The safety of pneumatic Nerf blasters is a topic of debate. The most prevalent opinion has been one of ignorance in that it treats the words pneumatic and dangerous as synonyms. In reality, any blaster can be dangerous regardless of it's method of operation.
Still, I feel a need to silence all critics of my blaster's safety. Safety was a paramount issue in FANG 2's design and I am not aware of any blaster designed with more concern for safety.
From a ballistics standpoint, all that can be controlled is kinetic energy density (KED). Kinetic energy density is the kinetic energy of the projectile (KE = 0.5 * m * v^2) divided by the impact area (A = (pi / 4) * d^2). A material can absorb a certain amount of energy per unit volume. The thickness of said materials can vary greatly, so the comparisons are made not including thickness and only impact area.
As all Nerf darts have approximately the same impact area, the kinetic energy of the dart is the most important. Keeping the maximum kinetic energy, the muzzle energy, at an acceptable limit will ensure that the dart is safe.
For this reason and to increase the number of shots per gas reservoir charge, power is limited. Much more than 100 feet range is overkill in most situations anyway, so the improvement in shots per charge are very acceptable.
FANG 2 was designed to easily have it's power limited further if complaints arise. The pressure regulator can be adjusted to reduce the pressure. The gas chamber can be replaced with a smaller pipe less easily, but this procedure is not difficult with the proper tools and a second pipe. This versatility allows for adjustments in power to be made as desired.
This point renders straight bans on the FANG 2 and similar blasters moot. The design is capable of any power level.
My attempts to use strong materials seem to have given the impression that the FANG 2 is extremely powerful as if these materials are the only ones that can do the job. On the contrary, FANG 2 does not use pressures atypical of a Nerf blaster and the use of metal components was chosen for safety reasons.
Most Nerf blasters use plastic components. Plastic is rarely used for gas pressure, in fact, manufacturers of the PVC pipe so common to most homemade Nerf blasters warn to not pressurize gas in their pipe and fittings because of the potential for explosive failure. Gas can store much more energy than the liquids plastic pipe is designed to hold. When PVC fails, it creates shrapnel and the situation is not pretty.
Metal is the only way to combine strength with favorably failure characteristics. All parts under continuous pressure are made from metal. A few parts under intermittent pressure (such as the turret pieces) are made from plastic, but they are made from ABS and will not be under much stress. The component under the most stress, the gas reservoir, has a safety factor of 4 over failure when at 150 psi, the higher pressure I plan to use with it. DOT certifications specify a safety factor of 2.5, so this is safer than typical gas cylinders.
The regulator acts as a safety when the flow through it is stopped.
Two pressure gauges allow the user to know the current pressure level.
A pop-safety valve prevents pressurization of the gas reservoir beyond 175 psi. The gas reservoir has a burst pressure of 600 psi, so this value does not even begin to approach danger.
A check valve prevents the QEV from firing when pressure is lost on the gas reservoir side. This can occur if anything on the gas reservoir side leaks or if the pop-safety valve is activated.
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©2007 - 2010 Ben Trettel
Last modified on 2009-04-04 13:48:44.