Roof Design

Report On Roof Design of a Car

Draft analysis of every parts of Roof:-

a. Front Roof Rail .

b. Rear Roof Rail .

c. Centre Bow Roof.

d. Bow Roof 1.

e. Bow Roof 2.

Roof:

For Curvature study we have to check two parameters:

1. Bow roof Prediction (W)

2. Snow Load Calculation (Qr)

Calculation Based on 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]

Fig.1

The value of the required parameters will be calulated as per fig-1.

The value of each parameter along with calculation is mentionded in the below table.

As from the above table, the value of "W" for all the four cases is below "2.7" . Which means , our bow roof prediction is OKAY. and we can go further for Snow Load condtion to check the strength of the roof.

Snow Load Prediction Formula

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]

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

Fig.2

For distance or length measurement we have to follow the above Fif.2

The above image is the value of all the required parameters.

The above talble shows the value of "Qr" for all the three cases

Where,

Qr1 (For Case 1) = 38.301

Qr2 (For Case 2) = 19.308

Qr3 (For Case 3) = 9.29

Clearly All the value of "Qr" is greater than "3.1" which shows that our design is good and satisfy the snow load condition.

Conclution: As from above calculation, we came to know that our roof design along with its different components such as Bow Roof, Centre Bow Roof, Front Rail Roof, Rear Rail Roof is perfect and carvature of the good and we can consider this design for manufacturing process.

Note: Ecxel File of above calculation is attached, please check for varification.

Report prepared By: Vikash Rai (Mechanical Engineer)