disassembling old LF lens

[wim_abbeloos]

I have a Rodenstock eurynar 24cm large format lense with a big

problem. Water has gotten between the 2 rare lens elements. I have

succeeded in removing the 2 front lens elements. How can I remove the

2 rare elements? Is it the silver ring I have to turn, or the black

ring? These rings are completely stuck, have tried everything to get

them removed, it simply won't move. Is it a left hand screwing ring

(that woudl surprise me)?

 

The glass elements are uncoated, should I put the entire lens (brass)

in acid to try to loosen the ring?

 

Please help me out here, or the lens will just rust away!

[mskovacs]

A photo sure would help unless you are fortunate enough that somehere here has one of these and has opened it before.

 

Acid would be suicidal - if anything you probably want to try a penetrating oil to free the corroded threads.

[wim_abbeloos]

Here are a top and side view:<div></div>

[wim_abbeloos]

...<div></div>

[dan_fromm2]

Turning the silver ring will remove the rear cell from the barrel. A big problem in doing this will be applying enough torque to the ring without distorting it. If distorted, it will bind. The classical solution (no kidding!) is to press the end of the lens against a tire's sidewall and then turn the barrel. The serrations on the ring will grip the rubber.

 

The black ring retains the rear element in the rear cell. If it has notches to accept the tips of a spanner wrench -- sorry, I can't discern them in the photo -- then get one and use it. Since you're not a native speaker of english and the dictionary will give you several inappropriate definitions of spanner, visit www.skgrimes.com and click on products to see the kind of wrench I have in mind.

 

Good luck, don't use acid,

[wim_abbeloos]

I have tried rubber. Put a rubber pad on the floor and grabbed the lens barrel with rubber and twisted: not moving. Then grabbed the silver ring with a special rubber tool while attempting to twist the barrel: not moving.

 

There are no notches so I can not use my wrenches... The silver ring is pretty much identical to what a filter ring looks like. It has the tiny notches on top to provide better grip (sadly not enough).

 

So should I attempt to get some oil between the silver ring?

[mskovacs]

The other thing that can be done is to cool the lens. Particularly if the chrome ring and brass are dissimilar materials, they will contract to different degrees which will help them to come apart.

 

Don't know if you want to put it in the freezer though with the water inbetween the elements.

[conrad_hoffman]

Don't cool the lens too much; if the fit of the elements is tight, they'll shatter as the metal mount shrinks. One trick I use is to put a few drops of alcohol at the junction of the parts. This is very low viscosity and will get into the threads, sometimes freeing them up or providing a bit of lubrication. Penetrating oil may also work. Just as a start, get a spanner wrench and remove what elements you can. I've never seen left handed threads on any lens assembly.

[richard_oleson]

You also might try some "Liquid Wrench" if you have it available... this is a penetrating fluid (not really an oil) that is designed for loosening stuck threads, and it works pretty well. A very thin oil might help in the same way, if it's thin enough to get into the threads.

[wim_abbeloos]

Thank you very much for the suggestions, all of you. I will first try cooling (to about 8 degrees shouldn't cause to much problems). If that doesn't work I'll try some fluids. I I still can not get it removed I might have to "create" notches for my spanner wrench...

[silent1]

Almost certainly irrelevant to this lens, Conrad, but most if not all geared focus TLRs have a left hand thread on the front element of either taking or viewing lens. My Kodak Reflex II, for instance, has the taking lens first element left hand threaded into the helical which is part of the second element, which is right hand threaded into the shutter. My Argoflex EF has the left hand thread on the viewing lens, IIRC.

[paul ron]

From what I cansee in your pix, there is a ring inside what looks like filter threads... that inner ring should come out by using a rubber plug that just fits in that space. First feed in a tiny drop of WD40 in the threads and let that sit over night so it spreads nicely. You don't want to be putting too much oil on, it will get inside the lens barrle and you will be screwed if you can't open it.

 

What does the front of the lens have to take off? Is there a way in, maybe taking off a name ring, then a spanner retaining ring?

 

BTW, heatting the lens will loosen it's 100 years of caked up gunk that gets hard in the thread. Also something to consider, once upon a time, a drop of laquer or shelac was used as a lock tight in threads. Maybe a tiny drop of acetone or denatured alcohol will loosen the paint. WD generally is good enough but if all else fails...

[wim_abbeloos]

Cooling certainly did not work. Next on teh list of things to try is slightly heating it. Then I will try some alcohol, then WD40.

[cdewen]

As a source for camera repair tools, I've not found a better one than Micro-Tools: http://www.micro-tools.com

 

I looked in vain on their site for the tool that I would recommend - one that I've always referred to as a strap-wrench. The one I have is marked, "Newline"; I'm fairly certain I bought it from them. Perhaps someone else can suggest an alternate source.

 

A strap-wrench is just a handle with a strip of rubber mounted on it so as to form an adjustable loop at the end. It allows you to generate considerable torque without leaving a mark. It's the type of wrench used, for instance, to change a car's oil filter.

 

Good luck!

[brewer_shettles]

<p>Its years since this post was made; however, in light of disassembling a tight unmoving lens, I've been told "rubber wrenches" ie "strap wrenches" might due the job well by exerting even force to prevent the binding of a lens ring when severe pressure is applied. Strap wrenches are not narrow. That's where a CLA wrench (3mm wide) can do the job. No matter - be careful applying pressure - uneven force can break a lens. Use torque sparingly. Work slow and steady. Put a rubber kitchen glove over the lens between the CLA wrench and the lens. Take this advice at your own risk. Search / read - see what others do. Who's happy. Do what they did. Turn over every stone. Good Luck!!!</p>