THE CLIENT: Mark Novak Outreach Specialist Biological Systems Engineering The Needs: Hand Controls for Safe and Reliable Lawn Tractors Design Practical and Efficient Adaptable/Mobile Design

PROBLEM STATEMENT Create a practical hand-controlled device to operate the for/aft movement for a lawn tractor which can be used by individuals with lower body disabilities without impeding normal operation. It must be safe, reliable, durable, and removable whilst remaining both cost effective and mechanically efficient.

Brainstorming Joystick Box controls Alt kill switch * Pressure sensitive * Separate brake control Jet ski controls * Pneumatic hand controls * Cruise control Motor with gear Segway controls * Cane/stick Throttle Water proofs Motorcycle control * Wireless Pulley wire Mechanical brake 2 nd battery source

Evaluation Throttle (10) Mechanical brake (8) Joystick (4) Motor with gear (3) Separate brake control (2) Motorcycle control(1) Alt kill switch (0) Box controls Cane/stick Water proofs Pressure sensitive Jet ski controls Pneumatic hand controls Cruise control Segway controls Wireless Pulley wire 2 nd battery source

Decision of Throttle Design Basis of our Decision: Most votes Easiest to assemble mechanically Easy to control Most cost effective

Attachment of Throttle to Transmission Initial design modeling Test-bench/prototype Mounting of throttle Cross pieces/attachments to throttle Mounting plate Final product

Initial Modeling Designs Throttle is attached to a series of levers Levers are connected to for/aft transmissions Open circles are loose joints that rotate Cylindrical bar is attached to the mounting plate

Test-bench / Prototype Took measurements of dimensions from tractor and location of levers Constructed replica of tractor segments and operation of the throttle/levers

MOUNTING of THROTTLE Aluminum box shape Notch attaches to back of throttle Throttle slides down into the mounting piece

Cross Pieces / Attachments to Throttle 3 Types of Attachments 1.Flat rectangular steel bar 2. Solid cylindrical steel bar used for rotation of levers 3. Screws / bolts for attachment

Mounting Plate 2 aluminum plates that are mirror images of each other Placed on each side of the tractor frame and attached with screws Cylindrical bar is inserted through the bearings

Final Product Adjusted length of the pieces and size of the screws in order to accommodate within actual confinements Culmination of previous designs

Considerations We took the following into consideration: 1.Range of motion 2.Reduced physical exposure of product 3.Position of product on the tractor 4.Types of materials used 5.Strengths / durability of product

Considerations Considerations (continued) τ (ave) = P/A= F(force)/A (area) Shear, MPa of structural steel: 145x10^6 Mpa Area: π [(.25in)(2.54cm/in)(1m/100cm)]^2 Force= Aτ = 4129 lbs (max stress) “Calculations of Throttle yield” 4129x = F 1 yx = 5 inches, y = 9 inches F 1 = lbs (conservative number used, never put more than 2000 lbs force on throttle!!!) Shearing Stress calculations (Strength of Material):

Considerations Considerations (continued) 1.Excess motion that did not apply to for/aft movements 2.Tight fit of levers and throttle 3.Lack of proper testing 4.Weather resistant Critical Design Analysis:

Considerations Considerations (continued) 1.More time for testing and constructing 2.Greater budget for better materials 3.Customizable lawn tractor 4.Experience Steps for Improvement:

Through our ideas and intuitive thinking, we were able to complete the design of functioning hand-controls for the lawn tractor. We believe, you, the client, will accept our ideas and make improvements upon them and hopefully someday be able to apply it to the real world.