Minor update 1-Jan-15
This bow is based on a Chinese design at least 2000 years old.
At the time when I made this I did not know how the Chinese did their original design so I reverse engineered it adding my own modifications to make it more efficient.
Now I know how the string was released on the original design I am glad I used a modern ‘Nut’ design to release the string. The folding action of the ‘nut’ when the string is released is kinder to the string serving than the action of the ancient design.
The draw weight is 30 lbs with a draw length of 7.5”. The rate of fire is as fast as the leaver can be operated. This translates to about 1 bolt per second. The magazine contains 10 bolts, which are 9” long.
The bow is made from two limbs I made 30 years ago for a takedown recurve bow. Cutting off most of the recurve gave a good limb for this bow.
I had to adjust the ideal design to use wood / materials left over from previous projects to produce this so its all made of scrap bits.
I modified the original ancient design by making the bow (prod) rotate about a forward pivot. This compensates for the change in string angle that occurs between the braced position and full draw position. This improves efficiency by reducing friction between string and stock. The alternative is to make the bow centre shot as with my other bows.
The other significant modification is not to rely on gravity for feeding the bolts to the stock. Instead, the bolts are forced to the stock by 4 tension springs looped around 4 pulleys in the magazine. This improves reliability greatly and allows the bolts to feed to the stock even with the bow magazine inclined beyond 60 degrees in the horizontal / vertical planes.
Accuracy is good over the design range of 25 yards if the bow is clamped down to a bench to prevent movement when operating the lever. When hand held, operating the lever requires a last minute aim correction before the final movement triggers the bow, (Similar to shooting a double action revolver). This technique allows all bolts to hit an 18” boss at 20 yards.
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