Electronic control of air flow

Have a look at the sort of valve used on compressed air 'spud guns'. The
idea is to build up a resevoir at high pressure, and then let it out
rapidly. These valves are usually operated mechanically, but a simple
solenoid would suffice. Note that the solenoid valve only needs enough power
to start the firing operation. Once triggered, the main valve flips out of
the way and your compressed gas resevoir discharges down the pipe.

Making things work for multiple balls might be more tricky, and perhaps the
old 'two spinning wheels' launcher might be a more practical route. You
essentially trade off the weight of the motor versus the weight of a high
pressure resevoir.

Dave

Todd.J.Olson@gmail.com writes:


You want a solenoid valve with a very high throughput.

I suggest the Mead Isonic series 4 valves: we've used them in the past,
they're reliable, lightweight and Do Exactly What They Say On The Can.

<http://www.mead-usa.com/products/detail.aspx?id )&type=3>

If you want *really* light valves, then you want Lee:

<http://www.leeproducts.co.uk/>

cheers, Rich.

--
rich walker         |  Shadow Robot Company | rw@shadow.org.uk
technical director     251 Liverpool Road   |
need a Hand?           London  N1 1LX       | +UK 20 7700 2487
www.shadow.org.uk/products/newhand.shtml

How big and heavy is your Helicopter?  Remember Newtons 3rd law of motion.
You will only want to launch something as heavy as a tennis ball if you have
a relatively large and heavy helicopter.  Launching a tennis ball at much
speed will probably knock your helicopter out of the sky.
What country are you going to fly it in?  (I believe projectiles are illegal
in the U.S.  Correct me if I am wrong.)
May I suggest ping pong balls.  I think they will fit in a standard size PVC
sprinkler pipe.

Brent S.

The helicopter is about 25 lbs.  It will be flying autonomously, and
has very responsive correction on the flight controller.  It isn't
actually going to be a tennis ball, but an object about that size.
It's part of a school project sponsored by the DoD, so I think we're
legal.  Thanks for the input guys, I appreciate it.

Perhaps by adapting a commercial paintball gun.

-Brian
--
Brian Dean
ATmega128 based MAVRIC controllers
http://www.bdmicro.com/

A paintball gun mechanism would probably be ideal. Could be
operated from a single small light weight CO2 cylinder, and if
the projectile is large and light weight with a short range, the
barrel could be made from something light weight like drink
bottle plastic or drink can aluminum.

  A diaphram valve is used for some confetti launchers.  It is the same
sort of valve as used for electrically operated Garden Sprinkler
Valves. It allows a lot of air through very quickly.

  I have a design for a confetti launcher on my web site using one of
them.  I use a 12v valve, but only use a 9v battery to trigger it.

Joe Dunfee
www.dunfee.com