. Upthread, Steven mentioned that someone might have used a blowlamp (blowtorch in US) to remove the original mounting flange. Some more speculation:

I took a machinist's class in college (physics department shop) and we made a practice dingus using a press fit. An aluminum cylinder was fit into an aluminum disc similar to your flange. We machined the hole in the disc to have close to zero clearance, that is the hole was the same size as the cylinder. With zero clearance, you can't push the cylinder into the hole. We then cooled the cylinder and heated the disc - I forget how hot, but not red hot. Aluminum has a relatively high coefficient of thermal expansion for a metal, so this makes the hole just big enough for the cylinder. We then quickly set the two pieces together and slammed them home with a hand press. You only have a few seconds to do this, because once they are in contact they come into thermal equilibrium pretty quickly, and then they're stuck for good. Apparently press fits are pretty stressful even for experienced machinists. https://en.wikipedia.org/wiki/Interference_fit

Because your flange is aluminum and the lens barrel is likely brass, and aluminum has a slightly higher coefficient of thermal expansion than brass, you might be able to heat the flange enough to expand it and press it off the lens. I would be super careful with this because I think getting the cemented glass elements hot would be bad. (It's the cement, black paint, etc that would worry me; the glass itself can probably take a pretty high temperature).

This is an interesting possibility on how it might have been mounted. There is no apparent thing holding the two components together (lens and aluminum flange) other than friction. I would find it hard to believe that someone would put a camera lens through a press fit process as you describe because of potential damage to the lens. However, it does present an interesting option. I have no need to try to separate the two so I'm going to just leave it as is.