Nerf gun

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	== Product Study ==		== Product Study ==
		+	We conducted a product study of three NERF guns, the Big Bad Bow, The Buzz Saw, and the Rapid Fire 20, to determine their functionality, measure their performance, and to gather user feedback and suggestions.  From the results of the product study, we decided the the Big Bad Bow provided the most room for improvement.  During our user study, users were most attracted to the Big Bad Bow.  They often selected this bow fist due to its appearance, stating the they would like to test that NERF gun because it "looks cool."  While trying to operate the Big Bad Bow, many users struggled to figure out how to fire, and some grew frustrated with the difficultly of firing the bow.  Upon firing the bow, users expressed disappointment in its performance, and stated that they expected it to shoot further or do something more interesting.  Because of this marked difference between user expectation and user performance, there is opportunity to produce an improved design that is easier to operate and perform better to increase user satisfaction.
	=== Functionality ===		=== Functionality ===

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Revision as of 10:58, 20 September 2009

Contents 1 Executive Summary 2 Product Study 2.1 Functionality 2.1.1 Big Bad Bow 2.1.2 Rapid Fire 20 2.1.3 Buzz Saw 2.2 User Study 2.2.1 Big Bad Bow 2.2.2 Rapid Fire 20 2.2.3 Buzz Saw 2.3 Performance Studies 2.3.1 Distance Study 2.3.2 Accuracy Study 2.4 Product Dissection 2.4.1 Mechanical Function 2.4.2 Bill of Materials 3 Preliminary Analysis 3.1 Stakeholders 3.2 DFMA 3.3 FMEA 3.4 DFE

Executive Summary

Product Study

We conducted a product study of three NERF guns, the Big Bad Bow, The Buzz Saw, and the Rapid Fire 20, to determine their functionality, measure their performance, and to gather user feedback and suggestions. From the results of the product study, we decided the the Big Bad Bow provided the most room for improvement. During our user study, users were most attracted to the Big Bad Bow. They often selected this bow fist due to its appearance, stating the they would like to test that NERF gun because it "looks cool." While trying to operate the Big Bad Bow, many users struggled to figure out how to fire, and some grew frustrated with the difficultly of firing the bow. Upon firing the bow, users expressed disappointment in its performance, and stated that they expected it to shoot further or do something more interesting. Because of this marked difference between user expectation and user performance, there is opportunity to produce an improved design that is easier to operate and perform better to increase user satisfaction.

Functionality

Below are descriptions of the procedures for the designer's intended use of the three (3) blasters. Video Link of all Nerf Blasters Firing at Once

Big Bad Bow

General Description: The Big Bad Bow designed to mimic a compound bow. The ammunition are 8 in long foam cylinders launched with a spring loaded piston. The user pulls back the piston and then pulls on the trigger to release the projectile. The arms of the bow are non-functional.
Big Bad Bow Video

Step 1: User picks up the fully loaded blaster to hold by both handles.
Step 2: User aims at a target through the scopes.
Step 3: User pulls back the rear-most handle from the rest of the gun till a click is heard or felt.
Step 4: User pulls the trigger which fires the dart and unlocks the bolt.
Step 5: User retracts rearmost handle's sub-assembly.
Step 6: User loads second and third darts from the dart holders subsequently, and then follows steps 2 through 5 to fire darts.
Step 7: User retrieves the darts.
Step 8: User loads darts onto the gun's nozzle and the dart holders.

NOTE: The Big Bad Bow also has an initial assembly procedure for the consumer to perform prior to use. That procedure is not described here is not described here.

Rapid Fire 20

General Description:The Rapid Fire AS-20 is capable of automatically firing a series on 20 shots with one pull of the trigger in rapid fire mode or 20 individual shots in single shot mode. The single shot mode requires some finesse to only release one shot at a time. The shots are powered by a compressed air tank that is primed with a series of 30 pumps. The ammunition are 4in long foam cylinders with rubber suction cups on the one end.
Rapid Fire 20 Video

Step 1: User picks up the fully loaded blaster by the yellow handle.
Step 2: User pumps the orange handle 25 to 30 times to fully prime the blaster.
Step 3: User chooses single shot mode or rapid fire mode with the orange dial located on the side of the blaster.
Step 4: User points the blaster in general direction of target(s).
Step 5: User pulls the trigger to fire single darts or a stream of darts.
Step 6: User retrieves darts (20 per clip).
Step 7: User loads the darts into the barrels of the gun.

Buzz Saw

General Description: The Buzz Saw uses the inertia of a flywheel to propel it’s projectiles forward. Angular momentum is accumulated on the ~4 inch plastic flywheel by repeatedly pulling on a linear crank (pull handle). The projectiles are three 1” diameter foam balls loaded into a hopper on top of the gun.
Buzz Saw Video

Step 1: User picks up the fully loaded blaster by the green-gripped handle.
Step 2: User sturdily holds the green-gripped handle and pulls back repeatedly on the light blue handle until the desired amount of angular momentum is attained in the flywheel. This is an intuitive process for the majority of users. High angular speeds are indicated with a high pitch whining spooling noise from the flywheel and low angular speeds are indicated with a low pitch spooling noise.
Step 3: User steadies the gun and aims at target(s)
Step 4: User fires as many balls as desired, repeating steps 2 and 3 as necessary.
Step 5: User retrieves balls.
Step 6: User loads three balls into the hopper.

==== Summary ====
Each of the three guns has very different procedures for use. The Big Bad Bow has single-action priming and single firing. The Rapid Fire AS-20 has a significant amount of priming and preparation work for a rapid release of 20 darts or 20 single shots. The Buzz Saw requires spooling of a flywheel and offers 3 shots.

User Study

A user study was conducted on the three (3) Nerf blasters on Carnegie Mellon University's Campus. Details on the nature of the experiment as well as observations and paraphrased quotes from the users can be view at the Nerf_gun_userstudy Wiki page.

Big Bad Bow

General Feedback: People tended to initially think the gun was very appealing, but after using it were often disappointed in its performance.

User responses: (1) Sight was useful for lateral accuracy, not for vertical positioning (2)Large learning curve for an accurate shot (3)Not as exhilarating as other Nerf weapons (4)Ammo breaks easily (5)Shooting mechanism is complicated, Functionality of design is not apparent many misfires trying to get ready (5)Operation is not immediately apparent, unclear on how to hold it (6)Short Range

• Too big
• Fulfills a classic "image" (((((?)))))
• Can't de-cock the mechanism without firing
• Not immediately apparent how to cock it

*Confusing design, too much is cosmetic,

• Aesthetics and functionality do not align

Rapid Fire 20

General feedback: This weapon was praised as the most enjoyable to use, but there were frequent complaints people had about getting the gun ready to fire.

User responses:

• Takes forever to pump and load
• Good for crowds
• Is the most fun: most people would want to buy this gun after playing with all three
• Not very comfortable
• No pressure gauge, when should pumping stop?
• Pumping force is too great
• Tube behind grip is annoying
• Hard to aim, there is no sight
• Pump feels flimsy
• More satisfying to fire than other nerf blasters
• More "feedback" feel when firing
• Tedious to pick up all the fired ammo
• "Single Fire" mode does not function properly (fires multiple darts still)
• Wasn't apparent at first that it needed to be pumped to fire
• Not all of the darts fire; some get stuck.

Buzz Saw

Summary of user feedback:

1). Too much lag between trigger pull and ball firing
2). User loses time in steadying the gun after the winding phase (step 2) and before firing (step 4)
3). Sound is uncomfortable and prolonged for some users, but intimidating for the target
4). Sound does not accurately portray performance
5). User can vary projectile distance
6). Strength and experience limit gun performance
7). runs out of ammunition quickly
8). “Buzz Saw” is a violent name
9). Cannot pump and fire at the same time. Balls get stuck in gun when one is pulling on light blue handle; The design includes a ball release switch to address this issue
10). Balls gets stuck in top of hopper
11). Gun does not shoot at an angle greater than about 45 degrees
12). The loading phase (step 6) is time consuming

General feedback: People seemed to like the shooting mechanism for this gun, but generally it didn't seem as fun to play with.

User responses:

• Very accurate
• Jammed frequently, and the top ball often did not fall into the shooting mechanism from the loading station
• Makes an annoying sound
• Makes an awesome sound
• Is difficult or impossible to shoot at an upwards angle
• Difficult to remember to stop pumping before firing, making shots inaccurate
• Limited by the user's strength
• Seems the easiest to improve
• More obvious function
• Short Range if not primed well

Performance Studies

In order to compare the different guns in terms of performance, we set up experiments to test how the three guns compared with respect to distance and accuracy.

Distance Study

Set Up: Guns were fired indoors from a horizontal orientation from 33.5" above the ground, and the position where the ammo first hit the ground was measured. The gun was held very steady when being shot so that no extra forward momentum was imparted on the projectile. Tests were performed indoors, so there was no wind or other disturbances.

Big Bad Bow: 19.0, 19.2, 18.10, 18.10, 17.10, 17.2, 19.0, 19.1, & 18.7 (Average 18' 7")

Rapid Fire 20: 18' - 22' Spread

Buzz Saw: 26.10, 29.4, 29.5, 30.1, 32.2, 32.9, 29.3, 30.4, & 31.4 (Average 30' 2")

Pictures

Videos

Buzz Saw

Rapid Fire 20

Accuracy Study

Set Up: 3 people without previous nerf gun experience were selected at random to participate in the study. Each person was instructed to stand 17' away from a target and fire with each separate nerf gun at the target. Pictures were taken in order to discern their accuracy. Then one of our group members, after practicing with all three guns, did the same accuracy test and the results were recorded as well. By testing both groups, we will be able to figure out how easy each gun is to aim for a beginner, and for somebody with more experience.

Videos

Buzz Saw Accuracy Test

Rapid Fire 20 Accuracy Test

Big Bad Bow Accuracy Test

Results!!!

Product Dissection

Mechanical Function

Bill of Materials

Big Bad Bow

Part No.	Name	Function	Quantity	Material	Mass	Manufacturing Process	Picture
101	Bow Arm and Outer Cog	Cosmetic	2	Plastic	56g	Injection Molded
102	Small Inner Cog	Cosmetic	2	Plastic	5g	Injection Molded
201	Front Left Cover	Priming Mechanism Housing	1	Plastic	117g	Injection Molded
202	Front Right Cover	Priming Mechanism Housing	1	Plastic	118g	Injection Molded
203	Rear Right Cover	Barrel/Action Housing	1	Plastic	123g	Injection Molded
204	Front Left Cover	Barrel/Action Housing	1	Plastic	119g	Injection Molded
301	Nozzle	Air Delivery/Dart Delivery	1	Plastic	17g	Injection Molded
302	Nozzle Tip	Air Restriction/FOD Protection	1	Plastic	<1g	Injection Molded
303	White Tip Holder	Holds Nozzle Tip	1	Plastic	3g	Injection Molded
304	White Air Restrictor + Spring	Air Restriction	1	Plastic/Steel	3g	Injection Molded
305	Rubber Piston	Air Delivery	1	Latex Rubber	5g	Injection Molded
306	Barrel Lock	Action Lock	2	Plastic	2g	Injection Molded
307	Piston Shaft	Air Delivery	1	Plastic	26g	Injection Molded
308	Trigger Lock	Action Release	1	Plastic	2g	Injection Molded
309	Trigger	Action Release	1	Plastic	8g	Injection Molded
310	Spring Stop	Piston-Cylinder Spring Compression	1	Plastic	1g	Injection Molded
311	Cylinder	Air Delivery	1	Plastic	26g	Injection Molded
401	Eyepiece	Cosmetic	1	Plastic	4g	Injection Molded
402	Eyepiece Lens	Cosmetic/Aiming	1	Acrylic	<1g	Die Cut
501	Arrow Dart	Ammo	3	Styrofoam	5g	Molded/Glued
901	Screw	Fastener	18	Steel	0.5g	Forged/Machined
902	Spring for Barrel Lock	Action Spring	2	Steel	<.5g	Rolled/Bent
903	Short Trigger Spring	Release Mechanism	1	Steel	<1g	Rolled/Bent
904	Long Trigger Spring	Release Mechanism	1	Steel	<1g	Rolled/Bent
905	Piston Spring	Air Delivery	1	Steel	12g	Rolled/Bent

Preliminary Analysis

Stakeholders

Some of the main stakeholders in nerf guns are the children who play with them, the parents who buy them and supervise their use, the retailers that stock them, and the society that everybody lives in.

Children: The children in this case are the end users, the one who actually use the product. They are also the ones who probably nag their parents into buying them, so it's both important that the guns appeal to them before they are bought, and they are enjoyable. In particular, children will enjoy a gun if it is "fun" to play with (generally involves power, ease of use, & physical appeal)

Parents: Even though the children play with the toy, the parents have a large stake in it as well. If the gun ever doesn't work, the parent will of course have to deal with returning the gun, or buying a replacement (or replacement ammo). Also, if a child is ever injured while playing with the toy, the parent has to help heal the injured child, and probably reprimand another child. Parents will like most the gun that is safe to use (very little chance of injury) and reliable (no need for extra trips to the toy store).

Retailer: The retailer has the smallest stake in terms of day to day use, but their profit off the item is what determines if it stays available to purchase. The retailer will only like items that are popular (sell quickly, attract attention), have no customer support issues (no returns), and are easy to keep in shop (not breakable, easily storeable).

Society: While not as tangible, the society that everybody lives in has to deal with the possible consequences of the children growing up playing with weapons. While there can be no conclusive or definitive study to prove it, children who play with toy weapons as children will possibly grow up to be more violent and aggressive adults. To counteract this, nerf weapons can be marketed/advertised to be appear less violent.

DFMA

FMEA

DFE

Creating and selling a product has a significant environmental impact from increased production activity in it's sector and associated sector. Because the NERF gun does not require energy input for uses or additional accessory products for use, the environmental impact analysis focus on its production and end-of-life impact. In order to measure the environmental impact of production of a NERF gun, we used the Carnegie Mellon University's Green Design Institute EIO-LCA tool to quantify the increase in greenhouse gas production, conventional air pollution, and toxic releases caused by $1 million in sales in the doll, toy, and game manufacturing sector. Based on the results of the EIO-LCA, designing the NERF gun to use low energy, low toxic byproduct manufacturing processes would significantly reduce the environmental impact of the NERF gun production process. At the end of a NERF gun's life, the product is generally disposed of by the consumer. Most likely, the consumer will throw the NERF gun in the garbage, and it will be taken to a landfill. Since a NERF gun is made mostly from plastic, it will not easily decay, and as it decays, will potential release toxins to the environment. To reduce the end-of-life environmental impact of the NERF gun, it should be designed to be recyclable. We are in the process of determine what type of plastic is used in the NERF gun. If this plastic is not recyclable, the gun could be re-designed to use a recyclable plastic. The NERF gun should also be designed to encourage the consumer to recycle the product. If the NERF gun and its packaging included messages informing the consumer that the consumer that it is recyclable and encourage them to recycle, it would increase recycling of the product, thereby reducing its end-of-life environmental impact.

Greenhouse Gas Emissions

Greenhouse gas emissions are a particularly important consideration in design for environment due to the current concern with global warming and the likelihood of carbon taxes. The EIO-LCA analysis shows that energy generation accounts for 45% of the greenhouse gas emissions associated with doll, toy, and game manufacturing. Using a less energy-intense manufacturing process for the NERF gun would reduce greenhouse gas emissions associated with its production.

The chart below summarizes the greenhouse gas emissions of the top 10 sectors related with doll, toy, and game manufacturing sector.

The chart below depicts the contribution of each top 10 sectors related with doll, toy, and game manufacturing sector to the total greenhouse gas emissions associated with doll, toy, and game manufacturing.

Conventional Air Pollutants

Conventional air pollution are an important consideration due to its impact on air quality and acid rain. The EIO-LCA analysis shows that energy generation accounts for 80% of the conventional air pollutant emissions associated with doll, toy, and game manufacturing. Using a less energy-intense manufacturing process for the NERF gun would significantly reduce conventional air pollutant emissions associated with its production.

The chart below summarizes the conventional air pollutant emissions of the top 10 sectors related with doll, toy, and game manufacturing sector.

The chart below depicts the contribution of each top 10 sectors related with doll, toy, and game manufacturing sector to the total conventional air pollutant emissions associated with doll, toy, and game manufacturing.

Toxic Releases

Toxic releases are an important consideration due to their hazard to human, animal, and environmental health. The EIO-LCA analysis shows that plastic and resin manufacturing and doll, toy, and game manufacturing each account for 26% of the toxic releases associated with doll, toy, and game manufacturing. Using a plastic that produces minimal toxic byproducts in the NERF gun, and using manufacturing processes with low levels of toxic byproducts would significantly reduce the amount of toxic releases associated with its production.

The chart below summarizes the toxic releases of the top 10 sectors related with doll, toy, and game manufacturing sector.

The chart below depicts the contribution of each top 10 sectors related with doll, toy, and game manufacturing sector to the total toxic releases associated with doll, toy, and game manufacturing.