Bungee Ballista Part 6 PDF Print E-mail
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Tuesday, 27 October 2009 12:13

Bungee Ballista Part 6 -- Constructing the main beam frame

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Using the 1x4s laying flat as a rule, we marked straight lines where  the frame boards will go.    Holes were drilled all the way through the main beam.   Then the ballista was turned over and deck screws were put in from the top into the 1x5, which then was vertical and clamped into place.


Holes for Frame Box 


Deck screws are being driven into the holes drilled above.   If the 1x5 is carefully held in place right where the lines were, the deck screws should be nicely centered in the thin wood.

Deck Screws going into frame

The oak track boards are clamped as used as a straight edge to mark where they will be installed.

Planning the track

The oak track boards had holes drilled all the way through with a drill press to make them perfectly vertical.   A countersink was used to make sure the deck screws would not protrude above the surface of the track boards.   The shuttle will be riding on top of the track, so it must not have anything sticking up.   The aluminum angle is screwed to the outside edges of the track with very small wood screws.  The holes in the angle are spaced so the little wood screws will not line up with the deck screws which are holding the track pieces down.

Installation of track

  In hindsight, this design might not have been the best.   The shuttle must be very wide to extend beyond the angle on both sides, making it quite wide.    A better design might have the angle actually be attached on the outside of the track as it is above, but turned the other way so the aluminum extends over the track.  If a gap of 3/16" were left between the top of the oak track and the aluminum, the shuttle could have been much more compact.   However, there is no arguing that the design we went with worked great.



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Last Updated on Thursday, 29 October 2009 01:44

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