That’s cutting it as close as I dare on the acuteness of that string angle at full draw.

 

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An inswinger’s bowstring is prone to interfering with the projectile fins when we try and stretch too much limb rotation out of them.

The 65 degrees of limb rotation, seen above, is about as much as can be managed with Phoenix, and still have her limbs be as long as reasonably possible.   This limitation is very deliberate.  The type of torsion spring I am making,  seems to yield it’s best performance with short limb rotations of 50 degrees or so.   Firefly convinced me of this to the point I decided to embrace the principle and make Phoenix as compact as possible.  The shorter limb rotation means I can get away with a stock length that is perhaps 18″ shorter than would otherwise be possible with some kind of 110 degree, over-rotating, specimen.

Short, sharp, and violent in it’s stroke, our ballista limb needs to be both light and immensely strong.  All this mock-up work is being done to help intuit how much weight we can trim away from the limb irons.

I premise this attempt by accepting the well known idea that late model Roman ballistas utilized iron strips and bowstring hooks on their limbs.  Therefore, at this stage, the existence of full length, limb irons, is a non-negotiable tenant of this project.  Puzzling the geometry at full scale, is my focus at the moment.

 

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