The engineering report summarizes the design of a tubular space frame chassis for the Corvette C7. The chassis is made of AISI 4130 steel using metal inert gas welding. AISI 4130 was chosen over AISI 1020 due to its higher strength to weight ratio, which increases torsional rigidity while focusing on weight for the high performance sports car. The tubular space frame was designed using round and square steel tubes of varying dimensions, and features a triangulated structure to increase rigidity without shear stresses.

1. Engineering Report
Chassis Design – Corvette C7
Type of Chassis: Tubular space frame chassis.
Material used: AISI 4130.
Manufacturing process: Metal inert gas (MIG) welding.
Types of tubes used: Round tube, Square tube.
Assumptions undertaken while designing:
1. The car will be rear wheel drive with engine and powertrain unit
mounted in rear.
2. Independent double wishbone suspensions will be used as suspension
system for the car.
3. Hard points for the independent suspension were chosen arbitrarily as
main focus was on designing of chassis.
4. Tubular space frame chassis was designed according to dimensions of
the Corvette c7 cad model provided.

2. Material choice for chassis:
With the choice of material between AISI 1020 and AISI 4130 the latter was
chosen for the construction of tubular space frame chassis based on
following stat table.
Mehcanical Properties AISI 1020 AISI 4130
Tensile strength, ultimate 395Mpa 560 Mpa
Tensile strength, yield 295Mpa 460 Mpa
Poissons ratio 0.29 0.27-0.30
Modulus of Elasticity 200 Gpa 210 Gpa
Density 7.9 g/cc 7.85 g/cc
From the above mentioned information it can inferred that AISI 4130 will
have a higher strength to weight ratio compared to AISI 1020, this will
contribute in increased torsional rigidity of the chassis while focusing on
weight which will be relatively lighter compared to AISI 1020 tubular space
frame. This is very much desirable for high performance sports car like
Corvette C7 which led to choice of this material. Also AISI 4130 steel has
good strength and toughness, weldability and machinability.
Manufacturing processes:
1. Laser cutting: The round tubes will have to be laser cut to generate a fish
mouth structure at the ends of the tube before assembly and welding.
2. Welding: Welding of AISI 4130 steel can be performed by all commercial
methods. However MIG welding was chosen over other welding processes
because of its high welding strength and also ease of welding.
3. Heat Treatment: Due to stress concentration at welded joints, AISI 4130
tubular space frame would be required to be heat treated to relieve all
internal stresses and increases the strength of the chassis.

3. Selection of tubes and dimensions:
Round and square tubes were used for designing of tubular space frame
chassis. The dimensions of tubes used are as follows:
1. 25 x 2.5 mm – Round
2. 19 x 1.65mm - Round
3. 14 x 2 mm – Round
4. 20 x 15 mm – Square
 The round tubes with dimensions 25 x 2.5 mm was chosen for main roll
bars of the chassis. Main roll bars would be highly stressed under
dynamic conditions of the chassis and these tubes were chosen to be
with greatest outer diameter and thickness in the entire frame.
 The round tubes with dimensions 19 x 1.65 mm was used to connect
frontal impact structure, cockpit and rear engine bay and 14 x 2 mm
round tube was used as triangulation tube to increase overall torsional
rigidity of the structure.

4.  The square tube with dimensions 20 x 15 mm was used as bottom rail of
the frame as square tubes take greater bending loads such as of driver,
engine and entire powertrain unit whereas round tubes have greater
torsional resistance.
(*All tube dimensions were chosen in accordance with my past
experience in FSAE design competition.)
The Design:
The design was done using 3d sketch and Weldment features of
solidworks 2014 keeping in mind the rule of triangulation to avoid shear
stresses and induce just tensile and compressive stresses in the frame.

5. Assembly:
Figure 1 Assembly of tubular space frame with the body (rear view)
Figure 2 Assembly of tubular space frame (Front view)