Construction of Camera Bellows
Through necessity, I taught myself how to make camera bellows. I hope to share much of the information in this page to allow others to make just as much mess with glue, paper and fabric as I have! The pictures are a collage from a number of different bellows, so I apologise if the size and shape of the bellows hops around a bit between sections!
1. The MathsFor straight bellows, the maths is easy as each of the stiffeners is the same width and the angles for cutting are all at 45 degrees. For tapered bellows, life is a little more tricky as one of the stiffeners must be wider than the other in order to make the sides taper. The stretched length of the bellows should be about 1.5 times the required maximum working length. For example, if the stretched length is 600mm, the maximum working length will be 400mm.
If the stiffeners are an average of 20mm deep, then for 600mm, there will be 30 stiffeners and 15 folds (2 stiffeners per fold). If the stiffener was 100mm wide, the inside width when folded will be 100-20=80mm and the outside will be 100+20mm=120mm. Thus the basic stiffener depth and number of stiffeners can be calculated. It is possible to change the depth of the stiffener along the length of the bellows, but the mathematics is not easy (the stiffeners in my 8"x10" bellows are 20mm expanding to 25mm then reducing to 15mm).
If the bellows side is to taper, the stiffeners have the same average depth, but one side is deeper than the other. If the bellows go from a width of 100mm at the wide end to 50mm at the narrow end, each side must lose 25mm over the length of the bellows. If there are 15 folds, we need to lose 25/15=1.67mm per fold. Thus if one stiffener is 20.8mm deep and the other is 19.2 mm, the overall change is just enough to make the bellows taper in the folding.
There are geometrical methods to allow tapered bellows to be drawn out and the stiffeners to be drawn without having to measure accurately; I have made a PDF file of instructions that can be found here.
Most importantly, make a set using paper first to check the bellows will be the right size. Scoring in the fold lines by drawing along the folds with a ball-point pen works very well.
2. Marking out and cutting the stiffenersUsing a thin but stiff paper or card (the paper folders/ Manilla envelopes are ideal), mark out the stiffeners for one side of the bellows directly onto the stiffening material; often it is easier to actually do the top and one side of the bellows stiffeners at the same time as it means the line spacing and joins can be done more precisely (as in the diagram below). The ridge of a fold on one side will be adjoining a trough on the adjacent side of the bellows. The image below shows how I mark out the ends of the stiffeners.
|Marking out locations of stiffeners
Although not shown in these pictures, it is a good time to place long strips of masking tape diagonally across the latticework to help to brace it and make it more dimensionally stable; if it twists when gluing it, the bellows will warp and not fold properly.
|Cutting gaps between stiffeners
|Stiffener sections cut and joined together
3. Gluing stiffeners to first layer
|Stiffeners laid out ready
Place a sheet of newspaper along the 'fold line' of the panels 2 and 3 and then fold the sets 3 and 4 back over the paper; the rack of stiffeners is effectively folded in half now.
|Gluing one section at a time
|All stuck down and support strips cut away
Use paper as a mask and then spray the cloth flap with glue and also the trailing edge of the stiffeners of panel 4 and the region of cloth overlap. When the glue is ready, cover panel 1 with newspaper and fold panel 4 over. check the stiffeners of panels 4 and 1 align properly (they will be next to each other at this point) and then slide out the paper and press the glued surfaces together.
The bellows will now form a tube but it is best to leave them folded flat at this point. Alternatively they can be placed on a cardboard former that has been cut to taper in the same way as the bellows.
|Gluing joint in the cloth along the face of side 4.
|The bellows forming a tube.
4. Gluing Last layerThe outer covering is glued in a similar manner by spraying the two sides to be joined with contact adhesive. The process starts with panels 1 and 4 and ends with the material joint on panel 2 (which will be the bottom of the bellows when in the camera). For each panel, the bellows can be re-folded flat so that the panel being glued is facing upwards.
|Gluing outer layer
|Gluing with bellows on a former; liquid glue was used here.
5. FoldingOnce the bellows are glued, they must be left to dry a fair bit before being folded as the glue will soften the stiffeners and make them liable to distort.
Start folding at the wide end of the bellows so that you have the maximum aperture available at the narrow end to get your hand in. If the narrow end is very narrow, then fold that first as access will be restricted whatever. Feel for each stiffener and then start the forward/back process on each band of stiffeners. It takes a little practice, but pay attention to forming each corner properly as you go. It helps to have old bellows (or the paper prototype) handy to remind yourself of what they should look like!
Bulldog clips are useful to keep the already folded sections in line as you go.
|View inside bellows as they are being folded.
|Glueing into the camera.