Easy Access for the Disabled:
Mounting and Dismounting a Zero Turn Lawn Mower (ZTL)
Team Members: Kohen Newsome, Crystal Schreck, Nancy Shahbazi, Brandon Paustian, Kaylee Tillery
Faculty Advisor: Dr. Thomas
Background
Final Design
Results and Conclusions
Sponsor/Client: Mr. Jimmy Hill with FarmAgain and Agribility
Over 1.2 million individuals with some form of physical disabilities have agricultural backgrounds[1]. Programs like Farm Again and AgrAbility help farmers with disabilities regain a sense of independence by finding and funding assistive technologies for everyday use. Due to the very few solutions that exist on the market today, we were tasked with designing a universal, safe, and cost effective device for individuals with lower extremity disabilities to mount and dismount their zero turn lawn mowers. Through our design we hoped to give some freedom back to these people so they could successfully continue routines in their day to day lives.
Initial Design Simulation Testing
The initial design key criterion were determined by a decision matrix. These include: ease of use, manufacturability, modification of the mower, safety, and affordability. Considering these criterion, our initial concept was the basic design geometry modeled in Figure 1. As seen, a deflection analysis was conducted using ANSYS software on the geometry of the design. The analysis parameters were set as simple supports along the two bottom end edges of the board, and two 400lb force loads on the top faces of the board. The analysis resulted in a maximum deflection 0.0248in. This result indicated a structurally sound geometry for further development and testing.
The final design model, as seen in Figure 2, included several modifications from the original geometry. Two hand holes were added to aid with movement up the board and a latching tab was placed on the mower end of the board to secure the board underneath the mower seat. When building the final model we used No. 2 White Pine which was selected based upon material properties, availability, and price point for prototyping.
Directions for Use: (1) Lock the wheelchair in place. (2) Secure the board between the mower and wheelchair making sure to secure latch tab to the mower seat. (3) Swing legs over the width of the board. (4) Transfer along the board sideways using hand holds. (5) Once safely in seat, unlatch board and place beneath feet for safe mowing. (6) Reverse and repeat for dismount.
We conducted testing with a focus group of 12 students to physically use and assess our model. We used a post-test questionnaire to evaluate participants’ perceived design safety, ease of use and effectiveness. The post-test results indicate that 100% of focus group participants concluded that the sliding board was secure, easy to use, and very effective in it’s design. Additionally, 100% of participants were able to successfully transfer using the sliding board. Feedback from our survey included suggestions for additional safety straps and comfort accommodations. Further modifications would include a narrower board design for comfort and ease of entry onto the board, safety straps that would be located on either side of the board to secure it to the mower in a semi-permanent installment, and rubber or foam comfort grips on the handles to make maneuvering up and down the sliding board easier and more comfortable.
Figure 3: Final Prototype in Simulated Use
Figure 1: Model 1 on the left and model 2 on the right.
Figure 1: ANSYS Modeling of Initial Prototype
Figure 2: Final Design Dimensions and Assembly
Sources
[1] "Farm Again FAQ." Farm Again Services, Web. 05 Dec. 2016.