Roof challenge

REPORT

                                                                                  ROOF 

 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.The components present in the car roof is 

• Front Roof Rail
• Bow Roof 1
• Center Roof Rail
• Bow Roof 2
• Rear Roof Rail

Front Roof Rail is joint with windshield and body side outer.Rear Roof Rail is joint with back door and body side outer.Center Roof Rail is at the center of the roof and the b piller of the car.Bow Roof 1 is between the fornt and the center roof rail.It is at the distance 27-30% form the total distance of the roof.Bow Roof 2 is between the center roof rail and the rear roof rail.It is at the distance 75% form the total distance of the roof.The Reinforcement is used to strength the component and it is not nessery when their is no sun roof.The thickness of the roof is 0.75mm and all the other components present in the roof is also 0.75mm.

 

TOOLIND AXIS

The direction in which the mold or core and cavity opens is the tooling axis.

DRADT ANALYSIS

Draft analysis is done after determining the tooling axis, draft analysis is used to check whether the minimum draft (7 degrees) is maintained or not.The minimum draft angle of all the componts in the roof is 7 degrees.

• Front Roof Rail Draft Analysis

• Bow Roof 1 Draft Analysis

• Center Roof Rail Draft Analysis

• Bow Roof 2 Draft Analysis

• Rear Roof Rail Draft Analysis

Bow–Roof Calculation Table

SL.NO	BOWS	Rx	Ry	R	l	L	t	R^2/t	W	OK/NG
1	FR&1st	5706.82	2910.58	3855.027	413.55	2125.79	0.75	19814977.56	1.82	OK
2	1st&CTR	6665.55	4855.75	5618.51	397.61	2125.79	0.75	42090206.16	2.21	OK
3	CTR&2nd	10883.53	3918.62	5762.46	429.31	2125.79	0.75	44274593.67	2.29	OK
4	2nd&RR	14459.49	3315.31	5393.89	248.59	2125.79	0.75	38792065.78	1.98	OK

Heat Distortion Criteria is OK

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]

Judgment Condition

OK< 2.7

EXAMPLE CALCULATON

      R = 2(Rx*Ry)/(Rx+Ry)

          =2(5706.82*2910.58)/(5706.82+2910.58)

          =3855.027

     W=[1.73 x 10^(-3) x 2125.79] + [1.85 x 10^(-8)  x (3855.027^2)/0.75] + [ 1.10x10^(-3) x 413.55] - 2.68 

          =3.678+0.3665+0.455-2.68

           =1.82< 2.7

Heat Distortion Criteria is OK

Snow Load Table

S.NO.	BOW	Iy	α	Lx	Ly	Y	s	Rx	Ry	t	Qr	Determination(Qr)
1	FR&1st	10748.10	1.09	1133.039	2125.79	540.16	507.28	4444.54	2726.61	0.75	85.04	OK
2	1st&CTR	9838.99	0.92	1081.26	2125.79	474.39	489.74	3794.26	6610.99	0.75	45.38	OK
3	CTR&2nd	9370.73	0.91	1055.26	2125.79	505.09	482.62	4303.65	11523.62	0.75	19.16	OK
4	2nd&RR			1041.46	2125.79	460.14		3882.14	17067.93	0.75

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

Snowed Condition OK.