Tuesday, April 14, 2015

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.

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!!!!!
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