Roof Design

AIM:

• Design a Roof with its components by following the master section of the front roof rail (at least 1 Front roof rail, two bow roofs, 1 centre roof rail and 1 rear roof rail) with all the design parameters mentioned in the videos.

• Perform Draft Analysis for all the parts.

• prepare a report which includes the curvature study on the roof based on the Bow roof prediction calculation as well as the manufacturing techniques.

Introduction:

An automobile's roof greatly influences both its practicality and visual appeal. Car roofs are available in a variety of styles and materials, each with a distinct function and set of requirements. Also, car roofs act as barriers to keep people safe from the outside world and possible dangers.

There are different roof types of car roofs, and here are some examples such as:

• Solid Roof

• Panoramic Glass Roof

• Convertible Soft Top

• Retractable Hardtop

• Targa Top

MANUFACTURING PROCESS:

There are various procedures involved in the production of automobile roofs:

1. Outer Plate Processing:

This is the initial stage of processing the roof's outer plate1.

2. Strip-shaped Assembly and Annular Assembly Processing:

In this stage, two M6 screw nuts are positioned at the ends of a strip-shaped assembly and several M6 screw nuts are placed on one side of an annular assembly using spot welding. Through spot welding, the strip-shaped assembly is placed at the opposite side of the screw nut that corresponds to the annular assembly. Furthermore, slots are punched for alignment in the annular assembly and the strip-shaped assembly.

3. Automobile Roof Side Beam Processing:

An outer plate's inner side is where the annular assembly is welded. Through spot welding, a car roof side beam is positioned at the inner side of the outer plate.

4. Automobile Roof Combining Process:

Lastly, burr grinding and finishing are essential processes for car roofs.

Roof design:

Every design parameter that is discussed in the videos is taken into consideration when designing the roof and its components by following the master section given.

1. Front Roof Rail:

2. Rear Roof Rail:

3. Bow Roof :

4. Center Reinforcement Rail:

Draft Analysis:

1. ROOF TOP:

2. Front Roof Rail:

3. Rear Roof Rail:

4. Bow Roof :

5. Center Reinforcement Rail:

Bow roof prediction calculation:

1. Heat distortion criteria:

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]

Judgment Condition

OK< 2.7

2. Snow load criteria:

Snow Load Prediction Formula

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

Note: The Qr value given over here is correct. There was a typo error in the formula given in the video.

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]

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

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

The width of the roof panel is 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]

Roof panel X curvature radius of length s in Side view

Judgment condition

Qr ≥ 3.1

250 ≤ s ≤ 380

Conclusion:

• Created a roof and all of its parts by adhering to the master sections that were provided and including all of the design guidelines that were discussed in the videos.

• Finished the draft analyses for every component and obtained satisfactory results.

• Carried out the curvature study on the roof using the snow load prediction formula and the bow roof prediction formula, with successful results.