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Centre Locking Wheel Hub
Formula StudentCompetition in which universities design, build and run their vehicles with the aim of scoring as many points as possible in the following areas: • Design • Business Plan• Cost• Acceleration • Skid Pan • Sprint• Endurance & Fuel Economy
Key PointsWhat is Formula Student• Small engine displacement – 600cc• Very narrow coned track• Emphasis on agility not outright
power or speed
Design a centre locking wheel hub and nut system for the Formula Student Vehicle
Brief
Exploration• Performance Increase• Headline Feature• Quicker Wheel
Change-oversConstraints
• Fit the specified wheel
• Interface with other components
• Meet the requirements of the management team
Timeframe• Final designs to be
reviewed at the end of January
• Manufactured by June
Research - Centre Locking SystemsSystem 1 – Large Nut System 2 – Small Nut
• High performance• High Cost • Performance compromises
• Lower Cost
• Braking System Design – Chris Seagrave
• Drive train Design – Ross Dewsnapp• Team Management – Scott Thompson
– Ben Johansson
Research
Collaboration
Materials• Stronger• Lighter• Cheaper• 7075 – T6
Previous Years Hubs
PFK – 01 Front Hub Assembly
• PFK-01 - Aluminium Front hub- Steel rear hub
• Standard bolt pattern used
Development – Initial IdeasFront Hub
Rear Hub
Research
Longitudinal Loading:• Maximum force under braking at 1.5 G• Force per brake bobbin mount – 931 N• Force per drive stud hole – 1397 N
Expected Loads at the Hub
Lateral Loading:• Corner radius at 70mph – 63.7m• Force at outside rear tyre – 2446 N• Force required at nut – 15678 N
Maximum Loading• 931N Bearing load at each brake
bobbin mount• 1397N Bearing Load at each drive
stud hole
Development - FEA
Advantage of FEA• Weight reduction – more critical on rotational parts• Stress management – Increase low stress areas and reduce high stress areas.• More accurate factor of safety• Optimised Component
Development – General DesignFront Hub Rear Hub
• 6 Arm design• Same size bearings• Main geometry fixed
• Utilising same design front and rear• Same bearing sizes front and rear• Brake Bobbin mount method differs
Development – Drive Studs• Milled Stud
• Threaded Stud
• Press Fitted Stud
Development – Centre Locking Thread
• Accurate model of threads were created at 2mm 3mm 4mm pitch sizes
What Size Thread?
• The model configurations were put under various simulated loads using FEA
• The results were plotted onto a graph for comparison
Development – Centre Locking ThreadStress v Axial Load – Centre Locking Nut
FOS < 1.0FOS < 1.5
FOS > 1.5
FOS Not Feasible
Development – Tripod JournalPFK-01 Rear
HubiFOUR - 11 Rear Hub
New Tripod Journal
• Steel rear hub• PCD 46.5mm • Aluminium rear hub
• PCD 36mm• 7843 N per drive face
Development – Tripod JournalPossible solution…
Steel insert
Development – Bearing SelectionDeep Groove Ball Bearing Tapered Roller Bearing
• Proven set-up in previous cars• Relatively easy to assemble • Designed for this application
• Will improve durability and reliability
Development – Lock Nut
• Designed to keep the upright and bearings in place• Is also used as a wheel speed sensor to allow traction control and launch control to be utilised• Ultimate in lightweight design, utilising aluminium construction with metallic paint
Design
Development – Centre Locking NutInitial design
Developed designFinal design
Final Design
Final Design
Summary
• Front Hub assembly – 983g• 32g lighter than PFK-01• Rear hub assembly – 1092g• 815g lighter than PFK-01 • Both hubs are of 7075-T6 aluminium construction• Approximately 6 rotations of nut to tighten• Total saving of over 1.6 Kg front and rear
Questions?