Slingshot Cannon

Step 11: Pivot Points

Installing the pivots is very similar to the method used for drilling the holes for the latex tubing.  It is best to drill them at 180* angles about 12" from the rim.  First level the entire barrel using a larger level, then use a combo square with a level in it to mark at top dead center.  Mark the two points that the level touches in one position then move it around so that another point is 180* from the point on the side of the barrel.  After they are marked drill a 1-1/4" hole on each side (I tried a 1-1/2" bit the first time to fit the PVC but there was to much play in the pivot mount for me.)  You may need to shave the sides of the hole to allow the PVC pivot tube in.  After the tube fits use Epoxy to attach the pivot tubes to the barrel.  You will want to leave as much PVC sticking out of the barrel to make it easier to mount to the cradle.