Challenge

Roof Design

SSanthosh Kumar8 Dec 2022

AIM

To design a roof with all the components like front roof rail, rear roof rail, and bow roofs by following the given master sections and the high-quality surface, considering all the design requirements as per the OEM standards.

ROOF DEFINITION

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.

These include

Convertible roofs. Roof modules. Roof modules.
Hardtops.
Sunroofs.
T-tops.
Targa tops.
Vinyl roofs.

OBJECTIVE

To design a roof of the car with all the reinforcement from the given styling surface.
To perform the curvature study on the roof by considering Heat Distortion and Snow load criteria.
To calculate the moment of inertia for the reinforcements.
To Perform the draft analysis for analyzing the components' manufacturing feasibility.

TYPES OF SECTIONS

Front roof rail
Rear roof rail
Bow roof rails
Center rood rail

MASTER SECTION FOR ROOF RAILS

FRONT ROOF RAIL

Front Roof rails are long bars that run along the length of car's roof, in a front-to-back orientation. Many vehicles are readily equipped with some form of roof rails — which you may notice when buying a car. Some manufacturers may offer these rails standard, while others provide them as an option instead.

REAR ROOF RAIL

A rear roof rail is a passage between an inner side panel at a corner side of the tailgate and an outer side panel is blocked to provide a reinforcing force, such that, in case an automobile is parked on a block of a footpath with only one wheel, a torsional stress is not applied to the tailgate to thereby facilite opening and closing of tailgate, and vibration generated from a running automobile is blocked by the passage to prevent in advance the noisy sound resounding phenomenon from being transmitted to a pillar panel, the rear roof rail reinforcement structure for automobile, the rear roof rail for automobile where an inner side panel and an outer side panel are detachably formed at a predetermined space there between a rear roof lower rail is overlapped by and welded to the inner side panel and the outer side panel is overlapped by and welded to a rear roof upper rail and a roof panel, where in the rear roof lower rail is bent at a tip end there of and welded to connect the inner side panel and the outer side panel respectively, and comprises a reinforcement for blocking a passage formed between the inner side panel and the outer side panel.

BOW ROOF RAIL

Bow roof rails are free-standing arched frames that are easy to build, light-weight and low cost. Structural strength comes from the arch shape formed by their bows. They can be 10 to 20 feet wide and any length. The free-standing frame allows covering with any sort of roofing, including plastic sheeting.

CENTER ROOF RAIL

roof rails are positioned mostly on the center portion of the roof or at the B Pillar of the vehicle i.e, the most flatter region of the car which is susceptible to failure under the action of load.

ASSEMBLY PROCESS

HEAT DISTORTION CRITERIA

Heat distortion temperature is the temperature at which the metal softens and deforms under a specific load. This study is done to check the ability of the roof to withstand high temperatures concerning the positioning of the reinforcements which contribute to increased strength.

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]

Judgment Condition

OK< 2.7

SNOW LOAD CRITERIA

A snow load study is done to check the ability of the roof to withstand snowfall and bounce back to its original position without undergoing permanent deformation upon the removal of the load.

Formula

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)

t = Roof plate thickness [mm]

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

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

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]

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

Judgment condition

Qr ≥ 3.1

250 ≤ s ≤ 380

MOMENT OF INERTIA FOR FRONT ROOF RAIL

MOMENT OF INERTIA FOR REAR ROOF RAIL

MOMENT OF INERTIA FOR BOW ROOF RAIL 1

MOMENT OF INERTIA FOR BOW ROOF RAIL 2

DRAFT ANALYSIS

Draft Analysis is carried out to check the manufacturing feasibility of the roof and all the reinforcements rails. All the components should be designed by considering at least the minimum draft value of 7 Degree.

Draft analysis for front roof rail

Draft analysis for rear roof rail

Draft analysis for bow roof rail1

Draft analysis for bow roof rail 2

Draft analysis for center roof rail

Draft analysis for outer roof

CONCLUSION

Thus the roof is designed with all the necessary reinforcements and roof rails according to the given master section and the styling surface, by considering all the design parameters. Also, the curvature study is done by taking the heat distortion and snow load criteria for determining the strength of the roof.

Roof Design

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Ship work like this
in your own course.