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?