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working Ur-Leica?


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now (almost) all of the stocks arrived and the build can proceed...

It was clear to me from the start, that I would not get the original film support back into the camera. It was heavily distorted and I did not like that it was a construction made by bending. This way you can never assure, that the film plane will be level, flat center and perpendicular to the focal plane.

I went for an assembly of individual parts that will be adjusted and soldered separately:

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The file plane will be ground on a glass plate to guarantee its flat. FInally the positioning will be done by a jig that fits to the outer lens diameter on one side and through the 24x36 window of the film support on the other.

part of the jig:

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the film advance roller is finished and a couple of other components are also kind of finished with minor work left:

I would still need to modify the bottom bracket to take the sprokets for the increased gear ration between advance roller and curtain roller and to prepare the curtain. I might go for a smaller slot than the 8mm considering that the selection of films in the 100iso and below range is reduced compared to the 400 and as I like to use the lenses wide open, maybe going towards 1/500 is the better choice.

Also a mysteriose bag with 2 50 teeth sprokets arrived. I wonder what they will be used for.... 😉

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  • 2 weeks later...

the build progresses. During the last days I needed to wait for some more brass stock to arrive and I am still missing some gears for the shutter speed dial. Anyway, I am quite happy how things worked out and there is not much work left to complete the camera. Since the last post I ended up remaking some of the parts that were already finished because I did not like the way I constructed them and came up with better designs. There will be not a single original part going back into the camera. Almost all parts are new except for the two brackets that hold the rollers but even they were modified to take the changed gear ratio for the roller actuation and the modified tensioning roller axle diameter, which now needs to turn freely for the shutter speed adjustment instead of being screw fixed. It is odd but it seems more complicated to work within the constrains of and almost working camera to make it work rather than build one from scratch.

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a couple of pictures from the build to fill things with life:

grinding the film support to have a flat base

prepatarion for soldering the stripes at the bottom are the film guids

 

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film support with guids in place

ready for tagging it all together. The black box in the middle is an alignment jig to position it all correctly in the camera. The two pins lock into the position of the roller bearings and ashure a propper clearance to the film support frame

straight after tagging, the glass plate shims the film plane to be exactly planar to the back of the camera

this is what it looks like from the back

 

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after finishing the soldering

next to one of the brackets, which needs repositioning the gears to accept the new ratios. Closing the existing thread

now it is ready for the new parts

here is the reason why I needed to close the old thread, the new one overlaps the old position

I also rounded off the bracket like it used to be in the original camera (not just a U-trim with a cutter on a mill) but don't have a picture of it

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the tensioning roller assy. The gear to adjust shutter speed (it is a too laarge one, new once on order), brass inserts and bushes to fit it to an aluminum roller. Spring and top thread from a Zorki. The roller is a bit rough to have better adhesion to the glue. It is also no black yet.

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the curtain roller is done in a similar way but no Zorki parts, here it is already assembled

the pressure plate, nothing special but I tried acid dipping it with a higher dillution and it did not turn black

it is bent up on the sides and at the bottom to allow easier inserting the film

Edited by zwieback
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even though not belonging to the camera assembly, I did a take up spool. I left the top and the bottom unfinished and raw to see if it contributes to  th finish of a prototype camera. some scratch marks are left on  too. Soldering at the bottom is poor...

So now I am waiting for some materials to build the light seals and some gears for the shutter speed adjust to continue.

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  • 2 weeks later...

time for a few more updates.

Starting with the shutter speed knob. The original knog has got a M2.5mm thread, which I thought was not up to the job of clamping the dial securely to the sproket that would actuate the tensioning roller. I wanted to upgrade it to M3 size, so a replacement needed to be made, next to it, the original screw:

finished screw in place:

The preparation of the tensioning roller is completed. It now has got the sproket to turn its axle to adjust tension and shutter speed. All parts new:

The actuation of the tensioning sproket needed to be brought to life as well. The wheel in the dummy camera has not theeth to operate anything. A replacement needed to be made:

 

All parts required for the shutter speed adjustment, only the adjustment know is a carry over:

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this is how it would be assembled:

 

old and new:

the way it will be arranged in the camera, illustrating how it will function:

 

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some more parts to play with. They will not go into the camera...

but serve a different purpose

maybe you can already guess where this will take us but more in the next episode:

 

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  • 2 weeks later...

I am very proud of Mr Zwieback for pursuing this challenge of converting the UR Dummy into a working model. It is wonderful that he is sharing the process with the Leica community! I also think that he is doing a very commendable job and is very careful to make sure every step is thought out. One worry I have is the diameter of the shutter drums. There is little room in that area especially since the lens collapses into the space between the drums and they have the shutter curtain that adds to their thickness. This was one of the great challenges that Mr Kim had and the final diameter of the drums and curtain left only a few millimeters of clearance with the collapsed lens barrel.
 

Related to this I finally drove to meet with Mr Kim at his new location that is located about 75 kilometers northwest of Daejeon. The reason I went there was to find out why Marks UR Dummy conversion has taken so long (It’s well over a year now). Turns out that he had a bad auto accident and was in the hospital for a few months. Now I understand why I did not have my text messages answered. He now seems to have recovered and to be in good spirits and obviously was happy to see me. Mr Kim had shutter drums were finished and he had cut a number of the gears on Marks conversion project and fit the 42mm Mikro Summar lens into the the correct location. Also I tested the shutter barrels tensioning system and they worked fine. So they were finished but he still had to made the shutter curtain. It was also obvious that there were about 25 other projects on his desk. They ranged from film movie cameras to high end prewar Zeiss lens and cameras. I also noted a number of complex Leitz zoom lens that are awaiting a CLA. I am sure the accident and the virus restrictions have held up progress on Mark’s UR conversion. I can understand why Mark has been complaining about this delay, but now I understand the reason for it and I sent him an email explaining all of this. 

 

Edited by George Furst
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The tessina loader is not needed.  The cassette itself is modified in that the spool inside is removed and the hole  covered with black tape.  The film is just tightly rolled and pushed into the cassette.  I load it tight, then pull out some some film to cut the leader, and the film pulls easily.  Depending on the film base, it takes about 18-20” of film.   The advantage is daylight loading with visual confirmation film is engaging sprocket and pulling.  Also, you Know when your film is all shot because the empty cassette rattles.  

Edited by Ambro51
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Thank you for the kind words and sorry for not given an update for two weeks now. I was covered in work (also good in corona times) and did not have much spare time to continue on the camera but then, there are also positive reasons that slowed me down. I finally decided to get a lathe again, even though now it is a quite small one, and a mill as well. I simply felt that I would need to increase my manufacturing capabilities again. Instead of just putting both on a table, I wanted to create a nice and fun to work in, space for my hobbies and that took much longer than anticipated. But now I can do much more than before if... if I would have more spare time, which is the issue right now. My working area does not look like Mr. Kim's desk now but it was well bejond in respect to the tools, materials and parts density - a complete caos, which almost stopped me from working at all. My best wishes to Mr Kim, it looks like he can work on cameras again.

On the camera the progress is little and I only managed to (almost) finish the release mechanism and to trim the film support to clear all parts inside the camera.

Regarding the rollers for the shutter curtain I can certainly confirm that this is very critical. This is why I build a jig to position the film suport correctly and to get enough clearance around the rollers. I accounted for a maximum diameter that can rotate inside the camera housing ,incl curtain, to be 12.5mm and with 10mm rollers that should be easy to achieve.

Last, zwieback is actually a kind of bread, a bit like a cookie, very dry and crispy, maybe you know it already:

Edited by zwieback
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