Tom,
It was written up in the March 09 QST.
I found that using an air jet with dead man throttle is the perfect
trigger, not the solenoid mentioned in the article. I had to
experiment with the sprinkler valves to understand how they work and
then found if I wanted to use the solenoid site, it was problematic
in that I needed to plug an air vent and enlarge another. And the
threads to the solenoid were not the same as the threads on the brass
coupler I needed to screw the air jet in. (I say "air jet" but it's
the squeeze valve at the end of an air hose you squeeze & aim to blow
away debris on a work bench to clean car brakes from dust and when
you release it, the air stops blowing. All of 7-8 bucks at an auto
shop.
I found the best placement for ease is to get a sprinkler valve with
a flow adjustment valve in the center of the bottom, remove that
casing from the valve to drill into it without hitting internal
components. Remove the adjustment valve, drill into the interior, run
a tap for the threads of the brass bushing to mate the air-jet/dead
man throttle and screw that into the newly threaded plastic using
plumber's tape on both threads. Assuming you installed the throttle
correctly, the trigger is ready to go.
In the Oct 09 QST page 20 there is a photo of a club that made them.
They chose to use an inexpensive PVC "twist" valve to release the
air, I thought about using one of those and probably should just for
my own knowledge but I believe what I do should be better.
The reason I say better is I discovered if I squeeze the trigger
somewhat slowly, the projectile starts its escape prematurely and it
will not go as far as quickly or accurately. Using the sprinkler
valve and squeezing the trigger quickly gives a serious snap and
projection like a one pound arrow with a bow to match.
These little suckers will definitely get your wire over the tallest
support. OK, it probably won't make it from the floor of the Grand
Canyon to the top but it's get it over your tallest tree with plenty
to spare.
I'll have to make some photos of the two I made & you can see the
difference in size and how I oriented things.
73,
Gary
KA1J
> Can anyone give me more information on Gary's 'Spud Gun'? I have
been using an angler's catapult, with monofilament line, for years to
put my topband wire halyards over trees, but the limit is about 60 ft
and the catapult is not too accurate.
>
> BTW I have found that nylon rope is much better than Dacron or Polypropylene
> for halyards over trees as it is much tougher and just won't break. Dacron
> (also known as Terylene or Polyester) will abraid on the tree branch and
> eventually wear through. Polypropylene is cheap and very readily available
> but is attacked by UV and gets very weak after a while.
>
> 73
> Tom G3OLB
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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