THE CLIENT:
Mark Novak
Outreach Specialist
Biological Systems
Engineering
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
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Joystick
Box controls
Alt kill switch *
Pressure sensitive *
Separate brake control
Jet ski controls *
Pneumatic hand controls *
Cruise control
Motor with gear
Segway controls *
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Cane/stick
Throttle
Water proofs
Motorcycle control *
Wireless
Pulley wire
Mechanical brake
2nd battery source
Evaluation
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Throttle (10)
Mechanical brake (8)
Joystick (4)
Motor with gear (3)
Separate brake control
(2)
• Motorcycle control(1)
• Alt kill switch (0)
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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 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:
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3.
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5.
Range of motion
Reduced physical exposure of product
Position of product on the tractor
Types of materials used
Strengths / durability of product
Considerations
(continued)
Shearing Stress calculations (Strength of Material):
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!!!)
Considerations
(continued)
Critical Design Analysis:
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
Considerations
(continued)
Steps for Improvement:
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More time for testing and constructing
Greater budget for better materials
Customizable lawn tractor
Experience
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.