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Digging deeper...HERShovel™ for Women

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Get Technical

  • Effects of various handles, blade (lift) angles, and use of auxillary D-grip
  • Penetrometer testing of force necessary to insert blade
  • Comparison of final (redesigned) prototype with earlier prototypes

Get Technical

The HERS™ design incorporates findings from research supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under Agreement No. 2009-33610-19668 of the Small Business Innovation Research Grants Program. This grant enabled Green Heron Tools to conduct interviews and focus groups with women farmers throughout the U.S. and to engage a team of engineers and ergonomists from Penn State University to support the design and testing of several pre- HERS™ prototypes. Thanks to engineering doctoral candidate Jesun Hwang and engineers Andy Freivalds and Aaron Yoder for their pivotal roles in conducting the USDA-funded research, highlights of which include:

Effects of various handles, blade (lift) angles, and use of auxiliary D-grip

Field and laboratory testing measured the effects of handle or grip type, blade (lift) angle, and use of an auxiliary D grip mounted partway down the shovel shaft on two physiological measures – volume of oxygen consumption (VO2) and heart rate (HR). VO2 and HR both relate to the amount of energy expended during shoveling, with a lower energy expenditure being desirable. Field testing was carried out by volunteer women farmers, and laboratory testing, by graduate students. Participants were also asked which handles and angles they preferred.

Patty and Jesun Patty Neiner, a farmer volunteer, and Jesun Hwang

Results:

  • An Analysis of Variance (ANOVA) with full factorial design found statistically significant* relationships in laboratory testing between lift angle and VO2, handle type and VO2, use of auxiliary handle and VO2, and lift angle and HR. Specifically, a 36° angle (the largest tested), a wide D-handle and use of the auxiliary handle all reduced the physiological costs of digging and shoveling.
    • Statistical significance is a measure of the likelihood that results are “real” as opposed to having occurred by chance. A relationship is statistically significant only when there is at least a 95% likelihood that the observed results are real.
  • User preferences of women farmers who participated in the field tests, as well as participants in a Pennsylvania Women’s Agricultural Network field day who tested the prototypes more informally, also favored the larger angle, auxiliary handle and wide D handle.
Aaron and Andy using a penetrometer Aaron Yoder and Andy Freivalds using a penetrometer

Penetrometer testing of force necessary to insert blade

A soil penetrometer was adapted to measure the force necessary to insert various blades into various types of soil and into lab foundry sand. The blade eventually chosen for HERS™ was found to be superior to all other blades tested -- round, flat and serrated flat -- in both mediums in which it was tested (soil in a Penn State high tunnel and laboratory foundry sand). This meant that inserting the HERS™ blade required less force than inserting other blades.

Comparison of final (redesigned) prototype with earlier prototypes

The final prototype featured the HERS™ blade, a wooden shaft approximating the length of the medium-size HERS™, and an extended D grip approximating the width of the later HERS™ D grip.

Results

The redesigned prototype was found to be superior to both the best earlier prototype (the 36° angle, wide D handle and auxiliary handle, with serrated flat blade) and a commercial garden shovel with square-point-flat-steel blade. More specifically, a two-sample t-test was used to determine differences in oxygen consumption, heart rate, perceived exertion, perceived discomfort and perceived fatigue.

  • In comparing the combo prototype with the commercial shovel, statistically significant differences were found in all variables, all favoring the final prototype.
  • In comparing the combo prototype with the best earlier prototype, statistically significant differences were found in all variables but normalized heart rate; again, all data favored the newest, redesigned prototype.

Figure 18: The effect of shovel type on physiological and subjective variables

Table showing the effect of shovel type on physiological and subjective variables

*Significant differences between commercial or old best and redesigned (combo) shovel

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