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bc_69
9-Apr-2017, 04:29
The aperture ring on a Cooke Triplet (barrel lens) I have received is siezed, it won't budge. First of all I'm not sure what causes this, and more importantly can it be fixed? There's no external sign of unusual wear, corrosion, dents or any damage, everything looks as it should but the ring refuses to move. I can remove the three glass elements no worries leaving just the part with the stuck iris.

Can anyone point me in the right direction to remedy.

BC

bc_69
9-Apr-2017, 16:03
I've noticed there are two small screws on the barrel just behind the flange. One appears to be locking pin, perhaps could be the one that moves the iris blade mechanism if it was working because I can see it through a small hole on the opposite side where the aperture turning ring would normally cover it and it goes through the outer ring into a slot in the inner ring. I've been able to remove the aperture turning ring without any problems, it just screwed off. The second screw which is to the side of the first one is sitting up higher and I can't see where it goes. Both can be turned with a screw driver but I haven't taken them out not knowing what they are for.

I've since read on this site that the series iia are noted for having this problem. This is a Taylor Hobson version lens, not a TT&H, with a patent number on the aluminium aperture ring. It is not a soft focus lens. The problem I've read is the grease on the thread of the outer ring has dried up causing the mechanism to seize.

My question is, will removing the screws allow me to remove the outer ring to clean and lub it again? Or is it more complex than that.

bc_69
10-Apr-2017, 01:49
Doh, stupid me, the aperture ring hasn't been removed, it is the problem and won't turn. I removed the front and rear elements.

I've decided to put a small amount of Zippo lighter fluid on the aperture ring thread to see if it loosens it up, no luck so far. The trouble with Zippo is it evaporates quite quickly. I need to find some of the stuff Jim Galli refers to in this thread on the same problem

http://www.largeformatphotography.info/forum/showthread.php?128407-How-to-fix-frozen-iris-in-a-Cooke-Portrait-Soft-Focus-Series-II-8x10-13-quot&highlight=fix+frozen+iris

domaz
10-Apr-2017, 08:26
The aperture might be seized because the blades have become undone from their pins or have bent. In that worst case the only thing to do is to remove the aperture ring (rotating ring that sits on top of the aperture blade) and reset all the blades one by one. You may possibly need to bend them back straight as well. I had to do this with a Cooke 150mm f/2.5 lens that came off a Graflex RB. Basically the aperture blades had bent and the pins had come out on some of the blades. I straightened the blades, and used "shaped" JB Weld in place of the Aperture pins. The aperture now works but it was a few days project to fix.

bc_69
10-Apr-2017, 14:10
The aperture might be seized because the blades have become undone from their pins or have bent. In that worst case the only thing to do is to remove the aperture ring (rotating ring that sits on top of the aperture blade) and reset all the blades one by one. You may possibly need to bend them back straight as well. I had to do this with a Cooke 150mm f/2.5 lens that came off a Graflex RB. Basically the aperture blades had bent and the pins had come out on some of the blades. I straightened the blades, and used "shaped" JB Weld in place of the Aperture pins. The aperture now works but it was a few days project to fix.

The blades look to be in pretty good condition, no sign of damage or pins missing, everything seems in order. The whole lens is in great order excepting the aperture ring is seized.

I'll give the solvent experiment a trial over a week to see if it moves anything. I've just noticed there are two small holes on the front of the aperture ring which seem to go into a thread, but because of their orientation on the face rather than on the outside of the barrel I don't believe they will be the correct entry point for the solvent. If that doesn't work I'll chance my arm at removing the tiny screws to see if I can get access to the area where the grease should be and hope it has simply dried up and there is no other internal damage.

bc_69
10-Apr-2017, 15:17
Can this thread be moved to DIY by a moderator please

Jim Galli
11-Apr-2017, 13:23
Get some of this stuff (https://www.napaonline.com/en/p/BK_5651322). Accept no substitutes. It leaves no residue and does not attack any phenolics. Hose her down. It'll free up but keep drenching it while turning it to float all of the ancient gook out. The gook will leave a residue but easily wiped off.

B.S.Kumar
11-Apr-2017, 17:10
Jim, I get an "Access Denied" response on the napaonline.com site. Is there any other place that sells it?

Kumar

Jim Galli
11-Apr-2017, 18:10
Jim, I get an "Access Denied" response on the napaonline.com site. Is there any other place that sells it?

Kumar
The one I know about is their proprietary brand. The active ingredients are hexane, heptane and acetone so the possibility is there is something similar but not that I have knowledge of.

B.S.Kumar
11-Apr-2017, 18:12
Thanks, Jim. Can you tell me the product name? I'll search for the MSDS.

Thanks,
Kumar

Jim Galli
11-Apr-2017, 18:21
Thanks, Jim. Can you tell me the product name? I'll search for the MSDS.

Thanks,
Kumar

Tried to get their link off the page but it was just empty java. Trade name: Buffing Solution (Rubber Cleaner) will bring up sds

B.S.Kumar
11-Apr-2017, 19:05
Thanks.

Kumar

bc_69
12-Apr-2017, 04:00
Get some of this stuff (https://www.napaonline.com/en/p/BK_5651322). Accept no substitutes. It leaves no residue and does not attack any phenolics. Hose her down. It'll free up but keep drenching it while turning it to float all of the ancient gook out. The gook will leave a residue but easily wiped off.

Thanks Jim, I'll see if I can get some of this stuff.

bc_69
18-Apr-2017, 18:00
Well using solvent didn't budge anything so I took out the two screws which allowed me to take off the front external barrel that also has the aperture ring attached to it. This left two cylinders with the aperture blades. I still cannot rotate the blades. To complicate matters the blades are fully closed and some are bulging. I need to be able to separate the to cylinders to clean off the gunk and realign the blades. One half of one cylinder screws into the other. What i have is one smooth black cylinder and the half of the other one which is a ver fine brass thread that had the external barrel on it.

The two cylinder are tight together and can't be budge by hand. Any suggestions on the best way to separate the without doing any damage.

bc

Jim Galli
18-Apr-2017, 18:13
Well using solvent didn't budge anything so I took out the two screws which allowed me to take off the front external barrel that also has the aperture ring attached to it. This left two cylinders with the aperture blades. I still cannot rotate the blades. To complicate matters the blades are fully closed and some are bulging. I need to be able to separate the to cylinders to clean off the gunk and realign the blades. One half of one cylinder screws into the other. What i have is one smooth black cylinder and the half of the other one which is a ver fine brass thread that had the external barrel on it.

The two cylinder are tight together and can't be budge by hand. Any suggestions on the best way to separate the without doing any damage.

bc

Piece of wood on floor. Piece of rubber inner tube on wood. Barrels on top of rubber. A second piece of old inner tube on top of that, then place your foot squarely over the whole thing and with some weight on it, torque ccw.

bc_69
18-Apr-2017, 20:14
Piece of wood on floor. Piece of rubber inner tube on wood. Barrels on top of rubber. A second piece of old inner tube on top of that, then place your foot squarely over the whole thing and with some weight on it, torque ccw.Cheers Jim, I'll give that very technical method a go.

bc_69
27-Apr-2017, 19:59
Piece of wood on floor. Piece of rubber inner tube on wood. Barrels on top of rubber. A second piece of old inner tube on top of that, then place your foot squarely over the whole thing and with some weight on it, torque ccw.

This is proving to be more difficult that expected. Cannot budge it with this method either. I'm going to have to resort to more extreme/forceful methods with the chance I will damage the blades (might have already) which will leave me with a lens wide open, not ideal but not a complete disaster.

I'll post some photos of it for people to have a look.

bc_69
9-May-2017, 14:58
This has become an obsession and case study in perseverance. I've completely dismantled the lens. Some of the blades are warped, bent in places, mighty ugly, my heart sunk to my feet. My first thought was I had ruined this lens as a fully working one. I took a step back and began thinking through the likely ways to fix this, even though I had read this was practically a lost cause.

Without great expectations I began the process of trying to repair the damaged blades which I thought might be impossible given they are so fragile and pliable. With a bit of research on metal work forums I came up with a method of working to straighten then flatten them out. Straightening was simply done by hand to get them as good as I could manually, but still with noticeable kinks in the metal that would make them unusable. Next step was a matter of using a round metal handle of an old salad server to roll over the blade gently, the blade was on a block of hard sponge like material I found on the road so that there was some give when I put light pressure on the blade. That gave me an improved smoothness of the blade but it was now semi curled from the process and still with kinks that were barely noticeable but a problem. Next step was to place the blade on a smooth flat metal surface and run the cylindrical handle over it with minimal but increasing pressure, this was done a number of times, occasionally turning it over. Eventually I had a flat blade again. On the test blade there was a small bur in the inside curve where it was bent. This I removed using a very very fine small well smoothed Arkansas oil stone I've had since a kid in my fishing tackle box.

The test blade appears acceptable, to me at least, using this process, I'll now do the others and re-assemble the aperture and see if I have succeeded in achieving what I thought would be impossible to get it back to working condition. From what I've read it is a challenge to get the blades back into the aperture mechanism, and there is a precise method to lining up the mechanism so it opens and shuts to the f stop it is meant to be at. With this lens I think it relates to lining up the screw hole that holds the inner and outer barrels in alignment. If I get that far then that is the least of my problems.

BC

Jim Galli
9-May-2017, 16:51
Bravo. Perseverance pays dividends. If all of the little nubs that fall into the holes and grooves are present I have confidence you'll get it working fine.

bc_69
21-May-2017, 15:35
After many hours toiling away I've finally got the lens back together. I'll post some photos of the repair work on the DIY thread when I get a chance. Getting all the blades back into place was the most tedious time consuming part of the process but I got there in the end. That's the good news. There still seems to be a problem with opening and shutting the aperture, it's still stiff after cleaning all parts. Is there a special lubricant to use on the aperture mechanism that helps it turn nice and smooth? That's the only thing I can think of stopping it from working perfectly well.

Taija71A
22-May-2017, 07:58
Thanks, Jim. Can you tell me the product name? I'll search for the MSDS. Thanks, Kumar


Tried to get their link off the page but it was just empty java. Trade name: Buffing Solution (Rubber Cleaner) will bring up sds

Is this the Product that you were referring to Jim?
Thank-you!

-Tim.
__________

165204

Tire Repair Buffer & Cleaner Solvent.

Product Line: Balkamp
PART#: BK 5651322

Jim Galli
22-May-2017, 09:41
Yes. It works magic on aperture ring threads. The dirt of 80+ years will just ooze out as this stuff is applied.



Is this the Product that you were referring to Jim?
Thank-you!

-Tim.
__________

165204

Tire Repair Buffer & Cleaner Solvent.

Product Line: Balkamp
PART#: BK 5651322