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 44 users online :: 3 registered, 0 hidden and 41 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

QEV: Sealing Face MODS.

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

QEV: Sealing Face MODS.

Unread postAuthor: airatomic » Mon May 15, 2017 11:26 pm

Hello.

In an attempt to overcome the QEV under 500psi limits, which I assumed is due to the fact that the sealing face will be sliced off by the sharp opposite end, I came up with this:

http://imgur.com/a/Mnoq7

The left one is what we have come to know very well. The right one is the newly modded one, with o-ring attached, in an attempt to "soften" the impact when the sealing face and the opposite end kiss.

However, a few tests showed that the results are not efficient. The QEV won't trigger if its under 200psi and when it did trigger (above 200psi), the results not as powerful. Under 200psi, when piloting, the air comes out from the pilot side instead.

I think, this is all because, the o-ring's soft/smooth surface, matching with the equally smooth surface, become attached to one another in the event of high pressure pullout. Ever put 2 pieces of flat and smooth surfaces together and try to yank up quickly one of the surfaces? The first piece will still attach to the second one. What you call this law or principle?

I was thinking whether I should slide off the bevel part of the o-ring, creating a flat and "rougher" surface, for the sealing face to kiss. Might work, might not.

If the above not working, there is always the QEV/QDV combo to do, to break the limits of the traditional qev limitations.

P/S: What is the highest recorded psi on using the traditional QEV sealing face method?

Any thoughts?

Cheers.
  • 0


airatomic
Private
Private
 
Posts: 8
Joined: Sun Sep 04, 2011 9:33 pm
Location: Hawaii
Reputation: 0

Re: QEV: Sealing Face MODS.

Unread postAuthor: jackssmirkingrevenge » Tue May 16, 2017 9:35 pm

I think, this is all because, the o-ring's soft/smooth surface, matching with the equally smooth surface, become attached to one another in the event of high pressure pullout.


This is a legitimate concern with hammer valves for example, harder materials tend to result in better performance because they become "unstuck" quicker.

For high pressures, you don't really need a rubber sealing face. Here's an example of a t-shirt launcher where a solid aluminum piston seals against a Delrin face. The crucial element though is that it is well finished, any imperfections will leak. An undercut on the face will help maximize the pressure on the parts in contact and make a better seal.

P/S: What is the highest recorded psi on using the traditional QEV sealing face method?


We've seen commercial QEVs taken to 600 psi or so on this forum, here's an example. With a home-made epoxy piston I have made 800 psi launchers with no real problems as long as the valve face seat was big enough area not to dig into the rubber.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24532
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 84

Re: QEV: Sealing Face MODS.

Unread postAuthor: airatomic » Thu May 18, 2017 10:04 am

Ahh, the legend himself replied my first ever public message. *honored*

Thanks, JSR, for the tips. Actually, I got caught on this QEV bug only quite recently. Though it started 5-6 years ago (just made it, made it to work, without full understanding of the finer details of it or its technical specs), I moved away from it in favor of QDV, since its easier to fabricate the piston and didn't have to worry about flat sealing face.

But things suddenly changed, coz recently I had a chance to compare, side by side, these 2 valve types. Same chamber size, same ammo, with QDV one pumped to 800psi and QEV to mere 350psi, but firing both would instantly tell you which one was way way more powerful. From then on, I went back to QEV and now trying to come up with the most efficent type that I could do. Of course you guys way ahead of me in this, seeing all the posts from years ago. ;)

To be fair to QDV, I assumed if the trigger was not by hand (finger yanking the piston), but spring assisted, the outcome would have been different.

I am working on new prototypes at the moment. Once its done and tested, gonna post them. :bounce:

Cheers.
  • 0


airatomic
Private
Private
 
Posts: 8
Joined: Sun Sep 04, 2011 9:33 pm
Location: Hawaii
Reputation: 0

Re: QEV: Sealing Face MODS.

Unread postAuthor: jackssmirkingrevenge » Fri May 19, 2017 11:43 am

Ahh, the legend himself replied my first ever public message. *honored*


I suppose managing to survive so many epoxy explosions without injury is a dubious benchmark of sorts :)

But things suddenly changed, coz recently I had a chance to compare, side by side, these 2 valve types. Same chamber size, same ammo, with QDV one pumped to 800psi and QEV to mere 350psi, but firing both would instantly tell you which one was way way more powerful. From then on, I went back to QEV and now trying to come up with the most efficent type that I could do.


Fast actuation is definitely required for spool type QDVs, as at the moment of firing there is not quite the pressure imbalance that causes a QEV to open so quickly. There are pros and cons to both types of valve but in terms of performance, flow is more or less equal so it's opening time that will make the difference.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24532
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 84

Re: QEV: Sealing Face MODS.

Unread postAuthor: keks2033 » Sun Jun 11, 2017 12:42 pm

QEV хорошо работает на давлениях больше 50 атм. Поршень сделан из резины
  • 1


keks2033
Private First Class
Private First Class
 
Posts: 37
Joined: Mon Feb 08, 2016 2:37 am
Country: Russia (ru)
Reputation: 16

Re: QEV: Sealing Face MODS.

Unread postAuthor: jackssmirkingrevenge » Tue Jun 13, 2017 5:32 am

Love the side pilot! What does it look like on the inside though?
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24532
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 84

Return to Pneumatic Cannon Discussion

Who is online

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

Reputation System ©'