Go-kart Design and Fabrication

TEAM ROYALZ,  MADRAS INSTITUTE OF TECHNOLOGY

FINAL REPORT

 

Abstract:

This work concentrates on explaining the design and engineering aspects of making a Go Kart as mentioned in the rulebook. This report explains objectives, assumptions and calculations made in designing a Go Kart. The team's primary objective is to design a quality kart applying our engineering skills. The design of the kart was built around the driver ensuring his comfort. To achieve this goal, the team has been divided into core groups responsible for the design and fabrication of the major sub systems which were later integrated into the final blue print.

Introduction:

The Go kart was built by TEAM ROYALZ – the students of MADRAS INSTITUTE OF TECHNOLOGY. We set up some parameters of our work and the team has been divided into core groups namely Design, Engine and Transmission, Steering Brakes and wheels, Business and Management. The model was modified and retested and a final design was fixed. We approached our design by considering all the possible alternatives for the system and modeling them in CATIA and SOLIDWORKS and analysing them in ANSYS.

TECHNICAL SPECIFICATIONS

 

Dimensions:-

Length	1620mm
Height	600 mm
Wheel base	1054mm
Track width– front	945mm
Track width – rear	1054mm
Total mass	95 kg
Ground clearance	1.2”

 

Materials:-

Material used	Purpose
AISI 1018	Chassis
AluminiumA3105	Base plate
Aluminium sheet	Firewall of the vehicle
Fibre reinforced polyester	Side and front panels
Rear Axle Material	EN – 13 Steel

 

Performance:-

Maximum speed	62kmph
Maximum acceleration	3.87 m/s2
Turning radius	2.3 m
Braking distance at 45 kmph	6 m

 

3D Views of Kart

                   Fig 1. Isometric view 

                   Fig 2. Isometric view 2

                Fig 3. Front view

                 Fig 4. Rear View

               Fig 5. Right Side View 

 

              Fig 6. Left Side View

 

ENGINE:

 

The engine used is Honda shine, 125 cc

 

Engine technology	Air cooled, 4 stroke,  SI engine
Length*width*Height  (approx.)	300 mm* 200mm*250 mm
Bore x stroke	52.4 x 57.838 mm
Displacement (cc)	124.7
Net power output	7.88 KW @ 7500 rpm
Net torque	10.30 Nm @ 5500 rpm
Overall Reduction Ratios	1st gear: 33.528 2nd gear: 19.624 3rd gear: 13.246 4th gear: 10.185
Fuel tank capacity	3.5 liters
Dry weight	12.2 Kg
Oil capacity	0.5 L

 

Design Methodology

ERGONOMICS CONSIDERATION:
The driver was made to sit in his comfortable position and the position of each component was fixed in the coordinates around him. The seat and steering design was selected to provide comfort to the driver. The pedal position and the gear shifter were positioned in the best suited points. Heat from the engine was prevented from the driver by designing a proper fire-wall. Ergonomics was also considered for safe and fast assembling and dismantling of the gokart.

FLOOR PLANNING:
The basic chassis design was done in the floor using insulation tape for an overview which was further developed as a pipe model. The drive was made to sit and the engine was placed in the respective positions. Necessary changes in the layout were made and the final design was validated.

 

Images of frame and prototype:

 

CHASSIS MATERIAL:
 

The material AISI1018 is used in the frame design because of its good weld ability

                        1. Relatively soft and, strengthens as well as good manufacturability. Analysis was conducted by use of finite element analysis on ANSYS software  

                                  Material used: AISI 1018

                                   Ultimate strength: 440 MPa

                                   Yield strength :370 MPa

 

Chemical composition:

ELEMENT	% COMPOSITION
Carbon	0.14 - 0.20%
Phosphorous and Sulphur	< 0.050%
Manganese	0.6 - 0.9%

 

DESIGN:
The design was done to satisfy three conditions

• Driver comfort
• Good performance
• Compactness

Hence a snug driver region, greater torque multiplication and least possible wheelbase was designed.

Finite Element Analysis:

The vehicle design is tested for accuracy and stability under the situation of extreme impacts and loads acting in case of any crash during the operation or racing. The Finite Element Analysis (FEA) is done using ANSYS Simulation Software.  FEA was done taking the impact forces in three different directions. They are   

       1.Frontal impact 

            

                                    Fig 7. Frontal Impact – Stress

             
                               

                                Fig 8. Frontal Impact - Deformation

 

  2. Rear impact

             

                                         Fig 9. Rear Impact – Stress

 

            

                                         Fig 10. Rear Impact - Deformation 

 

3.Side impact

                

                                            Fig 11. Side Impact – Stress

 

           

                                                  Fig 12. Side Impact - Deformation

 

IMPACT LOAD CALCULATIONS  

FOR FRONTAL AND REAR IMPACTS:   

Weight of the kart 175kg

Initial velocity= 12.5m/s

impact time= .1s

work done = change in kinetic energies

                = .5*175*12.5*12.5

work done = 13671.875

s = impact time*vmax

   = .1*12.5

   = 1.25

force= W/s

       = 10,937.5 N

 

Braking

 

Brake Type	Single disc brake
Recommended fluid	Dot 3
Brake Disc	Diameter-195mm
Brake pad thickness	4.5mm
Master cylinder diameter	19.05mm
Caliper inside cylinder	32mm

 

As per norms the decceleration must be twice the acceleration.

We have a maximum acceleration of 3.87m/s2     

 required deccleration = 7.74m/s2                   

Under braking dynamic condition

MT=h.m.a/(l.g)                                

h=.02m 

l=1.04m       

m=200kg                                   

Mt= 3.1kg 

Wr=1145.62            

Treq=160Nm

Treq=Wr x R            

Assuming that we are applying a torque of 170Nm on the rotor

Frictional force on rotor = Tdisc/ Rdisc  

Rdisc=100mm F_friction_rotor=1700N

Frotor= F_friction_rotor /µ

Mu=0.5 and Frotor =3400N

Force on Calliper =fdisc/2 Fcalliper=1700N

Brakeline pressure=Fcalliper/area

C =1700/.03175

   =53.543E3 N/m2

Required Fmc= P.Amc

                    =53.543E3*.01905

                    =1020N

Force applicable by driver=400N

Pedal ratio req. to obtain Fmc is

PR=Fmc/Fdriver

    = 2.55

We take PR as 3

                                

              Fig 13. Disc Brake Assembly

 

              

               Fig14. Master Cylinder and Brake Pedal

 

POWER TRAIN AND TRANSMISSION SYSTEM:

 Engine: Honda Shine 125 cc 

 Transmission: 

Primary reduction =  3.35

   Final reduction = 1.86

Secondary reduction:

First gear	3.587: 1
Second gear	2.100: 1
Third gear	1.417: 1
Fourth gear	1.090: 1

 

Chain: #40 or 08B chain (pitch, p = 12.7 mm)

 

CHAIN − SPROCKET SPECIFICATIONS:

Sprocket 1 : 

No. of teeth (T1) = 14

Sprocket 2 : 

No. of teeth (T2) = 26 

Gear Ratio (r) = T2 / T1 =26/13=1.86

Centre to centre distance = 6.65 inches

                                                                           

                         

               Transmission system

                 Engine

 

Calculation of No. of teeth in Final Drive Sprocket

total powertrain ratio iA.

ratio iS of the moving-off element,

ratio iG ofthe transmission

final ratio iE,

iAmax = .13315*175*9.8*(.01cos10 +sin10) + 175*3.87*1.5

vehicle is designed for an acceleration of 3.87m/s^2

iAmax = 21.77

iA = iS iG iE

12.016iE= 25.596

iE= 1.8

Best near match was Sprocket with 26 teeth resulting in iE of 1.86.

 

CALCULATION OF MAXIMUM SPEED AND ACCELERATION : 

Maximum rpm at rear axle = maximum rpm at intermediate shaft / Sprocket reduction ratio

                                        = 8500/(3.35*1.09*1.86)

Maximum rpm at rear axle  = 1251.51

Maximum speed of the kart = Maximum rpm at rear axle * rear wheel radius * (2π/60)

                                        = 1251.51 * 0.13335 * (2π/60)

                                        = 17.47 m/s

 Maximum speed of the kart  = 63 km/h 

 

Transmission:

Engine sprocket speed (N1) =

First gear	458.47 RPM
Second gear	781.805 RPM
Third gear	1158.64 RPM
Fourth gear	1506.23 RPM

Axle sprocket speed (N2) 

First gear	164.327 RPM
Second gear	280.217 RPM
Third gear	415.283 RPM
Fourth gear	539.867 RPM

 

Max angular speed of the rear wheel (N):

Gear	Reduction ratio	Speed of the Rear wheel (RPM)
First gear	33.528	223.693
Second gear	19.624	382.185
Third gear	13.246	566.209
Fourth gear	10.185	736.377

 

Performance Prediction:

Max Speed of the kart:

First gear	3.28 m/s
Second gear	7.603 m/s
Third gear	12.45 m/s
Fourth gear	17.47 m/s

 

Max Acceleration:

First gear	3.87 m/s2
Second gear	3.19m/s2
Third gear	2.6m/s2
Fourth gear	2.2m/s2

 

CHAIN SPROCKET CALCULATION :

For satisfactory performance of chain-sprocket drive, smaller pulley should be at least covered by 120 deg by the chain. So we can calculate approximate centre distance as 

        

C = (d2-d1) / (2*cos600) = 6.238’’

Length of chain(L) = π(R+r) + {(R-r)^(2)}/C + 2*C       

                           =3.14(4.283) +{(4.283-1.164)^(2)}/6.238 + 2*6.238

                            =31.14

No. of links = 31.14/0.5

                 = 62.28

Since we should use only even no. of links , so no. of links = 64 

Final length of chain = 64*0.5

                              = 32”

Final center distance, C ={L -  π(R+r) – (π-2φ)*(R-r)} / 2*sinφ

                                   ={ 32 – 3.14*(4.283 + 1.164 ) – (3.14 – 2.0944)*(4.283 – 1.164 ) } / (√ 3)

                                   = 6.72

 

STEERING SYSTEM

NOTATIONS	VALUES
STEERING GEOMETRY	Ackermann
WHEEL BASE	1054mm
FRONT TRACK WIDTH	945
REAR TRACK WIDTH	1054mm
TURN RADIUS	2440.155mm
CASTER	3 degrees
TOE IN	2 degrees
KING PIN INCLINATION	8degrees
TIE ROD	Equal length of 340mm
STEERING RATIO	1:1
STEERING ARM LENGTH	460mm
STEERING ARM ANGLE	74.22 degree

 

Wheels: (in inches)

    Front = 4.5 x 10 – 5

    Rear = 7.1 x 11 – 5

 Diameter of the rear wheel (D) = 280 mm [circumference = 398.98 mm]

 

Steering Model

 

 

    Ackerman Percentage = 90.45%

 

 

Rear Axle Diameter Calculation:

Bending Moment Calculation:

 

 

 

Vertical Loading:

RA=504.32 Rb=671.68

Maximum Bending Moment=100.75Nm

Torque Calculation:

Max Torque applied= Braking Torque

Max Torque applied, T= 120Nm

Minimum Diameter for Solid Shaft:

Total Torque due to applied Torque and Vertical Loading =M2+T2

Ttotal=1202+100.752 = 156.69Nm

Shaft Material Steel:

Considering fatigue loading FOS of 3 is taken   Max Allowable Shear Strength= 121 MPa

Dmin=316Tt/max

Dmax=23.6mm is enough for the purpose

Considering availability and reliability a shaft of 30mm is used

 

Fabricated and pre-fabricated parts

Fabricated Parts	Acquired
Frame	Engine
Tie rod	Clutch and Gear box
Brake pedal	Sprocket and chain
Disc	Master cylinder and caliper
Fire wall	Bumpers
Steering column	Tyre and wheel
Hub	Steering wheel
Disc hub	Fuel tank
Sprocket hub	Spindle
All mounts	Kill switch

 

Since the engine used has a four gear speed variation system, some of the calculations below are done for each gear.

 

Validation Plan :-

Parameter	Method Of Checking
Minimum  Turning Radius	Negotiate a circle –  Distance between two diametrically opposite points.
Minimum Static Turning Effort	Weight pan to the steering wheel   Add weights till steering wheel start rotating.
Frame Loading	Slowly add weight to the assembled frame  After each addition of weight visually inspect the frame to make sure it is holding  Once the frame has proven to support drive system with no issues test its ability to hold the weight at different rpm Continue to increase the weight and the rpm while inspecting the rigidity of the frame.
Travel	Vehicle on a jack remove spring  Distance between the extreme positions of after travel.
Maximum Pulling Capacity	Attach a trailer to the vehicle  add weight subsequently  Weight previous to the one where the vehicle fails to takes off.
Stopping Distance and Time	Drive the vehicle at preset speed Apply brakes at a marked position Vehicle to a complete halt  Measure the stopping distance & time using stop watch.

 

WEIGHT OPTIMIZATION:

The components of the kart were designed and subjected to Finite Element Analysis and unwanted material were removed in order to produce a light and dynamic kart.

CONCLUSION 

This project gave us the opportunity to learn a variety of core knowledge, software and machine operation. It developed several soft skills in us. Our team made the best use of it and made a well engineered race spec 125cc four stroke gokart.

REFERENCES

[1]. http://www.bmikarts.com/Brakes-Accessories_c_198.html 

[2]. http://gokartsusa.com/Gokart-Mini-Bike-Minibike-Parts-Brakes.aspx 

[3]. http://en.m.wikipedia.org/wiki/Brake 

[4]. http://auto.howstuffworks.com/auto-parts/brakes/brake-types/brake.htm 

[5]. http://gokartguru.com/go_kart_steering_systems.php 

[6]. http://gokartguru.com/go_kart_building_bundle.php 

[7]. https://www.google.co.in/search?q=steering+system+in+go+karts&hl=en&noj=1&tbm=isch&tbo=u&souce=univ&sa=X&ei=_D20U5GnBpWjugS82IHACQ&ved=0CB8QsAQ&biw=1366&bih=657 

[8]. http://books.google.co.in/books?id=jK93oR47zkwC&pg=PA224&source=gbs_toc_r&cad=3#v=onepage&q&f=false 

Books 

[9]. Don Knowels 2002 “Automobile suspension & steering system” page-224 

 

Additional Sources 

[10]. Seda Joseph B. “Drive Train Paper Report August”. Paper #1 UPRM Mini Baja 2006-2007. SAE. 2006. 

[11]. Gillespie, Thomas D., Fundamentals of Vehicle Dynamics. Warren dale: SAE. 1992. 

[12]. Lerner, Preston. “Going Nowhere Fast”. Popular Science. November 2006. 

[13]. Thompson, Dale. “Ackerman? Anti-Ackerman? Or Parallel Steering?” Racing Car Technology, 2006. 

[14]. Reimpell, Jornsen., et all. The Automotive Chassis: Engineering Principles. 2nd ed. Oxford: Butterworth-Heinemann. 2001. 

[15]. Smith, Carroll. Racing Chassis and Suspension Design. Warrendale: SAE. 2004.

[16]. Smith, Carroll. Tune To Win.