Project IntroductionProblem Statement

• Design a car with multiple platforms integrated into a hybrid chassis

Concept

• The concept is a four wheeler, from which a two wheel vehicle can be detached and used independently

• While the car is powered by a front mounted, front wheel drive IC engine, the bike is designed to have a rear wheel electric drive.

Team Structure➔ Concept ➔ Design➔ Structure➔ Suspension➔ Engines➔ Transmission➔ Tyres➔ Safety

StructureBackbone Chassis

• Type a chassis that is similar to ladder type. Instead of a two-dimensional ladder type structure, it consists of a strong tubular backbone that connects the front and rear suspension attachment areas.

Advantages

• Single point connection which enables easy coupling and decoupling of the two modules

• Flexible design to accommodate design contraptions for transformations

SuspensionFour-wheeler module

• Idea 1- dependent leaf springso Lower torsional forceso Poor road comfort and road holding capability

• Idea 2- double wish-bone suspension with Mac-Pherson strutso Higher torsional forceso Better comfort, road holding capability

Idea 1 Idea 2

SuspensionTwo-wheeler module

• Based on independent Mac-Pherson struts

• Redesigned to fit in the steering mechanism of the bike

• Uni-fork design to act as fixed support for car and steering mechanism for bike

Rear Module Uni-fork design

Transmission

Fuel tank IC Engine Clutch Gear box

Differential

Front wheelsGenerator Bike battery

Clutch/Controller

Engine stalling rpm 1000

Engine max. rpm 4000

Wheel diameter 0.4826

Reduction at Differential (assumed) 3

First gear ratio 3.5

Second gear ratio 2.5

Third gear ratio 1.6

Fourth gear ratio 1.1

Fifth gear ratio 0.75

Reverse 3.5

first gear second gear third gear fourth gear fifth gear

min max min max min max min max min max

Vehicle wheel speed (rpm) 95.24 380.95 133.33 533.33 208.33 833.33 303.03 1,212.12 444.44

1,777.78

Speed in mps 2.41 9.63 3.37 13.48 5.26 21.06 7.66 30.63 11.23 44.92

Speed in kmph 8.66 34.65 12.13 48.52 18.95 75.81 27.57 110.26 40.43 161.72

Transmission in bike

Battery Motor WheelsDischarging

Charging

Powering

Braking

TyresMotor bike tyres are predominantly bias where-as car tyres are radial

Possible configurations:

• All radialo Improper cornering for the two-wheeler module; leaning the tyre is harder when it is flato Tyre strength while cornering is lesser compared to biaso The fuel efficiency will reduces if the motor-bike has radial tyreso Symmetry; Better handling characteristics

• Front radial, rear biaso Non-uniform brake forces might lead to oversteero Compromise on ride comfort

Final configuration: Front radial and rear bias

Tentative dimensions:

Radial: 140/65 15’’ (From Toyota Prius)

Bias: 140/50 17’’ (From Ducati) Outer diameter (Both) ~ 22’’

Hybrid Convertible- End review

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CAD Model

Engine - Car

Tractive forces:1. Aerodynamic Forces(Fae) = ½ * Cd* d*A*V2

2. Acceleration or Inertial forces(Facc) = M*a 3. Rolling resistance(Fr) = frr * N4. To overcome gradient = W*sint

● Equation of motion:

● Maximum Tractive force that can be obtained from the road for a real wheel driven car:

Maximum Force that can be achieved at wheel = 4920 N Maximum Torque that can be achieved at wheel = 1380

Nm

Mass (kg) 1300

gravity (m/s2) 9.8

mass distribution (front:rear) 60:40

rear wheel RR 0.02

front wheel RR 0.012

Drag coefficient (Cd) 0.4

width (m) 1.5

Proj. height (m) 1.2

Center of gravity height (m) 0.5

Tyre Diameter (inch) 22

Mu (friction b/w tyre and road) 0.75

Velocity (m/s) Acceleration (m/s^2) Gradient (deg) Torque at wheel (Nm) rpm of the wheel

0 3 5 1450 0

12 1 12 1360 410

45 0.75 3 760 1540

70 0 0 650 2400

Powertrain Design● Higher Gear (Nt4) assumed as 1.1 (close to direct drive)

● Differential Gear ratio (Nd) = ne* r / (Vmax*Nt4)

● Selecting Lowest Gear (Nt1) :

Gradient that the car can overcome =

Lowest Gear ratio =

Intermediate Gears: Usually gears are placed so that they are in geometric progression

Engine and Transmission specificationsAfter several iterations of1. Looking for available Torque vs rpm and Power vs rpm characteristics of IC engines2. Trying to fit gears so that torque and rpm needed at wheels matches with that of obtained torque

vs rpm curve

Differential gear ratio 2.13

First Gear 3.4

Second Gear 2.3

Third Gear 1.6

Fourth Gear 1.1

Maximum Torque 240 Nm at 3500 rpm

Maximum Power 110 kW at 5500 rpm

Engine capacity 2.9 litres

Engine type V6

Electric Two Wheeler Mass (kg) 150

Gravity(m.s-2) 9.8Mass distribution [front] 0.5Mass distribution [rear] 0.5

Rear wheel RR 0.02Front wheel RR 0.012

Drag coefficient [Cd] 0.7Width (m) 0.8

Proj. height (m) 1Length (m) 1.5

Wheel Base (m) 1.4Proj. area (m2) 0.8

Density of air (Kg.m-3) 1.22Height of CG (m) 0.5

Friction b/w tyre n road [μ] 0.75Tyre Dia (inch) 22

● The two wheeler at the rear when detached from the car frame runs on an individual electric motor powered by a battery which derives its charge from the IC engine.

● Maximum torque that can be generated at the wheel turns out to be 122 N.m based upon the parameters mentioned. Calculation approach is same as that used in the four-wheeler.

● Torque vs. rpm characteristics at wheel were found out through the desired vehicle performance parameters shown in the next slide.

Velocity acceleration grade rpm Torque Power

0 2 10 0 119 0

10 1 5 341.778689531629 98 3.5075161059413

20 0.5 1 683.557379063258 72 5.15390121689334

25 0 0 854.446723829073 66 5.90551181102362

Choosing the Appropriate Motor

Batterylithium ion battery pack.20 cell packcapacity: 70Ahweight : ~48 kgs

Final drive ratio (chain drive): 2.05

Brake force calculations

Braking Performance

Assumed brake force distribution 78:22For this condition front wheel locks up and a/g = 0.775

Vehicle parametersParameter Symbol Units Value

Mass M kg 1300

Wheel Base l m 2.2

Height of CG above ground h m 0.5

Fixed brake ratio frontrear

KbfKbr

_ 0.780.22

Braking force on front axleBraking force on rear axleTotal Braking force

FbfFbrFb

N7582.082138.549720.62

Tyre diameter d m 0.5588 (22 in)

Braking Torque on front axle Braking Torque on rear axle

TfTr

Nm 2118.43597.51

Stopping distance

Stopping distance =

= 194 massumed V1 = 200km/h

Cae = 0.02Additional stopping distance Sa (brake system response time) = tdV1

assuming td = 0.3 s

Total stopping distance = 210 m

Disc brakes

F = Actuation forceT = Friction torque

re = effective radius

Force location =

ri=inner diameter of the padro=outer diameter of the padѲ1, Ѳ2=caliper angles

Material Friction coefficient(f)

Maximum Pressure(Pmax, Mpa)

Max Instantaneous temp(°C)

Max continuous temp(°C)

Rigid MoldedAsbestos

0.31-0.49 5.2 500-700 230-350

Brake pad material taken: Rigid Molded Asbestos

We chose rotor of diameter 260 mm and with piston area 410mm^2

Parameter Symbol Units Value

Inner diameter of the padOuter diameter of the pad

ri

ro m0.098425(3.875in)0.1397(5.5 in)

Hydraulic cylinder diameter rc m 0.0381(1.5 in)

Normal pressure(max) pa Mpa 0.87

Actuation force Fa kN 6.59

equivalent radius re m 0.1022096

Reqd hydraulic pressure ph Mpa 5.7

Energy analysis of disc brakesBraking energy

Braking energy = 2302.4kNmAverage braking power = 131.4kW

Temperature analysis

Mass of disc brakeTemperature Rise for Brake Assembly

Overall Coefficient of Heat Transfer

Maximum Temperature of Brake Assembly

Backbone Structure

“I” frame with hollow circular shafts.

Static loading, acceleration and braking for front and rear shafts

Shaft-2

Acceleration

Braking

Braking

Structure stresses

Max stress at static loading Max stress at acceleration Max stress at braking

9.92 Mpa 7.16 MPa 1.3 MPa

1.3 MPa 2.1 MPa 1.48 MPa

6.62 MPa 1.27 MPa 6.86 MPa

Final geometry and material parameters

L1 1.5

L2 3.6

L3 1.5

D1 0.15

d1 0.13

D2 0.15

d2 0.13

D3 0.15

d3 0.13

E1 210000000000

E2 210000000000

E3 210000000000

Cornering Stiffness SelectionParameters

C-alpha-f(N/rad) 59000

C-apha-r(N/rad) 53000

Wf(N) 7644

Wr(N) 5096

Turning Radius(m)

30

Lateral Vehicle Dynamics

Lateral Acceleration Gain

Velocity

Curvature GainYaw Rate Gain

Velocity

Velocity

Understeer Coefficient = 0.0334Critical Speed = 192 kmph

Suspension Characteristicssprung mass acceleration

sprung mass acceleration suspension deflection

Suspension stiffnesses Ks=11000 to 30000Damping Coefficient bs= 800 to 1200

Bounce and Pitch Frequencies

Kf = 1250 to 12000 and Kr= 11000 to 22000For these stiffness values, bounce frequency was between 1.2 - 1.8 Hz and the pitch frequency 1.8 - 2.3 Hz.

Thank You!