Minor update 15-Feb-2018

.45 Cal Ball Bow

The object was to produce a Bow Pistol that was as small as practicable and  drawn / cocked using a toggle mechanism.

The design brief called for:-

1) A magazine capacity of 6.    (8 Now achieved with new spring)

2) Capable of a draw weight of 100 Lbs.    (50 Lbs achieved due to cannibalising limbs from an old target bow. More powerful limbs are required)

3) Draw length of 5 to 6 inches.     (5” Chosen to limit limb stress levels. Pulley ratio  and toggle movement / geometry acceptable.)

4) Total draw force on toggle as small as possible    (10 Lbs Achieved for the 50 Lbs draw weight)

5) As light as possible and as small as possible.   (Weight acceptable, Size acceptable)

6) Make 100% of limbs ‘working’ to reduce weight and size.

7) To increase draw weight and control limb deflection using fulcrums. In effect to convert each limb into a ‘bow’ and have two bows working in unison.

I based the design on the use of .455 cal lead balls as used by black powder revolvers.

The Magazine will take eight balls with the current lighter spring; the original spring I obtained locally would only allow 6 balls with difficulty.

If I did the job again I would find a different way of feeding balls to the barrel. It looked easy when I started but became complex because the string is initially in front of the ball and is then drawn back to end up behind the ball.

One of the most difficult aspects was the need to make a controller to feed one ball at a time in order to avoid the balls jamming up as they feed into the barrel. The ball controller had to fit inside the magazine and be strong enough to take the force of the magazine spring. In order to ensure the fit of the magazine in the aluminum end support, the ball controller was designed to be assembled while inside the magazine, a bit like a ship in a bottle. It works very well.

The barrel was made from the handle of a very old scrap lawn mower. Unfortunately the tube was not round and not the seamless type so it had to be filed out to allow ball clearance. The bore is slightly oversize. More importantly it was badly corroded such that all the pit marks could not be removed which is why it looks tatty.

The magazine was made from the aluminum handle of a scrap shopping trolly. Again this was the non seamless type of tube requiring more attention to the bore so that the balls would fit.

Come to think of it, it’s all made from bits of scrap.

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