SpudFiles

ok so i don't really know where to get a shrader valve and i don't know if a 2 liter bottle will be safe

I'm trying to make a pneumatic but the largest pressure rated pipe i have access to is 2"

how much psi can a shrader valve hold, and how much can a coke bottle hold

im just confused and desperate

it all depends, coke bottles have been tested up to 150 psi I believe but I wouldn't go above 90 psi. and schrader valves range from anywhere between 60 psi and hundreds of psi.

Actually ive got them up to 160 before they burst, but its better to stay in the low pressure range as frank suggested. And i wouldn't recomend attaching the schrader valve to the bottle cause that plastic is extremely thin and once you put a hole in it, its usually extremely hard to get it to seal.

where can i get a reliable shrader valve?

Most auto parts store have them, or you can get an old bike tube and cut the rubber off the valve and epoxy it in to a piece of pvc thats part of your chamber (these are good to over 100 psi and you can get them for free at bike stores).

When you go to a tire shop to get a valve stem, do not pay the $2.50+ they want for them. First, ask if they will give you one for a school science project. If they will not give you one, offer to pay $.25 for one. When I was buying them 2 years ago, I paid $.11-.13 for each one. And I only had to buy 500 at a time. If they refuse to sell one for a quarter, tell them that $.25 will give them a 50% margin, so they should be happy. Note: these are the shorter rubber stems that you pay $6 for 4 at the automotive store. The longer ones cost the retailers about $.18 each and the chrome ones are $1.80-2.50. NEVER pay retail at a tire shop, you can always haggle the prices down, especially for one lousy valve stem.

Valve stems hold heaps of pressure, I wouldn't go beyond 130 psi with a standard one, but there are some (truck/chrome) that are meant for higher pressures. Do not worry about the stem failing, worry about the surface it is seated against failing. This is the reason we mount the valve stems to double wall material (pvc)

thanx man, it's really nice that you would give me pointers on how to haggle as well,

noble are those who teach!

Before you use a bottle, fill it with water and then pump it to 100 psi. If it shows no sign of streaching or bursting it should be ok to use. I would recomend you stay at 80 psi just to be safe.

Get a tubeless tire valve from a tire shop (the kind with the big rubber bulb at the end) and drill a hole in the thick plastic in the bottom of the coke bottle. Only drill the hole big enough to fit the stem of the valve, it should be impossible to get the bulb through. Put some blu-tac near the top of the valve's stem and then lower the valve through the neck of the bottle and drop it into the hole (I used a bit of wire to do this) Next, pull the scrader so that the blu-tac makes a seal, then wrap the exposed stem of the valve in electrical tape (it stops it falling into the bottle) This should hold with no leaks to a least 100psi.

Oh and when I went to the tire store and asked for valves, the guy gave me 2 valves for free!

Here's a diagram

the outpouring of advice..... i'ts beautiful man

I made something similar to this. I had a shrader valve just like in the diagram above and i drilled a hole into the lid of the bottle and simply pushed it in so it was sitting between 2 little notch type things on the valve. I didnt even use any glue/epoxy and I pumped it to 90psi without leaks. Even without glue I had to cut the lid to get the valve off so I could use it for something else.

Be careful who you haggel, ive been threatened before by a guy with a gun when i tried to negotiate a price about some pipe. Other then that, willard had some good tips.
Still, the ones out of old bike tubes are the cheapest becuse they're free and work just as well. If you go this route though (or even if you buy one from an auto parts store) make sure the valve part hasn't been knocked out. Look at the valve hole, and make sure there is a solid looking cylinder thing in the center of the hole.

Attach the schrader to the pipe that the bottle is connected to, much safer. I just finished a gun a couple minutes ago that works this way.

hey LGM i just looked at your post, but i had already done that exact thing, i have another valve so i might try both ways and pressure test to see what happens

if you get a brand new one, it should have 2 notch type things in it... just drill a hole(mine was 12.5mm) and it will be really tight to get in, no leaks at all.

Killjoy wrote:Be careful who you haggel, ive been threatened before by a guy with a gun when i tried to negotiate a price about some pipe. .

wow how glad am i that i dont live in the us