They open on applied pressure and collapse on release. Best for seconds but can function done to 1/10s of a second.
Will search Mcmaster again.
Unless you've taken the petrified bellows apart, I doubt that it was made in two pieces
I'm 99% sure that it was cast in a 2 piece mold and what you're seeing is the seam line on the outside.
Only way to be positive is to look inside the bellows around the seam area, it's it's smooth
it was cast.
I did find a more suitable flexible bellows in McMaster. Question is whether these are able to stand up to the pressure and whether the surface will accept bonding. I will procede with the bike inner tube project and report back asap.
This is the new "expansion unit" placed on top of the mechanism.
The forced streching (and glueing) of the inner tube makes the lateral compression of the rubber tube possible. I have measured the compression required to reduce the length of 3cm down to under 1cm as being around 400grams. This is fortunately not enough to start the opening process.
I have run out of suitable tubing so must wait until tomorrow to finish the job.
I have completed the drive bellows for the Grundner. I am fairly satisfied with it. The pressure exerted is easily enough to move the 100 years mechanical system everytime. The only doubt question is the glue used to hold the streched inner tube around the end discs. I have used both cycle repair glue (vulcanising fluid) and commercial contact glue. Neither is particular easy to use and with extreme pressure I have been able to break the rubber/zink disk seals. The search is on for a glue (or surface preparation) that can exclude the occasional failure!
Meanwhile I have made another version for a Norka shutter (double barn door type) which has the same basic design. This has thickness of f around 7mm collapsed and nearly 20mm expanded. The photos show the result.
Although it works OK, this is not something I will allow out of the house. I need a more secure bonding - butyl rubber is a notorious surface! If anyone has any good ideas I would be grateful .....?
Steven, I've been intriqued by your FS posting but had no idea what you were talking about until finding this thread of yours. FASCINATING! What are the dimensions of this shutter... and what kind of shutter speed do they deliver?
Also, the type of bellows you describe has been in use by organ builders for centuries, except the material used was thin leather. Two types of bellows are used by organ builders - the hinged kind and these linear-motion bellows.
The available sizes in 1911 were (diameter) 8, 9, 10, 12, 14 and 16cms.
Speed - perhaps not quite as fast as the Packard. Obviously, most useful in Studio lighting.
I suppose that to compete with Jim Galli and his primitive solution, I will have to make a U Tube demonstration of the Grundner and its silence in operation.
The "commissioned" bellows in post #18 turned out OK after a few days glue hardening and is reported installed and working as it is supposed to do.
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