Roof Design

AIM- To create a roof assembly from the given class A outer surface.

OBJECTIVE- Creation of Roof outer, front roof rail , Bow roof rails, center roof rail, Rear roof rail . Draft analysis of the parts, also evaluating the roof assembly for heat distoprtion ans snow load .

Master section provided-

THEORY-

Roof is the area of the vehicle whis is above the seating arrangement in a vehicle, it is usually a layer of sheet metal that provides protection to the interior of the vehicle from heat, rain, snow and other harmful elements of the environment. Accourding to designs of the roof they can be classified into mainly-

1. CONVERTIBLE ROOF
2. HARD TOP ROOF
3. SUNROOF
4. T TOPS ROOF
5. TARGA TOPS ROOF
6. VINYL ROOFS

In india we usually seevehicles with hard top, vinyl top, sunroof and few convertible. so we will mainly look and study the following types of roof used in vehicle.

HARD TOP ROOF

Hard top roof are most commonly used in vehicle as it is easy to manufacture, and is most duriable in terms of functionability, a hard top roof is basically integrated to the body of the vehicle with the help of pillers.

In the we can see the roof of a vehicle in hard top configiration ans the roof is linked to the body of the vehicle with the help of A B C pillers.

VINYL TOP ROOF

Vinyl top roof are usally made of fabrics or vinyls , they are not solid structures and has very limited strength in compare to that of the hard tops, they are usually used in a convertible vehicle but instead of sheet metel they have fabric or vinyls as material.

SUNROOF

Sunroof are now very trending in the contemperery vehicle market, it is basically a movable glass panel on the roof of the vehicle so that it allows air and light to enter the the sitting area.

CONVERTIBLE ROOF

Convertible roof are roof panels taht can be attached or dfetached to the vehicle as per the drivers need, it can be done manually or motorised for automatic application.in india it is very rear but in other part of the world it is very popular.

COMPONENTS OF ROOF ASSEMBLY

DRAFT ANALYSIS OF THE ROOF COMPONENTS

ROOF OUTER

FRONT ROOF RAIL

BOW ROOF RAIL 1

CENTER ROOF RAIL

BOW ROOF RAIL 2

REAR ROOF RAIL

DESIGN CONSIDERATION OF VEHICLE ROOF

1. VISIBILITY CRITERIS
2. HEAD CLERANCE
3. CURVATURE STUDY
4. HEAT DISTORTION & SNOW LOAD CONDITION
5. SAFETY PARAMATER (ROLL OVER/CRUSH TEST)

In this report we will mainly focus on heat distortion and snow load condition of the roof design and safety parameter test.

CRUSH TEST

Heat Distortion 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]

Judgment Condition OK< 2.7

SECTION TYPE	RX	RY	R	L	t	I	W	CONDITION STATEMENT
FRR TO BRL 1	5769.008	2238.247	3327.726	2023.057	0.75	332.741	1.136	PASS
BRL 1 TO CRR	4987.312	5886.792	5399.850	2023.057	0.75	476.053	2.080	PASS
CRL TO BRL 2	3921.927	10788.2	5752.57	2023.057	0.75	468.77	2.202	PASS
BRR 2 TO RRR	3306.935	14633.057	5394.714	2023.057	0.75	291.159	1.856	PASS

The design of the roof has passed the judgement criteria and ok for the heat distortion test.

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.

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

1. Qr ≥ 3.1
2. 250 ≤ s ≤ 380

SECTION TYPE	Ix	t	Rx	Ry	L1	L2	Lx	Ly	Y	Qr	CONDITION STATEMENT
FRR TO BRR 1	198.1	0.75	4650.05	2452.243	432.889	545.502	1107.676	2023.554	432.889	2.138	FAIL
BRR 1 TO CRR	775.4	0.75	3761.314	5860.299	545,502	543.1179	1061.441	2023.554	545.502	13.454	PASS
CRR TO BRR 2	13190	0.75	11179.624	4284.941	543.179	437.369	1042.142	2023.554	543.179	0.572	FAIL

From the table we can see that the design of the roof assembly is not appropriate for the snow load test as it has not meet the judgement condition.

CONCLUSION-

The design of the roof assembly is sucessfully done by keeping all the objectives in mind and we can conclude that the roof is ok for heat distortion test but we need to modify it for snow load condition.