Engineering 309: Machine Design I

Instructor: Dr. Min Lu

Presented by: Mike Kraft

Thanh Nguyen

Benchmarking Commonly used bicycle frame

measurements

Benchmarking Commonly used bicycle frame

measurements 21 – 23 inches for a European men’s

racing bicycle 18.5 inches for a men’s mountain bicycle Tubes of the frames are made of steel,

aluminum alloys, titanium, carbon fiber. Target population: mountain bike for adult

male

Template

Template was built using anthropometric data for an adult male.

Anthropometric Data

Template

Template was built using anthropometric data for an adult male.

The template was scaled by a factor of 1/2

Beam Model Used for design iterations It was expected that Beam Model is the best

choice for FEA analysis 3D beam element was used Aluminum alloy 2024-T4 was chosen

Young’s Modulus: 10.6 x 106 psiYield Strength: 47,000 psi Poisson ratio : 0.33

Factor of Safety: 3

Beam Model – Pre Processing

Beam Model – Loading Calculations

Design iterations were performed on 3 different load cases: 200lbf load concentrated on the seat, pedal, and handle bar

1. A tube size was chosen2. Apply load at the desired location3. Obtain deflection result from ANSYS

4. Calculate frame stiffness, kframe

5. Calculate equivalent stiffness, keq

6. Calculate static deflection, δst

7. Calculate DAF and Dynamic Load8. Apply dynamic load and obtain maximum bending moment

and stress from ANSYS Calculations were repeated for different tube size in order

to find the optimal tube size for the design

Conclusion Optimal tube size: 1”OD x 0.75” ID Max Bending Stress with FOS = 3:

Seat: 38,745 psiPedal: 12,377 psiHandle Bars: 6,886 psi

Max Bending Stresses for all three load cases are less than the yield stress (47,000 psi)

Choosing the Best Design

Solid Modeling High stiffness value, k May result in under performance Analyzes the volume of the structure

Surface Modeling Low stiffness value, k May result in over designing structure Analyzes the surface area of the

structure

Meshing of Solid and Shell

Solid Modeling Stress Analysis

Solid modeling meshes the volume of the model

Maximum stress: 61,075 psi

Surface Modeling Stress Analysis

Surface modeling meshes the surface area of the model

Maximum stress: 124,725 psi

Maximum Stress Analysis

Seat Pedals Handle Bars

o Applied force at the seat yields the highest stress

o Beams with stress above the maximum allowable

Final Design Beam method Isolate greatest maximum stress Choose beam size to lower stress as

necessary

Three beam sizes necessary1” O.D. with 1/8” Wall5/8” O.D. with 1/16 Wall1/2” O.D. with 1/16” Wall

Final Design Stress Analysis