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 :: 3 registered, 0 hidden and 59 guests


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

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

A way to fill it with a single stroke of a hand pump?

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

A way to fill it with a single stroke of a hand pump?

Unread postAuthor: boyntonstu » Wed Jul 01, 2009 3:56 pm

Is there any way to fill an airgun it with a single stroke of a hand pump?

Lets calculate:

Atmospheric pressure at sea level is about 14.7 psi.

2 Atmospheres means twice 14.7 psi or 29.4 psi.

If you take any size piston in a 12" long cylinder and you push it in 6" you halve the air volume and therefore double the pressure.

We have a rifle that needs 300 PSI in a 1/2" x 6" chamber.

1/2" x 6" is about 1.25 cu in.

300 PSI/14.7 = 20 Atmospheres.

IOW We need a 20:1 compression ratio with a final volume of 1.25 cu in.

Lets say that we can supply 150 pounds of force to the pump whose piston is 1 sq in.

(A car engine has about 150 PSI or so)

If we push our 1" piston a closed cylinder we can achieve 150 psi.

OK We are at 10 Atmospheres, half way to 20 Atmospheres.

We need to compress 12.5 cu in into 1.25 cu in. to get 300 psi.

If we take the 150 PSI and push a free floating 1/2 sq in piston (300 psi) in a ~12.5 cu in cylinder, we would reach our goal.

I calculate that we need about a 60" cylinder to achieve 300 psi.

Are my calculations correct?

BoyntonStu
  • 0

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

Unread postAuthor: Hotwired » Wed Jul 01, 2009 4:31 pm

Single Stroke Pneumatic systems have been around for a fair while in air rifles. Pretty consistent things if built well. However they do only compress sufficient to propel a pellet and not at high power either.

I really wouldn't do it if the volume you're after requires a 60" (~120"+ with rod extended) cylinder attached to the cannon. A separate pump would be far easier.

Also, hand pump and 150lb of force (at end of travel) doesn't seem right. If it was a floor pump that would be manageable by using body weight. But again... back to whether its worth the effort to have such a large pump on the cannon.
  • 0

User avatar
Hotwired
Lieutenant General
Lieutenant General
 
Posts: 2599
Joined: Fri Oct 13, 2006 5:51 am
Location: UK
Reputation: 0

Unread postAuthor: spot » Wed Jul 01, 2009 4:41 pm

I'll try to calculate it too :) I'm not used to using inches though... So I could be wrong :D

Volume of the chamber of the gun:
1/4" x 1/4" x PI = 0.19634375 square inches
0.19634375 x 6" = 1.1780625 cubic inches

Piston diameter?
Compression ratio of 20:1 (like you calculated)
=> volume cilinder must be 1.1780625 x 20 = 23.56125 cubic inches
Let's say we can supply 150 pounds of force: 300psi x surface of piston = 150
=> surface of piston = 0.5 square inches
=> radius: 0.5 = r x r x pi => r x r = 0.5 / pi => r x r = 0.159 => r = 0.396 " => diameter of piston = 0.793 "

Length of cilinder?
we needed a volume of 23.56125 cubic inches => 0.396 x 0.396 x PI x length = 23.56125 => length = 23.56125 / 0.159xPI = 47.1698 inches

According to my calculations you would need a 47.1698 inch cilinder with a diameter of 0.793"
  • 0


spot
Private First Class
Private First Class
 
Posts: 27
Joined: Wed Feb 14, 2007 6:52 am
Reputation: 0

Unread postAuthor: boyntonstu » Wed Jul 01, 2009 4:53 pm

Hotwired wrote:Single Stroke Pneumatic systems have been around for a fair while in air rifles. Pretty consistent things if built well. However they do only compress sufficient to propel a pellet and not at high power either.

I really wouldn't do it if the volume you're after requires a 60" (~120"+ with rod extended) cylinder attached to the cannon. A separate pump would be far easier.

Also, hand pump and 150lb of force (at end of travel) doesn't seem right. If it was a floor pump that would be manageable by using body weight. But again... back to whether its worth the effort to have such a large pump on the cannon.


The pump would not be part of the rifle.

The rod would be on only the first pump; use free pistons on the rest.

A 3 or 4 stage pump would make it more compact.

BoyntonStu
  • 0

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

Return to Pneumatic Cannon Discussion

Who is online

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

Reputation System ©'