From DDL Wiki

Client Comments on Report 1

We received your report, and we have some comments and questions. Your user study is fantastic and will help with phase two. It sounds like the product is well-optimized for DFMA and FMEA and that the biggest areas identified for improvement are the firing distance and matching between aesthetic expectations and functionality. Please respond point by point to the items below. We are looking forward to seeing your ideas in Report 2.

• Executive Summary: Thank you for the clear summary of findings.

- This section is good!

• Stakeholder Needs: Please summarize important needs as a bullet list. It seems you are missing some important ones, such as easy assembly, easy clean up (important for parents), easy to replace or difficult to lose ammo, storage, etc. It also seems that the issue of providing fun without reference to violence could be attractive to parents. There is no need to list obvious/generic needs like shareholder and retailer need for profit – let’s focus on needs that will manifest specifically in your design.

- This section was revised with new stakeholders and stakeholder needs. It is now in bulleted form. Please review this section.

• Use: Fantastic documentation of user studies. We particularly enjoyed the videos. These studies will be a big help in phase 2. If the Rapid Fire has a single shot mode dial, why does it require “some finesse” to release only one projectile? Error bars on the distances fired would be useful in assessing consistency as well as average range.

- This point has been further clarified in the same section of the report, basically when the trigger was squeezed at all, enough air was let in to fire more than one dart. In addition, error bars have been added to the distance graph (5%). A good suggestion

• Assembly: Clear picture at end of the report.

- This section is good!

• Mechanical Function: Relatively clear explanation.

- This section is good!

• Mechanical Analysis:

• What useful question are you able to answer using this analysis?

-How can the firing power of the gun be increased. This is now addressed in the introduction to the mathematical analysis

• Please include a complete free body diagram of the problem you are solving, and write out the equations and define your notation before plugging in the numbers, so that we can follow your analysis.

-A revised FBD has been included in the mathematical analysis section

• We would also like to know what assumptions you made in order to use these methods, such as the ideal gas law.

-Assumptions were put into a numbered list in the original report. Additional assumptions have been added to report I.

• What is the Hooke's Spring Law equation that you mention - why is the 1/2 term included?

-The 1/2 term for Hooke's Law was added by mistake, this mistake has been corrected on the report I calculations

• If all of the gas goes into pushing the dart as in your assumption #2, then why is the dart's velocity so much lower than it would be if pushed directly by the spring? Where are the energy losses?

-The calculations represent an ideal case. Further calculations to determine ideal distance fired have been added. The ideal vs. actual cases are compared and source of the energy losses are discussed.

• What should we be learning from the graphs you present?

-The graph show how altering cylinder pressure and distance of the piston from the dart alter the force applied to the dart. This is now explained further in report I.

• What is the conclusion of your analysis?
• You calculate the force on the dart, but how does that translate into dart velocity?

-additional calculations have been added to determine how force applied translates to dart velocity, and how velocity translates to distance fired.

• You mention that there is a "tremendous decrease in force between the spring and the dart", but how does your analysis show that?

-calculations of ideal distance fired has been added to support this conclusion.

• Bill of Materials: Thank you for the clear documentation.

- This section is good!

• DFMA: Good observations – it seems like the designers put a lot of thought into DFMA.

- This section is good!

• FMEA: We were not able to access the FMEA document from the link provided, so it is difficult to assess your FMEA findings.

- The FMEA link has been restored in the Wiki page: Big Bad Bow FMEA

• DFE: It looks like DFE is not a top concern for this product. What else is in the doll, toy, and game manufacturing sector (more information than the obvious)? Do you think it is a good representation of a Nerf gun, or is it too aggregate?

- More examples of items in the doll, toy, and game manufacturing sector have been added to the first paragraph of the DFE section, as well as our position that this sector is appropriate for Nerf weapons.

• If any of your images, figures, or text were taken from another source, please be certain to provide proper attribution.

- All of the pictures in report 1 were taken by our team