Stuck lens whenever on large Derogy

[Petzval Paul]

Hi everyone, I have this really big Derogy Aplanat (26" FL) that can be disassembled, except for the front element. I'm guessing that the whole ring (sometimes we see these painted black) behind the hood mount should come off? Does anyone have a similar model of which they can take a pic?

I got the hood of using this PB Blaster spray which worked really easily but I can't get this element or for the life of me! 209411

[Petzval Paul]

209412
209413

[Petzval Paul]

209414

[Tin Can]

Why not clean in place and let sleeping dogs...

[Petzval Paul]

Because it has no finish and I want to lacquer it.

[Two23]

Did you try a strap wrench on it?


Kent in SD

[Petzval Paul]

No, not yet. Headed to the hardware store today and will pick up a hose clamp, based on something I read elsewhere in this forum.

[karl french]

I have a No. 6. Both groups unscrew from the barrel. Mine is missing the hood, I suspect it was lost long ago. Oh, I should add my lens also has traces of black paint on the front.

[Tin Can]

I have used hose clamps and strap wrenches in all kinds of ways

Professionally!

They both have a non flexible disaster zone which places stress on anything round

Oil filters crumple...

Good luck



No, not yet. Headed to the hardware store today and will pick up a hose clamp, based on something I read elsewhere in this forum.

[Petzval Paul]

No, not yet. Headed to the hardware store today and will pick up a hose clamp, based on something I read elsewhere in this forum.

[Petzval Paul]

Thank you for that info! So the whole, formerly black, ring unscrews from the barrel, correct?

Tin Can, then what would you recommend to use?

[karl french]

Yes.

[Tin Can]

My only suggestion is leave it be

Paint always ruins value

[Steven Tribe]

I have the no. 7 - serial no. Is 18661.

Unfortunately, the front lens cell is part of the (very robust) lens hood assembly. Derogy sold lots and lots of these aplanats, so perhaps a design change was made to simplify production and servicing. Both the rear and front lens are mounted in the cell by a combination of a rilled beauty ring and a turned over brass edge. Lens mounting screw rings are not easy to make and makers did not consider that their lenses would be still in need of servicing in the 21st century. Suter used the same system for their aplanats. I’ll post photos if you like to see them?

It is very possible that your no.7 employs the same mounting seal. It can’t be seen as it is pointing inwards in the barrel. Your rear cell mounting probably employs the same system.

The slight different colour brass Section of the barrel looks ideal for the pipe hose system clamp system. Mount so that there is something solid to hit with a hammer (anti clockwise, of course) to get it started.

[Conrad . Marvin]

If you know a machinist you could have them make a ring out of aluminum of the exact ID as the OD of the part that you need to remove plus the thickness of a piece of paper. The ring would be about a quarter of an inch thick and as wide as you need. Saw a slit on one side so that it can tighten. I made one of these once when all else failed (strap, hose clamp...) and put it in a lathe chuck tightening it down ever so slightly and old lens and front ring separated with ease......just a thought if you really get stuck.

[Petzval Paul]

Mine is number 22598, waterhouse stops and the old style 'No.7' in block letters/numbers. Pictures would be a great help! Three ring on mine fits so perfectly that is hard to tell if it really is a separate piece. I tried the hose clamp yesterday asking with 48 hours soaking in PB blaster to no effect. I might message my local machine guy today and see what he thinks. Your pictures would help tremendously to explain the situation.

[Steven Tribe]

The first photo shows a selection of Derogy’s aplanats. The two on the left show the two versions of size no. 4. The top one - with lens in the lens hood assembly - is the early one. The second photo shows mine. Serial no. are around 18,000. The one underneath is the black extended barrel version which has the front lens mounted - this is the one the OP has. Engraving and optics are identical on these two versions,

[Petzval Paul]

Thank you for that. So your model's front element is mounted in the hood? That's definitely different from mine. My model's serial number is close to the No. 4 at the bottom of the pic and I would presume that the element is mounted differently from yours and that the black ring has to be removed from the body to disassemble it. I'll get in touch with my machine guy today. I appreciate everyone's help.