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roberto3912
11-01-2009, 03:31 PM
I've got a Cirkut Outfit camera, with a Century camera model 46 in front and a Cirkut mechanism (marked inside with #612) in the rear. The lens is a convertible type, marked, in the front cell, Gundlach 7 1/2 in. Anastigmat Ser. II f/6.6; the rear cell is marked only 11". The shutter is a Betax #2. On it, I find different f/ settings for 3 focal lenghts: 14", 11", 7 1/2".
The outfit came with a complete series of gears (25 in total, with number of teeths all different) and 2 "fans".
The outfit seems perfectly working, but I need help to solve some questions.
For example:
1) with both lens cells (front 7 1/2", rear 11"), an object at infinity focuses on the ground glass at a distance of 7.9 inches from the center of the shutter: is it consistent ?
2) vith only the front cell ( marked 7 1/2") the same object focuses at about 14" : again, is it consistent ?
3) if I put the rear cell alone (11") in front of the shutter, the focus is at a little less than 14";
4) and, finally, if I swap the cells (11" in front of the shutter, 7 1/2" behind) the focus is at about 6.3" (distance ground glass -> center of the shutter) .

Surely I'm thickhead, but I'm in a great mess. How should I sort the two cells to have the 3 focal lenghts marked on the shutter ?

Second group of questions.
Is there any formula (in case, available on the web) to determine "ex ante" the type of gear (i.e., the number of theets) to be used, according to the focal lenght, the distance from the the subject and the exposure speed ?
OK, a lot of questions. But, this forum is "source of knowledge" most complete ...

Thanks a lot in advance.
Roberto.

jamie young
11-01-2009, 03:53 PM
on question 1 it's 7.5 give or take a little, so 7.9 sounds fine. the "7.5" cell should be front and the 11" rear for your 7.5 focal length
on 2 the front cell is your 14" cell. Always best to put it behind the shutter when shooting
you should put your 11" cell behind the shutter when using it alone as well. Don't worry too much about distances from shutter to film plane with the single cells. Use the gear scales on the bed when setting up, and it should work okay. Do you have gear scales on the bed? Kodak usually set the cameras up pretty well. Thes are formulas for setting up gears floating around the net somewhere.
25 gears is a huge amount. The cameras came with 8-10 gears for a triple convertible lense. Camera usually had three to 5 fans, three being the most common. They should be marked with the shutter speed on them

roberto3912
11-01-2009, 07:13 PM
the "7.5" cell should be front and the 11" rear for your 7.5 focal length
So, to have the 7 1/2" I have to use both cells: correct ?

on 2 the front cell is your 14" cell
Mmm, I'm confused: if I remember well, there was only the 7 1/2" cell, in front of the shutter. I'll check again...

Use the gear scales on the bed when setting up, and it should work okay. Do you have gear scales on the bed? Unfortunately, no gear scales. But I'm sure that the number of the gear (that is, the number of teeth) depends on the focal lenght and on the distance (not sure about the speed), according to some cryptic "formula". The problem is the formula... Having it, you can use different lenses...
I agree that 25 gears are really execessive, most of them have a notation about the focal lenght and the distance. This is the list: 95, 94, 93 (120mm, inf.), 92 (120mm, 120'), 91 (120mm, 34'), 90 (120mm, 19'), 82 (135mm, 20'), 81 (135mm, 14'), 67 (165mm, inf.), 66 (165mm, 20'), 65 (165mm, 14'), 60 (7.5", inf.), 57 (7.5", 28'), 58 (7.5", 19'), 55 (7.5", 15'), 40, 39, 38 (11", 60'), 36 (11", 21'), 34 (11", 14'), 29, 28 (14", 60'), 26 (14", 22'), 25 (14", 17'). The fans are marked 1/4 and 1/12 . Probably, it's a collection of gears coming from cameras of different size. Quite interesting, but this doesn't help.

Len Robertson
11-03-2009, 04:14 PM
Gundlach only marked the rear lens cell as to focal length (11" for your lens). The front cell wasn't marked, except on the aperture scale on the shutter (as your scale is marked 14"). The two longer FL cells used together make the shorter FL (7 1/2" for your lens). It makes more sense to have marked both cells, but that isn't how Gundlach chose to do it. I suppose when the lenses were new, they included an instruction sheet that explained the FLs. They probably didn't think we would be using the lenses 80 years later without instructions.

I think you have a full set of gears for the three focal lengths of your Gundlach triple-convertible lens, plus gears to use 120mm, 135mm, and 165mm lenses. I assume these three lenses were not included with the Outfit you bought. Do all gears have a hole in the center to mount on a shaft coming from the bottom of the Cirkut Attachment? Gears for the later non-fan cameras had a short shaft with a threaded end built into each gear.

I have read a warning about not running the motor of a fan Attachment without a fan in place. The fan slows the motor down and it is supposed to be bad for the motor or spring or something to run it too fast. You can probably make different size fans yourself to achieve a wider range of speeds.

I may have a formula that will help you with gear calculations, but I need to find it. Give me a couple of days to look.

Did your Outfit include the tripod top/turntable with gear teeth around the outside? Also, did you get a groundglass focusing back for the camera body?

Len

roberto3912
11-03-2009, 07:30 PM
Gundlach only marked the rear lens cell as to focal length (11" for your lens). The front cell wasn't marked, except on the aperture scale on the shutter (as your scale is marked 14"). The two longer FL cells used together make the shorter FL (7 1/2" for your lens). It makes more sense to have marked both cells, but that isn't how Gundlach chose to do it. I suppose when the lenses were new, they included an instruction sheet that explained the FLs. They probably didn't think we would be using the lenses 80 years later without instructions.
Absolutely clear, thanks ! :D They didn't imagine that their cameras were so long lasting. And I cannot imagine the same will happen for my Canon EOS...


I think you have a full set of gears for the three focal lengths of your Gundlach triple-convertible lens, plus gears to use 120mm, 135mm, and 165mm lenses. I assume these three lenses were not included with the Outfit you bought. Yes, so it is. Probably, I could try (later on...) to use some of the lenses I have on my Graflex.
Do all gears have a hole in the center to mount on a shaft coming from the bottom of the Cirkut Attachment? Gears for the later non-fan cameras had a short shaft with a threaded end built into each gear. Sure they have that hole, and all of them fit perfectly onto the shaft.


I have read a warning about not running the motor of a fan Attachment without a fan in place. The fan slows the motor down and it is supposed to be bad for the motor or spring or something to run it too fast. You can probably make different size fans yourself to achieve a wider range of speeds. Sure, I'll do that. Later on .... :)


I may have a formula that will help you with gear calculations, but I need to find it. Give me a couple of days to look. :o :) :p :D Can you hear the sound of clapping hands ? The community of Cirkut newbies (and not only the newbies...) will be very, very grateful. Please don't forget it!
In http://photo.net/classic-cameras-forum/00FUVP you hinted at this formula, but the link to Clayton Tume's website is no longer working .

Did your Outfit include the tripod top/turntable with gear teeth around the outside? Also, did you get a groundglass focusing back for the camera body?
Len
Sure ! In "near mint" (or so..) conditions, with teeth perfectly grooved and undamaged, the top surface mirror-like and the rollers not worn-out.

Thanks very very much!

Roberto.

Len Robertson
11-04-2009, 09:15 PM
Roberto - Here is a formula I got years ago from the late Jim Lipari, a great Cirkut repairman and friend of Cirkuts.

(Constant) divided by (Number of Teeth of Pinion Gear) equals (Distance Of Nodal Point of Lens to Film Plane) For your #6 Outfit (assuming you have to correct 9 1/16" diameter gear head) the Constant is 438.46 inches or 11136.88 mm. I believe the concept of lens nodal point has been covered on this forum, or you can do a search for information. The important point is, as the lens focuses closer from Infinity focus, the Distance of Nodal Point becomes greater, and the number of teeth of the pinion gear changes.

However, if you actually want to shoot with your Cirkut, I would very much advise you ignore all this. Whoever put together the Outfit you have seems to have done all the calculations already. I think what you need to do is set up the camera body on a tripod with the focusing back on and make a focusing scale to match the gears you have. I would just make a scale for the 7 1/2" focal length, in order to simplify things. Focus the lens to the distance in feet for each gear and make a mark in your scale with the gear number - Infinity 60 gear, 28' 57 gear, etc. I would start with just one scale for the 7 1/2" lens and try shooting with it and see if it works for you. Forget all the other gears and focal lengths for now.

I don't know if you got any film or spools with your Outfit, but that is another subject.

Len

roberto3912
11-05-2009, 06:06 PM
Here is a formula I got years ago from the late Jim Lipari, a great Cirkut repairman and friend of Cirkuts.

(Constant) divided by (Number of Teeth of Pinion Gear) equals (Distance Of Nodal Point of Lens to Film Plane) For your #6 Outfit (assuming you have to correct 9 1/16" diameter gear head) the Constant is 438.46 inches or 11136.88 mm. I believe the concept of lens nodal point has been covered on this forum, or you can do a search for information. The important point is, as the lens focuses closer from Infinity focus, the Distance of Nodal Point becomes greater, and the number of teeth of the pinion gear changes.

However, if you actually want to shoot with your Cirkut, I would very much advise you ignore all this. Whoever put together the Outfit you have seems to have done all the calculations already. I think what you need to do is set up the camera body on a tripod with the focusing back on and make a focusing scale to match the gears you have. I would just make a scale for the 7 1/2" focal length, in order to simplify things. Focus the lens to the distance in feet for each gear and make a mark in your scale with the gear number - Infinity 60 gear, 28' 57 gear, etc. I would start with just one scale for the 7 1/2" lens and try shooting with it and see if it works for you. Forget all the other gears and focal lengths for now.
Len

Thanks, Len! It's the first time we can find on a NG or forum an example of that formula: a very precious information indeed. A lot of good adivices, moreover. It's proper to remember :( the "master repair technician" Jim Lipari.
The camera can be seen in
http://digilander.libero.it/foto_ras/images/Cirkut_full_left.jpg
http://digilander.libero.it/foto_ras/images/Cirkut_full_right.jpg
http://digilander.libero.it/foto_ras/images/Cirkut_bottom.jpg (with the fan for 1/12 s and gear # 60 for 7.5" lens). No tripod shown, because under re-polishing.

Len Robertson
11-06-2009, 11:58 AM
Roberto - Thank you very much for posting pictures of your Cirkut. It looks to be in wonderful condition.

I hope it is alright with Clayton Tume, but I couldn't locate his wonderful website, so I used web.archive and found archived versions of his pages:
http://web.archive.org/web/*/http://www.bigshotz.co.nz/panorama_cameras.html
I haven't looked at all of the pages, but I did open this one:
http://web.archive.org/web/20080415072329/http://www.bigshotz.co.nz/panorama_cameras.html
At the bottom of the page are a couple of links for the "Gears" program. I don't know if the link to download the actual program actually works, as I didn't try the download. In order to use the program, I believe you must have an exact measurement of the actual focal length of the lens, as measure on some sort of optical bench.

I didn't have any luck trying to recover the old Panorama mailinglist archives, which is very unfortunate, as there were many Cirkut related posts on that list. There is a lesson in the disappearance of that mailinglist. Whenever I see something online I consider really valuable information (such as anything related to Cirkuts), I always print out a paper copy and file it. i don't think there is any guarantee any internet forum or mailinglist will be online forever.

Len

roberto3912
11-06-2009, 08:04 PM
..... I don't know if the link to download the actual program actually works, as I didn't try the download.
It works. "Runs in DOS" (opens in a black window), that is you have to unzip to a folder and start "gears.exe". I prefer to rename "gearsInput.txt" so I can manually enter the data required. It's unclear if it is "universal" (as I suppose) or refers to a specific camera size; maybe the authors Bob Lang or Clayton Tume or someone else could help. A few lines of "help" could be useful. From the "readme.txt" :"A computer program to list CIRKUT CAMERA gear and subject distance combinations for any focal length lens with correction for pivot point location."
I perfectly agree with you that a "simplified approach" to Cirkut shooting is more challenging and rewarding, but the availability of that program is anyway a real improvement in knowledge and usability of that camera. I suggest that any passionate about Cirkut should store that program in his PC.


There is a lesson in the disappearance of that mailinglist. Whenever I see something online I consider really valuable information (such as anything related to Cirkuts), I always print out a paper copy and file it. i don't think there is any guarantee any internet forum or mailinglist will be online forever.
True, unfortunately, also for webpages. In a digital world everything can be "volatile" and fade in an "error 404" (whereas BW negatives 100 yrs old are still here...), due to a decision by a website host or by the author . I "print" them also as PDF files, making also backup copies in a different HD.

clay nz
11-08-2009, 01:47 AM
Roberto

did you get the program to run? I haven't used it for many years. The program originated from Bob Lang, his main use for the program was copying Cirkut prints. So he was shooting 1:1 and creating a full size copy neg.

I had a programmer friend rework the program so it was user friendly and posted it on my site for anyone to use. It will work with any Cirkut camera but you must accurately measure the camera for it to work properly. I used it setting up a #8 camera for some modern lenses. Once that was done I never used it again.

I took the website down because it needed updating and I was getting tired of all the spam that came through the email address for it. Also I was getting sick of answering all the silly questions that were coming through, I have better things to do with my time.

Hope you get the camera up and running properly, they're really challenging to get working well. They're lots of fun too.

Clayton

Len Robertson
11-08-2009, 07:52 PM
Clayton - I hope you don't mind too much I found the copies of your website and posted the link. It is one of my favorite sites, and I felt Roberto, as a new Cirkut owner, should see it .

I believe somewhere I have a copy of "Gears" on a floppy disc, I think directly from Bob Lang. I've never used it myself, due to the need for an exact measurement of the lens focal length. I suspect I could build a nodal slide and use my long Starrett vernier calipers to get an accurate-enough measurement of FL, but there are always 1001 other things to do.

From the information Roberto has posted, it seems a former owner of the Outfit has already measured FL and calculated correct gears. Clayton (or anyone), does my suggestion to Roberto to make a focusing scale based on actual distance measurements corresponding the those marked on his gears seem the correct way to get his Cirkut so he can focus it?

Len

clay nz
11-10-2009, 04:34 AM
Len

there's no problem posting a link. If anyone wanted to host some of the pages on their own website that's ok by me. Maybe I should put it all up on wikipedia?

I'm a bit vague on it now but I think when we got the program from Bob Lang, it was in visual basic and rewrote it in C+. He checked it and okayed the new version then it was put up on the website. There were 2 versions, one you could download and run on your pc the other was an online program that ran off the server. You just punched in the numbers and it spat out the answer.

I never used a focussing scale on my camera. All I did was focus the camera then select the gear to suit that focus distance. If you're shooting scenics you can use one gear for each lens, just the infinity gear. If you're shooting groups a 25 foot gear is all you need.

An easy test to see if your gearing is correct is to shoot a square target placed at the focus distance. When the film is processed measure the square horizontal and vertical. They should match, the vertical never changes but the horizontal does depending on gearing.

Len are you still shooting the Cirkut? I moved over to Roundshots a few years ago, a lot less hassle and easy to print any size, plus cheap film too.

Clayton

roberto3912
11-10-2009, 05:05 PM
To Len and Clayton:



........................................
Clayton (or anyone), does my suggestion to Roberto to make a focusing scale based on actual distance measurements corresponding the those marked on his gears seem the correct way to get his Cirkut so he can focus it?

Len
Well, as a matter of fact, there's a problem of focusing when used in panoramic way. In my camera, the film plane, with the panoramic outfit, is about 4.4 mm more away than the ground glass plane in "normal mode" (goes behind the ground glass plane); therefore, focusing on the ground glass and then fitting the Cirkut box gives deceptive results (out of focus). But, by knowing in advance the value of the difference among the two planes, is possible (with some artifact) to work out a "supplementary scale" for the "panoramic way". And, as reported further on, the program could help also for this issue.

As said previously, I suppose that (making reference to the drawing in http://digilander.libero.it/foto_ras/images/Cirkut_pattern.jpg) the camera should rotate around the axis of the lens in E (supposing the axis is there...), but actually, as I can see in pictures of other Cirkut cameras "at work" (and in mine too), the rotation is around the point F (pivot of the gear plate), and the distance between F and E depends on the diameter of A (the "small gear" actuated by the spring motor), with the camera connected to the tripod by the screw G, fitted in a sliding wooden plate, so that B and A can stay in contact.
But all the same I agree that for short focal lenghts and for a subject at infinite the axis of rotation is not so important: your experience is worth a thousand times the "theory" !
Furthermore, this issue seems less important with respect to panoramic digital rotating cameras, because in Cirkut cameras not the full frame is involved, but only the narrow central slit.
The problem is assembling the correct gear with the correct distance from the subject, for a given lens and for a given "size" of Cirkut camera.
The program, as I said, works, and works in DOS ("command prompt", under cmd.exe, in Windows).
It considers (and asks for typing) a number of "variables"; for a few of them is probably unclear how to deal with. But first it asks if you want to measure the subject distance from FILM PLANE or, alternatively, from the REAR NODAL POINT : can we suppose, just for the sake of convenience, that the latter is approximately on E ? In case of a subject at infinite, even if the RNP is not exactly in E, the shift seems not very significant. But, how can we type "infinite" at the "command line" ? With a very very high value in inches (or mm) ? one million inches?
The "variables" are:
1. - the actual focal lenght : no problem;
2. - the "large gear radius" : does it mean the toothed disc B ?
3. - the "Diameter of film drum with average amount of film": clear and no problem;
4. - the "Perpendicular distance from center of small gear to the LENS AXIS": assuming that the "small gear" is A, does it mean the distance between E and H ?
5. - Perpendicular distance from center of small gear to the FILM PLANE (NEGATIVE IF FILM PLANE IS BEHIND GEAR): does it mean the distance between H and C ? If we refer to the drawing, the value should be positive, I suppose;
6. - the "Slit width": clear, no problem;
7. - the "Gear pitch" : what does it mean ? Is it the distance between two contiguous teeth of the (large ? small ?) gear or something else ?

The output of the program is a file in .txt format (gearsOutput.txt), not well readable (at least, in my PC...) if opened as such in "Notepad" (see an example in http://digilander.libero.it/foto_ras/gearsOutput1.pdf). But if opened with Word is perfectly understandable : see an example in http://digilander.libero.it/foto_ras/gearsOutput2.pdf. Please note that the values given in input were "imaginary" and fictitius, just to test the program: therefore, the results are probably not realistic.
In output we get, for the values typed in input, the "gear #" needed for the various distances (some distances are negative: why?) and the "lens extension" (from film plane, I suppose...; isn't it? can anybody clarify this point? ).
Roughly judging by this rough test, the program seems well working, but needs some explanation/clarification for the above points.
And I confirm my opinion: the program deserves to be included in the IAPP website in the "Cirkut section".
Thanks for your help ! The discussion could look like "pure academy", but the Cirkut camera and the underlying "philosophy" (and technology) are a very important development in the history of photography.

Roberto.

jamie young
11-10-2009, 07:32 PM
On #2 the large gear radius in 4.5" for a 6 outfit. It's the radius of the toothed gearhead.
#4 it's the distance between the lense axis and the center of the small tooth gear center, at a right (90 degree) angle.
#5 You are correct, between h and c. On the #6 and # 8 outfits the film plane is in front of the gear. Not so with the #5, #6, #10 and #16 cameras.
See wikipedia or other source for pitch definition, but the pitch on a 6 outfit (as well as the 8, 10, and 16) is 32 pitch. The 5 and 6 cameras have 48 pitch gears.
I'm happy to put the gear program on my site if someone tells me how. I'm on a mac and not great at programing, but if the server is performing the operations it wouldn't matter.
http://jamieyoungphoto.com/cameras1.html
What are you planning to do for film Roberto?
Jamie

roberto3912
11-10-2009, 09:18 PM
On #2 the large gear radius in 4.5" for a 6 outfit. It's the radius of the toothed gearhead.
#4 it's the distance between the lense axis and the center of the small tooth gear center, at a right (90 degree) angle.
#5 You are correct, between h and c. On the #6 and # 8 outfits the film plane is in front of the gear. Not so with the #5, #6, #10 and #16 cameras.

Thanks for the info !

I'm happy to put the gear program on my site if someone tells me how. I'm on a mac and not great at programing, but if the server is performing the operations it wouldn't matter.
http://jamieyoungphoto.com/cameras1.html
No problem regarding re-programming, if the user is satisfied in using it as "stand alone", in no interactive form (inside a web page). I've copied it in
http://digilander.libero.it/foto_ras/images/Cirkut_gears.zip, just renaming it. It only needs to be unzipped and put in a folder; double click on gears.exe and it goes (in Windows; in Mac I don't know...). In my use I first deleted (better, renamed) the file gearsInput.txt, so I'm prompted to fill the line with the data of my own camera.
Please do not change the "credits": the programmer made a good job and a lot of thanks should go to Clayton Tume (clay nz (http://www.apug.org/forums/members/clay-nz/)) and to Len Robertson (http://www.apug.org/forums/members/len-robertson/) who was so clever in exhuming it from "Error 404 no-land". But I think that it should be accompanied by some "help", some descriptive note, also to solve the kind of doubts I had.
If inserted in a web page, I think some SW gadget would be necessary for interaction: sorry, I can't give any help...

See wikipedia or other source for pitch definition, but the pitch on a 6 outfit (as well as the 8, 10, and 16) is 32 pitch. The 5 and 6 cameras have 48 pitch gears. I've searched on Wikipedia for the definition, finding a lot of different things related to screws, gears etc. Maybe is it the "pitch circle", or "pitch diameter", in http://en.wikipedia.org/wiki/Gear#Pitch ? Seems logically consistent, but on my tripod the gear diameter is 23cm, that is 9.0551 inches; so, where can I get the value "32" ? Mystery!

What are you planning to do for film Roberto?
For the moment, I'm just practising with the camera, trying to undestand well how to use it. It came with two huge rolls of film, still wrapped in black plastic. I suppose it's quite old and probably I'll use part of it to test the mechanics of the camera and my ability. Later on, sure I'll have the problem of film availability: I've heard that Aerial Photo Lab has it, and another source could be (I hope...) at Kodak (http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=2608&pq-locale=en_US&_requestid=3225), according to the hint given by 45PSS in the "Help board" of graflex.org. Did you have (and solved) this problem ?
But, after that, I'll have the problem of processing the film: an amazing adventure, I suspect...

Thanks a lot.
Roberto

roberto3912
11-11-2009, 05:48 AM
I've copied it in
http://digilander.libero.it/foto_ras/images/Cirkut_gears.zip, just renaming it.
Roberto

Sorry, the correct link is http://digilander.libero.it/foto_ras/Cirkut_gears.zip. :(:(
Roberto.

roberto3912
11-11-2009, 08:03 PM
#4 it's the distance between the lense axis and the center of the small tooth gear center, at a right (90 degree) angle.
Sorry, but it is not clear. Do you mean, referring to the image in http://digilander.libero.it/foto_ras/images/Cirkut_pattern.jpg, for lense axis, the line "D" ? And for "center of the small tooth gear center", the line "L" ? But I can't understand how this connection could be relevant for the task of the program, all the more so if with the reference to a "90 degree angle" (of what with what?). The same expression "perpendicular" is used for #5, for which we both agree that is the distance H - C.

...... but the pitch on a 6 outfit (as well as the 8, 10, and 16) is 32 pitch. But mine, on the large gear on top of tripod, has, engraved, the #28.....

http://jamieyoungphoto.com/cameras1.html
Brave, surprising, expert, tenacious ! :o :)

Len Robertson
11-14-2009, 08:52 AM
Clayton - It would be wonderful if you could post your pages to Wikipedia, or somewhere. I don't know if pages found by web archive are good forever and ever, but I doubt it. I've heard there is a way to save entire web pages onto my computer, but don't know how to do it. I'm not shooting Cirkuts at all right now, mainly due to lack of time during periods of nice weather. Not many years until retirement, and taking a Cirkut out on a warm summer day is something I dream about.

Roberto - Regarding the focusing difference between your focusing back and Cirkut Attachment, I wonder if the camera body (or at least the focusing back) aren't original to the Cirkut Attachment? I have a 5X7 Kodak Pony Premo #9 that can be used with modern sheet film holders, but the ground glass needs to be installed backward (frosted side to the rear of the camera) in order to get accurate focus. I've never understood why, but I suspect it has something to due with the transition from glass plates to sheet film. There was a time when camera makers didn't all use the same standard depth-to-film for their film holders.

I believe gear pitch is a term indicating somewhat the number of gear teeth per length of measure. It may refer to number of teeth per inch of measurement around the circumference of the gear, but I'm not sure of that. I think the more formal name for pitch is something like pitch diameter or pitch circle and there is a formula that defines it. Somewhere online should be the precise definitions and formulas relating to gears. Another gear term is "pressure angle", relating to the profile of the individual tooth. As I recall, the pressure angle used for Cirkuts isn't as commonly used as it once was. Some people think you can go to a gear manufacturer's catalog and buy Cirkut gears, but getting the correct pitch, pressure angle, and number of teeth you want in a brass gear is very difficult. You are very fortunate to have obtained a Cirkut which includes gears for so many focal lengths of lenses.

Len

jamie young
11-14-2009, 09:57 AM
Roberto
the lense axis "d" goes through the camera back. The small gear center is offset from it. The distance is the amount of offset from the axis line " D" measured at a right angle from "d" The image you show is a side view which doesn't show the measurement needed. A top view would be better. Don't know about the #28 but it's probably a manufacturing #, not the pitch number. Your pitch is 32

roberto3912
11-14-2009, 08:25 PM
Clayton - It would be wonderful if you could post your pages to Wikipedia, or somewhere.
Gosh! My "ambition" is only to make italian collectors (and vintage photogaphy entusiasts...) a little more conscius that, besides Rollei, Leica and Linhof, other cameras existed in the world... ;) By the way, I was intrigued by the kinematics of Cirkut (a camera I dreamed for a long time to have...) and the "rationale" of its movement.

Regarding the focusing difference between your focusing back and Cirkut Attachment, I wonder if the camera body (or at least the focusing back) aren't original to the Cirkut Attachment?
But I don't worry for that: I'll put a shim, in front of the groundglass, exactly of the same thickness of the difference.

I believe gear pitch is a term indicating somewhat the number of gear teeth per length of measure.
Exact ! I counted the teeth: 290. Then measured the outer diameter: 232mm, that is 9.1338 inches. 290/9.1338 is 32 (rounded value) ! So, it's a "diametral pitch". See this drawing (original in http://www.engineersedge.com/gears/gear_tooth_parts.htm :
http://digilander.libero.it/foto_ras/images/gear_t3_1.jpg

And here the formulas for spur gears:
http://www.engineersedge.com/gear_formula.htm .

But, it would have been better, in the Cirkut formula, to use plainly the number of teeth, avoiding a "rounded value" .... :( After all, to explain the movements in a Cirkut camera and its relative "speed", it's all a question of ratios among teeth in different drives. Isn't it ?

A panoramic photo of Venice - Piazza San Marco, would not be so bad... Well, probably too many people going around. Some nice "blurring", however...
Kindest regards.
Roberto.