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Schrader valve attachment- leak?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Schrader valve attachment- leak?

Unread postAuthor: saefroch » Mon Mar 29, 2010 10:22 am

For quite a while I have been using a very ghetto attachment method to pressurize my pneumatic from a schrader valve- via air compressor or high-quality bike pump- and after working on this for a few months I designed a system involving an 1/2"-3/8" adapter, a 3/8"-1/4" bushing, creative cutting methods, and very well-applied and placed hot glue that makes an incredibly good and stable seal (I previously had issues with breaking the base off a schrader valve, this fixes those), but I am pretty sure that I have somewhere seen an all-metal construction for pressurizing off a schrader valve. I have searched the forum, and came up with nothing. Does anyone know where I can find instructions and/or supplies to build an all-metal schrader (or presta) fueling system for a pneumatic (or a piston hybrid as it may become)?

Any help would be appreciated.
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Unread postAuthor: boyntonstu » Mon Mar 29, 2010 11:05 am

I have used a rubber Schrader valve up to 550 psi.

Just push it through a smooth round hole smaller than the widest part.

The greater the pressure the harder it seals.

Just like on you car.

Why struggle?
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Unread postAuthor: Gun Freak » Mon Mar 29, 2010 11:49 am

Use a threaded one.
It screws right into your gun.
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Unread postAuthor: deathbyDWV » Mon Mar 29, 2010 12:27 pm

Yeah, I'd just use a threaded one. They're only like 5 bucks.
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Unread postAuthor: Gun Freak » Mon Mar 29, 2010 12:41 pm

Mine are a dollar fifty for a 1/8" one and $2.50 for a 1/4" one.
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Unread postAuthor: mark.f » Mon Mar 29, 2010 1:16 pm

Yeah, you can find 1/8" NPT threaded schrader valves in the pump section of Lowes or, sometimes, Home Depot.

The rubber ones aren't hard at all to install into a gun. Drill a 7/16" hole (for most sizes of valve) and pull the valve through, stem first, with a tire valve tool. The bead topmost on the valve will pop into place outside the gun on a single layer (steel, etc.). Install through a double layer when using PVC.

Speaking of which, the valve on my spare tire is leaking like mad at the moment. Might go fix that when I get my paycheck and buy a tire tool :roll:
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Unread postAuthor: boyntonstu » Mon Mar 29, 2010 1:36 pm

deathbyDWV wrote:Yeah, I'd just use a threaded one. They're only like 5 bucks.


But you have to seal the threads.

With rubber. Done! (And free.)
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Unread postAuthor: saefroch » Mon Mar 29, 2010 2:09 pm

Wow, thanks for all the replies. I've got a rubber one to seal pretty darn well, so i'll look for other sources of micro-leaking since it seems they are pretty reliable. Doubt the schrader is the source, but if it is, I now know where to go for metal fittings on one! Thanks!

The attachment system I am using now (that currently uses hot glue, soon to be replaced by epoxy) resulted from snapping the bases off three valves using the normal drill-a-hole-and-stick-it-through method. That works great except when the gun gets bumped around at high pressures the base of the valve breaks off, it leaks out the hole and risks shooting the valve :( .
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Unread postAuthor: boyntonstu » Mon Mar 29, 2010 5:08 pm

saefroch wrote:Wow, thanks for all the replies. I've got a rubber one to seal pretty darn well, so i'll look for other sources of micro-leaking since it seems they are pretty reliable. Doubt the schrader is the source, but if it is, I now know where to go for metal fittings on one! Thanks!

The attachment system I am using now (that currently uses hot glue, soon to be replaced by epoxy) resulted from snapping the bases off three valves using the normal drill-a-hole-and-stick-it-through method. That works great except when the gun gets bumped around at high pressures the base of the valve breaks off, it leaks out the hole and risks shooting the valve :( .


If you were careless to break it off one time why didn't you design a safety shield to protect it?


If you 'bumped' an epoxied Schrader, it could leak enough to trigger the pilot.


Primary rule: Never 'bump' a loaded/unloaded firearm into anything.


Be careful out there.
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Unread postAuthor: jhalek90 » Mon Mar 29, 2010 5:30 pm

boyntonstu wrote:
If you 'bumped' an epoxied Schrader, it could leak enough to trigger the pilot.

Primary rule: Never 'bump' a loaded/unloaded firearm into anything.


This has happened to me with a high pressure steel 1" porting piston valve...

Lucky for me... loading the projectile is the LAST thing i do before i pull the trigger.... Do everything in your power not to bump ANY loaded spudgun, as they are very prone to accidental firing.

And remember... accidents happens, load last, and live to load again.

Keep out hobby safe! or.... at least... as safe as possible. lol
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Unread postAuthor: saefroch » Mon Mar 29, 2010 7:54 pm

Yah, loading is always the last thing, it's pointed downrange during and after loading. The reason I broke off two is because I wasn't sure what happened to the first, but I realized my mistake after that
I designed a system involving an 1/2"-3/8" adapter, a 3/8"-1/4" bushing, creative cutting methods, and very well-applied and placed hot glue that makes an incredibly good and stable seal


That's the setup I'm using now, I'd include pics If I knew how to upload them (detailed help please?). I was thinking of upgrading the hot glue to epoxy, but you're making it sound like that's a bad idea... The hot glue has been working amazingly well, but i'm not sure how it will do at high pressures.

Just another thing to throw out there and hijack the thread I made- How much of a factor is piston weight? Will upgrading from a hot glue piston to an aluminium-wood composite for higher-pressure shots lose me power at all?
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Unread postAuthor: Crna Legija » Mon Mar 29, 2010 9:20 pm

i usually just take the rubber off and solder it in to a 1/2 inch end cap
tested it to 300 psi
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Unread postAuthor: saefroch » Tue Mar 30, 2010 9:42 am

I should try some solder, never thought of that as an attachment method. The only ones I've used are threads, hot glue, tar, and epoxy.
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Unread postAuthor: chinnerz » Tue Mar 30, 2010 5:48 pm

to this day i have never used epoxy, i srsly have no clue weather i can get it or not (probably can), hmm if you listen careful you can hear JSR's eyeballs hitting the floor...

i used solder to a fix my schrader into place. i don't have access to schraders in any other from other than attached to an inner tube of a bike ($4)

with a knife i didnt rly care about, i cut all the rubber of the valve, and then using some sand paper i cleaned the surface. i then found what i think was a 3/4'' hose connector, i cut off the barb part, so it was essentially an end cap with a hole in it. using a drill, i then made the hole in the connector about the size of the valve.
the next step was preparing the surfaces, again with sanding paper (tip put eh valve in a drill chuck and spin while holding the sand paper on the part which you want to sand down). then some flux is added to both surfaces.
i found my iron wasn't hot enough, and i didnt rly want to use a blow torch on the valve, so i used something called a heat gun (like an over powered hair dryer), heating both components, i added some solder and pressed them together with some pliers.

and done, here is a picture of the finished product:
Image

i know it holds at least 150 psi, but i think it should hold a lot more
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Unread postAuthor: saefroch » Tue Mar 30, 2010 7:23 pm

I might try that, since i've got the essentials at my disposal. Soon as I mange, i'm putting up the pics of my setup. Still don't like relying on solder though, since I've known that to fail. Any way to braze (i think that's how you spell it) the parts?

EDIT: Okay, I really need help posting pics
EDIT: Whatever, here's a link until I find out how

http://img31.imageshack.us/gal.php?g=schraderattachment008.jpg

EDIT: Slowly removing the ghettoness of my gun, so I'm using your solder method with a bushing. Awesome idea, thanks Chinnerz.
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Last edited by saefroch on Thu Apr 22, 2010 10:02 am, edited 1 time in total.
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