Team Members: Alyssa KennettEE Charles VeronneauEE Chris DiLalloME Christian KaszasME Kerry KlauderME Nick SaccoME Faculty Mentor: Robert Jenkins Company Contacts: Jim Peterson and Jon Funk Neuton Lawn Tractor Project

Short Intro to the Project  Starting Out: Mechanically driven lawn mower with mechanical steering system and gas power  Finish Line Product: Battery powered and electrically driven lawn mower with electronic steering and controls system. BEFOREAFTER

Final Project

Project Goals  Electrically driven, powered, and controlled Neuton Mower  Redesign steering  Environmentally friendly  Increase consumer appeal  2 hour run time

Original Framework - Eliminate mechanical systems found in current gas tractors - Powered by batteries without gasoline - Appealing aesthetics - Consumer market: year old, predominantly male - Designed to mow a 1 acre lawn - Mow time: 2 hours - Low noise level - Redesigned Steering - Efficient mowing - Easy maintenance unlike current gas tractors - Safety

Unexpected Obstacles  Battery size not as specified  Motor mounting position  awkward pulley assembly  Bearings order not fully processed  Wiring Difficulty

Discarded Concepts  Pancake Motors – weight on deck  Hub Motors - cost  Steering Wheel – complexity  Independent Battery Systems - no need for separation between systems, more batteries  Split-axle System – Fabrication difficulty  Hand-made motor controller – complexity, heat sinks, difficulty sourcing capable components

Main Features/Components  Framework  Drive Train  Motors  Batteries  Controls  Wiring

Framework Modifications  Rear/Side Battery Shelves  Control Arms  Mounting Block for Blade Motor

Side Battery Shelves  Located on left and right side  1-inch walls to hold battery in place  Full wall against tractor  Full back wall at wheels

Rear Battery Shelves  Mount above drive motors  Holds two batteries

Control Arms  Mounted to battery shelves  Both control arms hold a joystick  Right side also holds main user controls: key start, kill switch, on/off key switch for blades

Mounting Block for Blade Motor  Holds blade motor upright  Support for battery shelf  Constructed out of aluminum

Drive Train Options Original Possibilities Existing Hydraulic Drives Direct Drive Hub Motors Standard Motors Pulley System Roller Chain V Belts Synchronous Belts Solely Electric Driven Cost Support, Placement Weight, Noise Slippage Reasons for Decisions 2 Step Pulley System Increase in torque, decrease in RPM required 15.5:1 ratio Outer Diameter of V belt pulley on the order of the diameter of tire Synchronous belts of such ratios not available 2 Stages allows for 2 4:1 ratios Provide required strength with no slipping

Pulley System

Split Axle 2 Axles, supported in center by inverted block bearings Drawback: Difficult fabrication process Existing Hydraulic Casings Cases already known to have support strength No fabrication required* Allows use of existing parking break *Hydraulics were removed and stripped of any parts not used by parking break Support System

Extending the Wheel Base Tire overhang causes interference for mounting a pulley on the hub axle Solution: Extend the Wheel Base Adding an 2.5 inch extension to the hub clears the hub axle for mounting of a pulley Hub Spacers

Corporate Headquarters in Canton, Massachusetts Store in Williston, Vermont Canton location recommended use of Gates Design Flex® Selecting the Belts

Belts and Pulleys Selected From end mounted motor: P-22-8MGT-12, P-90-8MGT-12 pulleys MGT-12 belts From forward mounted motor: P-22-8MGT-12, P-90-8MGT-12 pulleys 840-8MGT-12 belts To wheels: P-24-8MGT-12, P-90-8MGT-12 pulleys 920-8MGT-12 belts

Motors Overview  2 Drive Motors  1 Blade Motor  1.5 kW, 24V Permanent Magnet DC Motors  Full Torque per wheel (70 N-m)  Regulations, Standards, Safety  Bidirectional, TEFC  80 FL  4 AWG and 10 AWG

Torque Calculations Calculations Top Speed (V): 8.5 mph Time to reach top speed (t): 5 seconds Wheel radius (r):.667 feet Angle to ascend (θ): 6° Assumed Weight (W): 730 pounds 24 pound mass Flat Ground Acceleration (a) = V/t = 2.5 ft/s 2 Required Force # = m*a = 59.6 lbf Required Torque # = F*r = 39.8 ft-lbf Up a Slope at constant speed: Required Force # = m*R*Sin(θ) = 80.5 lbf Required Torque # = F*r = 53.7 ft-lbf # Total force and torque required to move the mass. Full Torque required at each wheel Operator must be able to turn around while on a slope, therefore each wheel alone must provide the necessary power to move the tractor. Required Torque to each wheel is 53.7 foot pounds

Motor Output: 3.5 ft-lb Torque 3000 RPM Gear Ratio Calculations Required RPM = Velocity/(2∏r) =178 rpm Required Torque = 53.7 ft-lbf Gear ratio to increase torque: 53.7 / 3.5 = 15.3 Gear ratio to decrease RPM: 3000 / 178 = 16.9 Required torque is for constant speed directed up a slope and is greater than the torque required for flat acceleration, therefore the torque cannot be lowered below 53.7 ft-lbf. RPM and torque raised to accommodate. Gear ratio to increase torque: 54.2 / 4.7 = 15.5 Gear ratio to decrease RPM: 3000 / 194 = Step Gear Ratios: 54.2 / 4 = 13.55, / 4 = / 4 = 750, 750 / 4 = Gear Ratios of approximately 4 accomplish what a single gear ratio of 15.5 accomplishes Torque Calculations

Motor Mounting  Blade motor standing upright  Drive motors side-by-side  Allows for batteries to go on top

Power System Overview  4x120 Ah, AGM-SLA Batteries  13”x7”x8.5” = Good Fit  Cheapest choice, Deep-cycle, Ample run-time  24V Dual Eagle Pro Charger  Capacity to charge all batteries together  25 Amp output can replenish full charge in approx.

Controls System Overview  24V, 120A Kelly Controller  Contactors for Protection  Microcontroller  0-5V Digital output, determines reverse on/off  Joysticks  0-5V output, bi-directional, single axis  Other Controls  Key switch  Blade switch  Kill switch

Motor Controllers  Kelly Controller PM motor controllers  120 A continuous, 24 VDC  Capable of Reversing  Analog input in the range of 0-5V  Windows Interface for Programming

Microcontroller / DA Conversion   PIC16F887   44 pins, converts input to digital   Determines reverse on/off, output high/low   C compiler compatibility   MPLAB IDE   C code   Simple logic to analyze input   Output 0-5V instead of 0-2.5V and 2.5-5V   DAC (Digital to Analog Converter)   Convert from microcontroller to motor controller

Simplified Circuitry for Motor Control

Joysticks  Allow electronic control  Hall Effect Sensor  ~0-5V output  Miniature – need to extend levers

Prototype Handles  Modeled in Solidworks  Increased radius of movement  Angled for comfort  Ergonomic Grip

Body Design Courtesy of Jon Funk

Safety  Kill Switch  Belt Guards  Seat Sensor

What comes next?  Custom designed frame to fit purpose and additional parts  Adjustable control arms  Adjustable seat height/position  New body

Future Thoughts  Possibility of charging batteries through small wind turbine or solar panels.

METALWORKS, Inc. Thank You  Jon Funk, Jim Peterson, and Robert Jenkins for design, implementation, direction, and advice  Floyd Vilmont

Corporate Headquarters in Canton, Massachusetts Store in Williston, Vermont Canton location recommended use of Gates Design Flex® Thank You

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