Roof challenge

AIM:

This challenge aims to design a roof with the given master section and add necessary reinforcements and components.

INTRODUCTION:

The roof of a car is the part that is above the passenger which protects them from the sun, rain, and external debris. A Roof usually comprises a front roof rail, a rear roof rail, a center roof rail, and one or two bow roof rails.

Front roof rail:

The front roof rail is used to attach the roof to the front portion of the body and to the windshield. It is designed with respect to the front view criteria and based on the master sections.

Rear roof rail:

The rear roof rail is used to attach the roof to the rear portion of the body and it also has the rubber sealant which connects with the back door. It is also designed with respect to rear view criteria and the given master section design. The rear door is also made to be attached to the rear roof rail and the body.

Center roof rail:

The center roof rail is designed with respect to headroom criteria and the given master section design. This roof rail is attached to the mid section of the body.

Bow roof rail:

These roof rails are designed to create additional support for the roof. They are usually smaller than the center roof rail.

After designing the roof rails, a Draft analysis is done on the roof rails and on the main roof. Draft analysis is performed to assess the part's draft angle and to ensure ease while manufacturing.

Bow roof rails:

Center roof rail:

Rear roof rail:

Front roof rail:

Roof Outer:

CURVATURE STUDY OF THE ROOF:

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]

CASE	L	Rx	Ry	R	t	l	W	Result
FRR - BOW RR 1	2158.491	2109.555	5719.797	3082.305243	0.75	259.197	1.573654402	Ok
BOW RR1 - CRR	2158.491	5305.101	5193.151	5248.529101	0.75	348.939	2.11751642	Ok
CRR - BOW RR2	2158.491	9543.448	4188.362	5821.725607	0.75	408.959	2.34005906	Ok
BOW RR1 - RRR	2158.491	14439.458	3303.854	5377.334409	0.75	433.691	2.244504088	Ok

All the values are less than 2.7, So the roof design has passed the Bow roof prediction.

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

CASE	Iy	Rx	Ry	t	a	Ly	Lx	Y	My	L1	L2	S	Qr
FRR - BOW RR 1	9.80E+03	2211.745	4834.039	0.75	0.82004604	2158.491	1102.714	378.975	674392.0761	378.975	472.968	425.9715	1.27E+02
BOW RR1 - CRR	1.51E+04	5204.856	3762.55	0.75	0.910697113	2158.491	1068.818	472.968	797198.4423	472.968	532.941	502.9545	9.24E+01
CRR - BOW RR2	9.94E+03	9831.529	4160.407	0.75	0.967780453	2158.491	1056.936	532.941	866322.2426	532.941	595.171	564.056	2.09E+01
BOW RR1 - RRR	0	16185.292	4042.788	0.75	0	2158.491	0	595.171	930442.7277	595.171	0	297.5855	#DIV/0!

Conclusion:

With the given master section and skin of the roof, an entire roof has been designed with necessary components like roof rails. Draft analysis and Load prediction test are done to evaluate the design.