Bungee Ballista Part 2 PDF Print E-mail
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Tuesday, 27 October 2009 02:09

Bungee Ballista Part 2 -- Design Overview Continued

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The Shuttle
 This is a close up of just the main beam, the track and the shuttle.   The wood frame and track cross sections are shown in dark brown.   The shuttle is shown in grey with the aluminum bits shown in blue.   The aluminum angle which is attached to the track is also shown in blue.
  The grey block hanging down in the middle of the shuttle rides up the center of the track, pushing the projectile forward.   In the actual ballista, this block is only slightly narrower than the distance between the two track pieces.  It is this block that keeps the shuttle aligned with the track.
Shuttle Version 1.0Pictured on the left is the first try at a shuttle.  It was built out of light pine wood.  The hook on the back is for the winch to attach.  The bungee ropes attached to the two fittings on either side of the front.
  The shuttle's purpose is have something to attach the rope to.  The historical ballista examples did not use a shuttle.  Instead, the tension rope simple pushed the projectile directly.   This has the advantage that no energy is wasted accelerating a shuttle.   In our design, the intended projectile weighed more than ten times the weight of the shuttle, so not much energy was wasted.   
  By having a shuttle which fits perfectly in the track, and is held on to the ballista with the aluminum angle guides, we are free to use a variety of projectiles such as round balls which couldn't be accelerated by direct contact with the rope.   In addition, it is less likely for something bad to happen if a problem occurs during firing because the shuttle is secured to the track.


Last Updated on Thursday, 29 October 2009 02:17

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