2012 NASA Great Moonbuggy Race

19

th

_Annual

NASA Great Moonbuggy Race

OVERVIEW

Background

Design Strategy

Design Features

Modeling & Testing

Performance & Analysis

The Great Moonbuggy Race



Student Design Competition

◦

Replicates the design challenges

faced by the original lunar rover

◦

87 student teams

 College Division: 44 teams

 High School Division: 43 teams

◦

Design, fabricate and race

human-powered vehicles



April 13-14, 2012



U.S. Space and Rocket Center,

The Competition

Race Preparation

The Course

◦ Steep slopes, rough terrain



Best Time Wins

◦ Race time + assembly time + penalties

The Team – SpacePokes Design



Systems Design I & II Project



6

UW Team to Compete



Sponsored by Wyoming NASA Space Grant

Consortium

◦

$5000 budget

◦

$750 travel

From left to right: Davis Fay, Ryan Williams, Alisa Frohbieter, Lesley Young (Team Leader)

Design Goals



Finish without crashing or overturning



Place 5

or better

Design Specifications

NASA Regulations

 Human-powered

◦ 2 riders

◦ 1 male, 1 female

 Collapsible: 4 foot cube  Width, ground clearance

and turning radius restrictions

 Safety measures – brakes

and seatbelts

SpacePokes Specs

 15 mph maximum speed  Weigh < 150 pounds

 Assemble in < 10 seconds  Survive 15-foot radius turn

at 10 mph

 Complete stop in < 30 feet

Moonbuggy Design

3-Way Articulating Hinge Pedal

Arm Steering Arms

Retained Components



Drive System

◦

2-speed hub gears

◦

Split axles and differentials



Mechanical Disc Brakes



Wheels

◦

26-inch mountain bike wheels

Design Improvements

Problem

 Unstable during turns  Poor turn control

 Poor control in mid-air  Difficult to dismantle

 Poor brake performance  Obstacles hurt to hit

Solution

 Stability modeling

 Longer steering arms  Assisted-centering hinge  Bearing plates

 New brake splitter

Assisted-Centering Hinge



Turning Compresses

Spring

◦

Collar rotates about pin

◦

Spring force assists hinge

return

◦

300 inch-pounds torque



Improved Control and

Stability

◦

Facilitates course

correction

◦

Improves mid-air control

◦

Prevents “snaking”

Unarticulated

Steering Arms



Extended Steering Arms

◦

Adjustable turning radius

◦

Adjustable steering sensitivity



Improved Steering

◦

Better control during turns

Bearing Plates



Design:

◦

3/8 inch aluminum

plates

◦

Bolted to frame



Resisted lateral frame

forces



Drastically Reduced

Maintenance Time



Added Weight

Mathematical Modeling Performed



Turning Radius

Stability

◦ Stationary

◦ Turning*



Strength & Stiffness

◦ Axle ◦ Frame ◦ Pedal arm ◦ Wheel 

Hinge Performance*

Gear Ratio

Brake Forces

Turning Stability Model

 Calculated the Stability of the

Moonbuggy During a Turn at Constant Speed

 Sum of the Moments about a “Tip Line”

◦ Tip Line AB

◦ Forces: 𝑭_𝒊 = 𝒎_𝒊𝒗𝟐

𝝆

◦ Determine Moment Arms R_i

◦ Vector Multiplication:

◦ If 𝑴_𝒕𝒊𝒑 ≤ 0, Moonbuggy Overturns

 Model Ensured Stable Frame and Seat Designs

Schematic Diagram - Top View

x z B rwheel CG h_CG R_XZ b/2 A

Schematic Diagram - Front View

θ_XY θ_XY b/2 a b a B A 0 y x 𝑴_𝒕𝒊𝒑 = 𝒅𝒆𝒕 𝑨𝑩_𝑿 𝑨𝑩_𝒀 𝑨𝑩_𝒁 𝑹_𝑿 𝑹_𝒀 𝑹_𝒁 𝑭_𝑿 𝑭_𝒀 𝑭_𝒁

Engineering Testing



Compliance Testing

◦

Folded dimensions

◦

Frame and seat deflection

◦

Brake splitter performance

◦

Hinge performance



Performance Testing

Test Results



Weight: 165 lbs

◦

15 lbs over goal



Top Speed: 15 mph



Stopping Distance: ~ 31 ft

Pre-Race Qualifications



Assembly Time – 1:00 min

◦ 30 seconds to assemble

◦ 30-second penalty



Rear Axle Key Fell Out

◦ Keyway too long

◦ Lubricant dissolved adhesive

Race Performance – First Trial



Rear Pedal Arm Support

Failed on 2

_Obstacle

◦ Eye bolt broke on impact

◦ Rear rider could no longer pedal



Completed the Course

w/o Crashing or

Dismounting

◦ Course Time - 5:23

Race Performance – Second Trial



Front Drive Chain on 1

Obstacle

◦ Power link broke on impact

◦ Driver could no longer pedal



Several Dismounts

Required to Complete

Course

◦ Course Time - 7:27

◦ Course Penalties: 3 x 1:00 each

Final Results



Final Time – 6:23



6

Place – Collegiate Division



Most Improved Award – Collegiate Division

Budget & Schedule



Under Budget

◦

Materials: $1500

◦

Travel & Competition: $3600



2 Weeks Behind Schedule

◦

Lengthy redesign

◦

Cut into testing time



Total Time: 1384 Hours

◦

SpacePokes Team: 1320 hours

Recommendations



Rigorous Moonbuggy Testing

◦

Reveal unforeseen problems

◦

Requires accelerated schedule



Protect Against Impacts

◦

Increased factor of safety

◦

Impact modeling



Alternate Drive System

◦

Over 70% of race failures were

chain-related

Special Thanks

Dr. Dennis Coon

Professor Scott Morton

Dr. Robert Erikson

Wyoming NASA Space Grant Consortium

The College of Engineering Machine Shop

Lyle Lack

To Infinity Design

Pedal House

Karen Wisseman

Fun Fact:

The 20

_{Annual NASA Great}

Moonbuggy Race is going on

TODAY!!!

Check out

http://moonbuggy.msfc.nasa.gov/

for more information!

2013 UW Team Results

Day 1 Race Time – 6:37 (4

_Place)