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Does your pneumatic Air Gun has a leak?

Unread postPosted: Fri Jan 28, 2011 10:24 am
Author: nadjatee1996
Well, mine did, and I found an easy solution, this can be done with a sink or a fish tank, just stick the thing in there, pump a few times and note where the bubbles are coming from, then epoxy that baby in!

Unread postPosted: Fri Jan 28, 2011 10:29 am
Author: jackssmirkingrevenge
Also: Image

Unread postPosted: Fri Jan 28, 2011 11:03 am
Author: nadjatee1996
HEY, SOME PEOPLE MIGHT NOT KNOW >.<

Unread postPosted: Fri Jan 28, 2011 11:11 am
Author: jackssmirkingrevenge
nadjatee1996 wrote:HEY, SOME PEOPLE MIGHT NOT KNOW >.<


If so, they can't be trusted with projectile launchers ;)

Unread postPosted: Fri Jan 28, 2011 11:34 am
Author: qwerty
Jack will get angry about this but... My epoxy (UniBond metal stuff) never seals.

I always end up using endcaps of some sort instead.
No matter how much i sand and how much i layer it on i will allways get a leak.

Unread postPosted: Fri Jan 28, 2011 11:42 am
Author: Gaderelguitarist
The SOLUTION is to simply build the system correctly from the start.

Unread postPosted: Fri Jan 28, 2011 11:43 am
Author: FighterAce
If you have a hiss... go back to the hardware store and ask the gentleman how to use the PTFE tape....

If you can't hear anything but see bubbles... apply more PTFE, check if the fitting/pipe is tightened all the way and check for defects in the threads.

I wonder how you seal a leak on a cannon thats put together with epoxy... if you put some epoxy on the outside, the pressure would concentrate in that area and blow the epoxy patch right?

Unread postPosted: Fri Jan 28, 2011 11:51 am
Author: POLAND_SPUD
The SOLUTION is to simply build the system correctly from the start.
lol you heard the man... go get some threaded fittings

Unread postPosted: Fri Jan 28, 2011 6:23 pm
Author: Hubb
I'm not exactly sure that putting a 3' long chamber into a sink or fish tank is going to be as simple as you state. The better solution is just to use soapy water. Spray it on and note where the bubbles are at, then fix it.

Unread postPosted: Fri Jan 28, 2011 11:57 pm
Author: jackssmirkingrevenge
qwerty wrote:Jack will get angry about this but... My epoxy (UniBond metal stuff) never seals.


Jack is not angry, just upset :cry:

I put this one together using Araldite only, which I presume has similar properties to Unibond, at it held 800 psi without leaking.

This was for a small diameter project though, for bigger stuff at high pressure I would recommend something tougher and pourable.

Unread postPosted: Sat Jan 29, 2011 2:56 am
Author: qwerty
Threaded fittings = Big and bulky

Oh, i've tried Araldite many times, it's even worse.

Have you ever used the metal putty stuff?

Oh, and i can use PTFE tape, this is for a very small pistol sized gun.

Unread postPosted: Sat Jan 29, 2011 8:30 am
Author: POLAND_SPUD
Threaded fittings = Big and bulky
well yes and no
:wink:

Sure some iron fittings are a lot bulkier than they have to be but you're not limited to them only. Last time I checked brass fittings were just a little bit more expensive than cast iron ones.

It's the best thing for high pressures and it makes your gun serviceable in just a few seconds.

lol let's see what alternatives do we have...
PVC is good for ~ 100-150 psi, and it just isn't up to the job.

Welding is not an option for most users... well unless you're a qualified welder that has built thousands of pressure vessels in his life

Epoxy is just like welding... seems cool at first but unless you are jsr you can't be sure that your castings can handle more than 300 psi, or so

Copper pipes & fittings (soldered) are the only thing that come close to metal threaded fittings (but most copper guns have some threaded fittings anyway)

Unread postPosted: Sat Jan 29, 2011 12:48 pm
Author: nadjatee1996
qwerty wrote:Threaded fittings = Big and bulky

Oh, i've tried Araldite many times, it's even worse.

Have you ever used the metal putty stuff?

Oh, and i can use PTFE tape, this is for a very small pistol sized gun.


I used that, it works great, but it has some drawbacks, no leaks though, I found that my leak was at the meeting place of the hose handle and the trigger, epoxying that means that I couldn't fire anymore

Unread postPosted: Sat Jan 29, 2011 3:34 pm
Author: jackssmirkingrevenge
qwerty wrote:Oh, i've tried Araldite many times, it's even worse.


I used it to 800 psi, maybe you're doing it wrong?

Have you ever used the metal putty stuff?


Putty isn't really a good idea, you want something less viscous that will flow and really seal and adhere to the material.

POLAND_SPUD wrote:Epoxy is just like welding... seems cool at first but unless you are jsr you can't be sure that your castings can handle more than 300 psi, or so


Even JSR doubts himself sometimes ;)

Unread postPosted: Sat Jan 29, 2011 5:21 pm
Author: nadjatee1996
I used the putty, no leaks, but you gotta press hard on it, and shape it with a wet piece of paper towel