Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 70 users online :: 3 registered, 0 hidden and 67 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Google [Bot], Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Piston Valve Airgun 3/4"

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.
Sponsored 
  • Author
    Message

Unread postAuthor: Gun Freak » Sun Jul 31, 2011 4:33 pm

You don't really need a tutorial, it is rather simple.
Image
  • 0

OG Anti-Hybrid
One man's trash is a true Spudder's treasure!
Golf Ball Cannon "Superna"M16 BBMGPengunHammer Valve Airsoft SniperHigh Pressure .22 Coax
Holy Shat!
User avatar
Gun Freak
Lieutenant General
Lieutenant General
 
Posts: 4969
Joined: Mon Jan 25, 2010 4:38 pm
Location: Florida
Country: United States (us)
Reputation: 11

Unread postAuthor: DerpWithAGun » Sun Jul 31, 2011 4:34 pm

Wow! That looks so simple I'm so trying that right now! Thanks Gun Freak!

EDIT: There is two there which one is better? Or are they both the same thing just at different stages?
  • 0

Last edited by DerpWithAGun on Sun Jul 31, 2011 4:40 pm, edited 1 time in total.

DerpWithAGun
Sergeant First Class
Sergeant First Class
 
Posts: 144
Joined: Sat Jul 30, 2011 10:11 am
Reputation: 0

Unread postAuthor: Gun Freak » Sun Jul 31, 2011 4:35 pm

No problem, but in that picture it doesn't have notches cut on the washers in front of each o-ring that makes the floating o-rings act as a check valve. I can explain further if you don't get it.
  • 0

OG Anti-Hybrid
One man's trash is a true Spudder's treasure!
Golf Ball Cannon "Superna"M16 BBMGPengunHammer Valve Airsoft SniperHigh Pressure .22 Coax
Holy Shat!
User avatar
Gun Freak
Lieutenant General
Lieutenant General
 
Posts: 4969
Joined: Mon Jan 25, 2010 4:38 pm
Location: Florida
Country: United States (us)
Reputation: 11

Unread postAuthor: DerpWithAGun » Sun Jul 31, 2011 4:41 pm

lol, I don't get it. Are you saying i have to cut notches or I don't because of the rubber o-rings?
  • 0


DerpWithAGun
Sergeant First Class
Sergeant First Class
 
Posts: 144
Joined: Sat Jul 30, 2011 10:11 am
Reputation: 0

Unread postAuthor: Gun Freak » Sun Jul 31, 2011 4:59 pm

You cut the notches, like in the attached picture.

The o-ring cannot seal while the cannon is being filled, because the floating o-rings are not sealing against a round surface (because of the notches). When the pilot volume is exhausted, the chamber pressure shifts the o-rings to the rear position, sealing them against the washers behind each o-ring (the ones without notches), making a perfect seal and no chamber pressure is wasted out the pilot (theoretically). This is known as a piston with a built in check valve, because air can pass it while filling, but can't go back. How effective this really is compared to a piston without a check valve, I don't know. But, it is definitely worth making. Also, since the o-rings are floating, the piston has barely any friction and slides freely. So, with the added benifits of the check valve and low friction, this piston performs very well. Over time, the washers in the back will warp due to repeated abuse, but its a 50 cent fix to buy a few new ones. The whole piston only costs like 5 bucks so give it a whirl! This was built for a 2" piston valve, so all you need to do is scale it down for your needs, and it will be cheaper. O-rings can be expensive at big sizes. Hope this helps!
  • 0

OG Anti-Hybrid
One man's trash is a true Spudder's treasure!
Golf Ball Cannon "Superna"M16 BBMGPengunHammer Valve Airsoft SniperHigh Pressure .22 Coax
Holy Shat!
User avatar
Gun Freak
Lieutenant General
Lieutenant General
 
Posts: 4969
Joined: Mon Jan 25, 2010 4:38 pm
Location: Florida
Country: United States (us)
Reputation: 11

Unread postAuthor: SpudBlaster15 » Sun Jul 31, 2011 5:27 pm

DerpWithAGun wrote:lol, I don't get it. Are you saying i have to cut notches or I don't because of the rubber o-rings?


Depending on the pressure gradient, the o-ring will either see a net force on the front or rear face, causing it to seat against one of the washers in the piston assembly. Notching the front washer allows air to move freely from the rear side of the valve to the front, but when the flow direction is reversed, the o-ring changes position and seats against the solid rear washer, forming a seal.

Tada, you now have a one way valve!
  • 0

People should not be afraid of their governments. Governments should be afraid of their people.
User avatar
SpudBlaster15
Major General
Major General
 
Posts: 2385
Joined: Wed Oct 18, 2006 11:12 pm
Location: Canada
Country: Poland (pl)
Reputation: 3

Unread postAuthor: MrCrowley » Sun Jul 31, 2011 6:44 pm

Not shown (or not clearly obvious) in Gun Freak's picture is the epoxy used to seal the bolt and washers. If you don't seal them up with epoxy where they thread through the bolt, air can just leak past the o-rings. The valve will still probably work, but you wont get that air tight seal.
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Sponsored

Sponsor
 


Unread postAuthor: Gun Freak » Sun Jul 31, 2011 10:02 pm

I just recently jb welded the front before I sold it. Thanks for pointing that out Crowley.
  • 0

OG Anti-Hybrid
One man's trash is a true Spudder's treasure!
Golf Ball Cannon "Superna"M16 BBMGPengunHammer Valve Airsoft SniperHigh Pressure .22 Coax
Holy Shat!
User avatar
Gun Freak
Lieutenant General
Lieutenant General
 
Posts: 4969
Joined: Mon Jan 25, 2010 4:38 pm
Location: Florida
Country: United States (us)
Reputation: 11

Unread postAuthor: MrCrowley » Sun Jul 31, 2011 11:48 pm

You sell them? I find it frustrating enough to make one, let alone two. Epoxying it all together is by far the worst part.
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: DerpWithAGun » Mon Aug 01, 2011 1:10 am

Gun Freak, in the picture you posted, do I have to make that white part? If so what is it made from? I was building my version in the car today on my way to school and i left it in my mum's car and she is working late by half an hour which means when she gets back ill upload a picture of mine and you can help me. Ill also put pictures of my Piston housing and all that stuff. Then you can help me solve problems easier :D
Thanks for the help.
  • 0


DerpWithAGun
Sergeant First Class
Sergeant First Class
 
Posts: 144
Joined: Sat Jul 30, 2011 10:11 am
Reputation: 0

Unread postAuthor: Crna Legija » Mon Aug 01, 2011 1:33 am

I think that white one is his old one and no you don't need it.
  • 0

'' To alcohol... The cause of, and solution to, all of life's problems.”
--Homer Simpson

Add me on ps3: wannafuk, 8/11/11 cant wait
User avatar
Crna Legija
Major General
Major General
 
Posts: 2333
Joined: Sun Jul 20, 2008 5:14 am
Location: australia
Reputation: 0

Unread postAuthor: DerpWithAGun » Mon Aug 01, 2011 2:42 am

-Deleted-

Sorry i had some pictures but they didnt upload correct let me fix hold on
  • 0

Last edited by DerpWithAGun on Mon Aug 01, 2011 2:47 am, edited 1 time in total.

DerpWithAGun
Sergeant First Class
Sergeant First Class
 
Posts: 144
Joined: Sat Jul 30, 2011 10:11 am
Reputation: 0

Unread postAuthor: MrCrowley » Mon Aug 01, 2011 2:45 am

http://www.spudfiles.com/forums/posting ... 13190.html

:wink:

I put it into my gun and went to put pressure inside. I head the piston shoot forward and hit the barrel connector. After that air escaped around it and went through the barrel. This happened with my old piston I don't know what to do now. ALL help is appreciated.

Epoxy.

To quote myself earlier:

Not shown (or not clearly obvious) in Gun Freak's picture is the epoxy used to seal the bolt and washers. If you don't seal them up with epoxy where they thread through the bolt, air can just leak past the o-rings. The valve will still probably work, but you wont get that air tight seal.


You will also need to epoxy the sealing face to the front washer, the front washer to the front nut and bolt (and any spring washers), the back supporting washer to the sealing face and any spring washers and nuts holding the supporting washer in place.

Basically, epoxy everything except the area where the sealing face will seal against the seat (barrel).


Edit:

It appears you removed most of your message (please don't do that).
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: DerpWithAGun » Mon Aug 01, 2011 2:48 am

Ok this is my piston

Image
  • 0

Last edited by DerpWithAGun on Mon Aug 01, 2011 2:53 am, edited 2 times in total.

DerpWithAGun
Sergeant First Class
Sergeant First Class
 
Posts: 144
Joined: Sat Jul 30, 2011 10:11 am
Reputation: 0

Unread postAuthor: MrCrowley » Mon Aug 01, 2011 2:51 am

DerpWithAGun wrote:Argh! Can you please tell my how to put pictures on this from My Documents?

Read the link at the top of my previous post :roll:


Here are some pictures of my piston showing the epoxy to seal it all together:

You can sort of make out the JB-Weld in this photo
You can see some araldite used to seal the sealing face on this piston here
This photo shows araldite used to seal the sealing face that has become damaged and needed to be replaced


DerpWithAGun wrote:you can tell me where to epoxy :D


I already have:
MrCrowley wrote:Not shown (or not clearly obvious) in Gun Freak's picture is the epoxy used to seal the bolt and washers. If you don't seal them up with epoxy where they thread through the bolt, air can just leak past the o-rings. The valve will still probably work, but you wont get that air tight seal.

MrCrowley wrote:You will also need to epoxy the sealing face to the front washer, the front washer to the front nut and bolt (and any spring washers), the back supporting washer to the sealing face and any spring washers and nuts holding the supporting washer in place.

Basically, epoxy everything except the area where the sealing face will seal against the seat (barrel).
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

PreviousNext

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Yahoo [Bot]

Reputation System ©'