Richard Huth

Rendering of final SoildWorks model after design was completed.

Actual image of production unit. New tiller design features overmolded grips for extra comfort, height adjustable handles, and new front bumper with grip for easy transportation. This model has a 35cc engine and a 16" tilling width.

Actual image of production unit. Same features with a 22cc. motor and a 9" tilling width.

Male boundary ratios to determine handle height. Data is taken from the ANSUR database to determine a 95th percentile and a 50th percentile male boundary manikin between the ages of 18 and 65. "http://www.openlab.psu.edu/tools/calculators/boundaryRatio.html"

Female boundary ratios to determine handle height. Data is taken from the ANSUR database to determine a 50th percentile and a 5th percentile female boundary manikins between the ages of 18 and 65. "http://www.openlab.psu.edu/tools/calculators/boundaryRatio.html"

Adding a preference to a statistical model can be helpful in determining adjustability. It would be very time consuming and expensive to gather enough people in a focus group to evaluate preferred grip height across the entire spectrum of the U.S. population. To overcome this challenge we are able to create a hybrid model. We do this by making a prototype with ample adjustability and asking a small group of people to try the prototype. This example uses 18 people as our sample size; ideally we would like to use 30 or more participants for a good statistical value. We then create a linear regression model correlating the preferred grip height to stature. From this model we capture the equation of the line and the Root Mean Square Error. Now we are able to extrapolate this data to 1000 men and 1000 women from the ANSUR database based on stature. The equation y=mx+b+N(0,RMSE) is used to create a virtual population that has the variability of the original linear regression model.

Anthropometric hand data for grip position and design. "http://www.openlab.psu.edu/tools/calculators/AnsurDimensionSelect.php"

Bearing fit FEA study for the tiller.

Exploded view of grip.