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Revision as of 10:37, 3 October 2008

Client Comments on Report

We received your report. We were very impressed with your analysis, your findings, and the clarity and professionalism of your report. We are surprised to learn that the additional cost and complexity of the compound post hole digger does not provide an advantage to the user. Your FMEA results indicate that the pivot bolts are the most serious failure mode. This may be particularly true after significant use and corrosion and under dynamic loading in difficult applications. The LCA matches intuition - would it be meaningful to try reducing truck transport emissions by shipping the product in pieces to reduce packaging and have our retailers or customers assemble? Given your mechanical analysis, would you conclude that any rational consumer knowing the true properties of both products would choose the simple variant, or are there market segments or applications who would benefit from the compound digger?

Specific comments follow

• You have identified a good list of customer needs, but you seem to be missing some important ones like ergonomics, safety, robustness to variation in ground conditions, and speed/efficiency. Retailer needs may also include the footprint and weight of the product - especially one so bulky. Please provide a more comprehensive list and compile them into a bullet list.
• Your test to identify the human applied static load of 30 lbs seems reasonable, but did you consider dynamic loading? I would expect that the most extreme case will be when a user finds a difficult area of clay and applies a dynamic load.
• Your documentation of use of both products is excellent. One picture shows the dirt that falls out from between the blades when lifting. How much dirt is typically lost?
• Can you comment on the difficulty of lifting the digger and dirt out of the ground - does it put strain on the back? Is this unavoidable?
• You mention that the compound digger creates additional friction from the additional joints. Approximately how much of the applied force goes to resist this friction?
• You mentioned that the fiberglass handles are placed into the steel tubes, and the tubes are then compressed around the fiberglass. Is there evidence of this crimping?
• Nice DFMA and FEA analysis
• How is it that musical instrument manufacturing shows up as a top category for toxic releases related to post hole diggers? Can you comment?
• You mention that transportation was ignored. Did you use the EIOLCA producer price model, which accounts for transportation?
• Your mechanical analysis is clear except for the free body diagram of the complex digger. There are two pieces, and it is difficult to understand your model without two separate free body diagrams. Are you assuming that the reaction force in the pin at C is only in the vertical direction? What enables you to make this assumption?
• Your FEA results show a factor of safety of 1.7 at the weakest point. Is this sufficient given the potential for dynamic loading, fatigue, and weathering factors you mention?

We are looking forward to seeing your research findings and product ideas in the next report.

Client comments on the Mechanical Analysis

A well-done mechanical analysis, which includes both the free body analysis and the finite element analysis on the handle. I have only two comments:

• Please indicate the diameters of the wood rod and pivot bolt in your report.
• Please add the boundary condition explanations using textbox in Figure 8.1 because some clients may not be familiar with the graphical representations in the Cosmos software, e.g. the force and zero DOF settings in your model.

The reference for the wood material properties is great. I encourage you post the link onto the discussion board in Blackboard system in order to share the information with other teams.