Electronic control of air flow

Posted by on October 13, 2005, 9:36 pm

Hello,

I am interested in using air to launch a projectile from a remote
contolled helicopter. I am thinking of using a tank of compressed air
and having a pneumatic solenoid control the flow. Does anyone know of
a good supplier for such a solenoid. It would need to be able to
switch positions very quickly in order to accellerate the projectile to
a high enough velocity. The entire assembly will need to be very light
as well, since it is going to be mounted on a helicopter. Does anyone
else have a good idea for how to launch multiple tennis balls 15+ feet
horizontally with considerable velocity and accuracy?

Thanks for any info, -Todd

Posted by Dave on October 14, 2005, 9:28 am

> Hello,
> I am interested in using air to launch a projectile from a remote
> contolled helicopter. I am thinking of using a tank of compressed air
> and having a pneumatic solenoid control the flow. Does anyone know of
> a good supplier for such a solenoid. It would need to be able to
> switch positions very quickly in order to accellerate the projectile to
> a high enough velocity. The entire assembly will need to be very light
> as well, since it is going to be mounted on a helicopter. Does anyone
> else have a good idea for how to launch multiple tennis balls 15+ feet
> horizontally with considerable velocity and accuracy?
> Thanks for any info, -Todd

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

Posted by Rich Walker on October 14, 2005, 11:39 am

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

Posted by Brent S. on October 14, 2005, 3:12 pm

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.

Posted by on October 15, 2005, 12:53 pm

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.

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