Roof Design
Roof:
Front Roof Rail:
Real Roof Rail:
Bow Roof Rail 1:
Center Roof Rail:
Bow Roof Rail 2:
Assembly:
Calculation Part:
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]
Judgment Condition
OK< 2.7
Result:
| Case | Rx | Ry | R | L | t | l | W | Status | |
| FRR-BRR1 | 5730.71 | 2668.02 | 3640.94307 | 2117.89 | 0.75 | 387.7 | 1.74 | OK | |
| BRR1-CRR | 8179.94 | 5775.02 | 6770.254748 | 2117.89 | 0.75 | 318.59 | 2.46 | OK | |
| CRR-BRR2 | 4176.83 | 21754.78 | 7008.127744 | 2117.89 | 0.75 | 406.56 | 2.64 | OK | |
| BRR2-RRR | 2691.38 | 14007.52 | 4515.214676 | 2117.89 | 0.75 | 464.36 | 1.99 | OK |
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
Judgment condition
Qr ≥ 3.1
250 ≤ s ≤ 380
| Case | Rx | Ry | t | Ly | L1 | L2 | S(L1/2 + L2/2) | Ly | Lx | Y | Iy | My=Y(Ly-Y) | α = My x Lx2 x 10-12 | Qr = [Iy x t2] / [α x s x [(Rx + Ry)/2]2 x 10-8] | Status |
| FRR-BRR1 | 4453.95 | 2712.1 | 0.75 | 2117.89 | 475.03 | 875.28 | 675.155 | 475.03 | 1153.96 | 530.06 | 47.63 | 793836.4 | 1.05709135 | 523.8503846 | Ok |
| BRR1-CRR | 3753.25 | 5674.86 | 0.75 | 2117.89 | 400.24 | 1682.63 | 1041.435 | 400.24 | 1121.78 | 400.31 | 115.42 | 651577.4 | 0.819938724 | 806.4276106 | Ok |
| CRR-BRR2 | 4165.03 | 9885.84 | 0.75 | 2117.89 | 487.36 | 1087.45 | 787.405 | 487.36 | 1098.92 | 354.55 | 96.09 | 593300.7 | 0.716484857 | 681.855457 | Ok |
| BRR2-RRR | 4132.99 | 15587.62 | 0.75 | 2117.89 |