Monday, April 13, 2015

2. Some bellows basic concepts you should know

There are some characteristics you should be aware in building bellows, some are needed for basic structure, and some are for the need on building.



Bellows are built in three layers

Not like the practice we did on last link, building bellows in one piece of paper, a real bellows normally is built with three layers of material, there are outer layer, ribs, and inner layer.


Outer layer exposed under the sunlight, winds and sands, rain and mist, sometimes even snow, so it must be durable and strong on climates, manufactures always choose leather as outer layer.


Image shows a Linhof Technika bellows, outer layer is made of syntheticleather. But now to find leatherette that blocks light and thin enough for folding into compact size is hard to find.
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This bellows is built with a rather thick leatherette as outer layer, it has silky surface on a rubber lining. Half way at  folding step I gave up the building, for I had known it is too thick to fold on a field camera.
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Ribs are a piece of manila paper or kraft paper, cut in thin long shape according to the folds, to maintain bellows folding shape, you won’t see ribs, for it is sandwidched by outer and inner layer.


This is a bellows taken off from Polaroid 110A/B camera, all ribs shown for outer layer been ripped off, so you can see what ribs looks like.


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Look closely, you notice that all four side of ribs are actually cut from one manila paper, which shaped by a knife mold I believe, this is really cleaver, but for people who is planning to build only a few bellows, knife mold is price too high.
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Inner layer has matt surface to eliminate any possible diffraction inside the bellows, most of bellows has fabric material with matt black surface as inner layer.


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Linhof Technika bellows in early age seems to have a kind of paper as inner layer.
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Ribs are in pair, and tapered bellows has rib pairs in different width



Ribs are always in pair, for two ribs makes a fold.


The rib width refering to the “slope length” of the fold, rib width been noticed here because rib width is not always in same dimension.  


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It is all in same rib width if it is a rectangular shape bellows, like the one that we built with paper.


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But for tapered shape bellows, rib pair comes with two rib width.
Look carefully at the rib layout, you will notice some interesting facts.


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  1. Compared with red and grey rib pari, you notice that red rib is bit narrower than grey one.
  2. And in pair, the narrower rib is the shorter rib of the pair. That is, narrower rib is closer to the front opening.
  3. Greater difference between front/rear opening in dimension, bigger width difference of the rib pair.
  4. Each pair of ribs makes a fold, but how do you know which rib folds out, which one folds in? I will leave this to you to finding out.
  5. Fold ridge on this side, will be valley on its adjacent sides, and vice versa.


Outer layer seamed at the bottom side

This is more obvious for the outlook integrity, one side of bellows will face the camera rail bed, so placeing the seam at that side would be a perfect arrangement. Remember this when you laying out the ribs.

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