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  1. #1

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    Graphical Design of Bellows

    As I keep forgetting how to do it, I have written up a simple method for designing bellows graphically. The method allows for basic bellows with different tapers on the top/bottom and sides etc. as well as rectangular or square bellows. The approach also will let you start with one depth of fold, and end on another; the example bellows I have used for the write-up start with a 10mm fold depth and end with a 5mm fold depth. It is also possible to change the fold depth however you like along the length of the bellows: my 8x10 bellows start with a 25mm fold, increase to 30mm and then reduce to a 15mm fold.

    A PDF file of the design process is here.

    Best regards,

    Evan

  2. #2

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    Nice article--- I want to see the "diminishing" fold depth in action-- I foresee a project in my immediate future.
    * Just because your eyes are closed, doesn't mean the lights in the darkroom are off. *
    * When the film you put in the camera is worth more than the camera you put the film in... *
    * When I started using 8x10, it amazed me how many shots were close to the car. *

  3. #3
    Ian Grant's Avatar
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    There's a Spreadsheet online that calculates the folds etc (either here on APUG or LFPF.info) , marry your article to something similar and it'd be a Godsend

    I've made my own bellows a few times and it's a rewarding experience. I've a set to make soon for a US Museum, and also my £20 Thornton Pickard Triple Imperial I acquired at the weekend

    Ian

  4. #4
    Jesper's Avatar
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    A very handy description.
    Thanks for sharing it.

    Jesper

  5. #5
    Steve Smith's Avatar
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    Thanks. I have made bellows before but it's always nice to see the way other people approach it.

    This is my method: http://stevesmithphoto.webs.com/bellows.html


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  6. #6
    Steve Smith's Avatar
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    What is the reason for the tapering fold width towards the front? Does it give more flexibility when using wide angle lenses where most of the bellows will be compressed flat?

    I would be interested in seeing a set with a constant taper from front to back though I'm not sure if there is any benefit to this!


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  7. #7

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    Hi Steve,

    I like the laser cutting idea very much; cutting the strips by hand definitely counts as 'tedious'.

    The taper in the fold widths is a 'convenience' primarily, rather than adding in any extra flexibility. Using expanding and reducing tapers may help reduce the number of folds too, but the advantages are minimal. For example, on my 8x10, the bellows are removable and the bellows support frame for the rear standard is 12" square with a 10" aperture. This gives a 1" (25mm) frame width which is sturdy enough for the size of the frame so it will not break in my camera bag if I have bag bellows in the camera instead. It makes sense to have a 1" fold width a the rear standard as the bellows are easy to mount to the frames and the inner/outer dimensions match the frame size. The front standard plate on the camera has a width of 4 3/4" (120mm) and therefore a 1" bellows fold size does not leave much space for mounting large lenses. Having a bellows fold with of 15mm at the front standard means I can use a lighter construction bellows frame and have more space for large lenses. Therefore having the folds change in size from the rear to the front means that the bellows frames can be made in a proportion that is mechanically suited to the size of each standard.

    When I made the 8x10, I wanted it to be compact (well, as compact as an 8x10 can ever be!) so also wanted the bellows to fold as flat as possible. By starting with a 25mm fold width, expanding out to 30mm for most of the bellows, and then tapering back to 15mm, I minimised the number of folds and therefore layers of material. In practice, a taper from the 25mm down to 15mm would have been fine as the bellows fold very flat and a few extra folds would have been tolerable (picture of the bellows is below).

    I am in the process of constructing a stereo camera too and there, having a 5mm fold width at the rear standard means the two bellows can fit closely side-by-side. It is far more practical to have most of the folds 10 or 15mm deep running to the front standard however as they will fold flatter and be easier to make. In this case, the fold size would taper in the reverse direction from the rear to the front standard, while the bellows themselves are wider on the rear standard than the front.

    I got the idea from an old Kodak folder which had trashed bellows and I noticed that the fold size reduced as they reach the rear standard so that a narrow mounting width could be used. I examined the cardboard lattice from the bellows and then worked out how to apply the tramline taper to recreate the fold tapering effect.

    Best regards,

    Evan
    Attached Thumbnails Attached Thumbnails DSC_8273.jpg  

  8. #8
    Steve Smith's Avatar
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    Thanks for your reply... it all makes perfect sense. I might try some paper bellows with various forms of taper to see what I think of the idea.

    Having use of CAD which can then be used to directly run the laser cutter certainly helps. I wouldn't want to be doing it all by hand.

    All of the high schools around here have laser cutters, they probably have near you too so that could be an option if you wanted to try som laser cut stiffeners.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  9. #9

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    Not sure about the fold width decreasing towards the front, but there is a good reason for having the fold width increase towards the front. When I built a set of replacement bellows for a half plate mahogany folding camera I picked up cheaply, I wasn't sure if my new bellows would compress enough to fit into the space available when the camera was folded. When I followed the dimensions of the old bellows, with fold width increasing towards the front, I found that the bellows actually folded into itself, and assumed a total thickness that was less than the thickness of the material multiplied by the number of folds.
    Clever people those old camera makers!

    Alan

  10. #10
    Steve Smith's Avatar
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    Quote Originally Posted by AlanC View Post
    Clever people those old camera makers!
    I think the makers of lots of old things were clever because they had to be.

    I recently rewired a friends 1960 jukebox and was impressed by its memory system. Every record in the rotating cage has a pin. When a record is selected its pin is pushed one way. When it is played, its pin is pushed back the other way. After finishing one record, the cage rotates until the next selected pin is found.

    Much more impressive than wiring in a micro-controller and programming it!


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.



 

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