Roof Design

AIM

   To Create an ASSEMBLY by developing the essential flanges for the outer roof and creating the reinforcements.Provide appropriate dimensions and check for Draft analysis And curvature study on the roof and perform calculations to determine the position of the Bow-roofs.

DESIGN CONSIDERATIONS

• Front Visibility criteria
• Rear Visibility Criteria
• Head room clearance

JOINING TECHNIQUES

• Spot welding 
• Mastics

MASTIC 

• Mastic is an adhesive and sealant.This material has the task of filling the irregularities that may occur between two surfaces by isolating junction of materials of the same or different nature.
• Clrearance is 5mm

SPOT WELDING

• Spot welding process is used primarily for welding two or more metal sheets together by applying pressure and heat from an electric current to weld area.
• It has no clearance gap.

ROOF DESIGN

• It consist of four types of roof rail to be classified 

1.Front Roof

2.Rear Roof

3.Bow Roof 1&2

4.Centre roof

FRONT ROOF

REAR ROOF

BOW ROOF 1

BOW ROOF2

CENTRE ROOF

HEAT DISTORTION CALCULATION

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]

TABULAR COLUMN

HEAT DISTORTION CRITERIA
CASE	BOWS	Rx	Ry	L	l	t	W	RESULT
1	Front roof to Bow roof 1	2442.2137	5732.5601	2034.5604	438.8823	0.75	1.611	OK
2	Bow roof 1 to centre roof	6862.1208	4806.8320	2034.5604	471.6962	0.75	2.1465	OK
3	cente roof to bow roof 2	11174.8743	3861.6831	2034.5604	358.4217	0.75	2.04656	OK
4	Bow roof 2 to Rear roof	1490.0353	3233.6793	2034.5604	335.9219	0.75	1.3118	OK

Judgment Condition

OK< 2.7

 RESULT

   Thus, the Heat distortion criteria judgement condition is 1.3118 ~ 2.1465. So, it PASS the judgement condition.

SNOW LOAD CALCULATION

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

TABULAR COLUMN

SNOW LOAD CRITERIA
CASE	BOWS	Iy	Rx	Ry	α	t	Lx	Ly	s	Qr	RESULT
1	Front roof to bow roof 1	7.7505x 103	2686.8261	4471.6410	0.9715	0.75	1136.9230	1935.3035	538.4322	34.3973	OK
2	Bow roof 1 to centre roof	2.7036x 103	6804.5599	3810.5293	1.0834	0.75	1082.2883	1935.3035	483.6623	10.3025	OK
3	Centre roof to bow roof 2	943.0938	15727.5000	6367.2219	0.7293	0.75	1057.2573	1935.3035	432.7671	1.3772	NOT OK

Judgment condition

Qr ≥ 3.1

250 ≤ s ≤ 380

RESULT

 Thus, the Snow load criteria FAILS not satisfied the judgement condition

SECTION MODULUS

FRONT ROOF

BOW ROOF

CENTER ROOF

RESULT

   Thus, the ROOF DESIGN Curvature study HEAT DISTORTION CRITERIA is pass the judgement condition, But, its snow load criteria not satisfied judgement condition. so, here we added the longitudinal embosses.it increase the stability and also increase the thickness. It helps to PASS the judgement condition.

DRAFT ANALYSIS

FRONT ROOF

REAR ROOF

BOW ROOF 1

CENTRE ROOF

BOW ROOF 2

CONCLUSION

 Thus, the ASSEMBLY by developing the essential flanges for the outer roof and creating the reinforcements and appropriate dimensions and  Draft analysis And curvature study on the roof and perform calculations to determined the position of the Bow-roofs.