BASICS OF THE ATV A - ARM DESIGNING

WISHBONE ARMS :

Design for optimal geometry of the control arms is done to both support the race-weight of the vehicle as well as to provide optimal performance. Design of the control arms also includes maximum adjustability in order to tune the suspension for a given task at hand. The front A-arms are constructed of 3mm wall thickness, 1 inch diameter 4130 round Chrome moly tube. FEA was also performed on the front arms, and proved them to be capable of handling the stresses exerted on them in extreme situations. Also kinematic analysis on the control arms was done as shown in the figure below to determine the dimensions of cross-section of control arms.

FEM OF WISHBONE ARM (A-ARM ) :

Finite element analysis has also been conducted on the front arms. The stresses created in the part can be seen in Figure. The biggest reason for choosing this design is that it only requires one piece, using a simple jig, to be fabricated. It has been determined that the tubing used for the suspension arms will be ASTM 106a steel. It will be 1” diameter with 3” wall thickness. This was determined after comparing the weight and material properties for several sizes of tubings.

Determination of length of wishbone arms:-

The length of the wishbone is found virtually in CATIA V5R20. As we know the pivot points of wishbones as well as the ball joint points on the knuckle.

Roll Centre Height:-

The roll centre height was found in CATIA V5R20 by extending the wishbone arm axis to its instantaneous centre and then from the instantaneous centre a line is drawn through the tire centre on the ground which intersect the vehicle centre line, this point is called roll centre and distance of this point from the C.G is the roll centre height.

BASICS OF ATV SUSPENSION DESIGNING

                              BASICS OF ATV SUSPENSION DESIGNING

OBJECTIVE -

1. Designing a suspension which will influence significantly on comfort, safety and maneuverability.
2.Contributing to vehicles road holding/handling and braking for good active safety and driving pleasure.
3. Protect the vehicle from damage and wear from force of impact with obstacles (including landing after jumping)
4. Maintaining correct wheel alignment.

DESIGN METHODOLOGY -

The overall purpose of a suspension system is to absorb impacts from coarse irregularities such as bumps and distribute that force with least amount of discomfort to the driver. We completed this objective by doing extensive research on the front and rear suspension arm’s geometry to help reduce as much body roll as possible. Proper camber and caster angles were provided to the front wheels. The shocks will be set to provide the proper dampening and spring coefficients to provide a smooth and well performing ride.

FRONT SUSPENSION :

1. For our front suspension we chose one with a Double arm wishbone type suspension. It provided specious mounting position, load bearing capacity besides better camber recovery.

2. Front Unequal Non Parallel double wishbone suspension .

3. The tire need to gain negative camber in a rolling situation, keeping the tire flat on the ground .

                                             





REAR SUSPENSION                                                                       MONOSHOCK MOUNTING ON SWING ARM
For our Rear suspension we chose Swinging Arm with Monoshock type suspension. Using monoshock over dual shocks is advantageous due to ease of adjustment as there is only single damping unit and smaller unsprung mass.

BASICS OF THE ATV CHASIS DESIGNING

Designing purpose of this Quad bike is to manufacture an off road vehicle that could help in transportation in hilly areas, farming field and as a reliable experience for a weekend enthusiast. In order to accomplish this task, different design aspects of a Quad Bike. vehicle were analyzed, and certain elements of the bike were chosen for specific focus. There are many facets to an off-road vehicle, such as the chassis, suspension, steering, drive-train, and braking, all of which require thorough design concentration. The points of the car I decided to specifically focus on were the chassis, drive-train, and suspension. The most time and effort went into designing and implementing these components of the vehicle because it was felt that they most dramatically effect the off-road driving experience. During the entire design process, consumer interest through innovative, inexpensive, and effective methods was always the primary  goal.

                                                              FRAME DESIGN

The chassis is the component in charge of supporting all other vehicle’s subsystems with the plus of taking care of the driver safety at all time. The chassis design need to be prepared for impacts created in any certain crash or rollover. It must be strong and durable taking always in account the weight distribution for a better performance.

MATERIAL                             1018                     4130                      4130

                                                 STEEL                 STEEL                  STEEL

OUTSIDE

DIAMETER                           2.540 cm                2.540 cm              3.175 cm

WALL

THICKNESS                          0.304 cm               0.304 cm              0.165 cm

BENDING

STIFFNESS                            3791.1 Nm^2        3791.1 Nm^2       3635.1 Nm^2

BENDING 

STRENGTH                           391.3 Nm              467.4 Nm             487 Nm

WEIGHT PER 

METER                                   1.686 kg               1.686 kg                1.229 kg

4130 Chrome Moly Steel is the best suitable material so following it we selected it over 1018 Steel because 4130 Steel has a greater strength to weight ratio. Along with material selection, tube diameter was also taken into consideration. Different sizes of tube were considered for the frame. It was decided to create the Roll Cage using 1 inch OD and 3 mm wall thickness, 4130 Steel tubing as it was thought to be more structurally sound than a larger diameter tube

Finite Element Analysis (FEA) 

Finite element is a method for the approximate solution of partial differential equations that model physical problems such as: Solution of elasticity problems , Determine displacement, stress and strain fields. Static, transient dynamic, steady state dynamic, i.e. subject to sinusoidal loading, modes and frequencies of vibration, modes and loads of buckling. Roll cage analyzed at much higher forces than in real case scenario 

Loading Analysis 

To properly approximate the loading that the vehicle will see an analysis of the impact loading seen in various types of accident was required. To properly model the impact forces, the deceleration of the after impact needs to be found. To approximate the worst case scenario that the vehicle will see, research into the forces the human body can endure was completed. It was found that human body will pass out at loads much higher than 7 g. And the Crash pulse scenario standard set by industries is 0.15 to 0.3 sec. We considered this to be around 2.5 sec. It is assumed that worst case collision will be seen when the vehicle runs into stationary object.

FEA of Roll cage- 

A geometric model of the roll cage was constructed in CATIA and was imported into ANSYS Mechanical in IGES format. ANSYS was used to create a finite element formulation of the problem for both static structural analysis & Dynamic analysis. The Elastic Straight PIPE 16 element was used for creating frames and automatic fine meshing is done for the entire roll cage, with real constant as the thickness & diameter of the pipes

For AISI 4130 alloy steel-

Young’s modulus-205 GPa

Poisson’s ratio- 0.27-0.29 (say 0.28)

For all the analysis the weight of the vehicle is taken to be 272 kg s.

1. ROLL CAGE 3D CADMODEL (      CATIAV5R20)

2. ROLL CAGE   ( FABRICATED )

                        

                                   ROLL CAGE DESIGN SPECIFICATIONS 

                       Type                                                                  Space Frame

Material                                                                              Normalized AISI 4130 Chrome-

                                                                                             Moly. Steel

Mass of Roll cage                                                                 21.61 kg                                                             

Length of Roll cage                                                              64.14 inches

Width of Roll cage                                                               10.5 inches

Height of Roll cage                                                              22.29 inches

Total length of pipes                                                            13.04 m

Weld joints                                                                           42

No. of Bends                                                                        15

Cross section                                                                        Outer Diameter -

                                                                                             25.4 mm

                                                                                             Thickness - 3 mm

Static Analysis:-

1)Frontal Impact

2) Rear Impact

3)Side Impact

4)Roll over test

5)One wheel bump test

6)Torsional Rigidity analysis

7)Heave analysis

Frontal Impact Analysis – 

Frontal Impact                     6 G  (15303.6 N)

Max. Deformation                2.43 mm

Max. Stress                           150.331 Mpa

Factor of Safety                    3.05  ( > 2 Design is Safe )

Side Impact Analysis -

Side Impact                         3 G (7651.8 N)

Max. Deformation              2.95 mm

Max. Stress                         206.196 M pa

Factor of Safety                  2.23  ( > 2 Design is Safe )



Rear Impact Analysis –

Rear Impact                      3 G ( 7651.8 N )   

Max. Deformation            0.62 mm

Max. Stress                        53.962 M pa

Factor of Safety                 8.52  ( > 2 Design is Safe )

Roll Over Impact Analysis –

Roll Over Impact              3.5 G ( 8927.1 N)

Max. Deformation             0.46 mm

Max. Stress                         80.63 M pa

Factor of Safety                  5.70 ( > 2 Design is Safe )