Detailed Design Presentation

Mini Baja Suspension Group

Rob Johnson, Cheng Jin, Robert Perry, Eric Petersen, Ryley Nelson

Senior Capstone MET/MENG 490A

Introduction

Baja Suspension Team

● Design and Build Suspension System for

Eastern’s SAE Mini Baja Vehicle

Needs, Functions, and Features

● Minimum 10” of travel, front and rear

● Adjustability:o Ride Height

o Suspension Stiffness

● Sustain 3’ jump without bottoming out

shocks or breaking related components

Final Specifications

● 11” of travel, front and rear

● Designed to withstand:

o 4’ drop onto 4 wheels

o 2000 lb horizontal impact on each wheel (front to back)

○ Lowest factor of safety present: 2.34

○ Maximum factor of safety present: 5.1

● k values for shocks:

o Front: 160 lbs/in

o Rear: 200 lbs/in

● Ride height (distance from lowest point of vehicle to ground):

o Max: 17 3/16”

o Min: 10”

Description of Solution

● Dual A-arm style control arms front and rearo Allows full travel of suspension w/o interference

o Creates optimum camber angle for entire travel

o Light weight

● Adjustable ride stiffness and heighto Location of pushrod connection on cam dictates this

● Designed optimum geometry so that each

component can withstand required loads

Front Upper A-Arm (Drop Force)

Vertical Force - 800lb

Factor of safety - 2.764

Max Stress - 22.8 KSI

Front Upper A-Arm (Frontal Impact)

Horizontal Force - 1000lb

Factor of safety - 4

Max Stress - 15.8 KSI

Rear Upper A-Arm (Drop Force)

Vertical Force - 800lb

Factor of safety - 2.47

Max Stress - 25.5 KSI

Rear Upper A-Arm (Impact Force)

Horizontal Force - 1000lb

Factor of safety - 2.34

Max Stress - 25.5 KSI

Pushrod Buckling (Max Force)

Force - 1500lb

Static FOS > 5

Buckling FOS - 4.47

Front Cam Analysis

Force - 1500lb x 2

Von Mises Max - 12.9 ksi

FOS- 2.8

Material- A36 ¼” plate

Rear Cam Analysis

Force - 1500lb x 2

Max Von Mises - 13.8 ksi

FOS- 2.6

Material- A36 ¼” plate

Front Carrier Analysis (Drop)

Force - 800lb

FOS - 5.1

Rear Carrier Analysis (Drop)

Force - 800lb

FOS- 4.987

Summary of Evidence● Hand calculations provide evidence of

o Forces at wheel (worst case, 4 foot drop)

o Force thru carrier bearings/hubs (worst case)

o Force thru pushrod (worst case)

o Force thru cam (worst case)

o Force into spring and required K value (worst case)

● Solidworks modeling provide evidence thato Needed suspension travel is achieved

o Suspension geometry is desirable through full motion

o Factor of safety in weakest member is 2.34

○ In rear upper A-arm when dropped from a height of 4 feet

Budget and cost analysis

Schedule of Milestones and Major TasksStart: April 1, 2015

Finish: May 29, 2015

Questions?