Friction and Gravity

Insert a dart into your blow gun then give it a blow: Normally we would expect that the tip of the dart would slide on the bottom of blowpipe, right in the middle of the "way". Unfortunately this is only the very seldom the case!

Friction:

In reality there is friction between cone and wall of Blowpipe. The un-equal distributed friction forces will cause that the tip of dart does move to the right or left inside the blowpipe. Wort case it will even move straight up.
Result is that at each shot the dart leaves the muzzle in a different angle. It is obvious that this will cause a deviation of flight direction of dart. The dart does not hit the center of target. If the dart would leave the muzzle always in same angle it would be easier to hit the center of the target.

Methods to make Friction as low as possible:
  1) Use flexible film cones
  2) Every 15 shot clean Blowpipe with Dish Water Soap.
      Little soak a wadden with Dish Water Soap and push or pull it through the blowpipe.
      The Dish Water Soap has an additional very positive effect:
      It tends to disable moist condensation and therefore if tends to disable the growing of water drips on the inner walls
      of  blowpipe. Note: water drips cause unwanted drag to the dart cone movement ( kind of friction)
 

Gravity:

Another extremely critical situation is if the blowpipe is bend, and the bending direction is downwards (to ground)
Normally the gravity force would keep the tip of dart down at bottom of blowpipe.
The dart is traveling very fast through the blowpipe. If the pipe is bend downwards the tip can't fall that fast
downwards than the bottom seems to move down. ( more than one "G" acceleration is not possible)
The dart tip looses bottom contact and will move randomly left or right or up. Result is that at each shot the dart leaves the muzzle in a different angle. It is obvious that this will cause a deviation of flight direction of dart. The dart does not hit the center of target. If the dart would leave the muzzle always in same angle it would be easier to hit the center of the target.

Example: If you shoot your dart with 56m/s and your 2 meter Blowgun is bend 2.5cm downwards then the dart tip starts to loose bottom contact.

Methods for prevention:
1) use a blowgun which is absolutely straight.
2) bend blowgun a little bit (2 mm per meter), while shooting always hold the blow gun in a way that direction of bend is upwards.
 
 

Theory and table for comparison of Darts ( also available as excel file )



 
 


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