project: ergonomic design of bicycle helmet

GROUP 4

MOHD AZIM CHE AB RAHMAN ZAKI KGI 090008 HAMED HASHEMABADI KGC 090017 SHOKOOFEH HASSANI GOODARZI KGC 090018 MUHAMMAD ILHAM KHALIT KGC 090021 MUNIRATI AHMAD KGC 090022 MASNI-AZIAN AKIAH KGC 090023 CHAN CHOW KHUEN KGC 090024 ALLINA ABDULLAH KGC 090025 MOHANADHAS A/L KANAGARAJ KGC 090026 ZURINA AHMAD KGC 090027 AMIRABBAS TABATABAEI KGC 090029

ERGONOMIC DESIGN OF BICYCLE HELMET

OVERVIEW OF PRESENTATION

• Project development

• Background study

• Risks related to helmet use

• Objective

• Data Collection

• Statistical Analysis

• Conceptual Design

• Material Selection

• Design Evaluation and Analysis

• Manufacturing process (in general)

• Conclusion

PROJECT DEVELOPMENT

BACKGROUND STUDY

• Cycling facts [1]

80.6 million bicycle riders worldwide

750 – 1,500 individual killed in bicycle crash

450,000 – 587,000 are sent to emergency room each year

Men are more likely to suffer cycling injuries

70 – 85% of bicycle crash deaths concerns with head injury

Wearing a helmet can reduce injuries and deaths by 20 – 90% if it is worn properly.

[1] Diane Hales. An invitation to health 2009 – 2010 Ed. US. Cangage Learning (2009)

BACKGROUND STUDY

• Bicycle helmet Head gear intended for cycling protection.

Developed to reduce impact to the skull during a crash.

Able to prevent head and brain injury

• Design of bicycle helmet Should be level and stable enough to resist violent shakes

and hard blow.

Have to sustain certain level of force during impact.

Interference to vision during cycling should be avoided.

BACKGROUND STUDY

• Risks related to helmeted cycling activity the crash forces might exceed the design tolerance of the

helmet (eg. injuries involving collisions with motor vehicles)

the impact may occur outside of the design line of the helmet, injuring the cranium below the helmet line

the retention system may fail, allowing the helmet to shift substantially or even to come off during the crash

the helmet may be worn improperly, on the back of the head “bonnet style”

the helmet may not fit properly, thereby subverting their protective effects.

BACKGROUND STUDY

• Design benchmark

DESIGN ADVANTAGES DISADVANTAGE

• Cheap • Easy to manufacture

• Poor air circulation • Poor impact absorption • Heavy • High drag coefficient

• Low drag coefficient

• Poor air circulation • Relatively heavy • Expensive

• Cheap • Easy to manufacture

• Poor air circulation • Poor impact absorption • Heavy • High drag coefficient

• High safety level

• Poor air circulation • Heavy • High drag coefficient • Expensive

BACKGROUND STUDY

• General disadvantages of current design The weight

Inadequate ventilation

Inefficient drag coefficient

Helmet fit is not for all population

• Suggested improvement Different material selection for lighter weight

Redesigning air circulation / ventilation system

Changing the outer shell design for better aerodynamic result

Improved helmet fitting

RISKS TO HELMET USE (MSD)

• Inappropriate helmet will cause muscle spasm, especially at trigger points. The muscles of the neck such as the suboccipitals and the cervical paraspinals may be affected.

• Trigger points are frequently caused by direct blunt trauma, or by repetitive micro trauma, as is seen in overuse athletic injuries.

• If head posture is to forward position, it can put a lot of stress on the cervical spine joints, and cervical nerves such as C6 and C7

• Too heavy, causing the head to push forward. Stress on the cervical spine joints and cervical nerves such as C6 and C7.

RISKS TO HELMET USE (MSD)

RISKS TO HELMET USE (MSD)

RISKS TO HELMET USE (MSD)

RISKS TO HELMET USE (MSD)

Action level 2 (for left and right hand side) • Further investigation is

needed and changes may be required

Action level 3 (for left and right hand side) • Investigation and changes are required soon

RESULT

RISKS TO HELMET USE (COGNITIVE)

VENTILATION?

AMPLE? NOT

ENOUGH OR

TOTALLY NONE?

RISKS TO HELMET USE (COGNITIVE)

HOT!

NO COMFORT!

RISKS TO HELMET USE (COGNITIVE)

HOT!

MIGRAIN! LOSING

CONCENTRATION!

PROBLEM STATEMENT

• Extra load of helmet may affect the cyclist performance and lead to MSD (discomfort and hyperextension to neck)

• Poor helmet fitting lead to neck pain

• Back pain by overuse injury due to cycling posture which is adapted decrease drag coefficient

• Poor ventilation during cycling

• Helmet usage affect cyclist hearing (design)

OBJECTIVE OF PROJECT

Design of an ergonomic bicycle helmet for Malaysian

adult male cyclist to minimize injury risk related to race

cycling activity by focusing on:

• lighter weight helmet

• improved fitting to user’s population

• improved aerodynamics efficiency

• improved ventilation and humidity

• improved design without impairing cyclist’s hearing ability.

• Population selection Kepala Batas Community College students

Male

Age 18 – 23 years old

• Sample selection 31 male students (total student batch 2010 = 287 pax)

• Activity selection Cycling for race activity

DATA COLLECTION

DATA COLLECTION

• Measurement method Measurement point : anthropometry point as agreed by group

members

Tool used : Tailoring tape, Vernier caliper, Ruler

Photo taken during anthropometry measurement

DATA COLLECTION

• Anthropometry measurement point as highlighted in yellow in pic below

Reference : National Institute of Bioscience and Human Technology Japan, NIBH Technical Report

DATA COLLECTION

• Sketch for measurement point

DATA COLLECTION & STATISTICAL ANALYSIS

Table: Data collected from Kepala Batas Community college student

DATA COLLECTION & STATISTICAL ANALYSIS NO MEASUREMENT POINT %TILE VALUE

(mm) JUSTIFICATION

1 Head width 95th 190.0 Largest to fit

2 Diagonal head width 95th 230.0 Largest to fit

3 Anterior-posterior head 95th 220.0 Largest to fit

4 Diagonal head width 95th 220.0 Largest to fit

5 Occipital frontal circumference

95th 600.0 Largest to fit

6 Height of eyebrow to the top of the head

5th 87.0 Helmet should not block the vision of the person having the shortest forehead height

7 Anterior-posterior arc 95th 345.0 Largest to fit

8 Scalp height to ear 5th 100.0 Avoid tilt of helmet

9 Jaw height to ear 5th to 95th

180-205 Adjustable length

10 Arc distance between two ears

5th to 95th

420-445 Adjustable length

CONCEPTUAL DESIGN

• Design consideration Product weight

Product fit to user

Ventilation and humidity

Aerodynamics

User coverage

Manufacturability.

CONCEPTUAL DESIGN

• Concept 1 Redesigned contour of outer

shell - improved aerodynamics effect.

Ventilation slot - improved air flow and internal humidity during cycling.

Reduced product weight

Strap – same with benchmark design

CONCEPTUAL DESIGN

• Concept 2 Contour of outer shell

• added with new structure

• re-designed for improved aerodynamics effect

Ventilation slot – Improved air flow and internal humidity during cycling

Reduced product weight

Adjustable head grip and strap

Internal reinforcement

• maximise venting

• minimise bulk

• Comply to safety standards.

DESIGN SELECTION (VIA PUGH MATRIX)

CONCEPTUAL DESIGN OUTER SHELL

• Aerodynamic contour

• Ventilation slot to release internal heat and improve humidity

• Optimal cooling

• Keep the foam in place

• Curve – sliding effect during impact instead of direct hitting

INNER SHELL (FOAM LINER)

• Main protection component

• Absorb impact

• Minimum 20mm distance for 300g impact protection

INTERNAL REINFORCEMENT

• Maximise venting and minimise bulk

• Comply to safety standards

ADJUSTABLE HEAD GRIP

• Improved fitting for varying head size

ADJUSTABLE STRAP

• Provide external support to neck area

• Adjustable for varying head size

CONCEPTUAL DESIGN

• Ergonomic fitting for cycling helmet

Fitting of helmet strap

Fitting of internal

reinforcement

Fitting of adjustable head

grip

Fitting of foam lining

Fitting of outer shell

CONCEPTUAL DESIGN

• Critical measurement match to design

Picture: Cross sectional view of cycle helmet concept (a) Frontal (b) Sideways

(a) (b)

MATERIAL SELECTION

COMPONENT MATERIAL SELECTION REQUIREMENT

Outer shell • Enhanced surface features – sliding effect during impact • Able to mould for ventilation slot • Thin and light • Absorbs impact fairly

Inner shell / Foam liner

• Able to absorb most energy / unit volume instead of bouncing back to the user head.

• Redistributes a localised external force over a larger area, reducing the local stress on the skull.

• F = ma = 9kN (Max tolerable deceleration, a = 300g) To prevent F>9kN, plateau stress = 0.9 MPa

Strap (buckle and strap)

• Able to be adjustable • Fair shear strength (for sliding strap to tighten or loosen the

helmet grip)

Internal reinforcement • Able to absorb shock and does not bounce back to the head • Provide additional strength to inner shell

MATERIAL SELECTION

Example of inner foam material selection based on Cambridge Engineering Selector (CES)

MATERIAL SELECTION

COMPONENT MATERIAL OPTION MATERIAL SELECTION

Outer shell

• ABS • PVC Nitrile-Nitrex • Fiberglass • Lexan • PET • Polycarbonate

• Polycarbonate High heat resistance Able to mould vent slot

Inner shell

• Ultra low density balsa (0.09-0.11Mg/m3)

• Cork (low density) • Polystyrene foam closed cell

( = 0.05Mg/m3)

• Expended Polystyrene (EPS) Cheaper Lighter weight Durable at high and low

temperature No oxidation or corrosion

MATERIAL SELECTION COMPONENT MATERIAL OPTION

MATERIAL SELECTION

Internal reinforcement

• Polypropylene • Nylon • Metal mesh

• Polypropylene Not rusted like metal Able to withstand high

temperature

Buckle for strap

• Plastic • Rubber

• Plastic Cheaper Lighter weight High resistance to heat Robust

Strap

• Nylon • Polypropylene

• Nylon Higher strength property

(9.6psi)

DESIGN EVALUATION & ANALYSIS

• Product weight Mass analysis = 190.5 g (benchmark weight ~ 200-400 g)

Weight reduction contributed by material selection (low density EPS) for inner foam

Incorporate ventilation slot

• Helmet fitting Adjustable strap

Head grip

DESIGN EVALUATION & ANALYSIS

• Aerodynamics 20-25% of drag is due to the equipment (bike, helmet)

Additional structure at frontal area

Smooth curved contour

DESIGN EVALUATION AND ANALYSIS

• Ventilation Critical in hot weather for cooling, and cold weather to carry the

moisture away

Improved humidity

Interior channel : takes up most air through front vents

Exit channel : air released through side or top vent

Air channels can be left in fitting foam around the edges of a helmet to encourage air flow.

air in air out

DESIGN EVALUATION AND ANALYSIS

• Von Mises stress simulated analysis (front impact)

Impact energy absorption with helmet (mostly absorbed by foam liner)

Impact energy absorption w/out helmet

Frontal impact force = 9000 N Maximum von mises stress = 0.9 Mpa (comply to requirement)

DESIGN EVALUATION & ANALYSIS

Side impact force = 9000 N Maximum von mises stress = 0.9 Mpa (comply to requirement)

• Von Mises stress simulated analysis (side impact)

MANUFACTURING PROCESS (GENERAL) • Outer shell

Formed by injection moulding process Final product will be later glued to the inner shell.

• Inner shell Granules of EPS place in mould Expended in steam Pressured into cooler foam Can be made in layers for varying impact density

(depends on less impact or hard impact area)

• Internal reinforcement Placed inside the mould during inner shell expansion phase

• Straps Weaved and cut to final desired shape. Strap installed to the helmet assembly. Buckle of the strap is made from plastic injection moulding and is later

added to strap.

CONCLUSION

• Cyclists are exposed to various risks during cycling activity (MSD, cognitive effect)

• Product have to be manufactured in compliance with the safety requirement and can be used by majority of the population.

• Ergonomic design is an approach of solving work related musculoskeletal disorder (WMSD)

CONCLUSION

CYCLING RELATED PROBLEM ERGONOMIC SOLUTION

Inadequate product weight • Lead to neck pain • Lead to back pain • Lead to MSD

• Proper material selection • Proposed design weighs ~190.g

comparing to 200-400 g range of benchmark helmet weight

Product fitting does not tailor to all population

• Usage of anthropometry measurement for selected population.

• Design of adjustable head grip . • Design of adjustable strap.

Back pain injury due to effort made to reduce drag coefficient

• Curved contour to improve aerodynamics efficiency

Poor ventilation system and inadequate humidity within the internal section of the helmet

• Ventilation slot is created for the entire helmet system.

Cyclist may experience hearing impairment during exercise

• Design of overall helmet assembly by considering critical points of related anthropometry measurement.