Roof challenge

ROOF :

- ROOF IS A UPPER MOST PART OR COVER OF THE VEHICLE , IT ALSO JOINS FRONT WINDSHIELD , BACK DOOR AND BODY SIDE & SIDE DOOR.

TYPES OF ROOF :

- CONVERTIBLE ROOF

- SUNROOF

- HARDTOPS

- T - TOPS

- TARGA TOP

- VINYL ROOFS

- MOON ROOFS

- PANORAMIC ROOFS

COMPONENTS OF ROOF :

- ROOF LOOKS SIMPLE FROM OUTSIDE LIKE A SINGLE SHEET OR SURFACE BUT ACTUALLY IT AS SOME COMPONENTS IN IT

1. FRONT ROOF PANEL

2. REAR ROOF PANEL

3. BOW ROOF 1

4. BOW ROOF 2

5. CENTER REINFORCEMENT

- NUMBERS OF BOW ROOF DEPENDS ON TYPE OF VEHICLE AND ITS ROOF SIZE , THEY ARE SOME ROOFS WITH 3 BOW ROOFS ALSO.

- IN THE ABOVE 2ND IMAGE WE CAN SEE ALL PARTS.

- IN CASE OF SUNROOF WILL NOT HAVE BOW ROOF AT THAT LOCATION SO WE INTRODUCE BOW ROOF WITH CENTER REINFORCEMENT COMBINE TOGETHER.

WHY WE NEED TO PROVIDE BOW ROOFS ?

- SO THE ROOF IS NOT EXACTLY STRAIGHT ITS HAS LITTLE CURVATURE OR ITS IS CURVED.

- BUT THERE ARE SOME AREAS WHICH IS FLATE , SO TO INCREASE THE STRENGTH AT THE MOST FLATE REGION WE INTRODUCE BOW ROOFS.

FRONT ROOF RAIL :

- IT IS USED FOR REINFORCEMENT , SUPPORT FOR THE ROOF.

- ALSO THE CABIN LAMP AREA IS MOUNTED ON FR ROOF RAIL.

- IT JOINS ROOF WITH FRONT WINDSHIELD SUPPORTING THE A PILLARS.

REAR ROOF RAIL :

- IT CONNECTS ROOF WITH BACK DOOR.

- ALL THESE PARTS ARE ASSEMBLY TOGETHER TO GET ROOF.

- THEY ARE JOIN BY SPOT WELDING ON THE FLANGES PROVIDED AND FOR BOW ROOFS MASTIC ARE USED.

DESIGN CONSIDERATION FOR ROOF :

- LOCATIONS OF BOW ROOFS

- HEAD IMPACT ANALYSIS

- ENVIROMENTAL CONDITIONS

- DRIVER'S VISIBILITY CRETERIA

- SNOW LOAD ANALYSIS

- THICKNESS OF MATERIAL

- EMBOSS FOR STRENGTH

DESIGN OF ROOF :

- WE HAVE BEEN PROVIDED CLASS A SURFACE OF ROOF OUTER PANEL & THE MASTER SECTIONS FOR OTHER PARTS.

- FROM THIS I HAVE DESIGNED A ROOF ASSEMBLY AND THICKEN IT.

DESIGN CALCULATIONS :

1. ROW ROOF PREDICTION CALCULATION.

- WE HAVE GIVEN A FORMULA TO CALCULATE :

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

R = ROOF CURVATURE

= 2 ( Rx * Ry ) / (Rx + Ry)

Rx = X CURVATURE

Ry = Y CURVATURE

t = THICKNESS

l = BOW ROOF SPAN

FIRST WE NEED TO DO CURVATURE ANALYSIS WHERE WE WILL CALCULATE Rx & Ry OF THE ROOF.

- THIS IS HOW WE NEED TO CREATE A SKETCH , FIRST A LINE A CENTER FROM A OFFSET LINE AT 300 MM FROM THAT OFFSET TWO MORE OFFSET LINES EACH AT 100MM

- PURPOSE OF DOING THIS IS TO GET POINTS AT DIFFERENT POSITION OF ROOF SO THAT WE CAN CREATES ARC THERE.

- AFTER THIS WE HAVE 4 PORTION ON THE ROOF :

1 : FROM FR ROOF PANEL TO BOW ROOF 1

2 : BOW ROOF 1 TO CENTER REINFORCEMENT

3 : CENTER REINFORCEMENT TO BOW ROOF 2

4 : BOW ROOF 2 TO RR ROOF PANEL

- SO WILL A CENTER LINE AT EACH PORTION AND FROM THERE TWO OFFSET LINES AT 100 MM EACH AS YOU CAN SEE IN ABOVE IMAGE.

- NOW AT EVERY INTERSECTION CREATE A POINT AS SHOWN ABOVE JUST LIKE A PLUS SYMBOL.

- AND CREATE A ARC FROM THESE POINTS. (WILL HAVE 4 ARC FOR 4 PORTIONS).

- NOW WE CAN START WITH CALCULATION , WE WILL FIND W IN ALL FOUR PORTIONS.

CASE : 1

- MEASURE Rx & Ry ,

Rx = 3237.34 mm

Ry = 14872.47 mm

- MEASURE L ROOF LENGTH , L = 1924.16 mm

- MEASURE BOW ROOF SPAN , l = 996.63 mm (*NOTE* WHILE CALCULATING L & l AVOID FLANGE AND DICH AREA)

- THICKNESS IS t = 0.75 mm

RESULTS : AFTER SUBSITUTING ALL VALUE IN GIVEN FORMULA AND CALCULATING

Rx	Ry	R	t	l	L	W1 (CASE 1)
3237.34	14872.47	53172.5	0.75	996.63	1924.16	2.43

CASE : 2

- IN SAME MEASURE ALL VALUES LIKE Rx , Ry ETC.

RESULTS :

Rx	Ry	R	t	l	L	W2
10737	3948.86	5774.28	0.75	996.63	1924.16	2.56

CASE : 3

RESULTS :

Rx	Ry	R	t	l	L	W3
6708.48	4845.51	5626.80	0.75	996.63	1924.16	2.52

CASE : 4

Rx	Ry	R	t	l	L	W4
2954.14	5701.12	3891.71	0.75	996.63	1924.16	2.12

2. SNOW LOAD CALCULATIONS.

- WE HAVE FORMULA FOR SNOW LOAD PREDICTION :

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]

Width of the roof panel 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

THE CURVATURE ANALSIS WILL BE SAME AS WE DID FOR BOW ROOF CALCULATION BUT THIS TIME WILL USE ONLY FOR CENTER LINE.

- FROM THIS WE CAN CALCULATE Rx & Ry .

- NOW IN THIS FORMULA WE HAVE Iy , WHICH IS MOMENT OF INERTIA FOR THE BOW ROOF

CASE : 1

- Rx = 6366.2 mm L1 = 461.77 Y = 556.82 Ly = 1996.30

Ry = 2975.42 mm L2 = 305.2 t = 0.75 Lx = 1038.89

Iy CALCULATION :

Iy = 1.6375*1000 = 1637.5

RESULTS AFTER SUBSITUTING ALL VALUES IN FORMULA :

S	My	ALFA	Qr
383	801531.25	0.865	12.75

CASE : 2

- Y = 939.27 L1 = 459.88 Rx = 6642.46 Lx = 1038.89

t = 0.75 L2 = 619.99 Ry = 3798.19 Ly = 1996.30

Iy = 2.5588*1000 = 2558.8

RESULTS :

S	My	ALFA	Qr
540	992836.56	1.071	9.13

CASE : 3

- Y = 1480 L1 = 619.99 Iy = 1.5428*1000 = 1542.8

t = 0.75 L2 = 520.55

Lx = 1038.89 Rx = 11274.55

Ly = 1996.30 Ry = 4289.80

RESULTS :

S	My	ALFA	Qr
570	764124	0.8247	3.24

- FROM BOTH CALCULATUONS WE FIND VALUE W AND Qr IN THE GIVEN RANGE.

- SO WE JUSTIFY THAT THE DESIGN IS PASSING ALL CONDTIONS.

DRAFT ANALYSIS :

1. ROOF OUTER PANEL

2. FRONT ROOF RAIL

3. REAR ROOF RAIL

4. BOW ROOF 1

5. BOW ROOF 2

6. CENTER REINFORCEMENT

- ALL THE PARTS HAVE PASSED DRAFT ANALYSIS AT 7 DEG.