Design Proposal

Design Proposal

Problem Overview

                Commercially sold toy foam-dart guns, also known commonly as Nerf guns, are designed by most companies to only work with their foam darts. For example, Nerf brand guns only take darts designed and sold by Hasbro, while Buzz’Bee brand guns only take Buzz’Bee darts. Furthermore, different models of toy guns sold by the manufacturers might have their own special kind of darts. For example, Nerf sells guns that will only take a specific kind of Nerf dart. Some of the more common types of Nerf darts are Velcro, suction, whistler and streamlines (See "Dart Analysis" page to see more details on the types of darts.
 Figure A. Multiple Dart types (Note shorter Buzz Bee Dart in yellow)

Commercially sold Nerf guns that accept Whistler or Suction darts will not function properly with simple darts. This incompatibility becomes a major problem when organizing dart gun tournaments and games, as darts cannot be shared between the individuals playing in a tournament.
                Furthermore, most commercially sold foam dart guns (most commonly made by Hasbro and BuzzE’Bee) are designed only to shoot darts a maximum of about 30 feet in a straight line. This creates another logistical issue, as tournament arenas have to be limited to small enclosed spaces that do not exceed the dismal range of these guns. The creation of a gun that can accept a wide variety of darts and function well under long range requirements would solve both of these problems.

Design Constraints

                 This design is intended to be used in competitions, so the gun has to be portable. Typical Nerf guns extend somewhere between a foot (handheld pistols) and about three feet. Any toy gun design would have to be less than 3 feet long.
                 To keep the gun affordable for a typical customer, the budget has to be limited to no more than $50 per gun. 
The materials that can be used for this project have to be easily accessible, affordable, and machine-able. This limits the materials available for use to plastics, copper, and other cheap metals.
The tools available for use are limited to the machines at the Drexel University shop and hand tools such as Xacto knives, scissors, hammers, screwdrivers etc.
Figure 1. PVC tubing
Another design constraint is the time available for completion of this project. The project has to be completed within a ten week time frame. This includes time for designing, building, testing, and revamping a prototype of the gun.
Existing Solutions
                There are certain models of Nerf guns that can take in multiple types of darts at the same time. An example of such a model is the Nerf Quick 16. However, the Quick 16 has problems with performance and modding attempts are difficult. The Quick 16 also has a permanently fixed clip, which necessitates loading darts individually into the cartridge. This gives a slower rate of fire as you cannot switch out depleted magazines for full ones. As a result, the Nerf Quick 16 model is not a complete solution to the problems listed prior.
Figure 2. Nerf Dart Tag Pistol (Attached clip is shown disassembled)
                Another method of accommodating multiple darts types is to create a revolver like system. Revolver models can hold many different types of darts and fire them generally well too. However, in a rotating chamber gun, the darts have to be individually loaded in the revolver. This makes the rate of fire of the gun slow after the chamber is depleted. Furthermore, revolver models typically have a limited range as a result of the air seal between the revolving chamber and the plunger system.
                There are other models of Nerf guns that use a magazine fed dart system, as shown in Figure 3.
Figure 3. Clip system Darts and Mags

Unfortunately, the models that exist in the current market require the use of Streamline Darts. These darts are not the most effective as their lighter heads and longer bodies result in greater contortions while in flight, worsening accuracy. Additionally the use of a 'reverse- plunger' to fire the darts causes a lower seal on the plunger head, making ranges drop. While the system allows for a faster rate of fire, the deficiencies of the darts lower the use of the gun.

An alternative solution for using clips involves the use of shells in magazines. While one still have loaded clips, this system works very well, however once all rounds have been used, not only must the darts be reloaded in the mag, but also first loaded into shells as well, making reload time incredibly long. This system solves some of the range issues with a tighter seal against the shells however the slow rate of fire and complex mechanism work against it.
 Figure 4. Buzz Bee Repeater Rifle

                In conclusion, there are many attempts in the commercial market for solutions to the problems listed in the problem overview. However, no commercially available Nerf gun models solve both the problems listed (dart compatibility and range) in a single gun. As such, a new design that can effectively solve both of the problems listed above would be very helpful for competitions.

Design Goals

                This project aims to design a Nerf gun that can overcome the problems listed in the problem overview section, while staying within the constraints described above.
To solve the problem of incompatibility of darts between guns, this group proposes to build a magazine fed system. The gun will be able to take in streamlined darts, suction darts, Velcro darts, and Whistler darts without the use of shells. The gun will accomplish task through the use of a custom designed magazine. To accommodate the different sizes of heads of darts that could be put into the gun, the magazine will have a bent design. This design will allow the same size back sides of darts (See dart analysis for more information) to lie flush on top of each other, and the heads to have more room. 
Another goal of this particular design is to be able to shoot darts at an average distance of 80 ft. without losing accuracy. For this particular gun, a spring loaded, pump action design will be used. The use of a pump action gives the gun an advantage over electrically powered guns, as the energy required to push back a spring capable of propelling a dart over 80 ft. would be too large to be accommodated by portable batteries. Furthermore, the use of a pump action avoids the need for extra maintenance costs in the form of additional batteries. To accomplish the 80 ft. range, powerful, military grade springs from the AR-15 assault rifle will be used to propel the dart.
The materials used in the production of this gun will be limited as described in the design constraints section. The barrel of the gun will be made from a 1/2" diameter PVC pipe. The barrel will be held in a holding chamber made from 3/4" PVC pipe. The propulsion assembly (which includes the holding chamber, a piston attached to the spring that propels the dart out of the barrel, and a guiding chamber in front of the barrel) will be held inside a larger, 1" PVC pipe. The magazine will be built out of Acrylic plastic. A small chamber made of Acrylic will be made on top of the gun, over the bolt mechanisms in control of the pump movement for aesthetic purposes.
Detailed illustrations of the various parts of the gun can be seen in the "Design Plans" section of this blog. As the project continues, more detailed plans and any proposed changes will be recorded in the Design Plans section.
The following materials will be submitted at the end of the project:
·         Data for firing ranges and rate of fire of commercial nerf guns
·         Data for firing ranges and rate of fire of this design
·         Blueprints of design
·         Cost summaries
·         Finished product
·         Build stage documentation (pictures etc.)
·         Final report

The success of this project will be judged by the designers by comparing the initial test data (Data for firing ranges etc. of commercial guns) with test data from this design. Factors such as the functionality and reliability of the gun will also be assessed.

Our goals include, but are not limited to:
  1. One gun that can:
    1. shoot 4 types of darts
    2. average a distance of 40 feet to 50 feet (held at zero degrees)
    3. a firing rate of at least 10 shots per 30 seconds
    4. less than 2 misfires per 20 shots
    5. a minimum firing range of 25 feet
  2. Documentation that includes
    1.  test data
    2. assembly procedure
    3. drawings and CAD documentation
    4. photos and videos
    5. final report

Project Schedule

The project will follow a preset timeline as follows:
4/20/12                -              Project Design proposal
4/20/12                -              Cost Summary, Materials list
4/20/12                -              Test data for commercial Nerf Guns
4/27/12                -              Beginning construction (material cutting), Preliminary CAD models/Blue Prints
5/11/12                -              Finished first prototype, start testing/collecting data on design
5/26/12                -              Design improvements, retesting modifications

Project Budget

     Material for 3 Guns
Epoxy: $15
PVC tubing: $15
Copper Tubing + Heads: $15
PVC sheeting: $15
Action Springs: $15
Magazine Springs: $8

Total: $83 for three Guns
~ $28 per gun


1.  SG Nerf, Blogspot,
2. HomeDepot,
3. McMaster-Car,

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