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 29 users online :: 4 registered, 0 hidden and 25 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Balanced Hammer Valves

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

Balanced Hammer Valves

Unread postAuthor: jackssmirkingrevenge » Mon Dec 17, 2018 1:47 pm

A good article on the subject showing the different configurations:

Image


Image


Image


Image


Image


Image
  • 3

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25466
Joined: Thu Mar 15, 2007 11:28 pm
Country: Chad (td)
Reputation: 259

Re: Balanced Hammer Valves

Unread postAuthor: wyz2285 » Wed Dec 19, 2018 5:16 pm

Tried to make one and it did work, a lot of little holes tho. Kinda impressive open a 1000 psi valve with a light press of your thumb.
  • 0

CpTn_lAw wrote::D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
User avatar
wyz2285
Major General
Major General
 
Posts: 2357
Joined: Sat Mar 06, 2010 7:50 am
Location: Porto, Portugal
Country: Portugal (pt)
Reputation: 23

Re: Balanced Hammer Valves

Unread postAuthor: keks2033 » Thu Dec 20, 2018 2:43 pm

I tried to make a balanced valve and I did it. The flow area in the valve is now 8.5 mm, piston diameter 7 mm. Such a valve opens with a light drummer and soft spring, tested at a pressure of 70 atm. The lead ball after the shot went into the board by 30 mm, the air in the tee is enough for 2 shots.
  • 1

Attachments
IMG_20181210_213807.jpg
IMG_20181210_213521.jpg

keks2033
Sergeant
Sergeant
 
Posts: 86
Joined: Mon Feb 08, 2016 2:37 am
Country: Russia (ru)
Reputation: 51

Re: Balanced Hammer Valves

Unread postAuthor: mrfoo » Fri Dec 21, 2018 1:51 am

They're missing BtB's cbhv, which is like the balanced poppet valve, but rather than a vented piston, it has a closed chamber - when the valve opens, the chamber is pressurised, as the pressure drops in the barrel it closes.
  • 0

User avatar
mrfoo
Staff Sergeant
Staff Sergeant
 
Posts: 101
Joined: Wed Apr 29, 2015 11:05 am
Country: Afghanistan (af)
Reputation: 9

Re: Balanced Hammer Valves

Unread postAuthor: jackssmirkingrevenge » Fri Dec 21, 2018 8:58 am

keks2033 wrote:I tried to make a balanced valve and I did it.


I love the determination :) nice!

They're missing BtB's cbhv, which is like the balanced poppet valve, but rather than a vented piston, it has a closed chamber - when the valve opens, the chamber is pressurised, as the pressure drops in the barrel it closes.


Isn't the CBHV as Brian made it like the second diagram in my original post?

Image
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25466
Joined: Thu Mar 15, 2007 11:28 pm
Country: Chad (td)
Reputation: 259

Re: Balanced Hammer Valves

Unread postAuthor: mrfoo » Fri Dec 21, 2018 11:37 am

Nah, if you read the article, the chamber is explicitly mentioned as being vented to the atmosphere. Why anyone would bother to do that is anyone's guess.
  • 0

User avatar
mrfoo
Staff Sergeant
Staff Sergeant
 
Posts: 101
Joined: Wed Apr 29, 2015 11:05 am
Country: Afghanistan (af)
Reputation: 9

Re: Balanced Hammer Valves

Unread postAuthor: jackssmirkingrevenge » Fri Dec 21, 2018 12:01 pm

Ah I see what you mean. Well if it isn't vented, then the air within that chamber would need to compress for the valve to open, increasing the resistance. Also, you could have a leak from the main reservoir into this chamber and no way of detecting it, apart from a reduction in power due to the negation of the balanced effect.
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25466
Joined: Thu Mar 15, 2007 11:28 pm
Country: Chad (td)
Reputation: 259

Re: Balanced Hammer Valves

Sponsored

Sponsor
 


Re: Balanced Hammer Valves

Unread postAuthor: mrfoo » Sat Dec 22, 2018 2:29 am

IIRC, BtB had problems with failed o-rings on that chamber, which would have removed the counterbalance and effectively turned the valve into a standard hammer valve.

However, without failed seals, it's beautiful. The opening force is defined by the counterbalance ratio, once the seal is cracked it's the HPA which does the rest of the opening, QEV style, counteracted by the pressure in the counterbalance chamber, which acts as an air spring. As pressure drops in the barrel, it's overcome by the counterbalance chamber pressure, and that, acting as an air spring combined with the piston's inertia, provides positive valve closing action.

It's the positive closing action the others are missing.
  • 0

User avatar
mrfoo
Staff Sergeant
Staff Sergeant
 
Posts: 101
Joined: Wed Apr 29, 2015 11:05 am
Country: Afghanistan (af)
Reputation: 9

Re: Balanced Hammer Valves

Unread postAuthor: jackssmirkingrevenge » Sat Dec 22, 2018 8:34 am

mrfoo wrote:It's the positive closing action the others are missing.


A spring is implied in the other designs though, otherwise they wouldn't re-close.

The problem I found with a closed chamber is that the overpressure from valve opening tended to compress the air in the chamber behind the o-ring very quickly that led to cases where either the o-ring would fail or high pressure air would find itself in the chamber and stay there, leading to a reduction of the balanced effect. Venting this space eliminated the issue.
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25466
Joined: Thu Mar 15, 2007 11:28 pm
Country: Chad (td)
Reputation: 259

Re: Balanced Hammer Valves

Unread postAuthor: mrfoo » Sat Dec 22, 2018 10:30 am

either the o-ring would fail or high pressure air would find itself in the chamber

Any idea on exactly why this was happening? It seems a bit weird if other o-ring joints subject to the same (admittedly violent) forces aren't failing in the same way. A couple of things occur to me, viz:

  • Overheating caused by rapid compression, plus rapid cooling caused by the decompression of the propellant air, causing o-ring failure.
  • A floating o-ring being pushed back and forth as the pressure differential goes from +ve to -ve vs the chamber, with leakage at each change of differential.
Other options might be due to overly-generous clearances around the counter-piston, roughness in the chamber tearing the ring, or any number of other other machining issues, but I'm assuming based on your history that you're good enough with machine tools to get that right :)

I ask because, frankly, I find the spring-less nature of the design very elegant; with some very minor tweakage it could be performance tuned by adjusting the static pressure in the counterbalance chamber (indeed, to the point that the valve faces themselves could be of identical diameter, making the machining much simpler.)
  • 0

User avatar
mrfoo
Staff Sergeant
Staff Sergeant
 
Posts: 101
Joined: Wed Apr 29, 2015 11:05 am
Country: Afghanistan (af)
Reputation: 9

Re: Balanced Hammer Valves

Unread postAuthor: jackssmirkingrevenge » Mon Dec 24, 2018 5:12 am

The o-rings in my experiments were a tight fit in a perfectly smooth chamber and should not have been able to "float" so I assume that it was the extreme forces at the moment of firing that were causing the issue.

I find the spring-less nature of the design very elegant


It is on paper but I've found it to be a case of "sounds good, doesn't work" in practice, at least in the context of my limited experimentation in this area. I'm definitely a relative newbie when it comes to this sort of valve.

to the point that the valve faces themselves could be of identical diameter, making the machining much simpler


There's a lot of tweaking in the "proper" airgun community when it comes to hammer valves, much more that I've been aware of until recently. One of the areas of interest is the use of different materials as a seat for the stem valves as some "unstick" more easily and give visibly better performance. In that regard the use of a spool with an o-ring on each side seems to be less than optimal and indeed with sufficiently high pressure there's the risk that the o-ring will be blown out. In that context you'd want a bit of pressure differential in order to help the valve seal against the seat.
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25466
Joined: Thu Mar 15, 2007 11:28 pm
Country: Chad (td)
Reputation: 259

Re: Balanced Hammer Valves

Unread postAuthor: mrfoo » Wed Dec 26, 2018 2:00 am

jackssmirkingrevenge wrote:I'm definitely a relative newbie when it comes to this sort of valve.

If *you're* a newbie...

jackssmirkingrevenge wrote:In that context you'd want a bit of pressure differential in order to help the valve seal against the seat.

Yeah, that seems reasonable.
  • 0

User avatar
mrfoo
Staff Sergeant
Staff Sergeant
 
Posts: 101
Joined: Wed Apr 29, 2015 11:05 am
Country: Afghanistan (af)
Reputation: 9

Re: Balanced Hammer Valves

Unread postAuthor: jackssmirkingrevenge » Wed Jan 02, 2019 9:39 am

mrfoo wrote:if *you're* a newbie...


Not to pneumatics in general of course but when it comes to hammer valves there are a lot of enthusiasts that have been playing with this sort of valve since they are the dominant configuration for commercial airguns. I've been hanging around the GTA forums lately and it was eye-opening to see the levels to which such valved are modified and tuned, and the various technologies to optimize them, like say the Daystate "slingshot hammer". We're mostly concerned with dumping chambers on this forum but for commercial airguns, getting the most shots with consistent velocity is a higher priority and tinkerers engineer accordingly.
  • 0

hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 25466
Joined: Thu Mar 15, 2007 11:28 pm
Country: Chad (td)
Reputation: 259

Re: Balanced Hammer Valves

Unread postAuthor: Brian the brain » Fri Mar 29, 2019 4:41 pm

Mine does vent the area in front of the piston to atmosphere. A threaded rod serves as the valvestem. I filed it flat on one side to create a vent through the piston/poppet towards the barrel and hammer. So the third picture is accurate.This should also mean that once the valve opens pressure can flow the other direction..helping the valve to close..The vent fixed the O- ring problem. I can't remember having to replace it since.
  • 1

Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
User avatar
Brian the brain
Moderator
Moderator
 
Posts: 3519
Joined: Mon Dec 05, 2005 2:06 am
Location: Holland
Country: Netherlands (nl)
Reputation: 63

Re: Balanced Hammer Valves

Unread postAuthor: mrfoo » Sun Mar 31, 2019 2:58 pm

Ah, that clears that up. thanks, Brian.
  • 0

User avatar
mrfoo
Staff Sergeant
Staff Sergeant
 
Posts: 101
Joined: Wed Apr 29, 2015 11:05 am
Country: Afghanistan (af)
Reputation: 9

Next

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot]

Reputation System ©'