[chbot] OT ping pong balls at mach 1.2

[Mark Beckett]

There was pneumatic golf ball one in TheShed in May2010.
At 100psi they got 171 joules with a 42g golfball

( by comparison a .22 is only 135 joules )

not sure which side of 'legal' it was.....

Mark

Paul Davey wrote:
> I wouldn't be surprised if they serve the ball with a pair of rotating 
> wheels and have a slight difference in speed between them to introduce 
> spin.
>
> Next we should build one that uses hydrogen to propel the ball and 
> something else to propel the hydrogen :)
>
>
> On Tue, Feb 12, 2013 at 10:27 PM, Helmut Walle <helmut.walle at gmail.com 
> <mailto:helmut.walle at gmail.com>> wrote:
>
>     On 02/12/2013 08:21 PM, Mark Atherton wrote:
>
>         Kerry just found this :
>
>         http://www.gizmag.com/how-to-build-a-supersonic-ping-pong-gun/26082/pictures#3
>
>
>         or is this Off Topic ?
>
>         -Mark
>
>
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>
>     Did I calculate it right that the kinetic energy is 218 J at the
>     muzzle (at the standard mass of 2.7 g for the ball)? Pretty
>     impressive... however, due to its low ballistic coefficient, the
>     ball would slow down rapidly. I wonder, though, whether a
>     reduced-speed version of this would make a nice commercial product
>     - after all, there is quite a range of table tennis robots
>     available on the market, which brings it back on topic. I have
>     never bothered finding out how they work internally, but as they
>     produce spin as well, they probably really "hit" the ball with
>     something like a racket. But this is not to say that spin couldn't
>     be produced by a pneumatic gun like this one here. It might be
>     sufficient to provide a transverse pressure gradient, although
>     this could lead to issues with the ball touching the barrel wall.
>     Sounds like something worthwhile further experimentation! (Given
>     time...)
>
>     Kind regards,
>
>     Helmut.
>
>
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