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Assignment 3
Assignment 3 Link (if you have trouble reading format)
Problem Statement
A typical problem for running shoes is spike damage when walking on hard surfaces causing decreased spike performance. The purpose of this design is to prevent spike damages with a durable design that can lift a runner over shoe spikes and support large loads over time. 
Assumptions
Supports a runners weight
Prevents spike damages
Withstands loads over time
Durable
Comfortable
Safe
Decision Matrix
Rating Scale: 1 - 5
1 = Bad, 5 = Excellent
Thought Process on Evaluation Criteria
Durability: Ability to withstand forces over time and wear resistant
  • Typical human force exerted on shoe = 120 lbf - 180lbf
  • Must be able to withstand forces without passing yield stress of support material  (elastic deformation)
  • Hardness tests for wear resistance
  • High toughness ∫σdε
Spike protection: Prevents spike damages
  • The design must be able to resist permanent indentation 
Supports a load: Must be able to support weight of runner
  • σ=F/A
    • Example:σ = 150lbf/(36in^2) = 4.17 lbf/in^2
Manufacturability: Meets manufacturing requirements
  • Low cost
  • Low time
  • Environmentally safe
  • Flexible production methods
  • Ability for continuous product improvement
  • Quality at each manufacturing stage
Safety: Must not be a risk for running injuries
  • Ability to be flexible
  • Easy to put on or remove
  • No dangerous mechanisms
Cost: Cheap to manufacture and low price for consumers
Light weight: Less weight than shoe itself
  • Material is lightweight
  • Must not prevent running due to weight
Flexible: Material must flex while maintaining support ability
Aesthetics: Looks compare to running shoes
# of parts: Must have a low number of parts 
Chosen Strategy: Comfortable slip-on spike shield for a cross country runner
Multiple Solutions
Concepts will determine how the strategy will be implemented
Concept 1: Shoe support system with clamping mechanism

Force Analysis Concept 1

Friction: Friction resulting in clamp force

F = μN

μ = 0.68

Clamp force 10lbf

Normal force 10lbf

F = 6.8 lbf

Power: Power required to turn clamp screw

P = Tω

T = 10lbf

ω = 100rpm = 10.47 rad/s

P = 0.1903 hp

Concept 2: Shoe sole system with sliding rail

Force Analysis Concept 2

Weight:

w = mg

m = .050802345 kg

g = 9.81 m/s2

w = 0.498 N

Normal force:

N = 0.498N

Force of the user:

F(user) = 2N

Friction force experienced by bearing:

Ff= (mg)(0.1)(0.0508kg)(9.81) 0.0498 N

μ= 0.1 for plastics

Concept 3: Shoe covering with raisable stilt mechanism

Force Analysis Concept 3

Elongation under axial loading:

δ= FL/AE

F = mg= (70kg)(9.81) = 686.7N

L = 4cm  = 0.04m

A = Πd^2/4 = 0.0314m^2

E = 228 Gpa - carbon fiber

δ = 4 * 10^(-9) m deflection

Gantt Chart
Lessons Learned
  • More time should be spent to come up with equations 
  • Concepts are a means for providing a function
  • A concept should be described in rough sketches and static/dynamic analysis
  • There are different brainstorming methods
  • It’s important to compare evaluation criteria for each strategy and concept
Advisee Comments
  • Webpage not up yet at the time of checking
  • I’d recommend continuing your sketch method from assignment 2 for assignment 3
  • Very well organized