Roof Design
Aim: prepare report which includes the curvature study on the roof and calculation as well as the manufacturing techniques.
Roof is the top portion of the car, above the passenger sitting compartment. It protects you from direct sunlight, dust, rain and also helps to build close environment in vehicle. Most of the roof is made from steel sheet. Sports car also have carbon fiber roof.
· Heat distortion criteria
Prediction formula W=1.73 x 10-3x L+1.85 x 10-8 x R2/t + 1.10 x 10-3 x I -2.68
Judgment condition : ok < 2>< NG>
However, if the value is in the range of 2.7 < w <3>
L : ROOF length in X-direction
R : Roof curvature, R= 2 (RX x RY) / (RX + RY)
Rx : X Curvature
Ry : Y Curvature
t : Roof plate thickness (mm)
I : Bow Roof span (mm)
|
S.NO |
BOWS |
RX |
RY |
R |
I |
L |
t |
R2/t |
W |
OK/NG |
|
1 |
FR & 1ST |
5772.4 |
2862.1 |
1913.72 |
364.64 |
2030.92 |
0.7MM |
5231891.76 |
1.23 |
OK |
|
2 |
1ST & CTR |
4946.53 |
5845.7 |
2679.32 |
389 |
2030.92 |
0.7MM |
10255365.23 |
2.59 |
OK |
|
3 |
CTR & 2ND |
3978.8 |
10578 |
2887.57 |
430.81 |
2030.92 |
0.7MM |
11911515 |
2.31 |
OK |
|
4 |
2ND & RR |
3329.9 |
14461.4 |
2706.66 |
284.94 |
2030.92 |
0.7MM |
10465726.22 |
1.92 |
OK |
Snowed load pridiction criteria
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
S.NO |
BOWS |
iy |
α |
LX |
LY |
Y |
S |
RX |
RY |
t |
Qr |
Determination(Qr) |
1 |
FR & 1ST |
111.98 |
0.25 |
1105 |
2030.92 |
506.28 |
234.235 |
4352.2 |
2885.4 |
0.70 |
7.156 |
OK |
2 |
1ST & CTR |
4946.53 |
0.85 |
1085 |
2030.92 |
972.58 |
488.15 |
3771 |
6248.2 |
0.70 |
1.23 |
OK |
3 |
CTR & 2ND |
3978.8 |
10578 |
1071.36 |
2030.92 |
1,482.58 |
521.5 |
4277.1 |
11099.4 |
0.70 |
1.03 |
OK |
4 |
2ND & RR |
3329.9 |
14461.4 |
1064.63 |
2030.92 |
2,015.68 |
533.1 |
4081 |
5942.3 |
0.70 |
0.55 |
OK |
·
Draft Analysis
- Front roof rail.
2. 1st bow roof rail.
3. Center bow roof rail.
4. 2nd bow roof rail.
5. Rear roof rail.
Curvature Study
The data i used in heat distortion criteria
RY1 - R2862.1 RX1 - R5772.4
RY2 - R5845.7 RX2 - R4946.53
RY3 - R10578 RX3 - R3971
RY4 - R14461.4 RX4 - R3329.9
The data i used in Snowed load criteria
RY1 - R2885.4 RX1 - R4353.2
RY2 - R6248.2 RX2 - R3771
RY3 - R11099.4 RX3 - R4277.1
RY4 - R5942.3 RX4 - R4081
Parameter followed in Design
