John Ferrell wrote in
:

On Mon, 30 Nov 2009 10:31:12 -0800, Jim Lux
wrote:



3 9V batteries in series makes a fine source to actuate a sprinkler
valve. Put a 0.1 uf (or thereabouts, non critical) capacitor across the
pushbutton contacts to make it last a bit longer.

Got a little further today. It takes too many hands to twist the
valve, fiddle with the reel and aim the device. I black vinyl taped a
micro switch to the valve assembly with ONE 9 volt battery so that I
can thumb it to launch. I also moved the open face reel back to the
valve end of the barrel and fabricated (more black tape & paperclip)
an eye to pass the line through so that line retrieval with the reel
is less awkward. Today's final test was conducted in the dark so I was
unable to see much. I launched nearly 90 degrees and it was gone for
several seconds so I expect it did well.

VK2KC emailed me with some advice. He pointed out that it is usually
better to launch from the woods to an open space. I expect that will
be the case.

It seems to me that this device consists of three components: Barrel,
Valve and accumulator. It seems that to change to launching tennis
balls would be a matter of fitting a 2-1/2" barrel. I doubt that I am
going to find that in my area but I will keep my eyes open.

Tomorrow is another day!

John Ferrell W8CCW


Sorry if my post is as silly as it appears it might be, but just in case it
isn't... I've seen people walking dogs in a large park I run in a lot. They
have these slingshot/stick type affairs to throw tennis balls with for fast
strong dogs to get a lot of exercise fetching them while the owner has an
easier time of it. I've never tried one, but from what I've seen, even
unconscious practise seems to result in some accuracy, and distance certainly
isn't lacking. In short, it might be easier, cheaper and faster to practise
with one of those than to devise a more complex launcher. It seems to me that
accurately placing a thin line over a branch up to 100 ft high might be
easier than learning to fly-cast.

Another thing I remember, on a smaller scale by far, is a small stick and two
rubber bands, one binding the other over the end of the stick. I was about 6,
at a strange house competing with another boy to accurately and strongly
catapult nasturtium seeds by releasing them against the stick so the band
drew them near-parallel to it at speed. It's very effective because it eases
aiming and the recoil is just enough to cause the stick end to slew aside to
allow accurate clearance at the crucial instant, something that became
immediately apparent at the time I 'invented' it. If the thing were scaled
up, for example with a carefully prepared inner tube from a cycle tyre, then
maybe the thing can launch a weighted tennis ball and light line accurately
with one shot. The trial and error would certainly be a lot lower than the
dog-ball-slinger.