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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

A Non-Metallic Expanding Spring

Discussion about deployment systems including altimeters, timers, air speed flaps, servo systems, and chemical reactions.
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RebelRockets
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A Non-Metallic Expanding Spring

Post by RebelRockets » Tue Oct 12, 2010 10:44 pm

Hi everybody,

If anyone is looking for a non-metallic expanding spring for a deployment device, try to find some of this type of tubing. It was part of some kind of respiratory device that came home with an elderly relative after he used it briefly during a stay in the hospital. The hose was about a foot long. If you know someone that works in a hospital ask them if they recognize it, where to get one, etc.
blue bellows tubing.jpg
The sample in the photo is 1 3/8 inches long, 1 inch outside diameter, 3/4 inch inside clearance. It can be forcibly compressed to as small as 3/8 inch, easily to one third of its length. When compressed and released, it can lift up a 16 ounce can of beans :roll: while quickly expanding to its full length. Great strength for an ejection device! Even though I've had the tubing in my shop for probably a decade it is still remarkably resilient. It does not seem like the type of plastic that cracks quickly.

Dennis
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rockets-in-brighton
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Re: A Non-Metallic Expanding Spring

Post by rockets-in-brighton » Wed Oct 13, 2010 3:30 pm

Good find. Search terms like "accordion bellows", "medical plastic bellows" returned suitable hits.

How much does it expand laterally when compressed?


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Steve
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RebelRockets
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Re: A Non-Metallic Expanding Spring

Post by RebelRockets » Wed Oct 13, 2010 4:35 pm

I didn't notice any bulging sideways when it was compressed so I checked with a caliper to be sure. It probably expanded no more than 1/32 inch if even that when fully crushed by hand. It neatly accordian-folds on itself with no noticeable twisting or distortion as long as you compress the entire perimeter of the tube.

This plastic does not make any noise when crushed like most cheap plastic bellows do. If you have ever seen the new heat resistant silicon material in some cookware utensils, it resemble that.



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U.S. Water Rockets1
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Re: A Non-Metallic Expanding Spring

Post by U.S. Water Rockets1 » Sat Oct 16, 2010 9:47 pm

RebelRockets wrote:I didn't notice any bulging sideways when it was compressed so I checked with a caliper to be sure. It probably expanded no more than 1/32 inch if even that when fully crushed by hand. It neatly accordian-folds on itself with no noticeable twisting or distortion as long as you compress the entire perimeter of the tube.

This plastic does not make any noise when crushed like most cheap plastic bellows do. If you have ever seen the new heat resistant silicon material in some cookware utensils, it resemble that.
You should probably not be looking for "bellows" if the original function of the device was as a tube for a breathing apparatus. You should check for medical breathing masks and hoses, that sort of thing.


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filbie70
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Re: A Non-Metallic Expanding Spring

Post by filbie70 » Fri Sep 27, 2019 9:20 am

I realize this is an old post. Where you able to find a suitable material for a non-metallic spring?



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anachronist
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Re: A Non-Metallic Expanding Spring

Post by anachronist » Fri Sep 27, 2019 12:47 pm

I've used a cylindrical loop of plastic cut from a small soda bottle. Lightweight and reliable, and easy to replace. It's springy when squashed from a circle shape into an oval, or even bent double and allowed to snap back to circle shape. The spring strength is determined by the height of the cylinder.



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