Saturday, March 17, 2012

Cheiroballistra. Pt.1

Huh? What, a happy Starbucks employee?  No, a cheiroballistra was a Roman bolt thrower, circa 100AD,  mostly made of metal. I've been researching different ballistas for the shooting positions on the Long Walls, and thought this type looked Númenorean enough. The ballista I have from Zevzda, while nice, is too large for the walls, and too expensive for the number I need. Looks like I'll be scratch-building them.

Since nothing looks more like metal than metal, I decided to go with brass. I started by bending the arch in the flat strip at the top. Using a 52tpi razor saw, I cut a slot in both tubes. (For size reference, the tubes are 3/4" long.) Then I CA'ed the arch into the slots, being careful to make sure the tubes remained parallel to each other. When those joints were solid, I measured, cut, and glued the two bottom strips in place.  The bolt's trough was fashioned out of styrene, using a rounded-edge file to plow out the groove. More  strip at the rear to hold the rope spool which draws the string.

 I've attached a half-round piece to allow the thrower to pivot up and down. The spool is also in position.

 The pivot bracket made out of square tube, and shaped with a razor saw and files. There is not enough room on the wall for a swiveling platform like on the Mile Fort. That means the thrower itself would need to swivel. I CA'ed a small round tube into a small square tube. This will nest perfectly in the pivot bracket.

 I have seen both square and round bow-arms in drawings of this style thrower. I didn't have any square stock that small, so I went  round with thin rod at the ends.

 The pivot bracket is attached, as well as the windlass to pull back the drawstring.

 The base is made of styrene. The center post is only 1/2" long.

 The thrower on the base. Still need to install the drawstring and the ratcheting mechanism, but I'm pleased to this point. The figure at the bottom will be converted to the perfect operator.

If there is a problem with this model, it's that it is too big. I really need one a  bit smaller. And while I enjoy working with brass, I know I can make them smaller and faster out of styrene. Time to make some jigs.  Don

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