Roof Design

AIM:

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.

Suggest and implement remedies in the design if the criterion is not full-filling

Start with the creation of a roof ditch area with a tool opening angle of 7 degrees.

Develop the reinforcements as separate parts

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

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 center 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

Here are some Reference images for the Master sections - These images are just to give you a brief idea about the design.

Front Roof Rail Master section 

 

Master section of the Rear Roof Rail 

Master section of Bow Roof 

Master section of Center Reinforcement Rail

 INTRODUCTION:

 The roof of a car or other vehicle is the top part of it, which protects passengers or goods from the weather. The roof also protects the passenger from any injury when the car gets crashed or is rolled over or something heavy falls on the roof.

OBJECTIVE:

The mian objective of this project is to understand the design process to design the roof with all the roof rails and to understand the calculations behind it. We also get to learn about the different tools used in CATIA V5 for designing.

 

METHODOLOGY:

We get the model of the roof of the from the styling team. Then we will have to do all the engineering work. We create the ditch area for the roof and also the roof bows and roof rails for the roof which would we designed by us considering all the safety norms and regulations.

DESCRIPTION:

DESIGN CONSIDERATION-

• Visibility criteria
• Head clearance
• Curvature study
• Hear distortion and snow load criteria
• Draft analysis.

Components of roof-

1.Front Roof Rail-

The front roof rail is located on the front of the roof where the wind shield joins with the roof. The visibility criteria and the head room clearance of the passenger are taken into consideration for the bottom flange. One end of the rail is joined using spot welding while the other end is joined with the roof using mastic sealants for increased strength.

 

2.Bow roof 1-

Bow roof is an additional siffening member for the roof to increase the strength and so that it can satisfy the norms. Both the ends are joined together using mastic sealants to increase strenght and also since this would not affect the styling of the roof.

 

3.Centre Roof Rail-

Centre Roof rail or the reinforcement centre is located at the centre of the roof . The cross section of this is more since it needs to provide more strength to the roof. Here both are ends are joined together using mastic sealants.

 

4.Bow roof 2-

This bow roof also have the same purpose as that of the first one. This one is located between the centre bow roof and rear roof rail.

5.Rear Roof Rail-

• This roof rail joins with the back door and the roof. Inputs from the backdoor are taken into consideration for designing this roof rail.
• Here one end is joined using spot welding while the other end is joined using mastic sealants.

 

Calculation-

We then also make the ditch area around the roof.

Ditch area the extended portion of the main roof concealed by other BIW panels.

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 

Data X Curvature (Rx) Y Curvature (Ry) 2(Rx * Ry) Rx+Ry Roof Curvature Length I Thickness Total Span W Span1_Front_BR1 2426.811 5741.227 27865745.67 8168.038 3411.55926 336.272 0.75 2039.049 1.504542806 Span2_Center_BR1 6205.864 4970.208 61688869.8 11176.072 5519.727307 427.897 0.75 2039.049 2.069770412 Span3_Center_BR 10550.492 3983.494 84055643.16 14533.986 5783.38545 433.287 0.75 2039.049 2.149209969 Span4_Rear_BR2 14742.078 3256.937 96028038.59 17999.015 5335.182986 292.726 0.75 2039.049 1.871669748

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 center 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

Data Iy t^2 Y Ly My Lx^2 α = My x Lx^2 x 10^-12 L1 L2 s = (L1+ L2)/2 Rx Ry (Rx+Ry)/2 [(Rx+Ry)/2]^2 (Iy*t^2) [α x s x [(Rx + Ry)/2]2 x 10-8] Qr Snow Load Prediction 1 7701 1.5 466.728 2035.741 732302.2995 1048545.28 0.7678521198 382.538 432.502 407.52 10535.974 10623.224 10579.599 111927915 11551.5 350.2393425 32.98173163 Snow Load Prediction 2 7091 1.5 508.418 2035.741 776518.505 970492.9385 0.7536057257 432.502 435.468 433.985 10464.863 10824.883 10644.873 113313321.2 10636.5 370.5952746 28.70112149 Snow Load Prediction 3 7732 1.5 511.267 2035.741 779413.2486 930694.3256 0.7253954877 435.468 337.051 386.2595 10190.836 10275.495 10233.1655 104717676.2 11598 293.4093976 39.52838626

CONCLUTION-

• SINCE ITCOMES UNDER JUDGEMENT CONDITION IS SAFE.
• DESIGN IS SAFE
• TO SUPPORT THE 1 CENTER ROOF, 2 BOW ROOF IS ENOUGH.
• THE CONDITION Qr>3.1 IS NOT SATISFIED.
• THE ROOF MAY FACE BEND DUE TO SNOW LOADING, SINCE ITS NOT SATISFIED.
• OR IN ORDER TO MAKE THE ROOF STRONG WE CAN ADD EMBOSS TO THE OUTER ROOF.
• INCRESING THE EMBOSS DISTANCE, DUE TO CHANGEING THE SHAPE OF ROOF THE INERTIA VALUE WILL BE GREATER AND INCREASING THE THICKNESS OF THE BOW ROOF - THESE ARE THE WAYS TO SATISFY THE CONDITIONS.

Over All Drafting: