Roof Design
ROOF DESIGN
OBJECTIVE: For the Given Roof styling, create an ASSEMBLY by developing the essential flanges for the outer roof and creating the reinforcements.
Provide appropriate dimensions and check for Draft analysis.
Do a curvature study on the roof and perform calculations to determine the position of the Bow-roofs.
Suggest and implement remedies in the design if the criterion is not full-filling
Start with the creation of a roof ditch area with a tool opening angle of 7 degrees.
Develop the reinforcements as separate parts.
Roof
The component of an automobile that lies above the passenger compartment and protects the occupants from the sun, wind, rain, and other external elements is known as the roof or car top.
The roof consists of following reinforcements rails.
- Front Roof Rail
- Bow Roof-1
- Center Roof
- Bow Roof
- Rear roof
Factors which is to be considered before creating the ditch area,
- Head room clearance
- Visibility Criteria
- Back door assembly
- Windshield assembly
Front roof Rail
It is the rail positioned at the front portion for the roof & top of the front wind shield glass.
REAR ROOF RAIL
It is the rail positiioned at the rear part of the car roof it holds the back door when it is opened.
BOW ROOF
It is the reinforcement give at intermidiate protion of the roof to provide the roof additonal strength.
CENTER ROOF RAIL
Center roof rail is positioned at the center of the roof
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
From the above table it proves that the designed structure withstands heat distortion criteria.
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
SECTION INERTIA OF ROOF REINFORCEMENTS
FRONT ROOF RAIL
REAR ROOF RAIL
BOW ROOF -1
BOW ROOF-2
CENTER ROOF RAIL
SNOW LOAD CALCULATION TABLE
DRAFT ANALYSIS OF ROOF REINFORCEMENTS
FRONT ROOF RAIL
REAR ROOF RAIL
BOW ROOF -1
BOW ROOF -2
CENTER ROOF RAIL
From the the above draft analysis the roof reinforcement is good.