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  #1  
Old 03-05-2020, 05:35 AM
berntd berntd is offline
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Default How can this be made? Metal bellows.

I am seriously impressed by the brass bellows from a 1951 thermostat.

I am puzzling how one could make it.
There are videos on large stainless ones but there must have been a simpler way back in the day.

The whole thing is one piece, no seams.

Ideas?

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Last edited by galooph; 03-05-2020 at 09:13 AM.
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Old 03-05-2020, 09:54 AM
billfunk29 billfunk29 is offline
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Default Bellows

Hard to tell from the pictures, but looks to me like a hydro formed part. Reminds me of the bellows used as an actuator to control the cooling damper on a Corvair.
Other options: explosion forming or electroforming, where the part is electro plated on a sacrificial mandrel.
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Old 03-05-2020, 10:44 AM
Secant Secant is offline
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https://www.ameriflex.net/custom-pro...xoCFOIQAvD_BwE

Ask them-
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Old 03-05-2020, 11:37 AM
Marc Bourget Marc Bourget is offline
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Lots of videos on YouTube when searching on "how to make metal bellows"


Quick answer, hydroformed tubing placed in a split mold
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Old 03-05-2020, 11:41 AM
Marc Bourget Marc Bourget is offline
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lots of approaches, internal, external, rolling, etc. shown in YouTube videos after a "How to make" search
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Old 03-05-2020, 01:25 PM
hot rivet hot rivet is offline
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I have looked at doing this before, do some google patent searches- many of the methods described can be used on a smaller scale.
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Old 03-05-2020, 04:49 PM
berntd berntd is offline
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Quote:
Originally Posted by billfunk29 View Post
Hard to tell from the pictures, but looks to me like a hydro formed part. Reminds me of the bellows used as an actuator to control the cooling damper on a Corvair.
Other options: explosion forming or electroforming, where the part is electro plated on a sacrificial mandrel.
ALthough

I am not an expert in the electroforming plating field, but I did investigate it a while ago for something else. It is a very versatile process indeed.
However, I do not think one could easily create this part by plating since there would be no material transfer occurring in the tight gaps due to lack of current flow there.

EDIT: Looks like it can be done after all:
https://www.youtube.com/watch?v=OTR4SJRVcCo
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Last edited by berntd; 03-05-2020 at 06:38 PM.
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Old 03-05-2020, 05:09 PM
Jaroslav Jaroslav is offline
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I think it's made by spinning. Two shaped rollers. Made of tube on a lathe. Nothing complicated for a bigger series. But he could even make one piece. Is it needed? I guess I'd replace it with something new.
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Old 03-05-2020, 06:18 PM
berntd berntd is offline
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Quote:
Originally Posted by Jaroslav View Post
I think it's made by spinning. Two shaped rollers. Made of tube on a lathe. Nothing complicated for a bigger series. But he could even make one piece. Is it needed? I guess I'd replace it with something new.
That was my first thought as well. It would need a lot (!) of stretching of the brass though across relatively thin sharp rollers.
I see on youtube, they make the bigger ones one rib at a time bu pulling tubing in instead of stretching it. Very interesting.


I am thinking rollers with gaps that are far enough apart. They then roll the material and move closer together as they do it.
Then no stretching would be needed but it will be a complicated tooling setup.
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Last edited by berntd; 03-05-2020 at 06:23 PM.
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Old 03-06-2020, 02:21 AM
Jaroslav Jaroslav is offline
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If you divide the operations by an estimate of 3. This means 3 sets of tools. And to try and test. Trial and error. Maybe it could be done after one wave. Center the tube with the lathe tailstock and move it always after one wave. Warm and cool the copper or brass tube to make the material soft and try. Each stroke will harden the material. You can repeat the annealing. Good luck. Musical instruments also drag into crazy shapes. It's a similar situation.
What the point is. It must still be produced somewhere or be available for purchase. It's in some instruments, in a barometer, or in old cars.
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