EFFICYCLE SAE INDIA 2014-Electric Power Train Report

The objective of competition is to design and manufacture an energy efficient eco-

friendly tricycle. This competition helps students to face real world engineering problems

in design and manufacturing of automobile.

Electric Power Train:

Motor:-

An electric motor is a device which converts electrical energy to mechanical energy. The

direction of mechanical force is given by Fleming’s Left hand rule

and magnitude is given by;

F=BIl newton

The basic construction of electric motor is explained below:

WALCHAND INSTITUTE OF TECHNOLOGY, SOLAPUR Page 1

Main type of Motor:

The different types in electric motors world as follows.

Electric motors are broadly classified into two categories as follows:

i. AC Motors.

ii. DC Motors.

An AC motor is an electric motor driven by an alternating current. It basically consists of

two part, an outside stationary stator and an inside rotor.

DC motor is an electric motor driven by direct current.

Advantages of DC motor:

i. Torque vs. Speed characteristic is easy to plot.

ii. Easy to control speed with wide range.

iii. High starting torque.

iv. Accurate steep less speed with constant torque.

v. Have variable speed controller.

Types of DC motors:

The DC motors are divided mainly to:

i. Brush DC motors (BDC).

ii. Brushless DC motors (BLDC).

WALCHAND INSTITUTE OF TECHNOLOGY, SOLAPUR Page 2

Advantage of BLDC motor with respect to PMDC motor:

i. High efficiency.

ii. High power to volume ratio.

iii. High performance ratio.

iv. Large amount of torque over a vast speed.

v. Electronically communicated as no brushes.

vi. Life expediency is 10000hr.

vii. Responsiveness and quick acceleration.

viii. High power density and reliability.

Due to above reasons the BLDC motor is selected.

Calculation to plot traction hyperbola:

The starting torque of the cycle is calculated from the velocity vs. tractive effort

graph.

We get the value of torque by using formula,

RPM Direct= (60*v*i)/ (2*3.14*r)

FZ Direct= Pmax/v (m/s)

The tractive effort is calculated by:

Tractive effort=Wheel resistance+

Air resistance+

Gradient resistance+

Acceleration resistance

ρL = density of air in rainy season = 1.2 kg/m3 (Max air density is in rainy season)

Cd = coefficient of air resistance = 1.2

A = projected frontal area = 1.02 m2

V = velocity = 5 m/s

FZA= (T*i*rpm*efficiency)/r

PZ= (FZA*V)/1000

Velocity (kmph) Velocity(m/s) RPM Direct Torque G1 FZ Direct Fzb3 Fbz4 Fbz5 FZA G1 PZ G1

G1

0 0 0

0.72 0.20 62.6102201 2000 134.706 172.51399 210.416

1.44 0.40 125.22044 1000 134.754 172.56197 210.464

2.16 0.6 187.83066 666.6667 134.8339 172.64193 210.5439

2.88 0.80 250.44088 500 134.9459 172.75387 210.6559

3.6 1.00 313.0511 400 135.0898 172.8978 210.7998

4.32 1.2 375.66132 333.3333 135.2657 173.07371 210.9757

5.04 1.40 438.271541 285.7143 135.4736 173.28161 211.1836

5.76 1.60 500.881761 250 135.7135 173.52149 211.4235

6.48 1.8 563.491981 222.2222 135.9854 173.79335 211.6954

7.2 2.00 626.102201 200 136.2892 174.0972 211.9992

7.92 2.20 688.712421 181.8182 136.625 174.43303 212.335

8.64 2.4 751.322641 166.6667 136.9928 174.80085 212.7028

9.36 2.60 813.932861 153.8462 137.3926 175.20065 213.1026

10.08 2.80 876.543081 142.8571 137.8244 175.63243 213.5344

10.8 3 939.153301 133.3333 138.2882 176.0962 213.9982

11.52 3.20 1001.76352 125 138.784 176.59195 214.494

12.24 3.40 1064.37374 117.6471 139.3117 177.11969 215.0217

12.96 3.6 1126.98396 111.1111 139.8714 177.67941 215.5814

13.68 3.80 1189.59418 105.2632 140.4631 178.27111 216.1731

14.4 4.00 1252.2044 100 141.0868 178.8948 216.7968

15.12 4.2 1314.81462 95.2381 141.7425 179.55047 217.4525

15.84 4.40 1377.42484 2.94 90.90909 142.4301 180.23813 218.1401 112858.5 496.5775 6383.287

16.56 4.60 1440.03506 2.49 86.95652 143.1498 180.95777 218.8598 99928.99 459.6734 5651.027

17.28 4.8 1502.64528 2.036 83.33333 143.9014 181.70939 219.6114 85261.57 409.2555 4820.346

18 5.00 1565.2555 1.584 80 144.685 182.493 220.395 69097.05 345.4852 3904.88

18.72 5.20 1627.86572 1.22 76.92308 145.5006 183.30859 221.2106 55347.43 287.8067 3126.171

19.44 5.4 1690.47594 0.905 74.07407 146.3482 184.15617 222.0582 42636.02 230.2345 2406.256

20.16 5.60 1753.08616 0.565 71.42857 147.2277 185.03573 222.9377 27603.92 154.582 1554.915

20.88 5.80 1815.69638 68.96552 148.1393 185.94727 223.8493

21.6 6 1878.3066 66.66667 149.0828 186.8908 224.7928

22.32 6.20 1940.91682 64.51613 150.0583 187.86631 225.7683

23.04 6.40 2003.52704 62.5 151.0658 188.87381 226.7758

23.76 6.6 2066.13726 60.60606 152.1053 189.91329 227.8153

24.48 6.80 2128.74748 58.82353 153.1768 190.98475 228.8868

25.2 7 2191.3577 57.14286 154.2802 192.0882 229.9902

0 2 4 6 8 10 12 14 16 18 20-100

400

900

1400

1900

Traction Dia Efficycle

DirectFzb3Fzb5Fza G1"G1"

Velocity kmph

Trac

tion

N

According to rules of effi-cycle and above curve we require a motor of 24 V, 400

W motor.

From above graph and requirement of rulebook the motor is being finalized.

The specification of finalized motor is:

Motor specification:

Power = 400 watt

Motor type =BLDC motor

Volt = 24 volt

Current = 20 ampere

Max. Rpm = 1500 rpm

Max. Torque =3.92 N.m

Steady torque = 2.55 N.m

Battery:-

Definition: An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work.

Purpose of battery: Battery works as a source of energy in vehicle. It serves as a power storage and releases the same quickly to operate a starter motor .The battery must be able to carry out all the function over a wide temperature range in the order of 243 to 343K.This includes very cold starting condition as well as potentially high temperature under the bonnet.

Classification: The classification of battery is done according to the following categories:

Primary cells or non-rechargeable batteries

Secondary cells or rechargeable batteries

Batteries by application

Alkaline battery Aluminium–air

battery Aluminium-ion

battery Atomic battery Chromic acid cell Zinc–air battery Zinc–carbon battery

Flow battery Fuel cell Lead–acid battery Lithium air battery Lithium-ion battery Molten salt battery Nickel–zinc battery

Backup battery Car battery Common battery Electric vehicle

battery Inverter battery Nano batteries

As per the Efficycle 2014 rulebook the rechargeable battery must be used. Matrix table:

The characteristics of commonly used rechargeable batteries are shown in matrix form.

NiCd NiMH Lead Acid Li-ion Li-ion polymer ReusableAlkaline

Gravimetric Energy Density(Wh/kg)

45-80 60-120 30-50 110-160 100-130 80 (initial)

Internal Resistance (includes peripheral circuits) in mΩ

100 to 2001

6V pack200 to 3001

6V pack<1001

12V pack150 to 2501

7.2V pack200 to 3001

7.2V pack200 to 20001

6V pack

Cycle Life (to 80% of initial capacity)

15002 300 to 5002,3 200 to 3002

500 to 10003 300 to 500

503 (to 50%)

Fast Charge Time 1h typical 2-4h 8-16h 2-4h 2-4h 2-3h

Overcharge Tolerance Moderate Low high very low Low Moderate

Self-discharge / Month (room temperature)

20%4 30%4 5% 10%5 ~10%5 0.3%

Cell Voltage(nominal) 1.25V6 1.25V6 2V 3.6V 3.6V 1.5V

Load Current-    peak-    best result

20C1C

5C0.5C or lower

5C7 

0.2C>2C1C or lower

>2C1C or lower

0.5C0.2C or lower

Operating Temperature(discharge only)

-40 to 60°C

-20 to 60°C

-20 to 60°C

-20 to 60°C

0 to 60°C

0 to 65°C

Maintenance Requirement 30 to 60 days 60 to 90 days 3 to 6 months9 not req. not req. not req.

Typical Battery Cost(US$, reference only)

$50(7.2V)

$60(7.2V)

$25(6V)

$100(7.2V)

$100(7.2V)

$5(9V)

Cost per Cycle(US$)11 $0.04 $0.12 $0.10 $0.14 $0.29 $0.10-0.50

Commercial use since 1950 1990 1970 1991 1999 1992

Figure 1: Characteristics of commonly used rechargeable batteries

Lead acid battery:

Advantages: Inexpensive and simple to manufacture — in terms of cost per watt hours, the SLA is the least expensive.

Mature, reliable and well-understood technology — when used correctly, the SLA is durable and provides dependable service.

Low self-discharge —the self-discharge rate is among the lowest in rechargeable battery systems.

Low maintenance requirements — no memory; no electrolyte to fill.

Capable of high discharge rates.From the above matrix table and some of its advantages we finalized Lead acid Battery.

Principle of operation:

Batteries convert chemical energy directly to electrical energy. A battery consists of some number of voltaic cells. Each cell consists of two half-cells connected in series by a conductive electrolyte containing anions and cations. One half-cell includes electrolyte and the negative electrode, the electrode to which anions (Pb) migrate; the other half-cell includes electrolyte and the positive electrode to which cations (PbO2) migrate. Redox reactions power the battery. Cations are reduced (electrons are added) at the cathode during charging, while anions are oxidized (electrons are removed) at the anode during discharge. The electrodes do not touch each other, but are electrically connected by the electrolyte (H2SO4+H2O). Some cells use different electrolytes for each half-cell. A separator allows ions to flow between half-cells, but prevents mixing of the electrolytes.

PbO2+2H2SO4=2PbSO4+2H2O

Charging Discharging

Finalized Battery: As per the rule book the maximum specification of battery is12V-48V and max 35A-hr rating.Therefore, the selected battery has 24V volt, 18 Ahr rating.

We have,(Ah) = Device's Wattage (W) x Time to run (Hours) / Battery Voltage (V) 18=400*time/24Time=1.08hrRun time of single battery=1.08hr

So, the run time of 2 batteries in series is 2.16 hr.Thus from above calculation we have finalized two batteries in series as below:

24 Volt 18 Ah Sealed Lead Acid Battery.

Voltage: 24VCapacity:18AhSize: 7-1/8" long x 3" wide x 6-5/8" high (181mm x 76mm x 167mm)Type: Sealed Lead-Acid / SLAConnectors: Nut and bolt post connectors / T4Weight: 13.1 poundsItem # BAT-12V18A

The batteries are mounted below the seat.Innovation:- The charging mechanism of the battery is the innovation.The charging is done by pedalling. The diode is connected to motor and battery by terminal block; this is connected to the second rear axle through which the charging phenomena occur.

Steering MechanismObjective of steering system

I. To provide directional stability of the vehicle when going straight ahead.II. To provide perfect steering condition.

III. To minimise tire wear.

Design methodology:

The steering system for the vehicle has to be designed to provide better control, good ergonomics. The steering mechanism is accurate and easy to handle. Direct steering is employed because there is no urge requirement of rack & pinion steering system. All the requirement are fulfilled by using this mechanism.

Mechanism:

For the perfect steering we must always have an instantaneous centre about all wheels must rotate . Figure shows this mechanism. Links AB & CD are integral with front axle. This links are connected with each other through track rod BC with bell crank lever connected between them when the vehicle is in straight ahead position these links make equal angle (alpha) the dotted line shows position of vehicle when is turning left.

Construction-

Here, we are employed Ackermann mechanism .It consists of handle bar instead of steering wheel which is connected to the fixed pivot of bell crank through steering column,Arm is connected between track rod & link AD. Bell Crank is fixed at 20 cm apart from centre line of vehicle. Both end of the lever of bell crank is connected to tie rod end as shown in fig.

Working:

Case1, left turn In this case we require to move the handlebar in anticlockwise direction . The motion of handle transfered to lever of bell crank . The lever moves upward & RHS tie rod moves linearly to RHS side & steer the vehicle to LHS means vehicle take left turn. in case of right turn handle moves clockwise leads to move the left side lever to move upward & tie rod moves linearly to LHS side . Due to motion of steering arm the vehicle takes right turn.

Let, L= length of track rod=57.17 cm.R=length of link AB &CD= 150cm.

b=wheel base=150cm.

C=Distance between pivot centres =67.05cm.

A=wheel track=87.5cm.Steering angle= (alpha) =19.2degreeFormula to calculate turning radius,Turning radius = [(-b/sin Ѳ)^2+c^2+(2bc/tan Ѳ)]^1/2+(a-c)/2

Steering Angle (Ѳ) Turning Radius(m)5 17.910 8.9315 6.5420 5.0225 4.2630 3.6935 3.2839 3.03

40 2.9845 2.74

0 5 10 15 20 25 30 35 40 45 5002468

101214161820

Turning Radius(m)

Turning Radius(m)

Steering

Sr.no

Name of element Values

1 Length of each tie rod 150mm2 Steering angle 19.2degree3 Wheel track 87.5cm4 Wheel Base 150cm5 Steering ratio 1:16 Distance between pivot centres(c) 67.05cm7 Length of track rod(l) 57.05cm8 Bell Crank L=8cm,b=4cm9 Inside turning radius 228.125cm10 Outside turning radius 303.7cm11 Length of steering column 65cm12 Width of handle 65cm

Suspension

Principles of Suspension The suspension system isolates the body from road shocks and vibrations which would otherwise be transferred to the passengers and load.It also must keep the tires in contact with the road. When a tyre hits an obstruction, there is a reaction force.Sprung mass is that part of the vehicle supported by the springs such as the body, frame, and engine and associated parts.Un-sprung mass includes the components that follow the road contours, such as wheels, tyres, brake assemblies and any part of the steering and suspension not supported by the springs.

Objective of suspension: a. To withstand the component/vehicle in stable condition in pitching or rolling. b. To prevent the road shocks from being transmitted to the vehicle components.c. To safeguard the occupants from road shocks.d. To preserve the stability of the vehicle in pitching or rolling, while in motion.

Types of Suspension Spring 1. Coil spring2. torsion bar3. leaf spring4. independent/non-independent (beam axle) track control arms/wishbones

Modern passenger vehicles usually use light coil springs. Light commercial vehicles have heavier springs than passenger vehicles and can have coil springs at the front and leaf springs at the rear. Heavy commercial vehicles usually use leaf springs or air suspension.

Fig. Coil SpringTypes of damper:

1. Mono tube2. Twin tube

Elements of damper:

Main piston: In all dampers the main piston contains the primary valving components and produces the majority of the damping forces.

Compression Piston: Produces compression force based on the rod displacement through the Compression Piston. Note that the Monotube damper does not have a Compression Piston.

Gas Separator Piston: Keeps the gas separated from the oil. Main Piston Tube: This is the tube where the Main Piston operates.

Suspension used: HYDRAULIC SHOCK ABSORBER

Calculations: a. Helical Compression Springb. Axial force on rear wheel = 1.6 kN

We have designed 2 suspensions with axial force of 800 Nc. Spring index (C) = D/d = 5 . . . where D = mean dia. Of spring

d = wire dia. Of springd. Deflection = 25.4 mm = 1 inche. Material cold drawn steel wire with ultimate tensile strength = 1050 N/mm^2 f. Modulus of rigidity = 81370 N/ mm^2

1. Wire diameter:Wahl factor = 1.3105Ultimate tensile strength = 700 N/mm^2d = 6 mm

2. Mean Coil Diameter:D = 30 mm

3. No. of active coils:

N = 16 coils

4. Total no. of coils:Nt = Na + Ni = 16 + 2 = 18 coils.

5. Solid Length:Ls = 108 mm

6. Free length:Compressed length = 26.22 mmIt is assumed that there will be a gap of 0.5 mm between the consecutive coilsTotal gap = (18 – 1) * 0.5

= 8.5 mmLf = 108 + 8.5 + 26.22 = 142.72 mm

= 143 mm

7. Spring rate:K = 32 N/mm

8. Actual Spring rate:K = 31 N/mm

Suspension used: Hydraulic shock absorberSpring used: Coil suspensionDamper used: Hydraulic damper Suspension provided on only rear wheel only because axial force acting on front wheel be distributed on both the wheel equally; as the forces acting on front wheel is 820 N i.e. 410 N on each wheel. As the speed of this cycle will not exceed more than 30 kmph the shocks or vibration approaching on front wheel can be neglected/is very low. And this frequency cannot harm the vehicle as the acceleration is very less. Here wheel, tires and frame even in some condition absorbs the shocks i.e. they act as a shock absorbing system on front wheel.Suspension used on rear wheel; as axial force acting on rear wheel is high i.e. 1350 N; coil spring suspension is used. Material used for suspension is cold drawn steel wire as the tensile strength and modulus of rigidity is high as compared with other material. During calculation we don’t know the exact dynamic load approaching on cycle, so we have used factor of safety of 1.2 and made the remaining calculation. Suspension used is two in number and axial force acting on them is 800 N each.

Mechanical Design-

Tadpole Design-

In this design, there are two front wheels & one rear wheel. Factors considered are weight distribution & center of mass.

Brakes

Front Brakes- We can use disk brakes in both front wheels as Disk brakes can be mounted on the hub the wheels.

Advantages of using disc brakes

I. Greater braking powerII. Independence from wheather conditions

III. Reducing braking distanceIV. Disc brakes are less prone to brake fade

Rear Brakes- A reliable braking system for the rear wheel, V-brakes because of its higher mechanical advantage

V-brakes require separate tension springs in the left & right of the brake.If one of side’s springs gets weaker with age, the spring on the other side pulls the whole brake.

I. V-brakes are lighterII. V’s are cheaper

III. They are inexpensive & effectiveIV. Easy to install

Braking technique

There are several techniques for efficient braking on a standard, two-brake

bicycle. The one most commonly taught is the 25-75 technique. This

method entails supplying 75% of the stopping power to the front brake, and

about 25% of the power to the rear. Since the bicycle's deceleration causes a

transfer of weight to the front wheel, there is much more traction on the

front wheel. Therefore, the rear brake can exert less braking force than on

the front before the rear wheel starts skidding. For a more-detailed analysis,

see bicycle and motorcycle dynamics. If too much power is applied to the

front brake, then the momentum of the rider propels him/her over the

handlebars, thereby flipping the bicycle. The skidding of the rear wheel can

serve as a signal to reduce force on the front brake; a skillful cyclist in effect

becomes a human anti-lock braking machine, thus they must use both front

and back brakes.

Braking Force= 1362N

Rotor Diameter = 160mm

Velocity(m/s)

Stopping Distance(m)

Braking Force (N)

Deceleration (m/s^2)

Stopping Time (sec)

Braking Torque(Nm)

Braking Power

2 0.33 1362 6.06 0.33 600 1770

4 1.35 1362 5.92 0.67 600 3540

6 3.05 1362 5.90 1.01 600 5310

8 5.43 1362 5.89 1.35 600 7080

10 8.49 1362 5.88 1.70 600 8855

12 12.23 1362 5.79 2.07 600 10620

V- Brake arm length = 80mm

Stopping distance=d=v^2/ (2*X*g)

Where, X= coefficient of friction

Since, v=u + at v^2=u^2+2as

0 2 4 6 8 10 12 140

2

4

6

8

10

12

14

velocity vs stopping Distance

velocity

Velocity(m/s)

Stopping Distance (m)

Stopping Time (sec)

Braking Power(KW)

Braking Force(N)

Braking Torque(Nm)

Deceleration(m/s^2)

0 3 - 0 0 0 0

1 3 6.25 1.80955 36.8 22.08 0.16

2 3 3.03 7.46442 151.8 91.08 0.66

3 3 2 16.96460 345 207 1.5

4 3 1.50 15.04194 611.8 367.08 2.66

5 3 1.20 78.41415 956.8 574.04 4.16

6 3 1 67.85840 1380 828 6

7 3 0.85 92.28742 1876.8 1084.08 8.16

8 3 0.75 120.5114 2451.8 1471.08 10.66

9 3 0.66 254.4690 3105 1863 13.5

10 3 0.60 314.0336 3831.8 2299.08 16.66

11 3 0.54 380.0070 4636.8 2781.78 20.16

12 3 0.50 452.3893 5520 3312 24

0 2 4 6 8 10 12 140

10002000300040005000600070008000

Stopping Dis-tance(m)stopping time(sec)Braking Power(KW)

Why is Brake Biasing necessary?-

Brake biasing is nothing but brake balancing. It indicates the relative amount of pressure applied to front brakes. E.g. 52% would indicate that the front brakes were receiving 52% of the brake pressure & rear would be receiving 48%. A perfect brake balance occurs when all the wheels of vehicle lock at the same time. It is required for equal distribution of braking force.

Brake Fluids

Brake fluid plays an important role in braking function.

The 3 main types of brake fluid now available are DOT3, DOT4, DOT5.

Where, DOT stands for Department of Transportation.

DOT3 & DOT4 are glycol based fluids & absorb water while DOT5 does’nt.

DOT5 is silicone based fluid.

Brake Calculations-

Front Brake Disc brakes

Rear Brake V-brake

Braking Force 1362N

Brake Energy 1329.4J

Brake Efficiency 81.54%

Clamp load=T/(r*X*n)Where, T=torque R=rotor diameterN=no. of friction facesX=Coefficient of friction

Required torque=70.014Nm

Clamp Load=95.83NFor Disc Brakes- Diameter(mm)

Torque(Nm)

130 74.75160 92200 115

Hence, assume disc diameter= 160 mm

For V-brakes

Required torque=72.33N

Arm length(mm) Torque(Nm)65 61.7080 75.9490 85.38100 94.87

Hence, assume arm length= 80mm

Clamp load=75.34N

Brake Energy=mv^2/2=W*v^2/ (2*X*g)=(230*3.4^2)/2=1329.4J ,where, X=coefficient of friction

Brake efficiency= (Total brake force/vehicle weight)*100 = 81.54%

Stopping distance=d=v^2/ (2*X*g)

Where, X= coefficient of friction

Seat

Proper sitting contributes to the physical well being of a driver.

General Principles:

Rounding off the front of a chair avoids restriction of blood flow through the legs. The seat itself should be reasonably flat in order to allow freedom of movement and to prevent

hip-joint pressure. Padding that is too thick and soft can cause discomfort by immobilizing the legs.

Contents:1. Ergonomy2. Safety3. Bucket seat and bench seat4. Seat construction5. Material6. Climate control and ventilation7. References

A. Ergonomy: Lumbar and thigh support To get full efficiency while driving a vehicle say tricycle; ERGONOMICS plays an vital role; the best area through which the driver feel comfortable and distinct is the region in which he or she is placed in.Lumbar and thigh support are the most predicted region to which an ergonomists should design the seat such a way that one should feel comfortable; to achieve this inclination and such other things are made while designing seat.

B. Safety: A restraint system, also commonly referred to as a car seat, is a restraint which is secured to the seat of an automobile equipped with safety harnesses or seat belts, to hold driver and passenger in the event of a crash. As a safety equipment one can use seat belts, helmet, for eye protection – goggles, elbow card, etc.

C. Bucket seat and Bench seat: A bucket seat is a seat with a contoured platform to accommodate one person, distinct from a bench seat which is a flat platform designed to seat up to two/three people.

D. Seat construction:

Parts:1. Back rest2. Heat rest3. Seat base4. Total thickness

Calculation is carried out taking into account of average dimensions of normal car seat and Moto-sports car seat; and fitting it to the comfort level of a normal human being.

Seat base: Minimum seat length should be 14 - 15 inches (i.e. 35.56 - 38 cm)Why to use this dimension;2 drivers i.e. 2 seats required;(2 * 38) + 30 = 106

= 90 cm . . . (if we use bench seat)

Total maximum width of cycle provided;55 inch = 139.7 cm

Remaining clearance:139.7 – 90 = 49.7i.e. appro. 25 cm on both sides of cycle

Seat width approx. 17 inch = 43 cm . . . . at this width fatigue on driver is very lowIts angle from horizontal plane 7 degree . . . . to get the thigh at rest

In use: Bench seat; main reason why to use bench seat instead of bucket seat, according to above calculation the overall length of bucket seat approaches near about 40 cm for each driver i.e. 80 cm for both drivers and 25 cm clearance in between both seats to get the driver’s movement while taking turns, for relaxing, etcTherefore overall length comes to be 105 cm.

Now, if we design a bench seat of 90 cm it would be enough for both the driver to accommodate and to restrain through fatigue.From above both calculations, by taking into consideration of values there is saving of 15 cm in overall length of seat if we use bench seat; which is directly or indirectly proportional to saving of total weight and cost.

Back rest: Ht of back rest normally used is 16 to 22 inch i.e. 45 to 55 cmIn use: 50 cm; this height is enough to support lumbar region and is convenient to make it more comfortable.

Angle of back rest from seat base used normally is 105 to 115 degrees (seat pan angle)In use: 110 degree (with horizontal ); because in this position forces and stress acting on driver will be minimum.This acquires the concave portion of back’s lumbar region; comfortable and proper vision for driver at this position and minimizing the fatigue level of driver.

Head rest: Normally if provided we us 22 cm in width and its angle between back rest and back rest must be 30 to 32 degree for proper vision and comfort.Height will be near about 15 to 17 cm

In use: Width = 22 cmHeight = 15 cm

This height and width can be changed according to the driver comfort level.

Thickness: In use: 7 cmPadding that is too thick and soft can cause discomfort by immobilizing the legs. This is the best thickness to achieve comfort.

Center of gravity: X = 93.20 mmY = 162.01 mmZ = 0.01 mmThis is decided form the CAD drawing which is provided below

E. Material used: Most car seats are made from inexpensive but durable material in order to withstand as much use as possible. The most common material is polyester.1. Foam sheet

Density = 40 +/-1 2. Memory foam

Use: cushions

F. Climate control and ventilation: Some vehicles include the option of seat climate control (i.e. heating by seat warmers) and ventilation.

Material Property:

Ergonomics

In the machine design, the machine is considered as an entity. In Reality, the man machine working environment forms the system and this needs to be considered as a single unit.

By taking this into consideration, the parts are designed in such a way that the user does not get any kind of strain in his body while operating the machine.

Purpose of ergonomics is to design equipments and working environments which fit into capacities, needs and comfort of the user.

The goal of an ergonomics program is to ensure employees can work comfortably with their workplace demands or tasks, thereby decreasing the risk of injury or illness.

Anthropometry

The workplace should be designed to accommodate the body size of the user. Anthropometry is the measure of physical human traits that is applied to determine allowable space and equipment size and shape used for the work environment.

The goal is to provide a workplace that is efficient, safe and comfortable for the worker.

Biomechanics

Biomechanics is the study of the structural elements of the human body in relation to how the body functions and how much stress, acceleration and impact it can stand. Simply defined, it is the application of the principles of mechanics to living biological material.

Types of Movements of Body Members Positioning movements are those in which the hand or foot moves from one specific position to

another, such as when reaching for a control knob. Continuous movements are those that require muscular control adjustments of some type during

the movement, such as when operating the steering wheel of a car or guiding a piece of wood through a band saw.

Manipulative movements involve the handling of parts, tools and control mechanisms, typically with the fingers or hands.

Repetitive movements are those in which the same movement is repeated. Hammering, using a screwdriver and turning a hand wheel are examples of repetitive movements.

A static posture involves maintaining a body segment in a specific position for a period of time.

LeversDistance between load and fulcrum is “load arm”Distance between effort and fulcrum is “effort arm”

Law of equilibrium:

Load x Load Arm = Effort x Effort Arm

First type lever:First-class levers have the fulcrum placed between the load and the effort.

Second type lever:Second-class levers have the load between the effort and the fulcrum.

Third type lever:Third-class levers have the effort placed between the load and the fulcrum.

Ergonomic Injuries / Illnesses The most common types of ergonomic injuries and illnesses are musculoskeletal disorders (MSDs). Employees may suffer ergonomic injuries/illnesses when work tasks include reaching, bending over, lifting heavy objects, using continuous force, working with vibrating equipment, and/or performing repetitive motions.

Causes of MSDs

Contact stress Awkward postures Forceful exertions Repetition Vibration

Ergonomic Goals:

Finding ways to make strenuous, often repetitive work, less likely to cause muscle and joint injuries and still get the job done.

Keeping young bodies from wearing out prematurely, and mature bodies from giving out early.

Indication of ergo failure:

Awkward Postures

Being in these work positions for more than 2 hours total per day– Hands above head– Elbows above shoulder– Back bent forward more than 30 degrees– Neck bent more than 30 degrees– Squatting– Kneeling

High Hand Force

Highly Repetitive Motion

Repeated Impact

Heavy, Frequent or Awkward Lifting

Moderate to High Hand-Arm Vibration

How to reduce it . . . ???ERGONOMIC PRINCIPLES THAT CONTRIBUTE TO GOOD WORKPLACE DESIGNThe goal for the design of workplaces is to design for as many people as possible and to have an understanding of the Ergonomic principles of posture and movement which play a central role in the provision of a safe, healthy and comfortable work environment. Posture and movement at work will be dictated by the task and the workplace, the body’s muscles, ligaments and joints are involved in adopting posture, carrying out a movement and applying a force. The muscles provide the force necessary to adopt a posture or make a movement. Poor posture and movement can contribute to local mechanical stress on the muscles, ligaments and joints, resulting in complaints of the neck, back, shoulder, wrist and other parts of the musculoskeletal system.

Some tips to control ergonomics failure:

1. Seating arrangement:Almost 50 percent of workers in the industrial world are thought to suffer from back problems. Many back problems originate from improper sitting positions. Complications that may arise from poor seating conditions

2. Working area:Most of the efficiency increases by arranging the working area according to the ergonomics rules; the comfort level of the worker increases as he or she feels the less stress acting on the body.

Parts Value ReasonDistance of steering wheel from back rest of seat

550 mm According to the principles of ergonomics; riders arm must be attached with body so stress, strain acting on them must be minimum.

Distance of steering wheel from chassis

750 mm Perfect steering handling position for driver; whenever needed he/she can put their weight on wheel and can pedal with more force.

Elbow angle of rider 100° – 110° Avoids pressure acting on hands

Distance of pedal center from seat base corner end

450 mm Stress on thigh is less.

Leg angle with pedal disengaged

120° – 130° This angle is most stable for driver to put his energy to get more and more displacement of cycle.

Safety

Automobile safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of automobile accidents.

Types:

1. Active safety is used to refer to technology assisting in the prevention of a crasha. Good visibility form driver’s seatb. Good chassis balance and handlingc. Collision warning/avoidance

2. Passive safety to protect occupants during and after a crash.a. Passenger safety cellb. Seat beltsc. Emergency medical service

Phase of accident:

Accident Types – Direction of Impact by Numbers

From figure one can easily understand the most of the impact on every vehicle occurs or take place at front side; the safety precaution one can make calculation and have the result by providing a proper element for safety.There are mainly two types of impact i.e. pitching and rollover.When impact is done on the outside area of the vehicle and after or during impact the vehicle/ car tends to move in one direction as that of the impact force direction then that impact is known as “pitching impact”. Here 97% - 97.2% accident leads to pitching impact. When impact is done on the outside area of the vehicle and after or during impact the vehicle/ car tends to rollover its C.G. then that impact is known as “rollover impact”.Only 2.8% - 3% accident leads to rollover impact.

Elements for safety:a. Helmet b. Eye Protection c. Seat beltsd. Jacket e. Gloves f. Boots g. Head lightsh. High ground clearancei. Mud-guards for every wheelj. Chain coversk. Insulation to electric wiresl. Hornm. Mirror

A. Helmet: A motorcycle helmet is designed to absorb the impact of a blow

B. Head light, horn, mirror: These are also known as accessory part of vehicle. These are allocated to known the vehicle that is approaching us or vehicle that is ahead us; so that we can indicate them to avoid accident.

C. Insulated electric wires: One of the basic principles while using electric equipment is that all the circuits must be grounded and wires used must be insulated. Naked wires are very dangerous and have power to injure a human being badly. Taking this into consideration safety level can be increased.

D. Eye Protection: As we know that eye is one of the most precious part of human body; to protect it from foreign particle (dust, etc) use of eye protection is done while driving vehicle. Proper vision is most needed to avoid accident.

E. Seat belts: One of the most effective equipment with stand with driver/passenger during collision; it tries to

keep the driver in stationary and avoid impact of driver to any component. Mostly all the accident impact on front side; so in this case this must withstand the forces.

F. Elbow pad:

G. Knee pad: