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***All the steps are in the video***


​Explanation of mechanism (applying mechanics principle)

>>The trigger uses moment of force. Force to turn ball valve is supplied by tension from rubber

>>however, the perpendicular distance is zero. Thus, moment equals zero and the whole system is in equilibrium. The ball valve will not turn.

>>When triggered, the perpendicular distance is increased and moment increases. This should cause the ball valve to turn.


PRO:
1) cheap and simple. Does not use expensive or special parts like sprinkler valves or metalwork
2) allows to re-cock the trigger by just lifting the ball valve lever. thats all, then re-pressurize and fire again
3) sensitivity of trigger can be adjusted to varying trigger pull
4) bullpup mechanism, for close range shooting. Be honest, youre not gonna aim for something 100meters away with a homemade gun
5) breech loading but has a relatively good seal to not waste pressure
6) Has a stock but its non foldable

CON:
1) Misfiring. gun may fire if lever of ball valve is unintentionally displaced. you either waste energy to repump or have to call medic
2) May be unsuitable for left handed users. The pipe joined to metal ball valve may hit left forearm
3) Manual. It is not semiautomatic or full auto
4) Durability. Theres a possibility that the rubber bands will damage the gun
5) *insert other detectable flaws here*
6) *refer 5)*

Materials

1x 20mm tee
1x 15mm tee
2x 15mm endcap
1x 15mm metal ball valve
2x 15mm valve socket
2x 15mm 90 degree elbow
1x bicycle valve
~6 ft 15mm pipe (barrel and gun)
~1 ft 20mm pipe (rest of the gun)
what softwhere did you use
I was using google sketchup. once you have learnt the basics, if youre interested I can send you a template with pipe components so you can just arrange the components instead of drawing each part from scratch. email maybe? but learn how to use sketchup first

About This Instructable

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Bio: Im just a student. Doing A levels to try learn Mechanical Engineering in the UK.
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