Sports Engineering

Question 1

Why is there a concentration of material in the top and bottom flanges of an “I” beam?

Answer 1

To maximize bending resistance, as bending stresses are greatest at surfaces farthest from the neutral axis, thus efficiently resisting stresses while minimizing weight.

Question 2

Formula for axial strain due to axial displacement?

Answer 2

ε= Δl/l

Where:
ε = Axial strain (no unit)
Δl = Change in length (m or mm)
l = Original length (m or mm)

Question 4

Why is there a concentration of material in the top and bottom flanges of an “I” beam?

Answer 4

To maximize bending resistance, as bending stresses are greatest at surfaces farthest from the neutral axis, thus efficiently resisting stresses while minimizing weight.

Question 5

What is the difference between welded (seamed) and seamless bicycle tubes?

Answer 5

• Welded (seamed) tubes are formed from metal sheet rolled into tubes and welded (lower quality).
• Seamless tubes are formed from cylindrical metal billets without seams, resulting in higher quality and strength.

Question 6

Describe the manufacturing process for seamless bicycle tubes.

4 steps

Answer 6

• Heat billet above austenizing temperature
• Tube formed by either rotary hot piercing or extrusion
• Cold working (sizing and straightening) improves dimensions and surface finish
• Additional heat treatment applied if necessary

Question 7

What is tube butting, and why is it used?

What is is and two benefits

Answer 7

• Tube butting involves varying the internal thickness of tubes.
• Strengthens joint areas prone to weakening due to heat
• Reduces overall frame weight without compromising strength

Question 8

What is hydroforming, and why is it used in bicycle frames?

Answer 8

• Hydroforming is a process where high-pressure fluid shapes tubes externally, typically used for aluminum frames.
• Adjusts external tube geometry to enhance strength and stiffness in targeted areas

Question 9

Name two joining techniques for metallic bicycle frames.

Answer 9

• Brazing
• Welding (including TIG and MIG)

Question 10

What is brazing, and how does it differ from welding?

Answer 10

• Brazing uses filler metal (brass/silver) melted below the melting point of tubes. Tubes themselves do not melt.
• Welding melts both filler and frame tubes, fusing them directly.

Question 11

Why is flux used in brazing?

Answer 11

Flux prevents oxide formation during heating, ensuring a cleaner, stronger joint.

Question 12

What challenges arise when welding titanium bicycle frames?

3 challenges

Answer 12

• High contamination risk from atmospheric gases (oxygen, nitrogen, hydrogen)
• Sensitive to high heat, which affects structural integrity
• Often requires complex shielding and post-weld heat treatments

Question 13

Describe Tungsten Inert Gas (TIG) welding.

Answer 13

• Electric arc welding method using external filler similar to base material
• Shielding gas (argon) prevents contamination
• Precise and suited for thin tubes, providing good finishing

Question 14

What are the heat effects of welding aluminum bicycle frames?

2 effects

Answer 14

• Localized annealing (softening) due to aluminum’s high thermal conductivity
• Typically requires post-weld heat treatments or use of age-hardening alloys to restore strength

Question 15

What are the two primary methods for manufacturing carbon fibre bike frames?

Answer 15

• Lugged tubes (individual tubes bonded together)
• Monocoque construction (single-piece frames from moulds)

Question 16

What is the main advantage of lugged carbon fibre frames?

Answer 16

Allows custom sizing and easy adjustment since tubes are individually made and then bonded together.

Question 17

What are the main characteristics of carbon fibre sheets used in bicycle frames?

3 characteristics

Answer 17

• Pre-impregnated with epoxy resin
• Fibres can be woven or unidirectional
• Typically unidirectional sheets used in bicycles for optimized directional strength and stiffness

Question 18

What are the advantages and disadvantages of monocoque carbon fibre frames?

4 advantages, 3 disadvantages

Answer 18

Advantages: Strong, lightweight, excellent stiffness, integrated design.

Disadvantages: Expensive moulds, limited sizes available, less customizable.

Question 19

Describe how Vickers hardness relates to material properties in bicycle frames.

Answer 19

• Higher Vickers hardness indicates higher yield strength and lower ductility
• Often used to gauge the effectiveness of heat treatments in frame manufacturing

Question 20

What is sensitivity in sensor technology?

Answer 20

Sensitivity is the ratio of change in sensor output to the change in input, indicating how effectively the sensor detects small variations.

Question 21

Define linearity in sensor technology.

Answer 21

Linearity describes how closely the sensor output matches a straight line over its operational range, reflecting consistent sensor response.

Question 22

What does hysteresis mean for a sensor?

Answer 22

Hysteresis is the difference in sensor output for the same input when the measurement is approached from increasing vs decreasing values, indicating lag or memory effects.

Question 23

What are environmental effects on sensors?

Answer 23

Environmental effects describe how external conditions (temperature, humidity, pressure) influence the sensor’s performance and accuracy.

Question 24

Define drift in sensor technology.

Answer 24

Drift refers to a gradual shift in sensor output over time when exposed to constant input, usually due to prolonged use or environmental factors.

Question 25

Define accuracy in sensor technology.

Answer 25

Accuracy is how closely a sensor’s measurement aligns with the true or actual value.

Question 26

What does precision (repeatability) mean for a sensor?

Answer 26

Precision (repeatability) indicates how consistently a sensor can produce the same output when repeatedly exposed to the same input conditions.

Question 27

Define threshold in sensor technology.

Answer 27

Threshold is the minimum detectable input signal or the smallest input change that a sensor can reliably detect.

Question 28

Define range in sensor specifications.

Answer 28

Range refers to the span between the minimum and maximum input values that the sensor can accurately measure.

Question 29

What does resolution mean for a sensor?

Answer 29

Resolution is the smallest increment of input change that produces a measurable change in sensor output.

Question 30

How is linear sensitivity calculated in a force sensor?

Answer 30

Linear sensitivity= ΔV / ΔF Where: ΔV = Change in voltage (output) ΔF = Change in force (input)

Question 31

How is maximum hysteresis calculated for a force sensor?

Answer 31

Maximum Hysteresis=(Maximum difference of Voltage)/(Maximum Voltage)×100

Question 32

Name three human effects that can degrade sensor performance over time.

Answer 32

- Material degradation (due to sweat, moisture, temperature fluctuations) - Mechanical fatigue (due to repeated bending, stretching) - Surface contamination (skin oils, sweat, dirt)

Question 33

Describe a resistive sensor.

Answer 33

A resistive sensor changes its electrical resistance in response to physical deformation or strain, typically measured using voltage changes

Question 34

Give the formula for the output voltage of a resistive sensor in a circuit.

Answer 34

V_out=V_T x (R_f/R_s) Where: V_out = Output Voltage V_T = Input/Supply Voltage R_f = fixed resistor R_s = Sensor resistance (variable resistor)

Question 35

What is a capacitance sensor, and how is capacitance calculated?

Answer 35

C = εA / d Where: C = Capacitance ε = Permittivity of material A = Area of capacitor plates d = Distance between plates

Question 36

Why is human-equipment interaction crucial in sport equipment design?

Answer 36

Because mechanical equipment can fail if human factors like biomechanics, perception, and performance are not integrated into the design process.

Question 37

Name three key aspects considered in human-equipment interaction studies.

Answer 37

- Mechanical performance - Injury prevention - Perception and comfort

Question 38

What does a 3-point bend test measure in equipment testing?

Answer 38

It measures the force required to achieve a defined displacement, determining the stiffness of equipment components.

Question 39

How is stiffness calculated from mechanical tests (force-displacement curve)?

Answer 39

Stiffness = ΔForce / ΔDisplacement

Question 40

What is a cantilever bend test?

Answer 40

A mechanical test where one end of a component is fixed, and force is applied at the other end, measuring stiffness or resistance to bending.

Question 41

What is longitudinal bending stiffness in running shoes?

Answer 41

The resistance of a shoe sole to bending along its length, affecting running performance and biomechanics.

Question 42

Give the formula for longitudinal bending stiffness.

Answer 42

k = (Torque_end - Torque _start) / (θ_end - θ_start) Where: k = Stiffness (Nm/degree) Torque = applied torque (Nm) θ = angular displacement (degrees)

Question 43

What is running economy, and why is it important?

Answer 43

Running economy measures oxygen consumption at a given running speed. Better economy means less energy expenditure for the same speed, enhancing performance.

Question 44

How can midsole materials affect running economy?

Answer 44

Different midsole stiffness and hysteresis properties affect energy return, cushioning, and thus running economy.

Question 45

List 7 methods to minimize energy loss in running shoes.

Answer 45

- High-resilience foam materials - Low hysteresis polymers - Supercritical foams - Optimized polymer blends (EVA, TPU, PU) - Microcellular structures (fine-tuned cells) - Curved midsole and rocker design - Integrated stiffening plates ## Footnote Hot Legs Show Optimal Motion Control Performance

Question 46

What causes hysteresis in sensors? | 3 causes

Answer 46

The difference is due to internal factors such as friction, micro-structural rearrangement, and delayed elastic recovery

Question 47

How can the hysteresis effect in sensors be minimised? | three ways

Answer 47

- Material selection: use materials with minimal internal friction and faster elastic recovery - Sensor design operation: enhance sensor design by including reinforcing structures or coatings - pre-stretch treatment during test

Question 48

What is a smart textile?

Answer 48

Materials and structures which sense environmental/human body changes

Question 49

What is gore-tex?

Answer 49

Gore-tex is a waterproof/breathable fabric that is manufactured from PTFE into a laminated membrane.

Question 50

What are four properties of gore-tex?

Answer 50

- breathable - lightweight - waterproof - allows sweat to evaporate but doesn't allow raindrops to enter

Question 51

What are the five layers of goretex from exterior to interior

Answer 51

- abrasion resistant outershell - protection - gore-tex membrane - protection - soft inner liner

Question 52

Name three applications of micro-encapsulated fabrics

Answer 52

- Antibacterial socks - anti-body odour underwear - medical textiles

Question 53

What are micro-encapsulated fabrics

Answer 53

Micro-encapsulated textiles have micro-capsules embedded in the fibres which can be controlled to bleed due to an environmental change.