Team Name : Team Transryderz Racing

College Name : Sri Krishna College of Engineering and Technology, Coimbatore

Car #30
Design Report for BSI 2017
Abstract
Design of a BAJA All-Terrain Vehicle involves study, analysis and implementation of various engineering
concepts. Such a design process can be perfectly achieved through the Concurrent Engineering Design process
rather than Sequential design process. Various sub systems has been simultaneously designed in order to
overcome the shortcomings of sequential designing process. During the process various subsystems were
examined for its safety, SAE rules and performance. Roll cage was designed considering ergonomics and
structure integrity. Suspension and Steering systems were designed to perform favorable to the driver in various
terrains. Factors and parameters of transmission system was calculated such that they give required torque and
velocity. Braking system of the vehicle has been carefully planned to give effective deceleration and a minimum
stopping distance. Critical components of these sub systems were modelled using various modelling software
like SOLIDWORKS, PTC Creo 2.0 and tested for their safety in CAE software ANSYS.

Introduction
Team Transryderz Racing has continuously improved in the pursuit of designing and fabricating an All-Terrain
vehicle (ATV) from the time it first participated in 2011. The design phase was given a strong emphasis with
several brainstorming sessions which helps to meticulously evaluate every alternatives and to choose the best
based on the strength for safety, weight, cost and ease of manufacturing. Providing the utmost safety without
compromising the performance was given the highest priority.

Roll Cage
The roll- cage is a structure to protect the driver and to support all control systems like suspension, steering,
and the engine. The roll cage serves as a frame for supporting the body and different subsystems like pedal,
suspension, steering rack etc., of the vehicle. It should withstand the shock, twist, load, vibration and other
stresses. Roll cage provides safety, ergonomics and aesthetic look.
Design Objective
 Driver’s safety and comfort
 High strength to weight ratio
 Ease of subsystem assembly and disassembly
 Aesthetics
 Ease of fabrication
Design
.A strong chassis should be designed based on SAE BAJA International rules while accommodating driver
comfortably with easy access to gear shifter, pedals etc. An optimized Roll cage was designed after several
iterations from the initial design. The Roll cage was designed using the software SOLID WORKS and is tested by
various loads in the CAE software ANSYS.
Ergonomic Consideration
The vehicle is designed in such a way that the team’s shortest person can reach all controls and the tallest person
can easily accommodate into it.
 Fig 1 Roll Cage Final Design
 Egress time less than 5 seconds
 Gear shifter location
 Pedal mount for driver easy access
 Steering rack and steering wheel mount
Seats are designed based upon an average driver’s size and
comfort. This reduces cost, size and weight compared to the
commercially available seats. Seats are mounted at an angle which
gives highest comfort as possible to the driver. To neglect the
discomfort caused by fixed steering wheel, tilt steering system has
been selected which facilitates 10° tilt adjustment. Consideration
was also done for gear shifter location, so that driver can access
easily without taking much lime and loosing vehicle control.
Table 1 Material Comparison
Material Strength Cost Weight Availability Total
Material Selection MS ASTM
7 9 8 10 8.5
Material selection is the foremost 106 B
important part in roll cage design as this CHROMOLY
decides the cost, strength and 9 6 10 5 7.5
4130
manufacturability of the roll cage. Three
major materials were considered and AISI 1020 6 9 8 8 7.75
their factors rating out of 10 were
tabulated.
The material selected for roll cage is Mild steel ASTM 106 Grade B. It provides sufficient bending stiffness and
with high yield strength. This material is easily available in the market and is of comparatively lower cost than
Table 2 Material Properties other materials.
Material ASTM 106 B Design Validation:
Density 7850kg/m3 It is very important to check all failure modes of roll cage. Static analysis is
Carbon content 0.29 done by taking the forces as suggested by ENCAP (European New Car
Association Program). Fine mesh size is taken for all analysis in the testing
Poisson ratio 0.3 process. Front impact, rear impact, side impact and roll over tests were
Yield strength 350MPa made. Based on the stress and deformation analysis, the design has been
Tensile strength 440MPa modified for better factor of safety. In order to maintain the integrity of
the roll cage structure number of welds has been reduced as possible.
Elasticity
205MPa Table 3 Analysis of Roll Cage
modulus
It is necessary to keep the Test Maximum Stress FOS
Weld type TIG welding
center of gravity of the Front impact 98.35Mpa 2.54
vehicle as low as possible to
maintain stability at high speed cornering. Mounting heavier Rear impact 121.77Mpa 2.22
components such as engine, driver seat etc. directly on the lower Side impact 100Mpa 2.49
part of chassis is one way of achieving low center of gravity. This
Torsion 106Mpa 2.35
requires the roll cage to be designed with provisions for the
subsystems assembly as per the plan. Various Analysis results has been included in Appendix Section.
Suspension system
Shocks from the track are absorbed and some part of the load is transferred to the vehicle through the
suspension system. Suspension system also affects the vehicle traction at different track conditions. An all-
terrain vehicle must have a suspension system which maintains vehicle stability on various terrains.
Design Objective
 Effective Weight Distribution
 Ground Contact at all possible terrain conditions
 Ride Comfort
 Smooth Functioning of Suspension arrangement
 Favourable Vehicle behaviour at various track conditions
Design Considerations
Front & Rear Weight Distribution, Suitable type of Suspensions, Suspension Geometry Design, Suspension Arms
Design & Analysis and Optimization of Wheel Alignments were the considerations which decides the properties
of a suspension system
Weight Distribution Table 4 Weight Distribution
Weight distribution has a major impact on vehicle behavior and vehicle Weight % Weight
stability at different terrain conditions. A weight distribution in the range of Front 41% 123kg
35:65 to 45:55 (Front: Rear) is targeted for the most effective vehicle stability.
Considering the position of Center of Gravity of sprung mass and the required Rear 59% 177kg
wheel base, position of front and rear axles in the longitudinal direction with
respect to sprung mass is fixed.
Suspension Geometry
Suspension geometry plays a vital role in traction and vehicle dynamics. A larger Ground clearance make the
vehicle pass easily over different rocks and stones but increases the center of gravity height of the vehicle. Larger
Track width increases the suspension play but increases the weight of suspension arms and the vehicle’s overall
dimensions. Front view Instantaneous center is the point about which the wheel displaces vertically when
viewed from front. As far the instantaneous center from the wheel smaller is the camber gain. When the
instantaneous center is nearer, it causes a large amount of camber gain which in turn reduces the tire contact
of a particular wheel which runs over a bump. Instantaneous Center influences the position of Roll Center. Roll
center is the imaginary geometric point about which the body tends to roll when the vehicle approaches a
corner. Table 5 Suspension Geometry
Each of Track width, Ground Clearance, Center of gravity : 685mm or 27” (from ground)
Instantaneous Center, Roll Center and the Track Width : 51” or 1295mm
camber gain affects each other in one way
or the other. Optimized Roll center position, Ground Clearance : 11” or 280mm
Instantaneous center position, Track width Front: 403mm or Rear: 295mm
and Ground Clearance were arrived after Roll Center Height:
15.1” or 11.6”
several iterations of designing above
Camber Gain : Front : 0.07Deg/mm travel
geometric parameters.
Springs & Dampers
They effectively absorb, dampen and transfer shock loads to the vehicle frame. Suspension spring arrangement
design is based on the goal of having highest comfort level as well as highest endurance limit of the vehicle.
 Maximum Ride natural frequency decides the ride comfort and
Maximum Front
Condition Rear Wheel the wheel rates. Lower the frequency lower is the
Wheel Load
Load stiffness of suspension system and vice versa. A typical
ATV with a good ride comfort has frequencies in the
Static 588N 882N
range between 1.1Hz to 1.7Hz. Following is the table
Acceleration 369N 1177N showing desired ride natural frequency and the
Braking 1282N 325N obtained wheel rate.
Cornering 1895N 448N These Wheel rates have been calculated from the
vehicle’s loads at each wheel during different driving
Table 6 Load on each wheel conditions Table 7 Ride Natural Frequency
and during static condition. Front Rear
Motion ratio multiplies the force on the wheels to the spring. So a
Ride Natural
spring should be designed for the desired wheel rate obtained from 1.4 Hz 1.55Hz
Frequency
the desired ride natural frequency. Since front and rear wheels have
different wheel rates, motion ration was altered to obtain the Wheel Rate 4.91N/mm 8.6N/mm
desired properties.
Table 8 Spring Arrangement
In this design an OEM Air Suspension has been Front Rear
chosen for its property of light weight and its Spring Stiffness 26.3N/mm 26.3N/mm
additional feature of stiffness adjustments. Since the
stiffness has been fixed by the manufacturer, a Motion Ratio 0.44 0.58
suitable motion ratio and the mounting angle was Mounting angle 22o 18o
calculated to obtain the desired wheel rate.
Wheel Alignment Table 9 Wheel Alignment
Wheel alignments have a great impact on steering as well as Front Rear
suspension system of the vehicle. A slight negative camber KPI 7o -
nullifies the effect of wheel changing its camber to positive
at cornering. Castor angle favors the steering return ability Scrub Radius 40.6mm -
and makes the suspension play smoother when the vehicle Camber 3o(Negative) 0o
rides over a bump. Slight Toe in is used for the straight line
Castor 9o(Positive) -
stability. During the play of the suspension arms front vehicle
tends to change to toe out to accommodate the tie rod Toe 2o ( Toe in) 0o
length. Hence a small toe in position at static condition
maintain this effect as minimum as possible. After deciding the Castor angle, spring mount position and arms
mount position, Vehicle frame is slightly altered for accommodating the mount points effectively.
Suspension Arms Design and Analysis

Fig 2 Analysis of Rear Suspension Fig 3 Analysis of Arm Mounting Fig 4 Analysis of Front Suspension
Arm Tab Arm
 Suspension arms and tabs were designed such that it has with stand large amount of loads. Shape and material
usage has been optimized to reduce the unnecessary weight to a minimum level. A-arms of the front, Semi-
Trailer arm of the rear and the suspension mount tabs were designed in SOLIDWORKS software and analyzed
in CAE Software ANSYS to study its load withstanding capacity, stress distribution, Factor of safety and
deformation.

Steering System
The purpose of the steering system is to provide directional control of the vehicle which involves the turning of
the front wheels. Steering system has a major impact on vehicle’s behavior at various terrain conditions.
Design Objectives
 Control over the direction of travel of the vehicle
 Good manoeuvrability
 Smooth recovery from turns as the driver releases the steering wheel
 Minimum transmission of road shocks from the road surface
Steering Geometry
The steering system consists of steering wheel, steering column, rack and pinion and steering gearbox. Turning
of steering wheels depends on the steering ratio. It is the ratio between the angle turned by the steering wheel
and the angle turned by the road wheel. A higher ratio means that one has to turn the steering wheel more to
Table 10 Steering Geometry Parameters get the wheels to turn a given distance, and vice versa.
Steering ratio 8:1
Turning radius 2.17m
Inner lock angle 44.06°
Outer lock angle 27.02°
Ackerman angle 22.47°
Lock to lock turns 1.5 turns
Kingpin inclination 7o
Kingpin centre to
1155mm
Centre distance
Tie rod Length 386mm
IBJ to Center 177mm
OBJ to Center 564mm Fig 5 Steering Geometry
Ackermann Condition
cot(27.02) – cot(44.06) = 1295.40/1397
0.92=0.92
Steering Components
Several analysis were made for readily available OEM steering systems. Rack and pinion steering systems were
preferred over other types because of simple construction, low cost, less weight, smaller in size which can be
accommodated in smaller place in cockpit. The steering components undergoes combined stresses of
compression, tensile and shear. Hence the components should have enough strength to withstand all these
Stresses. The main component of steering system is the steering knuckle which experiences the highest loads.
Steering Knuckle has been designed in such a way to withstand all these loads but at the same time to be light
as possible. Aluminum grade 7075 is selected for the steering knuckle. It was designed in SOLIDWORKS software
and was tested in CAE software ANSYS.

Fig 6 Steering Knuckle Design Fig 7 Steering Knuckle Analysis

Drive Train
Drive train is a system composed of Engine, Transmission system and Wheels. The main purpose of this system
is to power the vehicle to move. An ATV is required to run at various terrains thus the wheels should have
appropriate torque and velocity. Drive train system effectively generates the energy, manipulates it according
to the requirement with respect to the track.
Design objectives
 To provide required torque
 To have highest possible acceleration
 A maximum possible velocity within the rules
Design
Drive train of the BAJA ATV comprises of a 305cc four stroke petrol engine from the company Briggs and
Stratton. Engine produces a maximum torque of 18.98Nm at 2600rpm and a maximum power of 9.8HP at
3800rpm. This torque from the engine is transferred to the wheels through a transmission system.
The first process in the design of transmission system is to find the total resistance acting on the vehicle. Vehicle
may experience different resistances in different track conditions. In order to make a safe design the maximum
possible resistance has been found. An optimum reduction ratio has been chosen to multiply the torque
produced by the engine to overcome these resistances. The torque obtained at the wheels must also be capable
to move the vehicle when it tows a load seven times larger than the load of the vehicle. This ratio in turns
reduces the velocity of the vehicle. Optimized reduction ratios were chosen to have the maximum possible
acceleration, required torque and the maximum velocity of 60Kmph.
Fig 8 Drive Train A vehicle experiences a maximum resistance when the
vehicle starts to move from rest. And the resistance
decreases as the vehicle moves further and increase the
velocity. So a gradually decreasing torque and gradually
increasing velocity with respect to engine rpm is required
to get the favorable behaviors. This requirement involves
the use of Continuously Variable Transmission (CVT) which
changes its speed ratio with respect to the running rpm.
Three different ratios were found which best suits for
different drive requirements. These ratios are almost
similar to that ratio obtained by coupling a CV-Tech®-AAB CVT Pulley with an OEM Gearbox from the Company
Mahindra & Mahindra. IC engines produce vibrations which generate fatigue stresses in the chassis. To ensure
 Table 11 Transmission Design
minimal transfer of engine vibrations to chassis, proper
engine mounts are to be placed on the frame. On survey Reduction Ratios in Max –15.66
of various mounts available, Neoprene Rubber pads is gearbox Min –6.53
known for its effective vibration damping property. NVH
CVT ratio 3:1 to 0.43:1
isolation is taken care of by use of these pads and also
to prevent noise from the power train system due to Acceleration 6.98m/s2
vibration.
Maximum Tractive
2787N
Tires & Rims effort

Tire is the most important component in a vehicle as it Maximum torque on 800.3Nm @ 2600rpm
is the point of contact with the ground and drives the wheels
vehicle. Tires are important to provide the ride height, Maximum Vehicle
59.7Kmph
required torque for acceleration and Velocity. One of Speed
the most important parameter for the selection of the
outer diameter of the tires in rear was the tractive effort
and the maximum speed of the vehicle. Width of the tire Table 12 Tires & Rim Data
has been to chosen to give the best grip at all possible conditions. Outer Diameter 23”
Rims should be as light as possible In order to reduce the unsprung
Tire Width 7”
weight of the vehicle. A suitable rim size has been selected such that the
weight should be minimum but should accommodate rotor of calculated Rim Diameter 10”
diameter with the caliper.
Aluminium Cast
Rim Type
Brakes – Non Rib Type

The hydraulic pressure that reaches each wheel's brake is then used to create friction to slow down and stop
the vehicle: the harder you push on the pedal, the more
pressure is applied to the brakes, eventually locking the
wheels.
Design Objective
 Hydraulic braking system
 Lock all four wheels
 Operates on single foot pedal
 Ease of fabrication
Fig 9 Brake Circuit
Selection of system
Hydraulically actuated disc
The advantages and disadvantages of Choice of brakes
brakes
different types of brake system studied.
OEM (Ambassador brake steel
The diagonal braking lines were used Brake line
pipe)
last year and minor errors were found
Loosely hanging pipes OEM (Hyundai Rubber tube)
in the system. That is, when one
Frictional coefficient 0.45
diagonal fails the vehicle would starts
Brake effort 400 N
skidding to one side and hence the
Deceleration value 29.07 ms-2
stability of the vehicle was lost. Hence,
this year in-order to overcome it, the Stopping distance 3.87 m
front rear split system is used. It was Braking force 9616.32 N
found that that this type of circuit has Pedal ratio 5:1
better biasing. Master cylinder pressure 7.05 MPa
Rise in brake disc temperature 14.25° C
Table 13 Brakes Design
Design procedure
First the maximum speed of the vehicle was taken & the force
required for stopping the vehicle was calculated. Using the
calculated force we bought the calipers and rotor discs. The force
required for the calipers to actuate was calculated and the
corresponding master-cylinder which was able to give that amount
of force was bought. Then the pedal force was fixed according to
which the pedal ratio was calculated and the corresponding OEM
pedals were bought.
Fig 10 Thermal Analysis of Brake Rotor
Electrical System
Fig 11 Electrical Circuit
The electrical system contains the brake lights and emergency stop
kill switches. There are two kill switches in the vehicle one over the
reach of the driver, and the other one at the top right side of the
rear body panels of the car. The second kill switch is also called as
an emergency switch which is mainly used by the team members,
volunteers and the judges at the competition in case of exigency.
The kill switches which when pressed connects the engine with the
ground terminal (fig) leads to engine turn off immediately. When
the driver actuates the brake the circuit closes which connects the battery with the brake light (fig ). However
pressing the kill switches does not kill the lights. .

Seat, Restrains and Safety

All restraints are SFI/ISI Rated as per the rules and requirements. They have been chosen based on harness
needs and belt thickness. Off Road racing seat is purchased from RECARO®
Seat and Restraints selection
The seat is slotted for a five-point harness restraint. We chose the Takata® latch-and-link-point harness due its
conformity with SFI standards. It provides good quality and reliability at a fair cost, thus justifying the team’s
selection. A Fire Extinguisher of required standard is used, and as a precaution another is carried. It is rated by
the Indian Equivalent of UL 5 BC rating. Proper mounts are provided to support them. Arm restraint is of SFI
standard, the neck support is a 360o wound type with SFI rating. The driver suit is a single layered SFI 3.2A rated
fire resistant suit. Helmet is motocross type with ISI rating. Hence all safety norms are perfectly met.

Conclusion
The goal of the project was to create an off-road recreational vehicle that exceed the SAE regulations for
safety, durability and maintenance, as well as to achieve a vehicle performance, aesthetics and comfort that
would have mass market appeal for the off-road enthusiast. This goal was achieved by the team with its
collective effort and coordination. The multidisciplinary gain of this project is what makes it successful and
surely a knowledgeable experience for the entire team.

References
 Shigley, J.; Mischke C. ; 
 Budynas, R. (2003) “Mechanical Engineering Design”. Seventh edition.
McGraw Hill.
 Spotts, M.F.; Shoup, T.E. (2004) “Design of Machine elements”. Seventh edition. Prentice Hall. 

 Miliken & Miliken ; “Race Car Vehicle Dynamics”
Appendix

Fig 1: Isometric view of Roll-cage frame Fig 2: Front impact analysis

Fig 3: Rear impact analysis Fig 4: Side impact analysis

Fig 5: Torsional analysis