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    New ballista: for projectiles, not arrows

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    Mr. Apol
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    New ballista: for projectiles, not arrows

    Post by Mr. Apol on Wed Nov 16, 2011 12:08 pm

    OK, I have collected a number of components I'd like to assemble into a ballista sized stonebow. For power I'll be using a car leaf spring and building a frame out of 4x4 timber. I want the ballista to hurl "bullets"--gourds, croquet balls, maybe even stones, etc. Since the leaf spring is a continuous piece of steel, I thought I would mount it like a stonebow, with a raised front end, a cutaway center stock, and a raised firing mechanism. (See various forms of stonebow in Payne-Gallwey to see what I mean). Because the spring is finished with closed loops at each end (where the mounting bolts secure it to the car frame), creating a double string and pouch to hold the projectile ought to be fairly easy . . . does anyone out there have any experience with stonebows or other bullet-throwing bows?

    thanks,

    Paul
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    Geezer
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    Re: New ballista: for projectiles, not arrows

    Post by Geezer on Wed Nov 16, 2011 7:03 pm

    I have only one thing to say about double-string stonebows. It is possible to make them shoot backwards. It will be a surprise when it happens, and it's no fun at all. That's why I don't make stonebows anymore. Geezer
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    Todd the archer
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    Re: New ballista: for projectiles, not arrows

    Post by Todd the archer on Wed Nov 16, 2011 8:18 pm

    Here is what Geezer is talking about

    http://www.youtube.com/watch?v=-OZjHjJToVo&feature=related



    Todd

    Mr. Apol
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    OK . . .

    Post by Mr. Apol on Wed Nov 16, 2011 8:32 pm

    Hmm, that kind of backlash is possible any time you use an elastic band, isn't it? It happens because the elastic stretches equally well in any direction, and if the projectile shifts, it could go anywhere?

    If I build a ballista with a steel spring bow and stranded steel bowstrings, will that reduce or prevent back firing?

    I was more worried about hitting my own frame and having the missile rebound at me, but this is daunting, I must say.

    Anyone have a stonebow they use nowadays?

    Paul
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    Geezer
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    Re: New ballista: for projectiles, not arrows

    Post by Geezer on Thu Nov 17, 2011 7:36 am

    Geezer here, concerning ball-firing catapults. What you want is a 'euthytone' ball-shooting balista. These machines use a broad web to propel a ball or similar projectile down a track, like a crossbow. They're not as friction-free as a stone-bow, but the string itself has less wind resistance, and they don't shot backwards on a whim.
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    jake-owa
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    Re: New ballista: for projectiles, not arrows

    Post by jake-owa on Fri Nov 18, 2011 12:59 pm

    If I were building a stone bow I would make a clap style cover for the string path. That way you eliminate the possibility of the string jumping and reverse firing the projectile. As long as your "serving" fits the string slot well and can't climb over your bullet you should be golden. This also eliminates the need for a heavy pouch that will rob your projectile of fps. Engineered correctly it should have very minimal friction and can also house a hopper or clip that drops bullets from above.

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    Re: New ballista: for projectiles, not arrows

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