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 :: 6 registered, 0 hidden and 38 guests


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

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Double Piston Valves

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

Double Piston Valves

Unread postAuthor: Jared Haehnel » Mon Mar 03, 2008 8:06 am

As I am working out the finial preparations to start building my new cannon I ran a simulation with two piston valves and noticed a considerable increase in power...in the order of 75 to 100 fps.

If you remember I'm dealing with about 1300 cubic inches of air so the increased flow would add considerably to power. And I think I can get by with shorter barrels with increase performance. However the restriction is the the increased flow is choked by a barrel smaller then 4 inches.

I'm wondering has anyone done it and is it worth it?

I did a quick search on the forum and didn't come up with any immediate results so if its been discussed before please just link me to it.

The piston valves are four inches in diameter with a 3 inch seat.
  • 0

User avatar
Jared Haehnel
Colonel
Colonel
 
Posts: 611
Joined: Tue Feb 19, 2008 4:15 pm
Location: White River Jct, Vermont
Reputation: 0

Unread postAuthor: SpudFarm » Mon Mar 03, 2008 8:51 am

if you want velocity you want a little choke because when the flow is choked the gasses have to accelerate and that is what you want in a small bore.
in a large bore you don't need all that velocity when the protectile has a great amount of mass.

you choose ;)
  • 0

User avatar
SpudFarm
Donating Member
Donating Member
 
Posts: 2563
Joined: Sat Nov 04, 2006 9:39 am
Location: Norway Trondheim area
Reputation: 0

Unread postAuthor: DYI » Mon Mar 03, 2008 9:19 am

There's really no problem with flow choke, as long as it's the barrel pipe that does the choking. You are wasting power, but it could allow for rather impressive velocities none the less.
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: jackssmirkingrevenge » Mon Mar 03, 2008 9:25 am

With two valves, assuming the seat is as big as your barrel, you're not gaining any real flow advantages. What you are obtaining however is a higher rate of flow increase.

Coaxial pistons provide their maximum flow after travelling 1/4 of the barrel diameter, but obviously the projectile will start to move before this theoratical maximum is reached. Whith two similar piston valves, they only need to move back 1/8th of the barrel diameter for maximum flow, so essentially what you have is equivalent to a faster opening valve.

There could be other issues at hand, like increased turbulence and dead space, that would conspire to decrease performance, but overall you should see a gain in velocity for a given projectile weight.

It's probably not worth the trouble compared to the ease of making a burst disk though, if it's performance you're after.
  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: Jared Haehnel » Mon Mar 03, 2008 9:36 am

Choosing seems to be the hard part. Does the increase cost and labor out weigh the increase in performance?
  • 0

User avatar
Jared Haehnel
Colonel
Colonel
 
Posts: 611
Joined: Tue Feb 19, 2008 4:15 pm
Location: White River Jct, Vermont
Reputation: 0

Return to General Spud Cannon Related

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'