GO-KART Project report submitted in partial fulfillment of the requirement of the degree of
Bachelor of Technology In Mechanical & Automation Engineering
Under the Guidance of
Mr. Devender Sharma
MECHANICAL & AUTOMATION ENGINEERING DEPARTMENT NORTHERN INDIA ENGINEERING COLLEGE (Affiliated to Guru Gobind Singh Indraprastha University, Delhi) MAY 2015
i
REPORT APPROVAL
This project report entitled “GO-KART” was prepared is approved for the degree of B.TECH (Mechanical & Automation Engineering).
HOD
Supervisor
………………………………. DATE ………………………………..
..................................................
PLACE ……………………………….
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CERTIFICATE
It is certified that the work contained in the project report titled “GO-KART” by the following student:
Name of Student Nikhil Garg Md. Ali Hussain Shrad Sajwan Praveen kumar gond Manish Taak Manpreet Ashwary Dikshit Narender Singh Sachin Kumar Md. Hasan Equbal Sandeep kumar Asad ur Rahman
Roll Number 03815603611 03115603611 00515603611 02415603611 02315603611 05615603611 00415603611 02515603611 00715607412 00315607412 00515607412 07096203611
Has been carried out under my supervision and that this work has not been submitted elsewhere for a degree.
Signature of Supervisor Mr. Devender Sharma Mechanical and Automation Engineering Department NIEC May 2015
DECLARATION I declare that this written submission represents my ideas in my own words and where others' ideas or words have been included, I have adequately cited and referenced the original iii
sources. I also declare that I have adhered to all principles of academic honesty and integrity and have not misrepresented or fabricated or falsified any idea/data/fact/source in my submission. I understand that any violation of the above will be cause for disciplinary action by the Institute and can also evoke penal action from the sources which have thus not been properly cited or from whom proper permission has not been taken when needed.
Name of Student Nikhil Garg
Roll Number 03815603611
Md. Ali Hussain
03115603611
Shrad Sajwan
00515603611
Praveen kumar gond
02415603611
Manish Taak
02315603611
Manpreet
05615603611
Ashwary Dikshit
00415603611
Narender Singh
02515603611
Sachin Kumar
00715607412
Md. Hasan Equbal
00315607412
Sandeep kumar
00515607412
Asad ur Rahman
07096203611
Date:
ACKNOWLEDGEMENT
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Signature
I would like to acknowledge the contributions of the following people without whose help and guidance this report would not have been completed. I acknowledge the counsel and support of my project guides Mr. Devender Sharma, Mechanical and Automation Engineering Department with respect and gratitude, whose expertise, guidance, support, encouragement and enthusiasm has made this report possible. Their feedback vastly improved the quality of this report and provided an enthralling experience. I am indeed proud and fortunate to be supervised by them. I am also thankful to Mr. Neeraj, H.O.D of Mechanical and Automation Engineering Department, Northern India Engineering College, New Delhi for his constant encouragement, valuable suggestions and moral support and blessings. Although it is not possible to name individually, I cannot forget my well-wishers at Northern India Engineering College, New Delhi and outsider for their persistent support and cooperation which needed during this work. I shall ever remain indebted to the faculty members of Northern India Engineering College, New Delhi. Finally, yet importantly, I would like to express my heartfelt thanks to my beloved parents for their blessing, my friends/classmates for their help and wishes for the successful completion of the project. This acknowledgement will remain incomplete if I fail to express my deep sense of obligation to my parents and God for their constant blessings and encouragement.
ABSTRACT The objective of Go-Kart project is to simulate real world engineering design projects and their related challenges. An aspect of this project is to compose a design documentation v
package that creates an overview of the vehicle‘s construction elements. The team has created this report to describe their design. The aim is fabricate Go-Kart by making not only the best performing vehicle but also the rugged and economical vehicle that will comply with all the Go-Kart design requirements. To achieve our goal the vehicle has been divided into subcomponents and each member is assigned a specific subcomponent. The team is focused to, design the vehicle by keeping in mind the Go-Kart requirements, driver‘s comfort and safety, and to increase the performance and drivability.
To achieve our goal the project has been divided into various groups and each group is assigned a specific component of the vehicle (Chassis, Wheel Assembly, and Steering, Brakes, Suspension, and Power transmission). This report only contains Designing information (chassis). For designing, analysis and optimization of the vehicle components various software like SOLIDWORKS (design, analysis and simulation), is used. The team has done a detailed study of previous vehicles and reports of the teams participated in past year events and we have come to the new well precise and accurate design. As a whole, the main objective of the team is to reduce the weight of the vehicle, augment the performance and minimize the power loss. Each part is being designed using SOLIDWORKS 2013, software by keeping in mind these objectives. A detailed analysis is being done on each part using SOLIDWORKS analysis application to remove the unnecessary and extra material. An iterative process is being used for the same. Benchmarking is done for selecting each component. A special attention is given to manufacturing process to improve the quality of the final product.
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TABLE OF CONTENT CHAPTER 1 2
3
4
5
6 7
8 9
TITLE Introduction Literature Review
PAGE NUMBER 5 6
2.1 History of Go-kart 2.2 Components of Go-kart 2.2.1 Chassis 2.2.2 Engine 2.2.3 Transmission Systems 2.2.4 Tyres Designing 3.1 Finite Element Analysis 3.2 Factor of safety 3.3 Interpretation of FOS Values 3.4 Prototyping & Force calculation 3.5 Impact Tests 3.5.1 Front impact test 3.5.2 Side impact test 3.5.3 Rear impact test Transmission 4.1 Advantage of manual transmission 4.2 Engine specification 4.3 Transmission Calculations Steering 5.1 Selection of steering systems 5.1.1 Rack and pinion steering 5.1.2 Pit arm steering 5.2 Main terms of steering 5.3 Steering geometry 5.4 Steering Calculation 5.5 Steering mechanism 5.6 Tie rod specification Braking 6.1 Braking Calculations Suspension 7.1 Basic Parts in suspension 7.1.1 Ball joint 7.1.2 Spring 7.1.3 Shock absorber 7.2 Front Suspension Results & Discussion 8.1 Scope of project Summary & conclusion
6 6 7 7 8 8 9 9 9 9 10 10 10 11 12 14 17 18 19 24 25 25 27 28 30 31 33 34 36 39 41 42 42 42 43 43 45 46 47
Appendix References
49 50
LIST OF FIGURES Figure 2.1 3.1 3.2 3.3 4.1 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 6.1
Title First Go-kart invented Front impact test Side impact test Rear impact test Honda Stunner Engine Steering mechanism Rack and pinion Steering system Pit arm steering system Ratings on different steering systems Kingpin Camber Angles Steering Geometry Correct steering Turning radius calculation formulae True steering Brake Assembly 2
Page Number 6 10 11 12 18 25 26 27 27 28 29 30 31 32 33 38
7.1 7.2 7.3 7.4 9.1 9.2
Ball Joint Springs Shock Absorber Front Suspensions Completed Go-kart Rear view of Go-kart
42 42 43 44 48 48
LIST OF TABLES Table 3.1 3.2 5.1 6.1 8.1
Title Interpretation of FOS values FOS in Different impact tests Tie rod Specification Difference between Disc & Drum brakes Summary of design of chassis
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Page Number 9 13 35 38 45
Chapter 1 Introduction Go-Kart Designing is first and basic step in fabrication and manufacturing of go-kart. We are fascinated by the fact that we can use our knowledge and enthusiasm of engineering and technology for building a machine, which rolls on four wheels powered by a petrol or diesel engine and driven by one single person, this machine is called as Go-Kart.
Go-kart designing and manufacturing has become a passionate competition in engineering colleges all over the India. Many engineering colleges in India organize several Go-kart designing and manufacturing competitions. They invite students of engineering colleges to take part in the competition. To participate in any such competition students make a team and divide the team into sub groups. These sub groups work in several sub departments for Gokart manufacturing, for example – designing department, transmission systems, suspension systems, steering systems, braking systems and fabrication and marketing department. We decided to take part in a competition named ‘International Go-Kart Championship’ organized by LPU, with an aim to win the championship. The main aim for the designing department is to prepare the complete design of the proposed Go-kart in suitable CAD software (Computer aided designing). Some very famous CAD soft 4
wares are Solid Edge, NX cad, Auto Cad, Solid Works etc. The complete procedure of designing a Go-kart is consisted of several important steps which are part of the methodology adopted by the designers. These steps are used to ensure the best design from every aspect. The steps are – Selection of material, Ladder chassis designing, Static impact from different sides of chassis, Buckling points, Finite element analysis, Improvisation in design, Final ladder chassis design. Each and every step will comprise this whole report. Designing the go-kart by keeping in mind the comfort of the driver, aesthetic as well as ergonomic considerations, and maneuverability of the vehicle itself is a task which will challenge our both technical and reasoning skills.
Chapter 2
Literature Review 2.1 History of go-kart American ‘Art Ingles’ is generally accepted to be the father of Go-karting. Currently gokarting is largely popular in Europe.
The first kart manufacturer was an American company, Go-kart Manufacturing Co. (1958). In 1959 Mc Culloch was the first company, to produce engines for karts. The McCulloch MC-10 was an adapted chain saw 2-stroke engine. Later in 1960s motorcycle engines were also adapted for go-karts.
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Figure2.1: first go kart invented by Art Ingles.
2.2 Components of Go-Kart Normally a go-kart is in single seated form while two seated karts can also be found in some countries.
Basically a go kart consist of four main components which include a chassis, engine, transmission system and tyres. Other than these main components there are some other parts such as brakes and steering. A go-kart may or may not employ suspension systems or seat belts. As the rear axle is rigid no differential is used in go-karts i.e. both the rear wheels turn at same speed. For the current design engine is placed behind the driver seat there is a fire wall between driver seat and the engine to protect the driver from the hot flames in case of engine fire. The engine may also be placed at the side of the driver seat, but this will increase the on track width of the vehicle (track width).
2.2.1 Chassis
The chassis is made of steel tubing (tubing material must be selected wisely). As there is no suspension system in many go-karts or even if there is, the chassis have to be flexible enough to work as suspension and stiff enough not to break. Kart chassis are classified as ‘open’, ‘caged’, ‘straight’, & ‘offset’.
Open karts do not have any roll cage. Caged karts have roll cage surrounding the driver; they 6
are mostly used on dirt tracks. In straight chassis the driver sits in the centre; straight chassis are used in sprint racing. In offset chassis the driver sits on the left side; offset chassis are used for left-turn-only speedway racing. Chassis should be designed in such a way that it can withstand overall load of driver’s weight and weight of all other components of the go-kart.
2.2.2 Engines
We only have two types of engines that are suitable to power the go-karts, which are – Twostroke-engines and Four-stroke-engines. Both the engines are petrol fuelled. Most of the go karts are using two-stroke-engine as the engine is small but powerful enough to satisfy the desired performance requirements, however due to environmental issues Four-stroke-engines are rapidly replacing Tow-stroke-engines in last few years.
2.2.3 Transmission Systems
Transmission system in an automotive is a mechanism that transfers the power developed by the engine to the wheels. In go karts since low power is to be transmitted from engine to the wheels so Chain drives are used. Using a gear drive will not only increase the cost of the gokart but it will also increase the weight of the go kart. This is the reason why all the go-karts employ Chain drive only, just like in motorbikes.
2.2.4 Tyres
The tyres used in a go-kart often depend on the conditions of the track. A wet weather condition would require Wet Tyres and the Slick Tyres are used for dry weather conditions. While some karts would use intermediate tyres that have a moderate level of grooves on the surface of tyre.
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Chapter 3 Designing 3.1 Finite Element Analysis Finite Element Analysis or FEA is a tool used to identify the performance of a model by stressing the model to obtain the specified results. The detailed visualization of where the parts would bend or twist and the distribution of stresses would be indicated through the simulation. Modifications could be done to improve the areas where the stress sustainability is weak. Finally, a final design review is performed to ensure the design is workable and ready for prototyping.
3.2 Factor of Safety While designing a component it is necessary to provide sufficient reserved strength in case of accident, it is achieved by keeping suitable factor of safety (FOS). A material starts to yield when the equivalent stress reaches the yield strength of the material. Yield strength of a 8
material is defined as a material property. Solid Works simulation software calculates the FOS at a point by dividing the yield strength by the equivalent stress at that point.
3.3Interpretation of FOS values Table 3.1: Interpretation of FOS values
FOS < 1
Material has yielded at
Design is not safe
FOS = 1
location Material at location has just
-
FOS > 1
started to yield Material at location has not
Design is safe
yielded Maximum force that a body can withstand is obtained by multiplying the yield strength with FOS.
3.4 Prototyping & Force calculation A prototype of the finalized design is built and the performance of the design is verified to comply with the design requirements. Calculation of force applied on chassis during impact on chassis, is based on maximum loads induced in dynamic conditions, applied on static chassis. This method uses Euro standard
which defines maximum force as:-
Where, Curb Weight (170 Kg), Maximum velocity (60 m/sec), time of impact according to Euro standards (250 milliseconds).
3.5 Impact Tests 3.5.1 Front Impact Test It is carried out to know the results of head on collision of the go kart, the deformation, factor of safety are the important parameters for the judgment of design performance. We try to determine how the go kart is going to perform in the real harsh conditions of driving. Figures 5.1 & 5.2 show the deformation induced in the front chassis members due to the front impact load application and the FOS calculated by solid works at that location respectively.
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Figure 3.1: Front Impact deformation results
3.5.2 Side Impact Test Sometimes while racing the go kart may get severe impacts from sideways by other go karts, so side protection is also necessary. Even though side bumpers are provided but still the impact should not reach the driver. The figure 5.3 shows the deflection of side beam in side impact test and figure 5.4 shows the FOS. Point to check here is that in this test we have not considered any side bumpers, but in actual go kart design side bumpers will add to the safety of the driver from the accidental side impacts.
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Figure 3.2: Side impact deformation results
3.5.3 Rear Impact Test Rear impact test shows the performance of the design in case of other karts hitting our kart from behind during the racing. The rear part of the chassis must take up the shock of impact and it should not allow the shock reach up to the engine. The figure 5.5 shows the deflection of the rear members of the chassis during the rear impact load application and the figure 5.6 shows the calculated FOS by solid works. 11
Figure 3.3: Rear impact deformation results
Table 3.2: Different values of FOS in Different impact tests
Tests FRONT IMPACT TEST
FOS 4.3
12
REAR IMPACT TEST
1.9
SIDE IMPACT TEST
2.7
FRONT WHEEL LANDING TEST
1
The above table 5.2 shows that the design is safe in every aspect. FOS is kept very optimum in every condition; these factors of safety values will ensure excellent performance even in very harsh racing or driving conditions. So we can move forward with this design for final ladder chassis.
Chapter 4
Transmission 13
Introduction of transmission A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmissions an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a live axle. Often transmission refers simply to the gearbox that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device. The most common use is in motor vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a relatively high rotational speed, which is inappropriate for starting, stopping, and slower travel. The transmission reduces the higher engine speed to the slower wheel speed, increasing torque in the process. Transmissions are also used on pedal bicycles, fixed machines, and where different rotational speeds and torques are adapted. Often, a transmission has multiple gear ratios (or simply "gears"), with the ability to switch between them as speed varies. This switching may be done manually (by the operator), or automatically. Directional (forward and reverse) control may also be provided. Single-ratio transmissions also exist, which simply change the speed and torque (and sometimes direction) of motor output. In motor vehicles, the transmission generally is connected to the engine crankshaft via a flywheel and/or clutch and/or fluid coupling, partly because internal combustion engines cannot run below a particular speed. The output of the transmission is transmitted via driveshaft to one or more differentials, which in turn, drive the wheels. While a differential may also provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds (essential to avoid wheel slippage on turns) as it changes the direction of rotation. Conventional gear/belt transmissions are not the only mechanism for speed/torque adaptation. Alternative
mechanisms
include torque
converters and
power
transformation
(for
example, diesel-electric transmission and hydraulic drive system). Hybrid configurations also exist.
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Objective of transmission
To harness engine’s power and torque and distribute to the ground in most efficient way.
Optimize the engine torque and speed catering to different situations.
It must reduce the drive-line speed from that of the engine to that of the driving wheels in a ratio of somewhere between 3:1 or 10:1 or more, according to the relative size of engine and weight of the vehicle.
Turn the drive 90 degree or perhaps otherwise realign it.
Enable the driving wheels to rotate at different speeds.
Provide the relative movement between engine and driving wheels.
When the engine is running, to enable the connection to the driving wheels to be made smoothly and without shock
Optimized multiplication of engine’s torque catering to different driving conditions.
4.1 Advantage of manual transmission 15
Pricing Of Engine
Vehicles with manual transmission are usually cheaper than vehicles with
automatic transmission. Fuel Consumption
Manual transmission has better fuel economy as compared to automatic transmission. This is because manual transmission has better mechanical and gear train efficiency compared to automatic transmission. Manual transmission also has certain fuel saving modes of operation (e.g. Keeping
the rpm low by shifting to the higher gear early) Maintenance
It is cheaper to maintain a vehicle in manual transmission because a vehicle with automatic transmission is more complicated device and
require more maintenance. Control
Manual transmission offers the driver more control of the vehicle compared to automatic transmission. It also better driving on steep and winding roads. Driver of manual cars can also downshift to a lower gear for more power, while an automatic transmission driver can only play with the throttle at the drive modes. That is why transmission of performance
cars are mostly manual in semi-automatic Moving a malfunctioned vehicle
Vehicles with manual transmission can be moved manually by pushing the vehicle at neutral gear when the engine malfunctions. This is quite useful in situations where the vehicle breaks down in the middle of the road, and must be moved to the side immediately
4.2 Engine Specification
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Engine selection – Honda Stunner
Displacement – 124.7 cc
Engine – 4 stroke single cylinder OHC
Maximum power – 11bhp@ 9500 rpm
Maximum torque – 11Nm @ 7500 rpm
Transmission – constant mesh synchronous gear box
Clutch – Wet clutch multiplate
Cooling type air cooled engine
Bore*stroke = 52.4*57.86mm
4.3 Transmission Calculations Assumptions Bike tyre size = 22inches = 0.5588m Go kart tyre size = 14.5inch = 0.3683m Engines max rpms = 9500 Figure 4.1: Honda Stunner Engine
Rear sprocket size of bike = 41 teeth Max speed of bike = 105 km/h
Measured speed of bike in different gears at 4000 rpms 1ST = 14km/h 2nd = 24km/h 3rd = 31km/h 4th = 38km/h 17
5th = 44km/h Calculation of bike’s reduction ratios Final reduction = no teeth of rear sprocket/ no of teeth of engine sprocket = 41/14 = 2.92 Calculation of tyre rpm at 44km/h 44000 = 0.5588*3.14*tyre rpm*60 Tyre rpm = 44000/ (0.5588*3.14*60) = 417.9 Calculation of tyre rpm at 38km/h 38000 = 0.5588*3.14*tyre rpm *60 Tyre rpm = 360.9 Similarly tyre rpms at 31km/h = 294.45 24km/h = 227.9 14km/h = 132.9 Total reduction in 1st gear = 4000/132.9 = 30.097 Total reduction in 2nd gear = 4000/227.9 = 17.551 Total reduction in 3rd gear = 4000/294.45 = 13.584 Total reduction in 4th gear = 4000/360.9 = 11.083 Total reduction in 5th gear = 4000/417.9 = 9.571
Engines reduction in 1st gear = 30.097/2.92 = 10.307 2nd gear = 17.551/2.92 = 6.010 3rd gear = 13.584/2.92 = 5.336 4th gear = 11.083/2.92 = 3.795 5th gear = 9.571/2.92 = 3.277
Factors effecting performance of a vehicle Air resistance Ar = ka*a*v^2 Ka = coefficient of air resistance 18
A = front area of go kart V = speed of go kart in m/s Ar for stunner bike at 47kmph speed = 0.1*0.552*13.05*13.05 = 10N (approx.) Ar at 47kmph speed = 0.45*.552*13.05*13.05 = 42.303N Gradient resistance = zero for go kart Rolling resistance = 0.18*weight of go kart with driver = 0.18*150 = 27N Rolling resistance for bike = 0.18*weight of bike with driver = 0.18*200 = 36N Total resistance at max torque for go kart = 42.303+27 = 70N(approx) total resistance at 47kmph for bike = 36+10 = 50N(approx.)
So total tractive force available for acceleration is In 1st gear = 1502-40 In 2nd gear = 869.52-40 = 829.52 In 3rd gear = 677.96-40 = 637.96N In 4th gear = 547.7-40 = 507.7N In 5th gear = 477.58-40 = 437.58N
ACCELERATION Taking total weight of go kart = 200kg with driver Acceleration in 1st gear = 1462/200 = 7.31m/sec^2 Acceleration in 2nd gear = 829.52/200 = 4.1476m/sec^2 Acceleration in 3rd gear = 637.96/200 = 3.189m/sec^2 Acceleration in 4th gear = 507.7/200 = 2.538m/sec^2 Acceleration in 5th gear = 437.58/200 = 2.187m/sec^2
Comparison of go kart with bike of which engine is used Calculating torque of bike 19
In 1st gear = 11*30.097*0.9 = 297.96Nm In 2nd gear = 11*17.551*0.9 = 173.75Nm In 3rd gear = 11*13.584*0.9 = 134.48Nm In 4th gear = 11*11.083*0.9 = 109.72Nm In 5th gear = 11*9.571*0.9 = 94.752Nm
Calculation of tractive effort In 1st gear = 297.96*2/.5588 = 1062.992N In 2nd gear = 173.75*2/.5588 = 621.868N s In 4th gear = 109.72*2/.5588 = 392.698N In 5th gear = 94.752*2/.5588 = 339.126N Considering total resistance of bike = 50N Total resistance of go kart
= 70N
Acceleration of bike Considering bike weight = 200kg with driver In 1st gear = 1012.992/200 = 5.064m/s^2 In 2nd gear = 571.868/200 = 2.859m/s^2 In 3rd gear = 431.317/200 = 2.156m/s^2 In 4th gear = 342.698/200 = 1.713m/s^2 In 5th gear = 289.126/200 = 1.445m/s^2
Giving a top speed of about 45 kmph in 2nd gear to go kart Calculating reduction required for 45 kmph top speed in 2nd gear 45kmph = (9500/reduction required)*3.14*.3683*60/1000 Reduction required = 14.64 Final reduction required = 14.64/6.010 = 2.43 Engine sprocket = 14 teeth so axle sprocket require = 14*2.43 = 34 teeth so a 34 teeth sprocket is chosen In 1st gear Total reduction = 10.307*2.428 = 25.025 Torque at axle = 11*25.025*.9 = 247.751nm 20
Tractive effort = 247.751*0.3683/2 = 1345.376n Acceleration = 1345.376-70 = 1275.376/150 = 8.502msec^2 Top speed = 9500/25.025 = 379.620*.36839*3.14*60/1000 = 26.34kmph In 2nd gear Max torque at wheels = 11*2.42*6.010*.9 = 144.4905nm Max tractive force = 144.490*2/.3683 = 784.634n Max acceleration = 714.634/150 = 4.764/sec^2 Top speed = 45.16kmph In 3rd gear Max torque at wheels = 11*2.428*5.336*.9 = 127.839nm Max tractive effort = 127.839*2/.3683* = 694.211n Max acceleration = 624.211/150 = 4.161m/sec^2 Top speed = 9500/12.913 = 735.692*3.14*.3683*60/1000 = 51.048kmph In 4th gear Max torque at wheels = 11*2.42*3.795*.9 = 90.918nm Max tractive effort = 90.918*2/.3683 = 493.726n Max acceleration = 423.726/150 = 2.824m/sec^2 Top speed = 9500/9.183 = 1034.520*3.14*.3683*60/1000 = 71.783kmph
In 5th gear Max torque at wheels = 11*7.956*.9 = 78.764nm Max tractive effort = 78.764*2/.3683 = 427.718n Max acceleration = 427.718-70 = 357/150 = 2.384m/sec^2 Top speed = 9500/7.956 = 1194.067*3.14*.3683*60/1000 = 82.853kmph
Comparison % of tractive effort = {(1345-1062)/1062}*100 = 26.6% more Tractive effort will be 26.6% more in every gear
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Chapter 5
Steering Introduction in Steering The main aim for the steering department is to design and fabricate such a steering system which allows the vehicle to follow the desired course. This is made possible by the linkages that connect the steering wheel to the steer able wheels and tires. We had used Solid works for designing the steering geometry .The steering system may be either manual or power. The steering system has components:
1) The steering wheel and steering shaft that transmit the driver‘s movement to the pitman arm.
2) The pitman arm that increases the mechanical advantage while changing the rotary motion 22
of the steering wheel to linear motion.
3) The steering linkage that carries the linear motion to the steering arms.
Ackerman Steering Principle describes the relationship between the front wheels of vehicle as they relate to each other when in a turn. The inner wheel will be traveling in smaller diameter circle than the outer wheel. All the wheels should move around a common point.
Figure 5.1: Steering Mechanism
Like in designing any subsystem, some suitable targets were thought off, the means to achieve them were found out and the effects of the system‘s performance on other systems were analyzed.
Typical target for a vehicle designer is to try and achieve the least turning radius so that the given feature aids while cornering in narrow tracks, also important for such a vehicle is that driver‘s effort is min. This is achieved by selecting a proper steering mechanism.
We had studied mainly two types of Steering Systems for this:
1. RACK AND PINION STEERING MECHANISM 2. PIT ARM STEERING SYSTEM
5.1Selection of Steering Systems 23
5.1.1Rack and Pinion Steering Mechanism
Rack-and-pinion steering is quickly becoming the most common type of steering on cars, small trucks and SUVs. It is actually a pretty simple mechanism. A rack-and-pinion gearset is enclosed in a metal tube, with each end of the rack protruding from the tube. A rod, called a tie rod, connects to each end of the rack.
The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack. The tie rod at each end of the rack connects to the steering arm on the spindle (see diagram above).
The rack-and-pinion gear set does two things:
1. It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.
2. It provides a gear reduction, making it easier to turn the wheels.
On most cars, it takes three to four complete revolutions of the steering wheel to make the wheels turn from lock to lock (from far left to far right).
The steering ratio is the ratio of how far you turn the steering wheel to how far the wheels turn. For instance, if one complete revolution (360 degrees) of the steering wheel results in the wheels of the car turning 20 degrees, then the steering ratio is 360 divided by 20, or 18:1. A higher ratio means that you have to turn the steering wheel more to get the wheels to turn a given distance. However, less effort is required because of the higher gear ratio.
24
Figure 5.2: Rack and Pinion Arrangement
5.1.2Pit arm Steering Mechanism
Simple linkage type Ackerman steering which is generally used in Go Karts, It has very less steering ratio but increases the effort of the driver.
Figure 5.3: Pit Arm Steering System
25
We have rated various steering system on a scale of 5 and obtained a result that pitman is most suitable for our go kart vehicle
Figure 5.4: Rating Of various steering system
5.2 Main Terms of Steering System The three main parts of the steering mechanism are Kingpins, Yoke, and Stub axles. 5.2.1Kingpins
The kingpin is the main pivot in the steering mechanism of a car. It is simply a pin made to allow the front wheels rotate freely. It has been made from 35mm O.D MS tubing having 8mm wall thickness. Tapping of 3/8” is provided on both sides to assemble the pin with the Yoke with help of bolts. The Kingpin is directly welded to the chassis by providing some angles to it relative to the frame.
26
Figure 5.5: Kingpin
Kingpin Inclination
King-Pin Inclination (KPI) is the inward lean of the king-pins relative to the true vertical line, as viewed from the front or back of the vehicle. KPI causes some of the self-centering action of the steering. This is because the straight ahead position is where the wheel is at its highest point relative to the suspended body of the vehicle - the weight of the vehicle tends to turn the kingpin to this position. A second effect of the kingpin inclination is to set the scrub radius of the steered wheel. This is the offset between the tire’s contact point with the road surface and the projected axis of the steering down through the kingpin.
5.2.2 Camber Angle
Camber is the degree to which the front wheels lean toward or away from each other, if the tops of the tyres are closer together than the bottom, then camber is negative and positive camber is the opposite of negative camber. To maximize grip when cornering, it is highly desirable to have as much of the two outside tyre’s rubber on the track as possible. Camber is the setting mostly responsible for maintaining maximum rubber on the road in corners. If the top of the wheel is farther out than the bottom (that is, away from the axle), it is called positive camber & if the bottom of the wheel is farther out than the top, it is called negative camber. Negative camber improves grip when cornering. This is because it places the tire at a 27
more optimal angle to the road, transmitting the forces through the vertical plane of the tire, rather than through a shear force across it. Another reason for negative camber is that a rubber tire tends to roll on itself while cornering. If the tire had zero camber, the inside edge of the contact patch would begin to lift off of the ground, thereby reducing the area of the contact. Excessive camber angle can lead to increased tire wear and impaired handling. Castor angle provided on our kart is 10 degrees and camber angle of 12 degrees
Figure 5.6: Camber Angles
5.3 Steering Geometry The next factor to take into consideration deals with the response from the road. The response from the road must be optimum such that the driver gets a suitable feel of the road but at the same time, the handling due to cornering is not affected. Lastly, the effect of steering system parameters on other systems like the suspension system should not be adverse.
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Figure 5.7: Steering Geometry
Specifications of steering system Steering ratio=3:1
Deflection of front wheel = 29.14deg
Angle turned by steering wheel on one side=29.14*3=87.42 degree.
Total angle turned by steering wheel = 174.84 deg.
No. of rotation of steering wheel=174.84/360 = 0.486 turns.
5.4 Steering Calculations Correct steering angle
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The perfect steering is achieved when all the four wheels are rolling perfectly under all the conditions of running. While taking turns, the condition of perfect rolling is satisfied if the axes of the front wheels when produced meet the rear axis at one point. Then this point is the instantaneous center of the vehicle. The requirement is that the inside wheel is made to turn through a greater angle than the outer wheel. The larger the steering angle, the smaller is the turning circle. There is however a limit to the maximum steering angle. The figure below shows the position of the wheels for correct steering. Referring to the figure, for correct steering:
Figure 5.8: Correct Steering
Figure 5.9: Turning Radius calculation Formulae
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This equation represents the basic condition for the steering mechanism to be perfect rolling of all wheels. To solve the above equation, trial and error method is used. In the above equation, c is the distance between pivot centers of the steering tie rods and b is the wheelbase. From the vehicle parameters,
c = 39inches, b=48 inches
c/b=.81
From the relation,
Cot Ø – Cot θ= 0.81
By trial and error method, the
Approximate values of angles are degrees and degrees respectively.
Hence, for perfect rolling conditions and no slipping condition on the tires, the angles of steering are
Ø= Outer wheel lock angles = 29.40 deg and
θ= Inner wheel lock angle = 14.40deg
a=c.o.m=21inch
Turning radius of vehicle = [a2 + l2* cot (average angle)] 0.5 = 3.45 meters.
5.5 Steering Mechanism
To achieve the correct steering, two types of mechanisms are used. They are the 31
Davis and Ackermann mechanism
This geometry ensures that all the wheels roll freely without the slip angles as the wheels are steered to track a common turn center. The simplest construction that generates Ackermann geometry is where the pit arm plate is located behind the swing axle and lines starting at the kingpin axis and extended through the outer tie rod ends when extended intersect the center of the rear axle. The angularity of the steering knuckle will cause the inner wheel to steer more than the outer wheel and a good approximation of the perfect Ackermann is achieved. The above explained
Method is shown below with a Fig.
Figure 5.10: True Steering
Ackermann Geometry a second way to design-in differences between inner and outer steer angles are by moving the pit arm forward or backward so that it is no longer on the line directly connecting the two outer tie rod ball joints. Another way to generate toe with steering is simply to make the steering arms different lengths. A shorter steering arm, as measured from the kingpin axis to the outer tie rod end will be steered through a larger angle than one with a longer knuckle. But this effect is asymmetric and applies only to cars turning in one direction, e.g. Oval tracks. Hence the method of extending the outer tie rod ends to intersect at the rear axle is most preferred. When the vehicle is in straight ahead position, these links 32
make equal angles α with the center line of the vehicle. The dotted lines indicate the position of the mechanism when the vehicle is turning to the left.
5.6 Tie Rod Specifications Maximum load Specification of tie road
Diameter of Rod =0.675
Moment of Area = (Π/64) D4
= (Π/64) * (0.675)4
= 0.0102 (inch) 4
Allowable force = (Π2*E*I)/L2
=105386 Newton.
Table 5.1: Tie Rod Specifications
Tie rod specification
Material
Mild steel
Length
12.75 inches
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Max allowed force
105386 N
Chapter 6
Braking
Introduction of Braking in Go-Kart Brakes are a mechanism with which we decelerate and stop the vehicle. Brakes are based on 34
the principle of friction. When the brake pedal is pressed, the force is transmitted through the brake lines and the brake pads are rubbed against the rotating brake disc and the disc is stopped due to friction. Heat is produced during the process in the form of kinetic energy.
Brakes are classified into various categories:
1. On the basis of mode of transmission of forcei)
Mechanical brakes
ii)
Hydraulic brakes
iii)
Electromagnetic brakes
2. On the basis of type of rotori)
Disc brakes
ii)
Drum brakes
3. On the basis of power boosters i)
Power brakes
Brake components:
Rotor- It is a round disc connected to the axle in our go kart. It is usually made of cast iron or aluminum. It has drilled holes in it to dissipate heat produced during braking. Caliper assembly is mounted on the disc. And during braking, brake pads are rubbed against this disc. When disc stops rotating, then so is the axle and tyres.
Master cylinder- master cylinder is connected to the brake pedal. When the brake pedal is pressed, it presses the piston inside the master cylinder and transmits the pedal force to the brake pads.
Brake pipes- brake pipes are narrow rubber pipes which connects master cylinder and caliper. It provides a path to the brake fluid and transmits the brake pressure to brake pads.
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Brake fluid- Brake fluid is the working medium of hydraulic brakes. We have used DOT 3 fluid in our go kart. Brake fluid transmits the brake pedal force to the brake pads. It is assumed to be incompressible. Brake fluid is contained in reservoir.
Caliper- caliper contains brake pads and piston (which presses the brake pads when brake pedal is pressed).
Brake pads- brake pads contain friction material and are pressed against the rotor.
In our go kart we have used the system of one master cylinder and one rotor.
There are two popular brakes- disc brakes and drum brakes. In our project we have used disc brakes due to following reasons:
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Table6.1: Difference between Disc & Drum Brakes
No.
Disc Brakes
Drum Brakes
1
Friction surfaces directly exposed to the cooling air
2
Friction pads are flat, wear in the linings are uniform. No loss in efficiency due to expansion. Better Anti-fade Characteristics. Simple design makes servicing and changing of Pad is easier. Weighs less.
Friction occurs on the internal surfaces from which heat can be dissipated only after it has passed by conduction through the drum. Friction pads are curved.
3 4 5
6
Loss in efficiency due to expansion. Lesser Anti-fade Characteristics. Design is little complex as Compared to disc brakes. Weighs more
Figure 6.1: Brake Assembly
6.1 Brake Calculations Forces and Pressure: Pedal force = 100 lbs = 450N 37
Pedal ratio = 6:1 Rotor size = 200mm Coefficient of friction = 0.6 Force on master cylinder push rod = 6 x 100 = 600 lbs = 2670N Master Cylinder piston diameter = 0.70” = 1.8 cm Master Cylinder piston area = (3.14/4) x (1.8/100)2 = 2.5 x 10-4 m2 Caliper piston diameter = 1” (measured) = 2.54cm Caliper piston area = (3.14/4) x (2.54/100)2 = 0.51 x 10-3 m2 No. of pistons in the caliper = 2 Total area of pistons in the caliper = 1.02 x 10-3 m2 Output force from caliper piston = 2670 x (1.02 x 10-3 / 2.5 x 10-4) = 10893.6N Average Circuit Pressure = 200 Kgs. / 2.5 x 10-4 m2 = 1358.2 Psi
Stopping Distance & Deceleration: Kinetic Energy = Frictional Work done X = V2 / 2μg V = 82 Kmph = 22.78 m/s μ = 0.7 (Assumed) Between Road & Tires g = 9.81 m/s2 x = 36 m (Calculated) Reaction time: 0.15 to 0.30 sec (Practical range) Assumed reaction time = 0.20 sec Distance traversed due to reaction time = 3.22 m
Total Stopping Distance = 36 + 3.22 = 40 m V2 = u2 + 2ax v = 0 (final velocity) u = 22.78 m/sec (top speed) x = 36 m (According to Kinematic Equations) Actual Stopping distance of the vehicle =4.5m 38
Deceleration, a = 7.33 m/s2 (Calculated).
Chapter 7 39
Suspension Introduction The suspension is the link between the tires and the frame of a car, and includes the springs and shock absorbers. If all roads were smooth, suspension would not be necessary. Specialized racing cars have been built without any suspension such as go-karts, which are very small and light compared to other vehicle. In addition to providing comfort, the suspension is used to tune the chassis for the best possible handling qualities. It is also to blame for most of the poor handling qualities you may be trying to get rid of. The chassis supports the engine, body and occupants. It rests on springs which insulate the chassis from road irregularities, and from the driver’s point of view the chassis bounces up and down on the springs. The weight of the chassis and all parts mounted on the chassis is considered to be spring weight.
Objectives for using suspension system
Supports the weight
Provides a smooth ride
Allows rapid cornering without extreme body roll
Keeps tires in firm contact with the road
Prevent excessive body dive
Allows front wheels to turn side-to-side for steering
Works with the steering system to keep the wheels in correct alignment
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7.1 Basic Parts in Suspension Systems 7.1.1 Ball Joints
Swivel joints that allow control arm and steering knuckle to move up and down and side to side.
Figure 7.1: Ball Joint
7.1.2 Springs
Supports the weight of the vehicle, permits the control arm and wheel to move up and down.
Figure 7.2: Springs of Shock absorber
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7.1.3 Shock absorbers
Keep the suspension from continuing to bounce after spring compression and extension . Shockers of Bajaj Pulsar 150cc were used. 4 shockers were used, 2 shockers in front with swing axle, 2 in rear with anti-roll bar. Jounce and bounce were approximated 1 inch.
Figure 7.3: Shock Absorber
7.2 Front Suspensions In years gone by a popular type of independent rear suspension was the swing axle. In this design each axle pivots about a u-joint next to the chassis-mounted rear-end housing. It has several nasty characteristics including a tendency to lift the car when acted on by a cornering force- called jacking effect. The suspension also has a very large variation in load. Except for simplicity and reduced unsprung weight the swing axle has little to recommend it.
In modern times, a great improvement on the traditional swing-axle suspension has been made. This is the single-pivot swing axle design, and it is used only at the rear of the car. To reduce the camber change and the jacking effect of the swing axle.
Suspension kinematics describe the movement caused in the wheels during vertical suspension travel and steering, whereas elasto-kinetics defines the alterations in the position of the wheels caused by the forces and moments between the tires and the road.
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Figure 7.4: Front Suspension System of Our Go-kart
7.3 Rear suspension: Anti roll bar (Measurements)
Material Used: - Stainless Steel
Volume: - 0.00012435 cubic meters
Diameter: - 0.5 inches
Horizontal Length: - 22.4 inches
Arm Length: - 7.44 inches
Angle of inclination: - 105 degrees
Mass: - 0.97736949 kg,
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Density: - 7859.9999 kg/cubic meters
Chapter 8
Results and Discussion As mentioned in the earlier section the design of go kart is inspired from the car body of formula 1’s car. The concept of having a cockpit is containing driver seat is implemented. Also along with suspension systems and other sub systems are installed on the chassis. The formula 1 car body can be considered as a full covered body with an opening for the driver to enter into the driving cockpit. However in our go kart design the chassis is built in an open ladder chassis style while maintaining the driver cockpit design. The complete chassis is designed with the purpose to ease the installation of engine and any other relevant mechanism. Nonetheless the ease of maintenance is another consideration for an open chassis. The report is a humble effort to clarify the methodology working out behind the selection of any kind of equipment or parameter that is going to be the part of the vehicle. The figure 6.1 shows the final design of the go kart chassis in this project. The final chassis is result of the hard work carried by the designers of the project team. We made different chassis model in the quest to pull out the best out of our sheer imaginations, which could ensure that we successfully me the maximum strength and least weight parameter at the same time. The table 6.1 below will show the pros & cons of our design.
Table 8.1: Summary of design of chassis
Pros
Cons
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Open chassis
Not a caged chassis
Ease of installation
Only one seat
Ease of maintenance
Potentially limited space in the
Low centre of gravity
driving cockpit
Large no. of welds & less no. of bends
Low weight
8.1 Scope of Project We see it as a golden opportunity to polish our technical skills as well as dome morale’s which is important in order to survive in this highly competitive and this cut throat competition. At the end of the project i.e. it reaches its apex we hope to see ourselves transformed in a positive manner.
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Chapter 9
Summary and Conclusion Basically, the objectives of the project are achieved. A go kart chassis is built by using AISI 1020 seamless tubing. The go kart chassis has been Simulated and Tested by solid works in terms of its bending deflection and torsional stiffness. The cost implied adequately suits with the project’s objective as the use of the material such as mild steel and GI tubing at the lowest price range. Although the design of go kart chassis done in this project could not be considered completely perfect, it can be said that there is always room for perfection.
As for the design that has been prototyped in this project, there are actually a number of rooms for improvement that can be done. However due to the timeframe provided, the improvements done are actually limited. Thus further study would be required in order to maximize the design performance and the application of some other chassis building material can also be looked for. Nevertheless from all the design and studies that have been done, it can be concluded that go kart chassis need not be in conventional tubular form, they can also be made from fiber glass composite materials, and also there is no restriction that suspension systems cannot be used in go karts. Thus by continuingly carry out the testing and researching in the design of the go kart chassis ad over all go kart, an innovative and creative machine can be developed while optimizing the performance of the go kart at the same time.
It must not be a matter of surprise if in the nearest future we will see Go-karting as the favorite motor sport of the young generation. The craze for the Go-kart making competitions in India is growing every year in engineering colleges of India. Inter-college competitions make it more challenging event. It gives the students a chance to showcase their technical talents and critical thinking skills. Figures 7.1 and 7.2 show the actual Go-karts fabricated in 46
this project.
Figure 9.1: Completed Go-kart
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Figure 9.2: Rear View of Completed Go-kart
Appendix-I
WHEELBASE :- 56”
FRONT TRACK WIDTH :-43”
REAR TRACKWIDTH :- 41”
WEIGHT DISTRIBUTION FRONT-46.24% REAR-53.76%
FVSA LENGTH- 1676 mm
FRONT ROLL CENTER HEIGHT-43.44mm, REAR-88.9mm
COG DISTANCE FROM FRONT WHEEL-0.62m
COG DISTANCE FROM REAR WHEEL-0.564m
COG HEIGHT-13.8” 48
HORIZONTAL LATERAL ACCELERATION- -0.823g
FRONT RIDE FREQUENCY – 2.182 Hz
REAR RIDE FREQUENCY- 2.016 Hz
ROLL RATE FRONT- 3304.324 lb-ft/radian
ROLL RATE REAR – 3102.62 lb-ft/radian
ROLL GRADIENT- 3.023 deg/g
FRONT LLTD- 51 lb
REAR LLTD- 54.52 lb
ROLL RATE DISTRIBUTION:- FRONT-51.56% , REAR-48.44%
LATERAL LOAD TRANSFER DISTRIBUTION:- FRONT-48.3% , REAR-51.7%
References 1. Automobile Mechanics by N.K.Giri (2008), 8th edition, Khanna publications. 2. Callister’s Material science and engineering (2014), wiley India pvt. Ltd. 3. Race car vehicle dynamics by Douglus L Milliken (1994), Society Of Automotive Engineers Inc. 4. Automotive Engineering (volume 1) by Kirpal singh, 12th edition, Standard publishers. 5. Manufacturing processes for engineering materials by kalpakjian, (2009), 5th edition, Pearson India. 6. Wikipedia.com (http://en.wikipedia.org/wiki/Kart_racing). 49
7. DIY Go-Karts (http://www.diygokarts.com/index.html). 8. Kartbuilding (http://kartbuilding.net/racingkart/index.html). 9. Go Kart guru (http://gokartguru.com/angle_iron.php).
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