[TowerTalk] EZ-Hang

[Jim Lux]

At 12:11 PM 12/13/2005, Pat Barthelow wrote:
>Folks:
>I had a friend in 6th grade lose an eye with a simple rubber band and
>paperclip that rebounded back into his eye when he shot it...Please wear
>Goggles....
>
>Also, a while back I came across the mother of all antenna launchers... This
>should have been featured in the show, "Home Improvement",   with "Tim The
>Tool Man Taylor..."


There was an episode of H.I. that had a pneumatic toilet paper roll 
launcher.  J.D.Streett was the effects supervisor on the show, and built 
it, pretty much as you describe.  http://www.jdsfx.com/


>The PVC pipe, compressed air, pneumatic system is fairly cheap, easily
>homebrewed, and sends tennis balls with antenna attached, as high as 160 ft.
>   Test shots send un tethered tennis balls 600 ft high...
>[600 ft is hard to believe, in my opinion, but would be VERY impressive, at
>field day, if true]

600 ft is a bit hard to believe, especially with a fuzzy standard tennis 
ball (they are fairly draggy and not very heavy).  If you didn't have to 
contend with air drag, that's a muzzle velocity of about 200 ft/sec to get 
to 600 ft, and 200ft/sec is very practical with a tennis ball and compresed 
air.

at 200ft/sec muzzle velocity, you get to about 200ft in about 3 seconds. 
Then you start to fall, but you quickly approach terminal velocity of 
around 54 mi/hr (78 ft/sec), so you actuall hit the ground at about 7 seconds.

Doubling the muzzle velocity to 400 ft sec only gets you to about 300 ft in 
3.3 seconds, and you're already a good fraction of the way to sonic speed 
(mach 0.4), so the drag is already increasing dramatically.  Even going to 
1000 ft/sec muzzle velocity and totally ignoring sonic effects, you're only 
up to about 460 ft.

The problem is the light weight of the ball.  Weight it up, so its around a 
pound, and you've got no problem making it to 600 ft.

However, you're unlikely to need to launch an antenna to 600ft, so the 
tennis ball cannon is actually a pretty good way to go.