Tapered bellows - square to rectangular

[walter23]

I'm trying to build the pattern for a new bellows for my 8x10 Conley. I've got the old bellows ripped apart, but of course accurately measuring dimensions is a bit tricky on old faded & stretched/deformed cloth with thick folds.

I'm trying to figure how to manage the different "drops" in the folds for the two different dimensions since the front lens board is a rectangle. The top of the front standard is a bit over 6" wide (I have the exact dimension at home), and the side is 5 and a bit tall. Since the back is square, this implies the different bellows surfaces have to "fall" at different rates - ie, the rise vs. fall segments have to be different lengths on the sides of the bellows vs. the top/bottom of the bellows. But obviously this wouldn't allow the bellows to fold, as the pleats have to align around all four sides of the bellows. How do you handle this?

I think figuring out *how* to build the bellows is probably 10x as hard as actually making the bellows itself. I have the old cardboard ribs which will save a lot of labour, but I just can't quite figure how to draw the pattern on my new cloth. All the descriptions I've found online have either been square bellows (the majority) or tapered bellows with symmetrical, square fronts. Nothing dealing with the complexity of a rectangular lens board.

Thus far this has taken me months longer than I anticipated, just because it's become a lot of hassle just to figure out how to pattern the thing.

 

[walter23]

I read it through once and got lost. I'll re-read it later when I have pen / paper handy to try to follow along.

So far I've sorted out the major dimensions of the overall pattern, but drawing the pleat lines is where I've got to figure stuff out.

 

[Colin Graham]

Sorry Walter, I missed the part where you said you already have the ribs. My method was for armature-type patterns, probably not much help at all for individual ribs.

 

[walter23]

Sorry Walter, I missed the part where you said you already have the ribs. My method was for armature-type patterns, probably not much help at all for individual ribs.

Now I'm totally lost. What's an armature-type pattern?

The ribs I have are just salvaged from the old bellows - they're styled like this (nabbed from: this page):

Zigzag ribs on the top & bottom faces, blunt-ended ribs on the other two. But tapered instead of square, obviously.

If there's an easier way than building a pattern around reusing my old stiffeners, which are kind of brittle anyway being 100 years old, I'm open to suggestions.

 

[Colin Graham]

Sorry- the ribs for each side are connected in one sheet. Like this method here.

 

[orto]

Walter, it's probably much easier to build bellows than to explain in words how to build them, :>)
If you look carefully at the way your old bellows fold, you can build whatever bellows of that type. The geometry of the movement and of the flattened pattern is not so difficult to fathom, the manufacturing of the bellows is worse. I know, I was making bellows from one piece of material and succeeded. No cutting, no putting together of some parts, but it takes a lot of patience and the necessary knowledge. Instead of looking for verbal explanations look at the folds and you will get the understanding in an easier way. That's how I did it. My 2 cents.

 

[ic-racer]

This thread might give you some ideas : http://www.largeformatphotography.info/forum/showthread.php?t=29267&page=5

Basically, if you have the original bellows material, measure it, and this gives you the dimensions of each side. Then measure the size of each pleat stiffener, and the distance apart. Then draw it out in a graphics program.

That should give you your pattern, which you can use for what ever method of construction you are going to use.