Roof Design

OBJECTIVE :

• The objective of this project is to design car roof with essential flanges and reinforcements like ditch area , front roof rail , bow roofs, central roof rail and rear roof rail for the the given styling surface
• Perform a curvature study on the roof and perform the calculations for the heat distortion and snow load criteria to determine whether the bow roofs are at the correct positions.
• Finding moment of inertia and section modulus for Bow roofs , central roof rail . front roof rail and rear roof rail .

CAR ROOF :

An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements. Roof is the structure above the wind shield glass having the reinforcements to provide the strength to the overall structure and to with stand the over head forces like snow.

If the roof is flat it is very weak and cannot able to with stand the forces like snow , so in order to increase the strength of the roof these reinforcements like front roof rail, central roof rail, rear roof rail and the bow roofs are introduced and joined to the flat surface of the roof with the different joining process

Different types of reinforcements that the car has are :

• Front roof rail
• Bow roofs
• Central roof rail and
• Rear roof rail

Bow – roof prediction Formula

W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-8) x (R^2)/t] + [ 1.10x10^(-3) x l] - 2.68

Where

L = Roof Length in X-Direction[mm](Roof dimension in 0-Y)

R = Roof curvature

R = 2(Rx*Ry)/(Rx+Ry)

Rx = X curvature

Ry = Y curvature

t = Roof plate thickness [mm]

l = Bow Roof Span [mm]

Judgement Condition : OK< 2.7> 3.1

FRONT ROOF RAIL

Moment of inertia maximum,( MAX) I _max =2.62568832× 10⁵ ( mm⁴)

Moment of inertia maximum ,( MIN) I _min =1.366596177 × 10⁴( mm⁴)

SECTION MODULUS

S= moment of inertia /distance from the neutral axis to any given fibre

S = I / y

Y = 61.6899 mm

FOR MAXIMUM MOI :

S= 2.62568832× 10⁵ ( mm⁴) / 61.6899 mm

S _max = 4256.26 mm³

FOR MINIMUM MOI :

S= 1.366596177 × 10⁴( mm⁴)/ 61.6899 mm

S _min = 221.526 mm³

REAR ROOF RAIL

Moment of inertia maximum,( MAX) I _max =1.276488× 10⁶ ( mm⁴)

Moment of inertia maximum ,( MIN) I _min =6.740193 × 10⁴( mm⁴)

SECTION MODULUS

S= moment of inertia /distance from the neutral axis to any given fibre

S = I / y

Y = 111.256 mm

FOR MAXIMUM MOI :

S= 1.276488× 10⁶ ( mm⁴)/ 111.256 mm

S _max = 11473.43065 mm³

FOR MINIMUM MOI :

S= 6.740193 × 10⁴( mm⁴)/ 111.256 mm

S _min = 605.8273 mm³