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 62 users online :: 4 registered, 0 hidden and 58 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

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

The Team
Administrators
Global Moderators
global_moderators.png CS

"Shut-Off Piston" to save air for (semi)auto

A place to ask general spud cannon related questions.
Sponsored 
  • Author
    Message

Unread postAuthor: boyntonstu » Sun Jun 28, 2009 1:08 pm

A possible solution:

Large chamber;manual valve; small chamber;firing valve.

BoyntonStu
  • 0

User avatar
boyntonstu
Brigadier General
Brigadier General
 
Posts: 1039
Joined: Sun Jun 28, 2009 8:59 am
Reputation: 0

Unread postAuthor: Brian the brain » Sun Jun 28, 2009 3:55 pm

wow...you have managed to completely miss the point...


The thing most senior members are after is to get more out of less..

More shots, less wasted air.
  • 0

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: 3494
Joined: Mon Dec 05, 2005 2:06 am
Location: Holland
Country: Netherlands (nl)
Reputation: 29

Unread postAuthor: boyntonstu » Sun Jun 28, 2009 4:04 pm

Brian the brain wrote:wow...you have managed to completely miss the point...


The thing most senior members are after is to get more out of less..

More shots, less wasted air.


I am sorry, I didn't explain it clearly.

I too, wish to get more out of less.

If you can dial in when to close the piston, you can also determine the volume of air to get the projectile to just clear the muzzle.

My 'fill' chamber is that volume.

BoyntonStu
  • 0

User avatar
boyntonstu
Brigadier General
Brigadier General
 
Posts: 1039
Joined: Sun Jun 28, 2009 8:59 am
Reputation: 0

Unread postAuthor: Brian the brain » Sun Jun 28, 2009 4:14 pm

If you do it like you describe..you get a very weak shot...
The volume will run out of "push" much earlier.

We intend to benefit from a large chamber volume, yet keep it from emptying completely.
That way it will fire as powerful as a large chamber-one shot -kind of cannon, yet it is quieter and capable of more shots from a set volume (perhaps including a secondary fill tank)
  • 0

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: 3494
Joined: Mon Dec 05, 2005 2:06 am
Location: Holland
Country: Netherlands (nl)
Reputation: 29

Unread postAuthor: boyntonstu » Sun Jun 28, 2009 4:50 pm

Brian the brain wrote:If you do it like you describe..you get a very weak shot...
The volume will run out of "push" much earlier.

We intend to benefit from a large chamber volume, yet keep it from emptying completely.
That way it will fire as powerful as a large chamber-one shot -kind of cannon, yet it is quieter and capable of more shots from a set volume (perhaps including a secondary fill tank)


I stand corrected.

Thanks
  • 0

User avatar
boyntonstu
Brigadier General
Brigadier General
 
Posts: 1039
Joined: Sun Jun 28, 2009 8:59 am
Reputation: 0

Unread postAuthor: psycix » Mon Jun 29, 2009 3:37 am

Thanks for clarifying brian, and also for reminding me that I still should prototype this theory...
I'll just need to find a way to open up that 1 1/4" chamber...
  • 0

Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

Spudfiles steam group, join!
User avatar
psycix
Donating Member
Donating Member
 
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands
Reputation: 0

Unread postAuthor: Technician1002 » Mon Jun 29, 2009 3:44 am

Brian the brain wrote:If you do it like you describe..you get a very weak shot...
The volume will run out of "push" much earlier.

We intend to benefit from a large chamber volume, yet keep it from emptying completely.
That way it will fire as powerful as a large chamber-one shot -kind of cannon, yet it is quieter and capable of more shots from a set volume (perhaps including a secondary fill tank)


I did some testing of this. Long barrel on a small chamber. Some test shots even had less than 1 atm at exit. High pressure, high flow, fast valve provided some very impressive tennis ball shots. The test was done on a 54 cubic inch chamber, 1 inch valve, and 7 feet of 2.5 inch SDR26 PVC barrel. That is almost a 1:10 C/B ratio. The video of a TB launch is online on youtube. With a 1/3 hp compressor, I can shoot at 100 PSI as fast as I can stuff in tennis balls.

Link to video http://www.youtube.com/watch?v=ZUTXomfdLTE
Link to the TB test http://www.spudfiles.com/forums/failed-attempt-at-a-silent-tb-launcher-t17989.html

I studied the diagram, and shutting off the flow instantly as the projectile leaves the barrel is difficult due to the force, speed, mass stuff of physics. Something about an object at rest and an object in motion..

Shutting off the flow much earlier in flow would provide almost no speed hit on the projectile but will cut air use drastically. The most efficient use of air (high energy efficiency) is to have no pressure left in the barrel as the projectile exits. If for example 10 ATM of pressure is used, it would expand 10X (not counting effects of supercooling at this point). In theory a chamber that is 1/10th the barrel volume can be filled to 11 Atm for an expanded volume at atmosperic pressure at projectile exit. (Air volume would be 1 in chamber + 10 in barrel)

It is true higher power shots can be had with large chambers and much more flow, but at the expense of much lower efficiency. If you hand pump your chambers, efficiency is nice. The power is not too bad either. Check GGDT. The most of the acceleration is in the first 3 feet of barrel.
  • 0

User avatar
Technician1002
Chief of Staff
Chief of Staff
 
Posts: 5190
Joined: Sat Apr 04, 2009 11:10 am
Reputation: 14

Sponsored

Sponsor
 


Previous

Return to General Spud Cannon Related

Who is online

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

Reputation System ©'