Roof Design
Roof Design
Develop the vital flanges for the outer roof also Create extra reinforcement like front and rear roof rails and in between some of bows with the help of given master sections.
What is Roof in Car ?
An Automobile roof or car top portion that sits above the passenger compartment protecting the Vehicle occupants from sun,wind,rain and other elements rashing towards vehicle while running.But some car do not have roof but they have front wind sheild.
Roof consists of Bow rails its a sheet metal part usually spot welded to the BIW inner frame,Forming the inner structure of the vehicle body.
Design Steps :-
Given Sheet metal part As a Styling class A input file Roof surface. As From given master Section of Front roof Rail ,Rear Roof rail , Bow roof and center Bow roof with reinforcements ,Inner roof too.
Using Commands like Law Extension ,Offset surface,face on curve ,emboss,intersection Curve ,datum plane ,project curve , trim sheet ,studio surface ,sew , Bridge curve and in the end Thicken.
Front Roof Rail :
Rear Roof Rail :-
Bows :-
Center Bow :-
Draft Analysis :-
Draft Analysis is step to check draft angle on different face of part with particular direction its said degree should be more than 7 degree.Below Figure shows draft analysis on the parts of Roof .
BOW ROOF CALCULATION
Considering
1) Heat Prediction Formula :
2) Snow load Prediction Formula :
Using Sketch Command
For Rx and Ry get point project on surface and measure surface radius.
For Heat prediction formula :
Heat 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] (0.75)
l = Bow Roof Span [mm]
Judgment Condition
OK< 2.7
For Snow Load prediction formula
Also moment inertia is need for snow load prediction make use Section inertia analysis so we get "Iy" :
Snow load Prediction Formula
Qr = [ly 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
In Above table we can see every condition of Qr is Ok because its above 3.1 .
But if the Qr comes lower than 3.1 We can get adjusted by changing Rx and Ry with help of design team.
Conclusion :
In Roof Design Parameters like Heat Prediction and Snow Load Prediction Formula are used to wheather the graphic design calculation with certain length is ready to Manufacture or not .Also before considering draft analysis and section inertia analysis.