Thursday, September 13, 2012

Dragon Repeating Crossbow Ring's Summer Evolution

In my quest to bring fruition to a creation that arguably adds little to no value to the advancement of mankind, I'm pleased to share the stages & the results of my Dragon Repeating Crossbow.

In stage one, version one worked occasionally.  However, repeatedly tinkering to get the arrows aligned for ejection was not the intended meaning of "Repeated" in the crossbow's title.  So, the chamber was expanded & polished and the trigger mechanism was completely reworked.  Initially, the two edges of the hinge that connected the arrow chamber (dragon head & neck portion) to the ring base would lift & release the rubber band which in turn propelled the arrow.  However, precision in construction was sacrificed in consideration for ease of assembly.  This in turn created wiggle room which allowed the two edges to release the rubber band out of sync. This created misfires and inconsistent propulsion power.

Upon determining the culprit for the sub par performance, I gleaned what the Chinese had done so only 2500 years ago.   I adopted their original push peg trigger solution and thus added another element of ancient tech to my dragon repeating crossbow.  This solution eliminates misfires and inconsistent propulsion power.  The initial decision to deviate from this simple yet solid trigger system was based on my design's structure.  At the scale I wanted to execute & the current configuration, certain sections would become too fragile to accommodate the inclusion of a push peg.  That fragility was also at a particularly stress laden section of the crossbow near the rear axle of the chamber.

Version 1 (on lt.)  Version 2 (on rt.) with push peg

So an extensive redesign was required to utilize the push peg trigger & retain a solid robust structure.  These images show version one & the redesign (Version Two) side by side.  Version two fired with power and consistency if the firing rate was very slow & controlled.  However, upon the elimination of one culprit, a masked culprit revealed its true self.  Part of the redesign of version one involved the addition of a rear chamber lip to prevent arrows from getting lodged & thus blocking the rubber band from reaching the rear notch.  It also included the deeper setting of said notch toward the rear of the crossbow.

Version 1 (on lt.) reps original trigger design w/o push peg.  Version 2 (on rt.) with push peg.

  I imagined that these adjustments would resolve my issue with jumbled arrows within the chamber.  While the trigger fired fine, arrows were not settling into the firing groove at the base of the chamber.  I had hoped that gravity alone would align the arrows.  I also believed expanding the chamber would facilitate the settling of my arrows into the firing groove.  My thinking was not flawed, it just couldn't observe the second main culprit to disrupt my crossbow's function.

It turned out that this culprit was the additional vectors of energy from the rubber band.  As the rubber band traveled back into the notch before release and fire,  said rubber band was twirling.  As the rubber band has a squared cross section, these edges would collide & dislodge my arrows within its the firing groove.  This would sporadically impact my arrows during the cocking & firing motions.  On occasion the added vectors would flip or even expel my arrows out of the top of the chamber.  This would occur frequently during the firing motion disrupting the following shot.  In effect, one would experience a jam & have to remove & reload.

This was not acceptable, so plans to design a barrel clips & or banana clips to increase ammo capacity were painfully complicated by the solution.  Version three would in short require a tiny little finger within the chamber to hold the arrows in place & set them consistently within the firing groove.  This finger would in essence be a tiny pendulum approximately the size of my arrows but with twice to triple the mass.  It would sit on top my arrows and counter the rubber band's added vectors, & this pendulum would swing down on top of each arrow to settle it into the firing groove.

Version 2 (on lt.)  Version 3 (on rt.) with Pendulum atop of full chamber of arrows

Testing make shift pendulums with version two immediately eclipsed past performances & reintroduced long since abandoned lofty ambitions.  Consistency, speed & fun improved immensely & the journey to why seemed answered at least fleetingly so.  All these improvements, shifted the balance of functionality & aesthetics back toward function as I envisioned epic skirmishes of tiny arrowed finger warriors throwing down well just about anywhere.  I Increased the size of his horns to provide more finger traction during firing motion.  And to provide more finger traction during the cocking motion I modified the fluid symmetry of the spinal hair on the rear.

Enuff said time for video.

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