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

Design

PROBLEM STATEMENTPROBLEM 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 • 2nd 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• 2nd battery source

Decision of Throttle DesignDecision 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 PiecesCross Pieces / / Attachments to ThrottleAttachments to Throttle

3 Types ofAttachments

1. Flat rectangular steel bar2. 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 ProductFinal Product

• Adjusted length of the pieces and size of the screws in order to accommodate within actual confinements

• Culmination of previous designs

ConsiderationsConsiderations

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

ConsiderationsConsiderations(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 = F1y x = 5 inches, y = 9 inches

F1 = 2293.89 lbs

(conservative number used, never put more than 2000 lbs force on throttle!!!)

Shearing Stress calculations (Strength of Material):

ConsiderationsConsiderations(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:

ConsiderationsConsiderations(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.