chassis design report 2016

TEAM SRIJAN

FORMULA SAE TEAM

BIT MESRA

CHASSIS DESIGN REPORT

(2015 – 2016)

i

TABLE OF CONTENTS

1. PROJECT OVERVIEW……………………………………………..1 1.1. Introduction………………………………………………….1

1.2. Analysis of last year’s chassis design……………………….1

1.3. Project scope………………………………………………....2

1.4. Design requirement………………………………………….2

1.4.1. Constraints……………………………………………..2

1.4.2. Criteria…………………………………………………3

1.4.3. Final design…………………………………………….3

1.4.4. Formula SAE rules…………………………………….4

1.5. Design decision……………………………………………….4 1.5.1. Chassis construction method………………………….4

1.5.2. Chassis material consideration………………………..5

1.5.3. Selection of type of tube………………………………..6

1.5.4. Rear bulkhead………………………………………….7

1.5.5. Weight of frame………………………………………...7

2. DESIGN METHODOLOGY………………………………………...8

2.1. Introduction………………………………………………….8

2.2. Design process………………………………………………..8

2.2.1. Mock chassis……………………………………………8

2.2.2. Solidworks modelling…………………………………10

ii

3. SIMULATION AND ANALYSIS…………………………………..14

3.1. Introduction…………………………………………………14

3.2. Frame analysis and validation……………………………..15

3.2.1. Torsional stiffness test ……………………………….15

3.2.2. Impact test…………………………………………….22

4. RESULT AND DISCUSSION………………………………………23

4.1. Introduction…………………………………………………23

4.2. Results ………………………………………………………23

4.3. Discussion……………………………………………………24

5. OTHER COMPONENTS………………………………………….25

5.1. Impact attenuator………………………………………….25

5.2. Anti-intrusion plate………………………………………..26

5.3. Floor and firewall……………………………………….....27

5.4. Jacking cum push bar……………………………………..27

6. MANUFACTURING………………………………………………29

6.1. Manufacturing of frame…………………………………..29

6.1.1. Cock pit………………………………………………30

6.1.2. Front………………………………………………….31

6.1.3. Rear…………………………………………………..32

7. CONCLUSION…………………………………………………….33

1 | P a g e

CHAPTER -1:

PROJECT OVERVIEW

1.1 Introduction

The purpose of this report is to provide a final summary of the Chassis Design for formula student

project. This document will present an overview of the project, the project scope, and the design

requirements, while outlining the selected final design. This year the chassis has been designed for

maximum adjustability, with focus on reliability, weight reduction and manufacturing. The

objective of the chassis design group was to design a chassis in accordance with the FSAE rulebook

along with providing a lighter, stiffer frame keeping in mind the aesthetics and ergonomics of the

driver. The design started with a thorough study of the rulebook. The areas which needed a

change were identified keeping in mind last year’s design. A mock chassis was constructed and the

dimensions of the cockpit and foot well area were noted. It was ensured that enough room is

given to the driver for egress and that he had improved visibility. The 95th percentile male rule was

kept in mind while deciding the heights of the roll hoops.

1.2 ANALYSIS OF LAST YEAR’S CHASSIS DESIGN

From last year’s chassis design it was inferred that the height of main hoop could be reduced

significantly keeping in mind the two-inch rule. This will not only reduce the mass of the chassis

but also lower the centre of gravity of the entire vehicle. Dimensions of cockpit also had to be

increased to incorporate shifter handle while satisfying cockpit template, as last year’s design was

not compliant with cockpit template rule. The part of the chassis behind the main hoop is

unnecessarily long and it could be made more compact. The additional tubes used for the

triangulation along with front hoop bracing and front bulkhead support could be reduced to save

weight. A large number of brackets were used to mount the floor and body panels which

increased the weight of the frame. Impact attenuator was mounted with bolts which led to its

damage. So, a new method of mounting was incorporated. Mounting the headrest was a problem

as it couldn’t sustain the force of 890 N.

2 | P a g e

1.3 PROJECT SCOPE

The chassis is an integral part of a formula-style race car; encompassing the frame, suspension,

steering, and hub and upright assemblies. For this project, the chassis is defined as including all

frame members, with the forward vehicle limit being the front bulkhead, and the rear vehicle limit

being the differential mounts. The project scope will include design selection, use of modelling

tools and simulation, iterative design refinement, and construction of the final design.

1.4 DESIGN REQUIREMENT

In order to select the final design of our project, the group has created several design

requirements which have been divided into constraints and criteria. These design requirements

are a combination of rules and self-set goals to improve upon the chassis of last year’s vehicle and

the success of the design group will be based on being able to effectively meet these

requirements.

1.4.1 CONSTRAINTS

The following requirements must be followed in the design of the chassis. If any of these requirements are not met, the design will be considered unsuccessful. General

Must meet all Formula SAE requirements, as outlined in the 2015 Formula SAE Rules.

Must ensure the safety of the driver at all times.

Frame

Weight of frame must be within 30-35 kg.

Torsional stiffness of chassis above 1800 N-m/deg.

All four design group members must be able to exit from the vehicle in 4.5 seconds.

Lowering of centre of gravity and polar moment of inertia by reducing the dimension of chassis laterally and longitudinally.

3 | P a g e

1.4.2 CRITERIA The following requirements should be followed in the design of the chassis. These criteria are not critical to the success of the chassis, however they will enhance performance. Frame

Strengthen the frame by minimizing the number of bends.

Including rear bulkhead in the design.

Using ANSYS software for torsional stiffness and modal analysis.

1.4.3 FINAL DESIGN

The Formula SAE rules were used as strict guidelines throughout the design process to ensure the safety and eligibility of the chosen final design. To select the final design, four chassis designs were compared. After subjecting each chassis to the design process outlined in the Design Selection Report, a final design was chosen based on the design requirements. TABLE 1.1

FRAME FINAL DESIGN

o CONSTRUCTION STEEL SPACEFRAME. o MATERIALS AISI 1018. o MANUFACTURING LASER CUT NOTCHED TUBES, MIG WELDING.

1.4.4 FORMULA SAE RULES.

The Formula SAE rules provide strict guidelines which must be adhered to for the frame to be able

to compete in the events. There are several templates which must be able to pass through all

points of the frame to ensure adequate spacing for the driver. The cockpit internal cross section

template and the cockpit opening template should be able to pass through the frame. The 95th

percentile male template was also used while deciding cockpit dimensions and angle of seat.

These templates ensure that the frame is able to fit drivers of all sizes, and ensures that the driver

is comfortable, can easily access controls, and can easily enter and exit the vehicle.

4 | P a g e

1.5 DESIGN DECISION

Following design decisions were made by chassis design group during the project. These decisions

were based on availability, procurement and manufacturability of materials.

1.5.1 CHASSIS CONSTRUCTION METHOD

Tubular spaceframe The most common frame type, the tubular spaceframe, is a structure composed of many small,

usually round tubes bent to shape and welded together. The Formula SAE rules dictate many of

the tubing sizes for a steel tubular spaceframe, and construction of any other type of chassis

requires proof that the alternate structure is as strong as or stronger than a similar tubular

spaceframe structure.

Metal Monocoque A monocoque chassis is a structure that constitutes both the frame and the body. By combining these two critical components into one piece, it is possible to build a torsionally stiff Car. In a metal monocoque design, the chassis and body are fabricated from aluminium or steel sheet, welded or riveted together.

Composite Monocoque

Composite monocoque frames are usually among the lightest. The strength to weight and stiffness to weight ratios of carbon fibre and similar composite materials are generally much higher than those of steel or aluminium, and the non-uniform nature of a moulded frame allows for a great deal of optimization. However, composite monocoques usually require a unique mould for production, and a design change generally requires a new mould to be made. Composite monocoques are rarely easily repairable, and the materials required for their construction are expensive and often difficult to work with.

Factors Cost Availability Manufacturability Weight Stiffness total

weightage 5 4 4 3 3 STEEL SPACEFRAME 4 5 5 2 2 72 CARBON FIBRE MONOCOQUE 2 2 2 4 4 50 SHEAR PANELS 3 4 3 3 3 61 TABLE 1.2: Decision matrix for selecting the type of frame

5 | P a g e

CONCLUSION: This makes it clear that spaceframe is the best option, despite the lack of stiffness. Therefore, tubular spaceframe chassis was chosen as the type of chassis as it was difficult to procure and fabricate carbon fiber monocoque chassis and team’s budget didn’t allow the use of CRPF.

1.5.2 CHASSIS MATERIAL CONSIDERATION

The team decided to use a tubular spaceframe due to cost, ease of construction, and facilities available. Because the chassis is a tubular spaceframe design, the materials used in its construction were limited to readily available and easily weldable materials. In the interest of simplicity, it was decided that all tube members would be made from the same type of material. The following materials were considered:

Steel

The most common material for tubular spaceframes, steel retains its strength and ductility after welding. It is inexpensive, easy to procure and fabricate. The Formula SAE rules dictate tubing sizes for steel, and the use of any other material requires the completion of a structural equivalency form.

Aluminium Aluminium, while not as strong as steel, is lighter. Its stiffness is roughly one third that of steel;

however, so is its weight. It can be welded with common TIG and MIG processes; however, it loses

significant strength unless heat treated. When used on a tubular spaceframe chassis, it must be

accompanied by a structural equivalency form.

Conclusion:

Additionally, the main and front hoops must be made from steel. For ease of construction, the

chassis is made from steel.

6 | P a g e

1.5.3 SELECTION OF TYPE OF TUBE

The design group had to select the tube to be used between SAE 4130 or AISI 1018. Comparisons

are as follows:

TABLE 1.3: COMPARISON

From the above tables we can see that SAE 4130 grade is more versatile than 1018 steel tubes.

Comparing them on above parameters we find that 4130 tubes has more tensile strength, yield

strength, hardness due to addition of molybdenum and chromium. But 4130 tube requires heat

treatment for its welding and we don’t have heat treatment facility in our college. Moreover 4130

is more expensive than 1018. Therefore we have decided to go with 1018 tubes as it provides

sufficient strength which is required to make a rigid frame.

7 | P a g e

1.5.4 REAR BULKHEAD

The last year’s car had large rear frame which increased the weight of the frame due to large

number of tubes. The frame can be made more compact by reducing the length of the frame and

thus the wheelbase. To overcome these problems rear bulkhead was incorporated which not only

reduced the weight and number of tubes but also helped in mounting of the differential. The

transmission shafts were kept outside the main structure thus making the frame design more

compact with significant weight reduction. The upper member of the rear bulkhead is chosen to

be a curved beam, as the bending stiffness of the curved beam is more than that of a straight

beam.

Figure 1.1 Rear Bulkhead

8 | P a g e

Figure 1.2 FEA of Rear bulkhead with max deflection of 0.03mm

Figure 1.3 FOS of Rear Bulkead - 5.1

1.5.5 WEIGHT OF FRAME

One of the main criteria for the frame was weight. Having a light frame is very important as a

lighter car allows for faster acceleration, better handling and more efficient fuel consumption. Last

year frame weight was 40kg and the team this year aimed for a frame weight within 30-35 kg. This

was accomplished through careful consideration of member placement. The goal was to maximize

the torsional stiffness within this target weight.

9 | P a g e

CHAPTER- 2:

DESIGN METHODOLOGY

2.1 INTRODUCTION

This chapter explains the steps that were taken in designing a spaceframe chassis and how the

simulation of the chassis was performed and also the factors that were considered while

designing.

2.2 DESIGN PROCESS

The design of the chassis was done in two stages. The first or preliminary design used mock

chassis to determine the location of all components and boundaries designated by the Formula

SAE Competition Rules. The second or detailed design used solidworks to detail all information

from the preliminary design packaging all components in their specific location. The use of

solidworks to finalize the design of the frame will make the manufacturing process of the chassis

simplified. The program gives all dimensions to all parts, including bend angles, notch angles and

joint fitting parameters.

2.2.1 MOCK CHASSIS

The first step in design process is to construct a mock model to validate the dimensions of cockpit

and foot-well.

Dimension that were to be identified from mock chassis were:

Main Hoop and Front hoop height, Cockpit dimensions (lateral distance between side

impact structures), Foot-well dimensions, Shoulder harness location.

The dimensions were obtained keeping in mind the Percy rule (2- inch rule).

Inputs required for proper mock model usage:

10 | P a g e

Seat location, driver’s visibility, pedal assembly dimensions, approximate Steering location.

A simple wireframe model of frame from bulkhead to main hoop was made in Solidworks, keeping

members to a minimum. Plywood and MDF boards were used for construction of Mock chassis. It

provided a very rigid structure and relatively it was easier to work on. Besides we also had the

flexibility of adjusting the dimensions as per the need of the driver. This provided us with accurate

dimensions.

Figure 2.1: Mock chassis construction

11 | P a g e

2.2.2 SOLIDWORKS MODELLING

After the minimum required dimensions of the foot-well was decided, the same was given to the

Vehicle Dynamics team for calculation of suspension A-arm end points or hard points. After

receiving the suspension geometry, design of frame was started from the front end of the frame.

It was kept in mind to keep the frame well triangulated so that only tensile and

compressive forces act on tubes.

Sketches were added for suspension brackets.

The end points of bracket sketches were the primary frame nodes where suspension

components would be linked. Same was done for the rear.

The requirements of the rules were kept in mind as the design proceeded (Front bulkhead,

Front bulkhead support structure etc.)

The cockpit and foot well dimensions from mock were used to generate the final

wireframe model of the front end.

For the rear, we made used of Engine CAD model to design the engine box. The differential

was added after the engine box.

After the sketch was ready, weldments were added to the sketch. Tubing sizes were added

according to the rules for roll hoops, bracings etc. Trim and extend feature was used for profiling

of tubes with the aim to attain a simpler profile.

12 | P a g e

Figure 2.1: WIREFRAME MODEL OF CHASSIS 1.


13 | P a g e


14 | P a g e

Figure 2.4: wireframe model of chassis 4

With the given suspension geometry, 4 different designs of frame were constructed and analysis

was done for the same using solidworks keeping in mind the FSAE rules.

15 | P a g e

CHAPTER 3

SIMULATION AND ANALYSIS

3.1 INTRODUCTION

After the initial design for chassis is developed it must be analysed. Conventionally in FEA, the

frame is subdivided into elements. Nodes are placed where tubes of frame joints. There are many

types of elements possible for a structure and every choice the analyst makes can affect the

results. The number, orientation and size of elements as well as loads and boundary conditions

are all critical to obtain meaningful values of chassis stiffness.

Beam elements are normally used to represent tubes. The assumption made in using beam

elements is that the welded tubes have stiffness in bending and torsion. If a truss or link elements

were used, the assumption being made would be that the connections do not offer substantial

resistance to bending or torsion. Another aspect of beam elements is the possibility of including

transverse shearing effects.

While modelling the stiffness contribution from each part of the frame, method to apply the loads

and constrain the frame plays significant role for an accurate analysis. Accurate analysis means to

predict the stiffness of frame close to actual stiffness as the frame operates in real conditions. The

problem here has normally been how to constrain and load a frame, so to receive multiple load

inputs from a suspension, while it has been separated from that suspension and many other such

problems. For practical reasons, it is recommended that the load on the chassis frame, including

its own weight should be applied at the joints (nodes) of structural members. These point loads

were statistically equivalent to the actual distributed load carried by the vehicle.

16 | P a g e

3.2 Frame Analysis and Validation:

To determine the stiffness of a proposed frame design before construction, finite element analysis

could serve the purpose. The analysis of chassis was done for two loading cases, in first torsional

load was applied on the chassis, second, impact test was done to check the safety of the different

frame models.

3.2.1 Torsional stiffness test:

An ideal chassis is one that has high stiffness; with low weight and cost. If there is considerable

twisting, the chassis will vibrate, complicating the system of the vehicle and sacrificing the

handling performance. Thinking of the chassis as a large spring connecting the front and rear

suspensions: if the chassis torsional stiffness is weak, attempts to control the lateral load transfer

distribution will be confusing at best and impossible at worst 1 . Therefore, predictable handling is

best achieved when the chassis is stiff enough to be approximated as a rigid structure. There are

numerous reasons for high chassis stiffness. A chassis that flexes is more susceptible to fatigue

and subsequent failure, and “suspension compliance may be increased or decreased by bending

or twisting of the chassis.

To check the structural integrity of the frame, a torsional load was applied on the front control

arms while the rear control arms was fixed. This load is created by a positive static load on one

side of the chassis and negative on the opposite side through the centre of the wheel.

This analysis is the most critical since it defines the reaction of every member throughout the

chassis while cornering.

The torsional stiffness analysis was done in solidworks 2014 using FEA beam model. The load and

constraints applied are as below:

The front wheel centers were connected to the suspension hard points of the frame using truss

members. This was to simulate wishbones and pushrods which transfer loads to frame axially.

This setup is equivalent to the frame being twisted by an applied torque at the front while it is

fixed at the rear.

17 | P a g e

F: Force applied

Τ: Applied Torque d: Distance between wheel centres δ: Deflection of wheel centre φ: Angular deflection of wheel centre

CHASSIS 1:

Figure 3.1: torsional load on chassis 1.

F=500 N

d=1.105m

For left wheel:

δL = 3.278 mm

φL= 𝐷𝑒𝑓𝑙𝑒𝑐𝑡𝑖𝑜𝑛 𝑜𝑓𝑙𝑒𝑓𝑡 𝑤ℎ𝑒𝑒𝑙 𝑐𝑒𝑛𝑡𝑟𝑒

𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑜𝑓 𝑙𝑒𝑓𝑡 𝑤ℎ𝑒𝑒𝑙 𝑐𝑒𝑛𝑡𝑟𝑒 𝑓𝑟𝑜𝑚 𝑣𝑒ℎ𝑖𝑐𝑙𝑒 𝑐𝑒𝑛𝑡𝑟𝑒𝑙𝑖𝑛𝑒

18 | P a g e

= δL

𝑑/2

= 3.278𝑚𝑚 552.5⁄ 𝑚𝑚 = .00593rad

For right wheel:

δR = 3.209mm

φR = δR

𝑑/2 = 3.209𝑚𝑚 552.5𝑚𝑚 ⁄ = .005808 rad

φav = (φL + φR)/2 = .00587 = 0.3363 °

Torque applied, Τ = F x d = 500 x 1.105 = 552.5 N-m

Torsional Stiffness = Τ / φav = 552.5 N-m/ 0.3363 ° = 1643 N-m/deg

CHASSIS 2:

Figure 3.2: torsional load on chassis 2.

19 | P a g e

Torsional Stiffness calculation:

F=500 N

L=1.068m

For left wheel:

δL = 3.923mm



= δL

𝑑/2 = 3.923/534.4=7.341X10-3 rad

For right wheel:

δR = 3.912mm

φR = δR

𝑑/2=3.912/534.4=7.320X10-3 rad

φav = (φL + φR)/2 =0.4200deg

Torque applied (T)= F X L=500 N X 1.068m=534 Nm

Torsional Stiffness= torque/average deflection= 1271.428Nm/deg

20 | P a g e

CHASSIS 3:

Figure 3.3: torsional load on chassis 3

For left wheel:

δL = 2.719 mm



= δL

𝑑/2

= 2.179𝑚𝑚 533.5⁄ 𝑚𝑚 = 5.09 x 10-3 rad = 0.29 degree

For right wheel:

δR = 2.704 mm

φR = δR

𝑑/2 = 2.704 533.5𝑚𝑚 ⁄ = 5.06 x 10 -3

φav = (φL + φR)/2 = 0.275 °

21 | P a g e


Torsional Stiffness = Τ / φav = 533.5 N-m / 0.275 ° = 1940 N-m/deg.

CHASSIS 4

Figure 3.4: torsional load on chassis 4

For left wheel:

δL = 3.586 mm



= δL

𝑑/2

= 3.586𝑚𝑚 533.5⁄ 𝑚𝑚 = 6.74 x 10-3 rad = 0.385 degree

22 | P a g e

For right wheel:

δR = 3.592 mm

φR = δR

𝑑/2 = 3.592 533.5𝑚𝑚 ⁄ = 6.73x 10 -3 rad = 0.385 degree

φav = (φL + φR)/2 = 0.385 °


Torsional Stiffness = Τ / φav = 533.5 N-m / 0.385 ° = 1385 N-m/deg.

3.2.2 IMPACT TEST:

Figure 3.5: impact test on chassis 1.

23 | P a g e

Maximum von mises stress = 3.41x10⁷ N/m2

Yield strength of the material=350x106 N/m2

Factor of safety= 𝑦𝑖𝑒𝑙𝑑 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ

𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑣𝑜𝑛 𝑚𝑖𝑠𝑒𝑠 𝑠𝑡𝑟𝑒𝑠𝑠

= 350 X10^6

3.41 𝑋10^7 = 10

Figure 3.6: impact test on chassis 2.

Maximum von mises stress = 4.12x10⁷ N/m2

Yield strength of the material=350x106 N/m2

Factor of safety= 𝑦𝑖𝑒𝑙𝑑 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ

𝑚𝑎𝑥𝑖𝑚𝑢𝑚 𝑣𝑜𝑛 𝑚𝑖𝑠𝑒𝑠 𝑠𝑡𝑟𝑒𝑠𝑠

= 350 X10^6

4.12 𝑋10^7 = 8.5

24 | P a g e

CHAPTER-4:

RESULTS AND DISCUSSION

4.1 INTRODUCTION

The results of the analysis done in the previous chapter for torsional loading is discussed in this

chapter and the results are tabulated and compared, so as to select the best chassis.

4.2 RESULTS

The finite element analysis of the three proposed design for torsional loading was done in

solidworks’14. Maximum stresses, maximum displacement and torsional stiffness were recorded

for each design in the table below.

Chassis Torsional stiffness WEIGHT (Kg)

Maximum stress (N/m2)

Factor of safety

Maximum displacement (mm)

Chassis 1 1643 N-m/deg. 32.336 1.018x108 3.5 0.341

Chassis 2 1271 Nm/deg. 29.85 6.086 x107 5.9 3.923

Chassis 3 1940 N-m/deg. 35.74 1.05x108 3.3 2.719

Chassis 4 1385 N-m/deg. 31.31 1.007x108 2.6 3.592

Table 4.1: torsional analysis

4.3 DISCUSSION

4.3.1 CHASSIS 1

Uniform stress of 5.092x107 N/m2 was observed with maximum stress of 1.018x108 N/m2 at

few points. Maximum translational displacement of 3.278 mm was noted. Almost all other

areas were found to be safe with approximately no stress and displacement.

25 | P a g e

4.3.2 CHASSIS 2


few points. Maximum translational displacement of 3.278 mm was noted. Almost all other


4.3.3 CHASSIS 3


few points. Maximum translational displacement of 2.519mm was noted. Almost all other


The chassis 3 as shown in table 4.1 not only gave the highest torsional stiffness (1940N-m/deg),

but also met our torsional stiffness requirement of 1800 N-m/deg.

Factors Torsional stiffness Weight total

Weightage 5 4 -

Chassis 1 4 3 32

Chassis 2 2 4 26

Chassis 3 5 3 37

Chassis 4 3 3 27 Table 4.2: decision matrix table

The above decision matrix makes it clear that chassis 3 is the best option, despite being a bit

heavier than the rest of the proposed designs. Thus chassis 3 is the design which the best

amongst the proposed designed and it will be manufactured in the workshop.

26 | P a g e

CHAPTER- 5:

OTHER COMPONENTS

5.1 IMPACT ATTENUATOR.

The rule requirement for an impact attenuator makes it a component that needs a lot of time and

resource to be devoted to its design and testing. The monetary resources required for its testing

ruled out its in-house development. The alternative was to go for a Standard Impact attenuator.

This would save us man hours, allowing us to concentrate on more critical components. The cost

of a standard impact attenuator was comparable to what it would cost to test a self-made IA. The

fabrication costs would have been extra and were not calculated.

Figure 5.1: IMPACT ATTENUATOR

27 | P a g e

Figure 5.2: IMPACT ATTENUATOR SIDE VIEW.

5.2 ANTI-INTRUSION PLATE

Steel was chosen as the thickness was specified in the rule book and aluminium of required

thickness hardly gave any weight advantage, and had the added problem of welding it to the

bulkhead. The thickness of steel installed is 2mm.

28 | P a g e

5.3 FLOOR AND FIREWALL

Aluminium Plate was chosen as it provided significant weight reductions and stiffness. The added

components were brackets welded to the frame to which firewall was bolted using M6 bolts. The

floor was pasted using BOSS PU25 adhesive which eliminated the need of additional bracket

needed to mount the floor. Last year floor was mounted using brackets which increased the

weight of the frame along with causing lot of noise due to vibration.

5.4 JACKING BAR CUM PUSH-BAR

Figure 5.3: FEA analysis of jacking bar

29 | P a g e

Jacking bar is used to lift the car (heavy object). In designing of jacking square tube is used as it is

lighter in weight and can take more bending stresses. First, a cad model of jacking bar was made in

solidworks’14. The dimensions were taken from last year’s jacking bar and was verified form FSAE

2015 rulebook .To check whether the design can take the weight of the car finite element analysis

was done. The weight of the car was assumed to be 300kg, so a static load of 3000N was applied

at the joints as shown in the above figure.

The minimum factor of safety for the above load condition was coming out to be 9.8, thus the

jacking bar designed can take the weight of the car.

This year we have integrated push-bar with jacking bar by fabricating it with square tubes.

Figure 5.4: jacking bar jacking TSI-16

30 | P a g e

CHAPTER-6:

MANUFACTURING

6.1 Manufacturing of Frame

Out in the workshop at last. We will now have a look at what’s involved in the manufacture of a tubular spaceframe. We have already considered that we are using AISI 1018 mild steel round tubes.

Our first requirement was a flat surface. For this we labelled the ground and used a base steel plate dimensioning 2500mm X 1250mm X 5mm. Fixture positions were printed on a paper and pasted on the base plate.

Figure 6.1: Base Plate

Fixtures were welded in position with the help of gussets that can hold the different members of the spaceframe in the right place. This is to ensure maximum accuracy and alignment of the final chassis. When the fixture was ready, we were ready to start the assembly of the chassis on the fixture.

Figure 6.2: Fixtures welded on base plate

31 | P a g e

The tubes for frame member were laser cut by our laser cut partner MAGOD LASER. The tubes for rear bulkhead tubes were profiled in house which involved fish mouth preparation.

Figure 6.3: Tubes laser cut Figure 6.4: Fish mouth

6.1.1 Cockpit:

Fabrication of frame started with cockpit as accurate construction of this part will reduce error in front and rear structure of frame. This included main roll hoop, front roll hoop and side impact members. Main hoop and front hoop were placed at their position in the laser cut fixture plate grooves and then joined by side impact members. The lower side impact member (LSM) was placed in between main hoop and front hoop, bolts were passed through the holes made in the fixture plates to keep it aligned in position and tack welded at point of contact of LSM and front hoop and LSM and main hoop at the bottom. This was cross checked with 2D drawing of top view of frame pasted on base plate to attain a greater accuracy.

Figure 6.5: Cockpit

32 | P a g e

Tack welding means applying a small bead of weld at several positions on the joints to ensure that it has no freedom of movement (normally at three locations in round tubing).

6.1.2 Front Section:

With the completion cockpit area front structure was fabricated in a similar way. This portion consisted of Front hoop, Front Bulkhead, Front hoop bracings and front bulkhead support members.

Figure 6.6: Front bulkhead Figure 6.7: Front bulkhead supports

Figure 6.8: Front hard points

6.1.3 Rear Section:

Similarly rear structure of frame was fabricated which involved fabrication of rear bulkhead, main hoop bracing and hard point triangulation tubes.

33 | P a g e

Figure 6.9: Rear bulkhead design Figure 6.10: Rear bulkhead Figure 6.11: Rear

Jacking bar tube was welded with bottom member of rear bulkhead with the help of two supports. Main hoop bracings were welded after mounting engine.

Figure 6.12: Final frame

34 | P a g e

CHAPTER-7:

Conclusion:

This design report has considered a variety of chassis designs with an emphasis on Formula SAE

cars. The construction of the chassis frame was completed in time and thus the car will be

competing this year’s competition in FSI-2016. With stiffness targets in mind a finite element

model approach was applied for design and fabrication of the chassis frame.

Last year the design weight of frame was 40 kg weight and a torsional stiffness of 2250 N-m/deg.

These values were significantly reduced in this year’s design to attain a lighter frame ( 35 kg)

having sufficient torsional stiffness of 1940 N-m/deg. The completion of the chassis is a major

annual milestone for every team. A completed chassis provides motivation to complete other

parts of the car because the team members can now visualise what has been in the design phase

for months. Every team sets a goal to complete their frame early, giving them a chance to test the

car for two to three months before each completion.

To finish the chassis by deadline that is put in place by the team, the designer needs to have

his/her design fully completed by the time construction starts. Our design was ready before

construction started.

Steel tube space frame construction gives team members an opportunity to learn basic fabrication

skills through sheet metal work, tube fitment and welding. This also induces a sense of pride in

members that make tubes that are used in an integral part of the car.

The chassis design and construction process is a cornerstone of the FSAE project. The many details

that must be considered during this procedure provides great practice to aspiring engineers and

gives them a leg up on their completion.

chassis design report 2016

Documents