Roof Design

INTRODUCTION

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.

Vehicle roofs can be subjected to high heat conditions or load during snowy conditions. To make the roof withstand these conditions, various calculations are done. This ensures the safety of the passengers in the vehicle.

Fig: Shows the roof of an automobile.

OBJECTIVES

For the given roof styling, create an assembly by developing the essential flanges for the outer roof and creating the reinforcements.

DESIGN CONSIDERATION

1. Visibility criteria

2. Head clearance

3. Curvature study

4. Hear distortion and snow load criteria

5. Draft analysis.

DESIGN AS PER MASTER SECTION

Fig:the design made as per the master section.

CALCULATIONS

CALCULATIONS FOR HEAT DISTORTION CURVATURE STUDY:-

Formula used:- 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]

Value obtained as per design.

Rx	Ry	R	l	L	T	W	Criteria
2500.765	5740.252	3483.798	478.44	2037.04	0.75	1.669739	ok
6497.011	4897.75	5585.152	319.24	2037.04	0.75	1.964693	ok
9978.09	4101.864	5813.764	314.47	2037.04	0.75	2.023726	ok
13952.15	3378.314	5439.524	468.1	2037.04	0.75	2.088837	ok

Judgment Condition

OK< 2.7

CALCULATIONS FOR SNOW LOAD CRITERIA:-

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

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

Inertia values

Value obtained as per design.

ly	a	My	Ly	Lx	Y	s	Rx	Ry	t	Qr	Criteria
1956.5	1.059286	862224	2037.04	1108.4	600	480.385	4370.37	2848.15	1.3	49.88014	ok
2489.5	1.212146	1036891	2037.04	1081.212	996.34	396.205	3781.2	6418.02	1.3	33.68603	ok
1968.59	1.015262	897230.1	2037.04	1063.744	1392.89	492.175	4210.76	10324.92	1.3	12.60473	ok

Judgment condition

Qr ≥ 3.1

FINAL FILES

https://drive.google.com/drive/folders/1P5bXBCSEX6yG1IYl7FarC5TfHQUhywkV?usp=sharing

above is the link provided for all the design files.

CONCLUSION

For the given roof styling, flanges and reinforcements are created also, and heat distortion criteria and snow load calculations are done.