Roof challenge
Design of Car Roof
Introduction
An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle from sun, wind, rain and other external elements.
Roof consists of rail section at front and rear, bow roof and centre roof and reinforcement. front and rear roof rail are sketched using the given master section,here these section are used to support o r protect outer panel of roof.
Outer roof
Outer roof panel is designed by considering aerodynamics and other factors, its consist emboss for strengthen and sun roof if needed, its thickness is about 0.75mm.
Front roof rail
Front rail is done using the given master section. It is designed in such way that passenger are able to see road and head clearance is considered and here wind shield glass are placed over it using sealent. Its thickness is about 0.75mm
Draft Analysis
It is used to obtain visual feedback on the back draft condition of our parts and to define an optimum die press direction that minimizes back draft.
Section Modulus
Section modules is a geometric property of the cross section used for designing beams and flexural members. It is used to identify how much load can it withstand i.e strength.
Bow roof
Bow are placed between the rail and centre rail as they are used to strengthen or to support the roof on flat surface to prevent from crash. Here two bow roof are used in this design. Its thickness is about 0.75mm
Bow 1
Draft Analysis
Section modules
Bow 2
Draft Analysis
Section modulus
Centre roof rail
Centre roof rail is also used to strengthen the roof will also contain reinforcement for more support, here the small room lamp can be fixed to the rail if needed. Its thickness is about 0.75mm
Draft Analysis
Section modulus
Rear roof rail
Rear rail varies from the front because here back door is placed or fixed and here also head clearance is considered. The back door roll up while opening and closing so it is designed according to it. Its thickness is 0.75mm.
Draft analysis
Heat distortion formula
W= (1.73*10^-3 * L + 1.85*10^-8 * R^2/t + 1.10*10^-3 * l) – 2.68
Judgement condition W is ok < 2.7 > 3.1
Where,
L is roof length in X direction in mm (roof dimension with OY)
R is roof curvature R= 2(Rx+Ry)/(Rx*Ry)
Rx is x curvature and Ry is y curvature
t is thickness of roof in mm
l is bow roof span in mm
|
S.no |
Bow position |
Rx |
Ry |
l |
L |
t |
R^2/t |
w |
Ok/ng |
|
1 |
Fr-bow 1 |
5780.67 |
2379.11 |
364.99 |
2092.69 |
0.75 |
15150533.3 |
1.62 |
Ok |
|
2 |
Bow 1-centre |
5052.08 |
5916.03 |
385.15 |
2092.69 |
0.75 |
39603749.3 |
2.07 |
0k |
|
3 |
Centre-bow2 |
4108.22 |
9944.00 |
409.00 |
2092.69 |
0.75 |
45075310.2 |
2.23 |
Ok |
|
4 |
Bow2- rear |
3302.36 |
14453.84 |
461.21 |
2092.69 |
0.75 |
38549379.6 |
2.16 |
0k |
Snow load formula
Qr = ( Iy*t^2) / (α x s x[(Rx+Ry)/2]^2x10^-8
Where,
α = My*Lx^2*10^-12
My = Y(Ly-Y)
t is roof plate thickness
Ly is distance between the front and rear roof rail with OY (mm)
Lx is distance between the left and right end of the roof on the roof bow
Y is distance from front roof rail to roof bow (mm)
S is distance for which roof bow bears divided load (mm)
S = L1/2 + L2/2
Iy is moment of inertia of roof bow
Rx is lateral direction curvature radius of roof panel Y-cross section on roof bow (mm)
Ry is longitudinal direction curvature radius of the roof panel X cross – section on roof bow (mm)
Judgement condition = Qr ≥ 3.1
|
S.no |
IY |
α |
LX |
LY |
Y |
S |
Rx |
Ry |
T |
QR |
Ok/ng |
|
1 |
238.42 |
0.89 |
1114.5 |
2034 |
453.40 |
374.9 |
5780.67 |
2379.11 |
0.75 |
6.9 |
Ok |
|
2 |
3355.0 |
0.84 |
1076.02 |
2034 |
463.18 |
397 |
5052.08 |
5916.03 |
0.75 |
18.8 |
Ok |
|
3 |
240.40 |
0.84 |
1055.94 |
2034 |
488.76 |
435.1 |
4108.22 |
9944.00 |
0.75 |
7.4 |
Ok |
|
4 |
- |
- |
- |
- |
550.91 |
- |
3302.36 |
14453.84 |
0.75 |
- |
- |
Views of Roof
Conclusion
Roof of car is successfully designed and heat distortion & snow Load condition it is statisfying the condition.