5. Ribs Cut

Practically camera bellows is made by three layers, there are inner layer, ribs, and outer layer. Two layers sandwich ribs, so each fold of bellows is formed.

To ensure ribs will guide us how to fold the bellows when sandwiched layers cover up them, cracks between ribs are necessary, and thus reduce the thickness at the tip of folds.

And to simplify the building procedure, we will cut off the ribs at corner, as  above image shows. This is a popular way of building bellows, especially for mass production. I myself prefer to extend the ribs to the corner, for that provides maximum shape forming and light blocking function.

Rib material selection

Tempura Paper (oil-absorbing cooking paper)

I found this in the market and tried it on ribs, you know what, it is PERFECT! The thickness, the stiffness, and it absorbs glue so well, I love it, you should try this!!

(image borrowed from internet)
 

Name Card Paper

It is made of plastic material or mixture with stone powder, so sometimes I heard them call it stone paper. It is tear-resistant and often you receive name cards that is thin but can not be torn into pieces, that’s it!
It is not easy to buy in sheets, I found no for retail, you have to order in a minimum quantity from factory, and you won’t want to know that figure!
So if you can have some sheets in hand, congratulations! If not, self adhesive pp printing paper can do the same job.
 

Self Adhesive Printing Paper

Well if you are lazy as I am, don’t want to spray glue on ribs by yourself, you shoul consider this, after laying out the template, take off the wax layer of the paper with tip of kraft knife, then it is ready to paste! If you don’t make so many bellows, you can pick this as sheets, any store sells printing paper for inkjet printers has it as 10-sheet pack, best to get matt surface, for you will apply glue for it.

(image borrowed from internet)
 

Kraft Paper

This is most common use for ribs, for it is thin, a little bit stiff, and durable, and very easy to get. I use it not only as ribs, I use it for plotting templates also.
Here in Taiwan Kraft paper sold as “majhong paper” in rolls, with 20 or more sheets of size about dining table, people lay it on top of table while playing majhong.

(image borrowed from internet)
 

Ribs for shapes 

Layout

4 sides of bellows need ribs, and they are all in the same rib width interval, so if your tools and material allows you, why not make them in one shot?
Let's assume that each side of bellows has 18 pairs of rib, including exceeding ones for frame gluing. If you trim each rib pairs one by one, there are 36 trimming for one side, then 4 sides would take you hundred more trims, spare your eyes and waist, they are innocent!

By simple layout, you can solve all the trimming in one job, if your tools and material allows you.

However, due to my tools limitation, I would have rib pairs for two sides in one trim. Shape A and B have different slant sides, build them separately could reduce confusion in work.
1. Draw a line on Kraft paper, at least the length about 2 times bottom+ top side of shape A.

2. Align with shape A template at end of line, draw two slant lines, connect both ends, this parallelogram is the area for 2 shape A.


And with shape A template, draw a slant line at extended line. Notice you align the right side of template.

3. Now with zigzag ruler, draw zigzag lines at the left most and right most slant lines. Connect each zigzag tip to correspondent tip, now you have all the guides of rib pairs.

Rib Cuts

Measure rib pair carefully, you will find that ribs are in two widths, it is the nature of taper bellows, only square bellows has unique one width of ribs. And if you inspect the image more carefully, then you can tell that wider ribs are always the longer one in rib pairs.

I got about 6.0 mm and 8.0 mm for rib width, but I will leave space for rib gap.

Rib gap width varies as the size of of bellows, small bellows for 120 folders, 5x4 cameras, are set at about 0.8~1.5 mm. It should be at least double the thickness of bellows made by outer layer, rib, and inner layer. I assume my bellows will be made in the thickness at about 0.4 mm or less, so I will set the gap at about 1.0 mm.
So what rib stripes I need to trim will be in 5.0 mm and 7.0 mm.
1. To trim paper stripes in 7.0 mm and 5.0 mm width, better there is an aid to to the job.  Cut a piece of template plastic, made it in this shape.

In fact, I made both side of guide for different rib width, dents should be larger than the paper you prepare for ribs stripes.

2. Trim rib stripes with the help of stripes guide. Here I pick tempura paper for ribs, I like the quality of the paper, it is made in very good fiber, a little bit stiff in touch, and it surely will be great at absorbing glue, it is made for absorbing.
In my bellows, I need to trim about 40 strips both for 7 mm and 5 mm version.

Here I paste both ends of stripe guide to the steel ruler with tapes, this will make cutting even easier, you can see the results in video below.

 

Ribs for shape B

Now back to shape B layout, do the same job and get the rib guide on kraft paper, and cut the ribs that shape B needs.
Shape B has different widths of ribs from shape A, but they are so little in difference, so I decided to ignore them, and prepare 7 mm and 5 mm stripes for shape B too.

4 Layout the templates

Templates

Template plastic is what bag designers or cloth designers use as templates for fabric products. It is semi translucent with frosty grain, flexible and easy to draw and cut. There are two kind of thickness, in 0.3 mm and 1.0 mm, I use 0.3 mm most of time. They sold in variety of size, mine is 45 x 60 cm, you should find them easily in DIY shops.
Buy some more of these sheets, for we will need them when building bellows.

(http://thehabygoddess.bigcartel.com/product/template-plastic-47cm-x-32cm)

Tracing and Cutting

Place template sheet onto the drawings we just finished, trace the patterns by pen, then cut them by utility knife.
Be carefully tracing and cutting templates as precisely as possible, for this template will define bellows detail.



I would leave some space for top and bottom of the shape A/B as images show, it would help when outlining extra rib pairs.
So totally there are 3 templates now, shape A, shape S and zigzag ruler for rib pairs.
Below we will build the last template: Bellows layout template.
 

Bellows Layout

1. with a big sheet of paper (I use roll kraft paper for packing parcel, or majhong table paper), trace first taper A.

2. Place zigzag template by the inner side of shape A, make sure the zigzag tip exactly at the taper bottom corner, trace the zigzag. Be sure the zigzag line extends out the taper, at least two folds.

Do exactly same zigzag line tracing at the other side of shape A, but in opposite direction.

3. Now place the template B, make sue taper edge align the zigzag tips, and taper bottom corner exactly at the zigzag tip, AND ONE STAIR BELOW the shape A, trace the first shape B.

4. Follow the step 2, draw zigzag line at the other side of shape B.

5. Repeat steps mentioned previously, draw another shape A and B, with zigzag lines. What you should get on kraft paper looks like this.

6. Outline the rib pair limits
Leave at least one pair of ribs away from the shape edge, draw the lines at both ends indicating the rib pair limits.
What the shape A/B indicate are the precise bellows size we are building, and those exceeding ribs make sure we leave the space for frame gluing.

As we did to other 3 templates, tracing the layout onto template plastic, then cut it out. Notice that zigzag lines are not necessary to trace.


This concludes the fourth and the last template: bellows layout template.

 

Extended Study

During template layout, you should notice that shape A and Shape B, thought they have same height 195 mm, but the length of their side are different, it shows when you draw shape B next to shape A sharing the same slant side.

• Why?
• Does it matter?
• Which one should I follow?

The bellows lenght was set as 195 mm, but it seems that zigzag tip does not fall exactly at the end.
Why?

• Does it matter?
• Both end of slant side, rear or front end is more critical to meet the zigzag tip?
• Should I make bellows longer or shorter than 195 mm?

When in layout, shape B is one stair below the shape A.

• Why?
• Why not place both shapes at the same level?
• Any different result if shape B is one stair above shape A?

3. Bellows templates drawing

Bellows templates will save you times and a lot of tedios job, and it is easy to build, but before that we should set the bellows dimension we need.

Dimension setting

Some important dimensions defined by your bellows front/rear frames, measure both of them and note the inner and outer dimensions.

(image from ebay http://www.ebay.com/itm/Bellows-Replacement-Metal-Frames-For-Linhof-Toyo-Arca-Swiss-Sinar-Horseman-/271430073486)

Some tapered shape bellows has a front frame which is a metal plate with round hole in center, and screws at corners to lock on front standard, this kind of frame would need no inner measure.

Another important dimension would be bellows length.

I would suggest the longest focal length lens  x 1.25~1.4 would be your bellows length.

Polaroid 110A/B camera equipped with a 127mm lens, and with a

20mm extend range rail, so it has a bellows in the length of 160mm.

Byron camera has short rail, inherited from 110 A/B cameras, and the longest focal length lens it can use is 150 mm, so I would set my bellows around 190~195 mm (150 x 1.3).

If your camera has enough rail extension for macro photography and you do plan to do that, you can set bellows length base on rail extension x1.25. but be aware that folds increased maybe stacked some thickness.

Here is my bellows basic dimension
Back opening frame is slightly bigger than real frame opening (120x90 mm), and you can tell that rib pair width is 14 mm (135-121 mm), meaning each rib has about 7 mm width.

Front opening frame has only outer size been concerned. (66x60 mm)

And the length of bellows will be about 195 mm, as described above.

With these information, I begin templates drawing.

back opening: out (105x135 mm), in (91x121 mm)

front opening: out (60x66 mm)

length: about 195 mm

rib pair width 14 mm

Templates drawing

Basic Tapers

What we are going to do is shown as follow

1. With back and front opening frames,
2. we get the outer dimension, 
3. then to link the lengths/ widths from each frame, we have two taper shapes, 
4. and to stretch two taper to the bellows length we desire, then here we have bellows templates we need!

Here I take the narrower  (orange) taper as example

1. Draw a rectangle in size of 60 x 195 mm (width of front frame width, length of desired bellows)
2. Draw a second rectangle in size of 105 x 195 mm (width of back frame width)
3. Link two rectangle, you got the taper.
4. Keep this drawing, we will transfer it onto a template sheet.

Now draw another taper (brown) by yourself, these two tapers will help building bellows.

Rib Pairs

Last but the most important template is the one for the rib pairs.

As mentioned above, the rib pairs for this bellows is 14 mm, so I need such a template when drawing.

1. Draw a line with interval marks of 14 mm, This marks define each rib pairs. makes line length at least bellows length + 4 more marks, more the better, I left 8 more.

2. Draw a second line with same interval marks, 7 mm above first line, and also makes the marks 7 mm horizontal shift of the first line.

3. Link marks high and low, forming a zigzag line. This is rib pair template of my bellows.

Finished Drawing

What I have when all the drawings are finished, should be 3 shapes in hand, next step I will transfer these drawings into templates, and begin the layout.

I named the narrower side of shape "A", and another one "B", it would be easier to describe at later steps.

So, I believe these drawings are quite easy, no matter you draw them by hand and rulers, or by CG software, there should be no other easy way to have your own bellows template.

What are you waiting for? Draw your templates now!!!!!