[chbot] OT ping pong balls at mach 1.2

[Helmut Walle]

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
>
>
> _______________________________________________
> Chchrobotics mailing list Chchrobotics at lists.linuxnut.co.nz
> http://lists.ourshack.com/mailman/listinfo/chchrobotics
> Mail Archives: http://lists.ourshack.com/pipermail/chchrobotics/
> Web site: http://kiwibots.org
> Meetings 3rd Monday each month at Tait Radio Communications, 175 
> Roydvale Ave, 6.30pm
>
> When replying, please edit your Subject line to reflect new content.

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.