Roll cage Design: Finite Element Analysis Front Impact Side Impact Rear Impact Front Impact: Force=7G=24034N Stress Induced= 319MPa Side Impact Force=3G=10300N Stress Induced= 334MPa Rear Impact Force=5G=17167N Stress Induced= 123MPa
Roll cage Design: Human Ergonomics Side Impact Member Height: 9”; Kept close to minimum for less driver exit time. Steering Wheel Position: Fixed according to driver comfort. Driver Head Clearance: 7.5”; Kept greater than 6” as specified in rulebook. RRH Inclination: 8 deg, fixed according to driver back leaning. Width of chassis: Fixed such that there is clearance of 3” between any chassis member and driver body part.
Brake System Human Foot force = 40kgf+ 20kgf(emergency) Pedal Ratio = 4 Use of proportionate valve to achieve front: rear brake biasing. Calculated stopping distance: 3.6metres
Suspension Design: Kinematics Bump/Rebound travel: Front 200/-100, rear 200/-80 (mm) ; Roll angle: 5 degrees Static DataFrontRear Camber angle0 deg Caster angle7 deg0 deg Toe angle0 deg Kingpin angle8 deg6 deg Scrub Radius90mm120mm Caster Trail23mm0 mm Roll centre height400mm396mm Camber variation: Front: 0.85 deg/inch bump, 0.6 deg/deg roll Rear: 1.34 deg/inch bump, 0.42 deg/deg roll Toe Variation: ZERO bump steer and Roll steer
Suspension design: Spring selection To achieve desired ground clearance of 12” To achieve ‘oversteer’ while cornering. Objective: Spring selection: Rear springs: Maruti Zen Front struts Measured spring stiffness ‘k’ = 21N/mm Precompressive force= 140kgf Front Springs: Inhouse designed springs Target spring stiffness ‘k’ = 21N/mm
Wheel assembly components Hubs: Front hub: Designed hubs Torsion and Bending Braking Torque= 235Nm Bending force= 1800N Max Induced stress= 71MPa Factor of safety= 6.5 Rear hub: Maruti 800 front hubs
Powertrain: Engine Briggs and stratton 10bhp OHV engine Torque: approx 18.75Nm at 2600 rpm Power: 10bhp at 3600 rpm Engine mounts: Specifications: Operating frequency range: 25 Hz to 70 Hz Engine Mounts Natural frequency= 460Hz Maximum stress induced= 23 Mpa
Powertrain: Transmission Schematic: Engine-> CVT-> Reduction gearbox Continuously Variable Transmission 1. CVTech CVT Ratio= 3.6:1 to 0.59:1 2. Comet 780 series= 3.75:1 to 0.6:1 Reduction gearbox Constant reduction = 10:1 Final ratio= 36:1 to 5.9:1
Powertrain: Reduction Input from CVT Output to driveshafts Total reduction: Differential
Design Failure Modes And Effects Analysis (DFMEA) ItemsPotential Failure Mode Potential Cause of FailurePotential Effect Of FailureRemedies to avert Failure ChassisStructuralFront/Rear/Side Collision Driver Injury, Chassis deformation, Damage to engine/suspension. Incorporate bracing members, Nodal Structure, Use of Bumpers. FatigueResonance of engine frequency with chassis natural frequency. Failure of welded jointsUse of rubber pad below engine, Incorporate bracing to increase natural frequency Suspension (A-Arms, Springs, Shock absorbers) StructuralBending, compression, Force due to anti dive; Torsional shear failure of spring, Buckling Permanent buckling of spring affects ground clearance; Wishbone failure Rear twin Ball joint suspension, High Factor of safety TransmissionMechanicalCyclic loading, Radial loads due to CVT, Torsional shear stress in shafts Gear failure, Shaft failure, Misalignment of shafts in gearbox Use of standard shafts and gears, Bearings capable of taking high radial loads BrakesStructuralBrake fluid contamination, Bending of brake pedal, Bending of master cylinder rod Brake system failureMaster cylinder cap, Brake Bleeding, High FOS for pedal, proper Master cylinder mounting
Summary DataValue Overall Length90 inches Overall height58 inches Track WidthFront: 52 inches Rear : 50 inches Wheelbase66 inches Gear Ratio36:1 to 5.9:1 Estimated Weight of vehicleGross Weight : 350 kg Kerb Weight : 290kg Estimated Weight of chassis55 kg with all mounts and welds Safety 5 point harness. Battery placement: Away from rotating parts, Covered to prevent fuel spill on battery. Front and rear bumpers to protect tie rod and toe link. Master cylinder mount at height from base of chassis to prevent brake failure. Resilient foam material on all pipes of cockpit. Use of fire extinguisher.