Picture of Check Valve from bottles and a table tennis ball
ever wanted to presurize your water bottle rocket and couldn't find anything to stop the air from going out? ever wanted to transfer water or air from one place to another the easy way ? well you better try this !

Step 1: The idea + materials

Picture of the idea + materials
the whole idea behind it is to easiely transfre air or water to one direction While stopping them from going to another, that way you can have a brake in the middle of the transfer without having to hold a folded hose or stick your thumb up some hole (:p).

how does it work ?
well it's quite simple, when transferring the air (or water) pushes the ball up (thats why we use a really light ball), passes around it and gets out the other end. when air (or water) tries to go the other way the ball is pressed to the bottle creating a seal.
notice : the air (or water) flow can move only in one direction - upwards, and the system works only when held in an up-right position with the O-ring at the bottom side ( you can put O-rings on both sides so it won't matter which is bottom ) !

so, to make this you will need these materials :

1. 2x plastic bottles ( without any paterns near the cap )
2. 1x table tennis ball
3. cutting tool
5. epoxy glue ( super or crazy glue arn't meant to seal stuff )
6. optinal : for maximum sealing use an O-ring (*)

(*) to know what diameter to use - after cutting the bottle (accotding to the next steps) put the ball in the top side of the bottle and see where the ball toutches the bottle, then measure the diameter of the bottle at that line (asumin that the inner diameter is clise to the outer diameter) and that is the diameter you need - it doesn't have to be exact becaause the O-ring itself had defferent inner and outer diameters.
tosun_taha4 years ago
It works with air but not the water because density of ball is less than of water.
If turning it upside down doesn't work, you could try filling the ball with water, or just using a denser ball in the first place.
harari (author)  tosun_taha4 years ago
it will work if you set it upside down and connect the inlet to the top and the outlet to the bottom. that way the ball is compressed to the O ring which is on the top and will prevent liquid from traveling backwards.
Futrell8 years ago
Any word on the thumb? That thing is freaky:)
harari (author)  Futrell8 years ago
I do have relatively big hands and long fingers but not THAT long.. it might be the angle of photography or the shadows caused by the flash creating some kind of optical illusion. interesting ...
I also have big hands but m thumb is not quite that long and i was able to reproduce the illusion seen in your photo. it is just the lighting
Photo on 2011-05-18 at 21.02.jpg
butthead956 years ago
it would be really cool if you made it out of that acrylic tubing stuff cuz then it could hol like 100 psi
iProton6 years ago
Ingenious. I wonder whether it will be able to hold high pressures... 30 psi, maybe?
just use a tire valve and pump
How much presure can it hold
harari (author)  waterrocketsrule7 years ago
i don't really know, i guess it depends on the size, shape, material, glue type and isolation strength...
highmeat8 years ago
Good valve to use for draining and filling aquariums. I am wondering about his thumb in that last pic, optical illusion or extra long?
darkmotion8 years ago
You should construct something that can withstand a really high PSI.
Make it from bottles designed for fizzy drinks, and it will withstand quite high pressures.
sweavo Kiteman8 years ago
I think it would lose its strength as soon as you cut & glue...? Very good pics and instructions!
armindilo8 years ago
It's ok ledzeppie, at least I knew you were joking right off the bat! Good instructable!
MattDurr8 years ago
i saw it on mythbusters to but its cool how he shows us how to build it
dcshoeco338 years ago
thats cool