Roof Design
AIM
- Designing a car roof with essential flanges and reinforcements
- Perform a curvature study on the roof and perform the calculation for the heat distortion and snow load criteria to determine whether the bow roofs are at correct positions
- Perform the draft analysis for each reinforcement
CAR ROOF
An automobile roof is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain and other external elements. Roof is the structure above the wind shield glass having the reinforcement to provide the strength to the overall structure and to with stand the overhead forces like snow
MASTER SECTION USED AS REFERENCE
ROOF DESIGN
Roof Panel
Roof panel is designed form the given surface based on the given reference
Roof reinforcements
- Front roof rail
- Rear roof rail
- Centre roof and bow roof
I centre roof and 2 bow roofs are designed
Final Assembly
DRAFT ANALYSIS
Front Roof Rail (FR)
Bow Roof 1 (BR1)
Centre Roof (CR)
Bow Roof 2 (BR2)
Rear Roof Rail (RR)
CALCULATIONS
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]
Judgement Condition
ok < 2.7
|
Roof rail |
Ry (mm) |
Rx(mm) |
R(mm) |
L(mm) |
t(mm) |
I(mm) |
W |
Result |
|
FR-BR1 |
2535.922 |
5690.325 |
3508.336 |
2031.646 |
.75 |
376.626 |
1.55264 |
pass |
|
BR1-CR |
6210.33 |
4970.375 |
5521.596 |
2031.646 |
.75 |
419.073 |
2.04476 |
pass |
|
CR-BR2 |
10487.752 |
3986.211 |
5776.772 |
2031.646 |
.75 |
416.362 |
2.11590 |
pass |
|
BR2-RR |
13957.815 |
3293.051 |
5328.868 |
2031.646 |
.75 |
347.99 |
1.91799 |
pass |
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 centre 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 from 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
Judgement Condition
Qr ≥ 3.1
250 ≤ s ≤ 380
|
Roof rails |
Iy(mm^4) |
Ly (mm) |
Lx (mm) |
L1 (mm) |
L2 (mm) |
Ry (mm) |
Rx (mm) |
t (mm) |
Y (mm) |
S (mm) |
My (mm) |
α |
Qr |
Result |
|
FR-BR1 |
2092.42 |
2031.646 |
1141.676 |
512.721 |
501.282 |
4138.133 |
3885.31 |
.75 |
512.721 |
507.002 |
778784.745 |
0.99675 |
14.47148 |
ok |
|
BR1-CR |
2670.71 |
2031.646 |
1090.634 |
501.282 |
498.93 |
8437.746 |
3994.911 |
.75 |
501.282 |
500.106 |
767143.927 |
0.91250 |
8.51892 |
ok |
|
CR-BR2 |
2125.93 |
2031.646 |
1062.294 |
498.93 |
518.714 |
13758.074 |
4314.604 |
.75 |
498.93 |
508.822 |
764717.993 |
0.87883 |
3.27502 |
ok |
CONCLUSION
Roof is designed with reference to the master section and reinforcements are added and calculations for snow load condition and heat distortion are done