What is the optimal barrel length for maximum distance in a blow-gun?

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In summary, a user named Funkyreuben asked for help in calculating the optimal barrel length for maximum firing distance for mini-marshmallow blow-guns made out of PVC. Another user, Chris, suggests that the barrel volume should be such that the internal propulsive pressure reaches atmospheric pressure when the projectile leaves the muzzle. Trial and error may be the easiest approach, but Chris also suggests using calculus to maximize the escape velocity.
  • #1
funkyreuben
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I recently made a few mini-marshmallow blow-guns out of PVC and I noticed that different barrel lengths provided different firing ranges. Does anyone know how I can calculate the optimal barrel length for maximum distance? I haven't done anything physics related since college (2002) and I'm drawing a blank as to calculating this. Any help would be greatly appreciated.

Chris
 
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  • #2
Welcome to PF, Funkyreuben.
I'm not exactly sure how you would go about this. It depends upon the air source volume and pressure. Ideally, the barrel volume (area x length) should be such that the internal propulsive pressure reaches atmospheric just as the projectile is leaving the muzzle. If the barrel is too short, a lot of your air will be wasted; if it's too long, the marshmallow will begin to decelerate due to friction and air resistance before it can get out.
Trial and error might be the easiest approach.
 
  • #3
Thanks! I plan on doing some real world testing but I was hoping for a way to calculate it as well.

Chris
 
  • #4
if you were to write velocity as a function of either area or length you could use calculus to maximize the escape velocity... I don't know how hard that would be though
 

1. How does the length of a blow-gun affect its accuracy?

The longer the blow-gun, the more accurate it will be. This is because a longer blow-gun allows for a longer barrel, which means the air has a longer distance to accelerate and maintain its velocity, resulting in a more stable and consistent shot.

2. What is the ideal diameter for a blow-gun barrel?

The ideal diameter for a blow-gun barrel is between 0.4-0.5 inches. This allows for a good balance between air flow and air pressure, resulting in an optimal shot distance and accuracy.

3. How does the weight of a dart affect its trajectory when shot from a blow-gun?

A heavier dart will have a more consistent and stable trajectory than a lighter dart. This is because a heavier dart will have more inertia and will be less affected by external factors such as wind or air resistance.

4. Does the type of material used for the dart affect its flight when shot from a blow-gun?

Yes, the type of material used for the dart can affect its flight. A denser material, such as metal, will have a more consistent and stable flight than a lighter material, such as plastic. However, the shape and weight distribution of the dart also play a significant role in its flight.

5. What is the maximum range of a blow-gun?

The maximum range of a blow-gun can vary depending on factors such as the length of the barrel, the weight of the dart, and the force of the breath. Typically, a blow-gun can reach distances of 25-40 feet, but some skilled users have been able to achieve shots up to 60 feet.

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