Mamiya-Sekor C 2.8/45 hacked into Copal Press No. 0 shutter

[iangreenhalgh1]

A while back a bought a job lot of 4 abused lenses for spares/repair for the princely sum of 2ukp because it had a Mamiya 2.8/45 for 645. I gave the other three lenses away to forum members and set about repairing the Mamiya. It was a dead loss, had been dropped and had a huge dent in the front, the barrel was bent so focus was notchy and didn't turn all the way. Aperture linkage was all broken too, someone really abused this poor lens. However the glass was in decent shape, no haze or fungus, no separation, one scratch on the back surface and quite a lot of marks and scratches on the front, but no worse then my Nikkor 24mm or Canon FL 35mm and those both shoot beautifully.



I had read that you could remove the cells from Bronica SLR lenses and they fit into a #0 shutter. I wondered if I could do the same with this Mamiya so I dismantled it and removed the front and back cells. The front was actually two parts, and I was unable to work out what the spacing of these two parts was so I just glued em together and crossed my fingers, the back of the front cell isn't threaded and measured 28mm diameter. The back part was a single cell and threaded with what appeared to be a 29mm thread.

I needed a shutter and the cheapest source of them is often oscilloscope cameras, so when I spotted a Shackman 7000 on ebay I snapped it up for a very good price. It contained a Copal Press No. 0 shutter with a single plastic element in front and behind held in with oversized plastic retaining rings. It was easy to remove those rings but I had to take a hacksaw to the plastic body of the camera to get the shutter out. It's in great shape, the shutter and aperture blades are pristeen and it fires on all speeds without sticking, it has 8 speeds from 1 sec to 1/125 and the aperture, handily, goes from 3.5 to 32, but opens a little bit wider than the marked 3.5 so should be adequate for using with the 2.8 45mm Mamiya.



The cells fit the shutter but the rear cell is slightly smaller in diameter than the rear of the shutter. I wrapped a little bit of the sealant tape you use on pipework joints around the cell's threads then it screwed in perfectly. The front, having no threads, I wrapped that with more tape then it would also fit into the front and is held pretty securely. Of course, I have no idea if this gives the correct cell spacing or not, I'll just have to make some shots with this thing and hope they come out sharp.

Apologies for the awful pictures, but you get the idea:





I'll mount this thing on a temporary wooden lens board and try it on my Century Graphic 23, no idea if this lens will cover 6x9, it's for 6x4.5 so I've no idea what the image circle is, hopefully big enough to cover 6x6 at least, I wasn't able to find any info on image circles of Mamiya 645 lenses, but if anyone knows, I'd love to know. If i know the register (63.3mm) and the angle of view, I can calculate the image circle, right?

[luisalegria]

That's the good old tinkerers spirit!
Well done !
This hack deserves to succeed.

[iangreenhalgh1]

Cheers Luis. I hope it works, the two pitfalls are the cell spacing and the spacing of the two front parts I glued together.

If it doesn't work, I only wasted a couple of pounds on the lens, and I can pick up an abused Bronica lens instead, either the 40 or 50mm, and those do fit this shutter.

The one thing I'm missing is a retaining ring, so I'll have to use some blobs of hot melt glue to hold the shutter in a lens board for testing. The late Steve Grimes would hardly be impressed by my level of engineering, but if it works, it works, right?

I also found out today that the Copal works perfectly on the fastest four speeds but sticks open on the slowest four. I'm guessing i can take the face plate off and with some q-tips and lighter fluid clean out all the gunk and hopefully get it working, or maybe the marinade in a bag method, I'll read up on cleaning Copals.

[uddhava]

I am anxious to see the results of your experiment. I have been following this topic with interest although it is too far advanced for me to understand. Good luck!

[luisalegria]

I've only fixed two Copals. Easier to disassemble/assemble than a Compur, and simpler inside.
Problem with them is a delay linkage (not the clockwork, but attached to it) that does get stuck, does require lube, and is hard to fix, sometimes, without more disassembly than I like to do, having to reposition little fussy springs putting it back together, etc.
And it causes the problem you are seeing, with the slow speeds out.
I did get the first one fixed but with some anxious moments.
Lighter fluid is not a bad start and its easy to apply on a Copal. Good luck.

[iangreenhalgh1]

Cheers Luis. I'll squirt some lighter fluid at it and if that doesn't do the trick I'll send it for a CLA.

I tried the lens on my NEX today with some bellows. it seems sharp enough, not razor sharp but not too bad:

[luisalegria]

Not too bad at all !
I wouldn't have thought you'd get so close on the first attempt.
The tedious part is adjusting the cells spacing until you get the best possible results.
It looks like you have screwed at least one of them in, so you can adjust that.

[iangreenhalgh1]

Yes, the back one is screwed in, I had to pack the threads a little but it could be adjusted, the front one would be best left as it is, a couple of little blobs of hot melt glue added to hold it more firmly in place in a non destructive easy to remove again way.

The lower contrast will be due to some light leaking in at the back of the shutter as it was only held against the bellows by hand.

I think it will probably make good 6x6 shots as it is, but I'll try tweaking the spacing before I put it on a film camera, see if I can get some more sharpness out of it.

I also think it can be said this has been a success, which please me greatly, diy often goes badly wrong.

[uddhava]

Congratulations with your work so far. Nice results for your first tests!

[iangreenhalgh1]

Cheers uddhava, now I just have to put it on a film camera.