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A typical folded bellows allows for axial expansion/compression, lateral offset, and angular deflection. Is there a bellows fold pattern that can accommodate a relatively large torsional rotation about the longitudinal axis?

Motivation

I'm looking to prototype a waterproof (IPX67 or IPX68) flexible housing for DSLR cameras with large zoom lenses. A picture is worth a thousand words:

enter image description here
Dan Carr testing the RainCoat Pro 2 on a grizzly bear photo trip in British Columbia. From shuttermuse.com Photo: Rowan Thornton

The photographer in the kayak is using a rain coat, which merely protects from rain. But the thought of my kayak turtling with $10k worth of camera and lens exposed makes me pucker. So I'd like to begin prototyping a flexible watertight bellows to surround the lens and mate with a flexible "bag" covering the camera body.

Of course, a regular bellows (like a bellows plunger) will allow for a zoom lens to accommodate changes in length. The problem is accommodating control of the zoom ring on the lens, which is torsional rotation of the outside of the bellows. I anticipate the maximum rotation is about 135° (+/- 65° or so from mid-zoom).

Is there a fold pattern to allow a cylindrical surface to be torsionally deformed like I'm describing?

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  • $\begingroup$ Do you want only protection from water, or also mechanical shock? $\endgroup$ – mart Nov 4 '19 at 12:23
  • $\begingroup$ Just water. Long camera lenses are almost impossible to handhold, so they need to be mounted on a tripod. The photographer in the photo is using something like this pano-gimbal head. I'm not worried about the tripod foot mount for the prototype though; I already have some ideas for that. $\endgroup$ – scottbb Nov 4 '19 at 13:11
  • $\begingroup$ Google for "origami spiral". The "magic spiral cube" shows the basic idea with a square tube. $\endgroup$ – alephzero Nov 4 '19 at 13:12
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I don't see the neccesity for a bellows. I suggest you make an oversized tube from a waterproof, flexible plastic. Oversized means the diameter is significantly larger than the tele, then you should have enough flex. for the torsion. Be mindful that only the length ahead of the mount it really available for torsion.

(Take your time with accepting this answer, I have never designed such a system.)

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  • $\begingroup$ I agree with this approach - folds are more likely to leak after repeated motion, too. $\endgroup$ – Jonathan R Swift Nov 5 '19 at 8:10

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