Roof challenge
Aim: Create the essential flanges and reinforcements for the given styling and also measure the draft analysis and section modulus study for each section.
Roof: This is the important part of the automobile which protects occupants from environmental conditions like heat, rain, and winds. The roof is the assembly of the front roof rail, back roof rail, center bow reinforcements, bow 1, and bow 2. These reinforcements depend on the size of the car.
Roof Assembly:
The Master section is followed for the designing of the reinforcements.
Top:
Bottom:
Side:
All Components:
Centre Bow And Reinforcement:
Bow 1 & Bow 2:
Bow 1 Bow 2
Front and Rear Roof Rails:
front roof rail rear roof rail
Mastics Placement:
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
Judgement Condition : OK< 2.7> 3.1
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]
| S.NO | BOWS | Rx (mm) | Ry | R | I | L | t | R^2/t | W | OK/NG |
| 1 | FRR-B1 | 3341.88 | 14492.395 | 5431.321 | 261.95 | 2033.705 | 0.75 | 39,332,330.406 | 1.85 | OK |
| 2 | B1-CRR | 4071.773 | 10136.575 | 5809.76 | 336.72 | 2033.705 | 0.75 | 45,004,415.010 | 2.04 | OK |
| 3 | CRR-B2 | 5107.982 | 5910.474 | 5480 | 335.73 | 2033.705 | 0.75 | 40,040,533.333 | 1.87 | OK |
| 4 | B2-RRR | 5923.06 | 2318.02 | 3332.03 | 256.26 | 2033.705 | 0.75 | 14,803,231.894 | 1.34 | 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)
Judgement condition = Qr ≥ 3.1
250 ≤ s ≤ 380
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 reference point of the front and the rear.
Lx = Distance between the Left and Right end of the roof on the Roof BOW [mm]
Width of the roof panel 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 | BOW | Iy | Rx | Ry | Lx | Ly | t | y | s | α | Qr | ok/NG |
| 1 | FR-BI | 8.421*10^3 | 3912.465 | 4063.664 | 1113.025 | 2033.705 | 0.75 | 456.05 | 483.425 | 0.891 | 138.63 | ok |
| 2 | B1-CR | 1.821*10^5 | 3994.1 | 8441.218 | 1073.934 | 2033.705 | 0.75 | 510.80 | 510.855 | 0.897 | 867.320 | ok |
| 3 | CR-B2 | 1.883*10^4 | 4314.707 | 13883.708 | 1052.938 | 2033.705 | 0.75 | 510.91 | 510.459 | 0.862 | 592.004 | ok |