Roof Design

ROOF DESIGN

AIM:

creating an ASSEMBLY by developing the essential flanges for the outer roof and creating the reinforcements and Draft analysis.Doing a curvature study on the roof and perform calculations to determine the position of the Bow-roofs.

Introduction :

The car roof lining is also known as a headliner or headlining. It is a fabric material used on the roof of an automobile. Its primary purpose is to:

Main design considerations of a roof :

• Proper visibility of the car
• Proper head clearance
• Safety ( load criteria such as snow load and heat distortion).

Roof design :

To design the roof we need to design front roof rail, bow roof rail 1, center roof rail , bow roof rail2 , rear roof rail.

given data for design is :

Front Roof Rail Master section

DESIGN USING NX CAD :

Master section of the Rear Roof Rail

DESIGN USING NX CAD :

Master section of Bow Roof

DESIGN OF BOW ROOF1 USING NX CAD :

DESIGN OF BOW ROOF2 USING NX CAD :

Master section of Center Reinforcement Rail

DESIGN OF CENTER ROOF RAIL USING NX CAD :

ROOF OUTER PANEL DESIGN USING NX CAD :

ROOF ASSEMBLY DESIGN PICS :

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]

By using this Bow Roof prediction formula we will get the below values

			HEAT DISTORTION
S NO	ROOF AREA	Rx	Ry	R	L	l	t	W	OK/NOT OK
1	FR & BR1	5721	2772	3734	2023	434	0.75	1.63	OK
2	BR1 & CR	4923	3968	4394	2023	375	0.75	1.7	OK
3	CR & BR2	3909	10563	5706	2023	421	0.75	2.07	OK
4	BR2 & RR	3278	14357	5337	2023	343	0.75	1.89	OK

CONCLUSION FOR HEAT DISTORTION CRITERIA:

Heat distortion calculation is completly satisfies the curvature study and the bow roof placements are acceptable.

DRAFT ANALYSIS:

:

REAR ROOF RAIL:

BOW ROOF RAIL 1 :

CENTERBROOF RAIL :

BOW ROOF RAIL 2 :

SECTION MODULUS :

FRONT ROOF RAIL :

Here MOI minimum is 6.30e+03 [mm^4]

BOW ROOF 1 :

Here MOI minimum is 1.87e+03 [mm^4]

BOW ROOF 2 :

Here MOI minimum is 1.89e+03 [mm^4]

CENTER ROOF RAIL :

Here MOI minimum is 2.17e+03 [mm^4]

REAR ROOF RAIL :

Here MOI minimum is 4.83e+04 [mm^4].

CALCULATION OF SNOW LOAD CRITERIA :

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

					SNOW LOAD CALCULATION
SNO	state	Iy	t	Lx^2	My	s	Rx	Ry	[(Rx+Ry)/2]^2	alpha	Iy*t^2	Qr	JUDGEMENT
1	FRR&BR1	1876.3	0.75	316969	753710	512.5	4394	2805	12956400	0.23	1055	69.13	PASS
2	BR1&CRR	2173.7	0.75	292681	897128	477.5	3783	6429	26071236	0.26	1222	37.85	PASS
3	CRR&BR2	1895	0.75	278784	585144	460	4281	9631	48385936	0.16	1065	29.91	PASS
4	BR2&RRR	48,301	0.75	2,72,484	0	0	4001	16422	#############	0	#########	0

CONCLUSION FOR SNOW LOAD CRITERIA:

Snow load calculation is completly satisfies the curvature study and the bow roof placements are acceptable.