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Antenna launcher

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KB1FGC, Apr 27, 2021.

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  1. KB1FGC

    KB1FGC Ham Member QRZ Page

    I'm returning the Big Shot.I have a bad back and it was pretty rough to pull it down and get any height.At best I got about 40 feet but didn't get enough height for my tree. Guess I'll stick with the sling shot.
     
  2. KG7WGX

    KG7WGX XML Subscriber QRZ Page

    I saw a neat little modification using a standard archery release and a nylon strap which looks like you can get approx. 2:1 mechanical advantage to draw the sling back and hold it, without using your fingers to hold the sling or an awkward posture. Then you position the throw weight, aim and touch the archery release to shoot.

    No modifications to the Big Shot, except a hole in the rubber base cap for the coated hook on the strap.



    There are more complex versions of this using multiple pulleys for more mechanical advantage and less friction, but the nylon strap method looks like a good starting point.

    I use Scott archery releases for archery, (target shooting), so I just ordered another one. I know they hold until triggered and have a roller cam mechanism, rather than a simple sear.

    Also, they have the advantage of being mounted to a 1/2" nylon web instead of a rigid hinged post, which makes sewing one onto the end of the nylon strap an easy way to join the two.
     
    AK5B likes this.
  3. KB1FGC

    KB1FGC Ham Member QRZ Page

    Thanks for that.I'm not quite clear on how it works but it looks like it wasn't too bad watching the video.I had the Big shot trigger which held it back but the tension on it to pull it back was rough.
    73
    Rich
     
  4. KG7WGX

    KG7WGX XML Subscriber QRZ Page

    I recognized the release device, which is a "bow release". It typically is part of a nylon or leather "cuff" which the archer wears on his "draw hand" and is attached to a D-loop at the nock point.

    The video shows what looks like the entire release, including the wrist cuff, tied off to the end of what I believe is commonly called a "tie-down" strap, with one hook inserted into the end of the Big Shot pole, where it rests on the ground.

    I intend to use a release which uses an adjustable nylon strap to attach to the cuff, and discard the cuff. Then I'm going to bar-tack the straps together with heavy-duty polyester thread.

    The bow release only works with the correct diameter cord. The cord must be strong enough for the intended use and small enough to permit the jaws of the release to close completely. It also has to be easy to melt, so you can melt the ends to keep a knot from coming untied in use. (If you aren't an archer, you can buy this cord for around $7 for 12 ft to get exactly the right stuff.)

    For this application, you just tie a loop of this special cord around the normal pull loop below the pouch.

    The mechanical advantage of the tie-down strap comes from using the buckle as a moving component. The theoretical mechanical advantage is 2:1, but there is considerable friction. I ran across another video showing the same concept, except using ropes, a couple of pulleys and some kind of rope clamp. If there isn't enough mechanical advantage from the strap, I will try that next. (Also, it is easier to pull on something if you can use your entire hand instead of just your fingertips...)

    I think the main advantage of this is that you can "cock" the rig with the pouch empty. Just brace the end of the pole against something and pull the strap to stretch the rubber tubing. You might be able to come up with a re-positionable "foot loop" to let you cock it with your leg muscles while you hold it with both hands. It might take several 12 inch steps, but eventually you would have it where you want it.

    Then, after it is cocked, you set it up over your throwline cube and put the weight in the pouch. While aiming, keep your hands away from the bow release -- these things are a hair trigger. Last step, of course, is to touch the release. None of the rig moves with the pouch except the D-loop -- it just falls on the ground.
     
  5. KB0QIP

    KB0QIP Ham Member QRZ Page

    I've got a Joplin ARC launcher. Love it. Put a spinning reel on the forward side and 50 lb line. It does take some practice and no wind really helps, but it is the best launcher I have ever used. Last week I put up a new OCF antenna. The Main part is at 45 ft with the legs at 35 ft. I've played around and lunched a projectile 100 ft up and 300 ft downrange. That was at 90 lbs pressure. Did it once. wouldn't do it again as I don't know the pressure ratings . Usually with 35 to 50 lbs with a simple bike pump it does well.
     
  6. KC3RN

    KC3RN Ham Member QRZ Page

  7. WD4ELG

    WD4ELG Ham Member QRZ Page

    Another vote for the WB6ZQZ. Worth every penny.
     

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