Nerf Vulcan Modifications: An Engineering Perspective

Modifying this thing sure is a doozy. Before sketches are drawn, screwdrivers are pulled out, and the spray cans are rattled, we have to outline the problems. Here are some of them, and in the future I should discuss the practicality of a rapid fire vulcan versus stock specifications, and the possibility of an automatic sniper rifle (nerf dart blaster)

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Abstract
Adults and kids alike have been amazed by the Nerf Vulcan toy dart gun for a few years now. More engaged enthusiasts and engineers alike have been pondering “how can I enhance the performance of this toy?” I think that many “indie” users have experimented with design changes of this toy blaster, but overlook some critical factors, such as motor load, gear fatigue, and many more phenomena. It is entirely possible that an engineer will need to step in to solve the hidden and proprietary ideas…. of another engineer.



Original Goals
Originally the goal of our experiment was to increase the voltage of the Vulcan to fire more darts. There is a direct relationship between the rate of fire of the blaster and the voltage of the power supply. Modifying a stock toy gun to do these things without other considerations can shorten the life span of the toy, and in other cases may be dangerous. When looking at a practical solution to modifying the Vulcan blaster, we looked at these critical factors (in no order of importance):


+Ammo Capacity
+Ammo Characteristics
+Ammo Weight
+Assembly of the Power Supply
+Barrel Lengthening
+Dart Physics
+Gear Fatigue
+MAh total of the power supply
+Minimizing Internal Noise
+Motor Amperage Draw
+Motor Fatigue
+Motor Maximum Voltage Load
+Practical and Economical Charging
+Resistance of the Circuit
+Shock/Impact Protection
+Spring Strengthening
+Vibration Minimization
+Voltage of Power Supply









This report should address these issues and allow insight into problems that may be encountered while modifying this dart blaster.



Design Problems

Ammo Capacity
One has to consider the foam being put down the range. At stock specifications, the dart blaster fires approximately 3 darts per second (herein DPS), and 180 rounds per minute. The higher the voltage of the blaster, the more darts will be put down range. If one does not modify the ammo capacity, the user will run out of ammo faster. To compensate, a ratio must be found and increased to the original belt, or add another stock belt chain to the current belt. It is theorized that too many belt chains increases some force P acting downwards, working against the drive mechanism (primitively, a pulley) which must overcome this force P with some torque T supplied by the motor, which is connected to a shaft with mechanical advantages in between (gears).


Ammo Characteristics
The shape and weight of the ammunition will have an impact on the distance and path of the projectile. The weight should be placed at the end of the dart, with the weight loaded opposite of the beginning of the barrel (note: the belt clip IS an extension of the barrel). The diameter D of the ammunition will dictate the size of round fired, as well as the inner diameter Di of the barrel. Tolerances are within a thousandth of an inch for home improvement grade materials. This tolerance should be enough for the dart to fit, but also to travel down the barrel and accelerate. One should select a barrel material that meets their needs, specifications, and preferences.


Ammo Weight
The weight of the ammo should be placed in the front of the dart. The rest of the dart should be seen as part of a “delivery vehicle” that is a mechanical advantage. By aiding the weight to travel down the barrel, the foam also aids in the absorption of the force of impact when it hits the target. This minimizes the impact a target may feel (if the target is a person). Regardless, safety glasses should be worn at all times if the target is human. A dart too heavy will not fly in a parabolic curve, or may not reach its maximum potential because the firing force cannot accelerate the mass fast enough. On the other hand, a dart too light will be aerodynamically unstable by fish tailing.




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