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How can I make a piston? Answered

By that, I mean how can I make that disc that goes in the tube? I need it to be airtight (I'm planning  on using it in a homemade watergun). And if I can't make one, is there a non-online shop from which I can buy it?

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Sandisk1duo

Best Answer 8 years ago

what if you use a piece of stretchable rubber?
like form a balloon?

it should act the same way...

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ShagglepuffSandisk1duo

Answer 8 years ago

Do you mean like I should use it like a diaphragm or use it on the piston? And if you do mean use it like a diaphragm, I don't think it could stretch far enough. 

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Sandisk1duoShagglepuff

Answer 8 years ago

yeah, like a diaphragm!

it would work, if you used a whole balloon

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ShagglepuffSandisk1duo

Answer 8 years ago

Great idea, but a ballon will probobly break.

HOWEVER...

I f you used, let's say, a big sheet of rubber, it would effectively seal off the air from the water.

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Sandisk1duoShagglepuff

Answer 8 years ago

the balloon wouldn't burst, all it would be doing is separating the air from the water, it would transfer all the energy

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Shagglepuff

8 years ago

Here's a bit more info-
The piston is NOT for the pump, it's actually made to build a watergun that uses a piston to seperate the water from the air (like this one:http://www.sscentral.org/homemade/supercannon2.html). However, I don't really have spare pistons lying around, so this is why I want to make one. Also, because of this, it needs to be  fairly large (hopefully 4 inches) in diameter.

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ShagglepuffShagglepuff

Answer 8 years ago

Oh, and I want it to be airtight so that I can pressurize it and then keep it pressurized for the rest of the (watergun) fight. Then I can just take advantage of the water pressure from a garden hose to fill and pressurize it.

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seandogue

8 years ago

Several ways, but for the flex disk that is used as the cylinder seal, you need to make a punch of slightly larger diameter than the internal diameter of the cylinder bore.

For a small cylinder, say 2" or less, you can use a piece of metal pipe as the punch by grinding the end to form a blade

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Re-design

8 years ago

A circle of rubber the same size as the opening, clamped between two washers that are slightly less than the opening.  The rubber will squeeze out and make it a tight fit.

Make the rod out of a long bolt..

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Burf

8 years ago

For a water gun, it doesn't necessarily have to be air tight.  A snug, slip fit will work nicely.
Depending on the diameter of the tube, you could make piston out of a piece of hardwood; carve a groove around the edge and roll a rubber O-ring into the groove, or even make your own O-ring out of a piece of leather.
Think of how a medical syringe works and try to make something similar.

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lemonie

8 years ago

You'll be using PVC tube I guess? Got any PVC bits that would do? You'd want a rubber O-ring and some silicone grease too I should think.

L