It seems that all of our problems with strings snapping started when the buffers began to break down.  When the buffers become thin or severed like those above, it allows the limb to rotate further into the pocket of the curved stanchion.  The loss of a 1/4″ in the thickness of the buffer can translate into over 2″ of extra movement at the limb tips.  As mentioned in a previous posting, the force vector on an inswinger is in a direct line with the bowstring as the limbs complete their power stroke.  If the limbs over rotate because the buffers are missing, even the strongest bowstring will invariably snap or be severely compromised.  This begs the question, why do we have buffers at all?  I had included them originally out of an excess of caution, it was an attempt to reduce the shock load on the precious field frames.  Perhaps they are not necessary after all.  In a way the kamarion is a natural shock absorber and probably has enough give in the arch to mitigate any excessive shock to the field frames.  Also, the bundles themselves must have some give in them at the end of the power stroke; the limb hits the curved stanchion and rolls on around it as it acts like a  fulcrum.  At this point it seems reasonable to omit the buffers and have the steel brace on the limb contact the curved stanchion directly.  If this allows for a more precise and predictable movement of the limb tips, our loose string strategy will hopefully prevent any further string breakage.

Just for kicks, I tried a shot with a ridiculously loose string.  The string survived just fine, although the bolt did not.  It passed through the corner of the backstop and twirled away into the rocks at a high rate of speed.  The shock absorbent nature of the kamarion’s arch can be seen in the vibrations visible here in 4x slow motion.  The field frames do not appear particularly stressed out by their role as a stopping point for the speeding limbs.  Click for slomo:  ultra-loose

Could it be that the Romans included the arch not just because it provided better visibility, but also because it meant they didn’t have to fuss with pesky buffers?  It seems clear that a reliable and predictable length of travel for the limb tips is essential for gauging how long to make the bowstring.  Without buffers that break down, this should be easy enough to figure out.  Therefore, it may well be that the famous iron arch of  these late model Roman ballista’s, was as much about shock absorbency and protecting the field frames, and ultimately dispensing with fungible buffers that lead to unpredictable stresses on the bowstring, as it was anything else.

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