On 6 dic, 15:22, John Ferrell wrote:
On Fri, 04 Dec 2009 22:48:38 -0600, Lostgallifreyan

wrote:

No, no, the snags are going to win. Friction can be a vicious mistress.
Which might mean that very cold wet conditions favour the business, as it
happens...

One thought... how acccurate is this launcher? Any chance it can be aimed to
hit the branch above target and bounce to assist further directed travel?
(Sadly I wouldn't trust my stick and elastic trick with that move).

Too many non-precse variables for accuracy. Air pressure, temperature,
elastic accumulator, projectile geometry and line drag.
John Ferrell W8CCW
John Ferrell W8CCW

Hello John,

In my opinion pneumatic systems can have good shot to shot
performance. When you use projectiles of about 0.1 kg width about 25mm
diameter, the required muzzle velocity is in the 25 m/s range (to
reach 70 ft). As this is far below speed of sound, mass of the gas,
hence temperature effect should be negligible.

The weight to diameter ratio assures that air friction has less then
10% influence on height and distance. Maybe you can add something to
avoid tumbling of the projectile.

When you have a large bore fast opening valve ( 10ms) you should have
good performance with relative low pressure (50 psi). When you
experience bad repeatability, it must be the valve. If you like to
experiment further, you may construct your own piston valve that
interfaces directly with the barrel (coaxial structure).

Over here (Netherlands), law is very strict. Even pneumatic spud guns
are weapons and you may not make them as far as I know.

Good luck with the launcher!

Wim
PA3DJS
www.tetech.nl
remove abc in case of PM.