Roof Design

AIM / OBJECTIVE:

For the given roof styling. Create an ASSEMBLY by developing the essential flanges for the outer roof and creating the reinforcements.

Provide appropriate dimensions and check for Draft analysis.

Do a curvature study on the roof and perform calculations to determine the position of the Bow-roofs.

INTRUDUCTION:-

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. Because the earliest automobiles were designed in an era of horse-drawn carriages, early automobile roofs used similar materials and designs.

TYPES OF ROOFS:-

Convertible roofs

Roof modules

Roof modules

Hardtops

Sunroofs

T-tops

Targa tops

Vinyl roofs

FRONT ROOF :-

• MASTERSECTION:-

CROSS SECTION FRONT ROOF RAIL:-

BOW ROOF RAIL:-

MASTER SECTION BORE ROOFS:-

CENTRE ROOF RAIL:-

Master section of Center Reinforcement Rail

RARE ROOF :-

MASTERSECTION OF RARE ROOF :-

OVER ALL DESIGN:-

CALCULATIONS:

For our study, we are considering the following conditions for testing the roof.

• Heat Distortion Criteria:

The heat distortion study plays a major role in sheet metal usage. Heat distortion temperature is a temperature limit above which the material cannot be used for the structural applications. This study is used to predict the heat distortion temperature at where the material starts to soften when exposed to a fixed load at elevated temperature. In order to avoid bending or damages on the roof, based on the heat distortion temperature, this study will predict the bow roof position which helps to strengthen the roof.

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

For the above, we can find can record and calculate as shown below:

Result:

From the above table, we can conclude that the positions at which the bow roofs are placed satisfy the heat distortion condition and is good to go for manufacturing.

• Snow load Criteria:

This test is done to know how is the roof behaving when there is a snow over. Normally due to the snow weight the dent will happen. But the roof should be designed in such a way that when the snow is removal, the roof should go it its original position . This is the basic requirements for snow load criteria.

• Qr = [Iy x t2] / [α x s x [(Rx + Ry)/2]2 x 10^-8]

Where

α = My x Lx2 x 10-12 , My = Y(Ly-Y)

Judgement condition = Qr ≥ 3.1

250 ≤ s ≤ 380

t = Roof plate thickness [mm]

Ly = Distance between the front and rear roof Rails on the Vehicle along with 0Y[mm]

Length of Roof panel with the center point between Roof rail Front /Rear as the reference point of the front and the rear.

Lx = Distance between the Left and Right end of the roof on the Roof BOW [mm]

Width of the roof panel exposed on the surface.

Y = Distance front Front Roof Rail to Roof BOW[mm]

s = Distance for which Roof BOW bears divided load [mm]

s = L1/2 + L2/2

Iy = Geometrical moment of inertia of Roof BOW (Y cross-section )[mm4]

Rx = Lateral direction curvature radius of roof panel Y cross-section on Roof BOW [mm]

Roof panel curvature Radius of the Length Lx in Front view

Ry = Longitudinal Direction curvature radius of the Roof panel X cross-section on Roof BOW [mm]

Result-

SECTIONS OF MODEL:-

ROOF :-

FRONT ROOF:-

BOW ROOF RAIL:-

BOW ROOF RAIL 2:-

CENTRE ROOF RAIL:-

RARE ROOF RAIL:-

CONCLUSION: