Roof challenge

Design of an automobile roof

Objective: To find out if the bow roofs meet the design and criteria for heat distortion and snow load conditions

Design Considerations

• Visibility criteria
• Head clearance
• Curvature study
• Heat distortion and snow load criteria
• Material thickness

Introduction:

An automobile roof or car top is the position 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.

Components that were designed with the given styling roof

• Front Roof Rail
• 1^st Bow Roof
• Center Reinforcement Roof Rail
• 2^nd Bow Roof
• Rear Roof Rail

Front Roof Rail

The Front Rail Roof is the first component to be used in the assembly of a roof. The passenger head clearance was taken into design consideration as well as giving the necessary mounting position for the windshield.

1^st Bow Roof:

The Fist Bow Roof gives strength and stability to the overall roof structure of the vehicle. This is later then welded by spot welding and giving it a mastic sealant wherever necessary.

Center Roof Rail:

This component supports the roof right at the center giving it strength and stability. They are either spot welded or joined using a mastic sealant.

2^nd Bow Roof:

Serves the same purpose as the 1^st Bow Roof

Rear Roof Rail:

Finally, the rear roof rail is created, adding the necessary mounting points for the rear windshield along with its hinges for the backdoor. Having the head and visibility clearance.

Section Inertia of the Bow Roof’s

Curvature Study, Heat Distortion

This Study Shows us that, when the temperature is uniformly spread on the roof, it gives us an idea where the bow roof’s position could be placed and will give us an idea of how to maintain the overall strength of the roof. If the given requirements are not met, then the following value would be a no-good condition.

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

Judgement Condition: OK< 2.7> 3.1

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]

The following condition meets the required heat distortion criteria

Snow load Prediction formula

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

The given snow load criteria don’t meet, hence an NG condition. Thus emboss have to be given on the vehicle's roof to satisfy the load thereby adding strength and stability.

Images

Kindly, Please find the attached google drive link to the roof part

https://drive.google.com/file/d/1ZQsahD4PuvVY5tETkvA4H_NIbx0WYPIs/view?usp=sharing