team stratos baja preliminary design report 2010

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Team Stratos B.I.T

Design Report

Manish.O Team Captain

Dr. T. Jagadish Faculty Advisors

ABOUT THE EVENT

The objectives of the Baja SAEINDIA 2010 competition are to design and manufacture a fun, versatile, safe, durable, and high performance off road vehicle.

Team members must ensure that the vehicle satisfies the limits of set rules, while also generating financial support for the project, and managing their educational responsibilities.

This vehicle must be capable of negotiating the most extreme terrain with ease.

INTRODUCTION

Baja SAEINDIA is a collegiate design competition sponsored by the Society of Automotive Engineers (SAE) that attracts engineering student teams from all over India. Each team’s goal is to design, build, test, promote, and race a prototype of a single seat off-road vehicle hypothetically intended for production and eventual sale to the weekend off-road enthusiast. Team Stratos comprises of 20 students of mechanical engineering from the BANGALORE INSTITUTE OF TECHNOLOGY, BANGALORE. Team Stratos’ main design objective was to ensure its vehicle design is able to complete all tasks without any breakdowns, whilst being an appealing vehicle to potential customers. Team Stratos met its design objectives by dividing the vehicle into major component subsystems. The team was divided into groups, with each group being responsible for a specific subsystem that was designed according to the team objectives and within set rules. An open source approach was adopted for all the designing and analyzing work. Hence, contributions from other members of the collegiate club were also encouraged.

INNOVATION

RACE ERGONOMICS – A wide field of vision will be incorporated by increasing distance between A-pillars. This will allow ease of maneuverability and cornering ability.

DRIVER ERGONOMICS – A spacious driver cabin will allow easy ingress and egress from the vehicle and a riding position designed for maximum driver comfort.

FRAME - A light and rigid chassis will ensure good vehicle handling while increasing driver safety in a race.

SUSPENSION – An independent double wishbone suspension at front and rear intended to give a comfortable ride whilst not compromising on shock absorption in an off-road terrain.

STEERING – Rack & pinion steering assembly to minimize force feedback from track conditions. Disc brakes installed in front will enable quick braking.

POWERTRAIN – Spacious engine bay for easy serviceability and repairs under intense track conditions. Directly coupled (4+1 reverse) transmission.

MAIN SECTION

FRAME DESIGN

Initially the general shape of the frame was sketched using sketcher software (Google Sketch Up). Different shapes and sizes were considered. Finally a frame shape was chosen with form and function in mind. (Fig 1)

Before the chassis design was finalized, a 1:1 mock up of the frame was built out of bamboo.

The mock up allowed the team to visualize the frame in 3D, as well as mock up the powertrain, steering, and brake systems to ensure that there is adequate space.

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1

(Fig 1)

(Fig 2)

Basic geometrical calculations were done to obtain vehicle dimensions. All main chassis members were scrutinized to ensure compliance with set competition rules. An optimum riding position and driver leg room was finalized.

Position of steering wheel, control pedals, side impact members, and seat were considered with a view to maximize cabin room and driver comfort.

Horizontal spacing between A-pillars was maximized at the base to improve the driver’s field of vision.

Engine bay area was enlarged to fit powertrain members and leave space for easy servicing.

Different hard points for location of suspension, springs, steering, etc were considered. (Fig 3)

(Fig 3)

After studying the mock-up and making necessary changes to the frame, a CAD model of the frame was made with a view to perform finite element analysis and testing. (Fig 4, 5, 6)

(Fig 4)

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(Fig 5)

(Fig 6)

In the CAD model, the final geometrical specifications of the vehicle were implemented.

Adequate bracing was given to reduce stresses in main chassis members and ensure proper transmitting of forces to chassis. All corners of the roll cage were braced as shown.

The CAD model was analyzed using ANSYS FEA software for static analysis under self-weight, frontal impact, side impact, and roll-over impact as well as natural frequency and torsion analysis. FEA model used beam elements.

Under self-weight, the frame was deforming very little. Stress was maximum in the front of the roll hoops and firewall members. The firewall itself will act as additional bracing here. (Fig 7)

1

MN

MX

XYZ

0

.019307.038615

.057922.07723

.096537.115844

.135152.154459

.173767

JUN 4 200920:22:57

NODAL SOLUTION

STEP=1SUB =1TIME=1USUM (AVG)RSYS=0DMX =.173767SMX =.173767

(Fig 7)

In the frontal impact analysis, a 5KN force was used as it was assumed impact would be with a stationary object. The deformation was minimal and proved the frame was rigid enough to withstand a crash. (Fig 8)

1

MN

MX

XY

Z

0

.019844.039688

.059532.079376

.09922.119064

.138908.158752

.178595

JUN 6 200915:58:05

NODAL SOLUTION


(Fig 8)

In side impact, hypothetically with another Baja vehicle, a 3KN force was applied to the side impact member. Deformation was again in the roll cage. (Fig 9)

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MN

MX

XY

Z

TEAM STRATOS-BIT

0.013972

.027943.041915

.055887.069858

.08383.097802

.111773.125745

JUN 6 200915:26:44

NODAL SOLUTION


(Fig 9)

The natural frequency was analyzed using modal analysis in 3 sub-steps. Maximum vibrations and consequently displacements were occurring again in the roll cage members. Deformation was within limits, but powertrain etc will be well isolated using rubber bushings to cancel vibrations. (Fig 10, 11, 12)

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1

MN

MX

XYZ

0

.064413.128826

.193239.257652

.322065.386478

.450891.515304

.579717

JUN 6 200915:10:32

NODAL SOLUTION

STEP=1SUB =1FREQ=1.463USUM (AVG)RSYS=0DMX =.579717SMX =.579717

1

MN

MX

XYZ

0

.071934.143868

.215802.287736

.359671.431605

.503539.575473

.647407

JUN 6 200915:10:50

NODAL SOLUTION


1

MN

MX

XYZ

0

.038391.076782

.115172.153563

.191954.230345

.268735.307126

.345517

JUN 6 200915:11:11

NODAL SOLUTION


(Fig 10, 11, 12)

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MN

MX

XYZ

0

.085391.170783

.256174.341566

.426957.512349

.59774.683132

.768523

JUN 12 200916:40:52

NODAL SOLUTION


(Fig 13)

In rollover analysis, a 2KN force was applied at an angle to the top front of the roll hoop. The Maximum deflection was observed in the roll hoop (fig 13).

1

MN

MX

XYZ

0

.5717841.144

1.7152.287

2.8593.431

4.0024.574

5.146

JUN 12 200916:46:35

NODAL SOLUTION

STEP=1SUB =1TIME=1USUM (AVG)RSYS=0DMX =5.146SMX =5.146

(Fig 14)

The design was also tested for torsional loading and was found to be stable enough to withstand a load of 10KN.This was applied as a couple on the extreme ends( in side view perpendicular to the plane of the paper) .

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(Fig 15)

For analyzing the wishbones, the A-arms that support the shock absorbers were chosen. These were the lower arm in front and the upper arm at the back. A force of 800N in Y direction and a force of 400N in Z direction was applied. (Fig 16b)

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MN

MX

0

.688E-03.001376

.002064.002751

.003439.004127

.004815.005503

.006191

JUN 11 200920:42:28

NODAL SOLUTION


(Fig 16a & b)

SUSPENSION:

TENTATIVE DIMENSIONS FOR THE WISHBONES:

Upper wishbone length: 405.11 mm Upper wishbone angle: 30.23 degrees Lower wishbone length: 438.72 mm Lower wishbone angle: 15.87 degrees Distance between mounting points on hub: 141 mm Distance between mounting points on chassis: 236 mm SAL (distance between the intersection of the hubs and the wishbones): 514 mm

STEERING AND BRAKES:

Steering used on the vehicle will be a rack and pinion type.

Brakes will be single rotor disc brakes with single/multi calipers, depending on the braking force required the no of calipers will be decided/

POWERTRAIN:

The Differential gearbox is a 4 forward 1 reverse type from a Mahindra Alfa. It will be directly coupled onto the final driveshaft. This can be done by using universal couplings.

GEAR TRAIN:

The Gear train will be a synchro-mesh type.

SAFETY AND ACCESSORIES:

The front part of the vehicle has provisions to incorporate a crumple zone before eventual manufacture and sale to the consumer. This is apart from the fire extinguisher and the firewall already provided. A 4/5 point seatbelt, an adjustable bucket seat setup, Specification tail lamp and headlights. Foam padding on the roll cage.

MATERIAL USED:

All the analysis has been done using SAE 1020 carbon steel as the frame material. We have chosen this steel because it is a general purpose mild steel, low-carbon machinery steel, having good over-all mechanical properties. Easily machinable and weldable. It has a nominal carbon content of 0.20% with approximately 0.50% manganese

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FINAL MODEL

(With tentative specifications)

Ground Clearance for now has been calculated as 12” Height of the vehicle 55”

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CONCLUSION:

The final design of the vehicle is as shown above. The figures provided in the analyses and the dimension lists have been approximated to the least extent possible. These have been made keeping into account the fact that there might be changes to the design in later stages of the competition. A sincere effort has been made to keep the report simple and extensive.

APPENDIX:

Page No.

Ergonomics 01

Introduction 01

Innovation 01

Frame design 02

Model analysis 03

04

05

Final Specifications with model 06

Suspension 01

05

Steering and Brakes 05

Powertrain 05

Material used 05

team stratos baja preliminary design report 2010

Documents

vehicle design

impact members

team members

baja vehicle

appealing vehicle

vehicle dimensions

chassis design

design objectives