Dis/mounting Grandagon 90mm 6.8

[Edward McLaughlin]

Hello.
I recently bought a Grandagon 90mm 6.8 lens mounted on a plate.
I need to put it on another plate.
I can loosen the retaining ring but this still leaves both rear and front
assemblies firmly fixed to each other, with the plate merely loosened between the two.
This is unlike other lenses I have dealt with which only require the retaining
ring to be loosened and can then be dismounted.
Do I need some kind of wrench to further loosen the rear assembly?

[BradS]

Unscrew the rear group first. Then loosen the retaining nut.

[Sheldon N]

I recently had this problem as well on the same lens. The rear group on this lens comes apart in two pieces - first the cell with the optics then a spacer, and the retaining ring is beneath both.

I could get the rear optics off, and the retaining ring loose, but the spacer remained firmly in place. I have never seen something this stuck before, took quite some doing to get it off.

I ultimately used a rubber jar opener (flat piece of tractioned rubber for getting open stuck jar lids) combined with a pair of wide mouth vise grips. I had to hold the shutter very carefully to not bend any of the levers, and also take great care to make sure that the rubber stayed between the vise grips and the rear spacer (don't squeeze too tight). Ultimately it wasn't brute force that got it off, but carefully working it loose.

Hope this helps!

[Dave Moeller]

I purchased a mounted lens on eBay, and I couldn't get the retaining ring off. (I have the SK Grimes adjustable wrench...a great tool...but even it wouldn't shift the ring.) I put the whole assembly into a heavy platic bag (a "Hefty One-Zip" freezer bag) and left it in the freezer for 24 hours. When I took it out, I was able to unscrew the retaining ring with my bare hands.

(I put everything back into the bag quickly, along with a couple of silica gel packets, and left it to warm up for 24 hours. There was no condensation on the lens elements when I took it out again.)

[BradS]

I recently had this problem as well on the same lens. The rear group on this lens comes apart in two pieces - first the cell with the optics then a spacer, and the retaining ring is beneath both.

I could get the rear optics off, and the retaining ring loose, but the spacer remained firmly in place. I have never seen something this stuck before, took quite some doing to get it off.

I ultimately used a rubber jar opener (flat piece of tractioned rubber for getting open stuck jar lids) combined with a pair of wide mouth vise grips. I had to hold the shutter very carefully to not bend any of the levers, and also take great care to make sure that the rubber stayed between the vise grips and the rear spacer (don't squeeze too tight). Ultimately it wasn't brute force that got it off, but carefully working it loose.

Hope this helps!

Yeah! Those little rubber (?) jar lid removal thingys are great for unscrewing stubborn lens cells. My Grandagon unscrewed easily but, I've had a couple of Ektars that were very stubborn and their litte rear group doesn't give much to grab on to. The rubber mat thing is the ticket!

[Edward McLaughlin]

Well! How good does it get?
Only asked yesterday and today I have full info on how
to get the job done.
Thanks very much to all.