Roof challenge

                                                                                                                    DESIGN OF ROOF PANEL 

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 roof 

• Convertible roof 
• Hardtops 
• sunroof 
• T-tops 
• Targa tops 
• vinyl roof 

MASTER SECTION FOR ROOF DESIGN

Components of the Roof Panel 

• Front roof rail
• Central roof rail
• Bow roof 
• Rear roof rail

1. Front roof rail 

This part of the roof panel gets assembled with a windshield panel and it is designed while considering the headroom clearance area.front roof rail comes under the roof outer panel .

2. Central roof rail 

This is the part of the reinforcements which provide sufficient strength to the roof panel.it is the major part of the roof panel.

3. BOW ROOF 

 Bow roofs are the reinforcements parts of the roof panel design which provide support to the roof panel. their positioning is important because later they will be used for the crash test. Mastics are used to join this part to the roof panel 

4. REAR ROOF RAIL 

 this is the part that is attached to the backdoor assembly. while we designing this we have to consider the rear visibility criteria and rear head room space. Spot welding is used to join the rear roof rail with a backdoor asembly.

 

CURVATURE STUDY 

HEAT DISTORTION 

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            

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]

Snow load calculation 

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)

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 front and rear reference point.

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

        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