Design of a Car Roof
OBJECTIVE
- To design an automobile roof with the given master section.
- To perform heat distortion and snow load criteria checks for each part.
- To perform draft analysis with 3 degrees tooling angle.
INTRODUCTION
- Roof:- An automobile roof is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements.
- Front Roof Rail:- Front roof rail is used to provide strength to the roof panel. It also acts as a link between windshield glass and roof panel. Headroom clearance and visibility criteria are important factors for the design of the front roof rail.
- Center roof rail- This is a roof rail placed at the center of the roof to provide strength and stability.
- Bow roofrail - Bow roof rails provide additional support to the roof panel by increasing its strength. They are positioned on the basis of the strength at various parts of the outer roof panel.
- Rear roof rail - Rear roof rail is alsoused to strengthen the roof. It acts as a link between the roof panel and the back door of the car.
Front Roof Rail:
- Reference Image:
- Master Section:
- Part View:
- Front View:
- Top View:
- Isometric View:
Rear Roof Rail:
- Reference Image:
- Master Section:
- Part Views:
- Front View:
- Top View:
- Isometric View:
Centre Roof Rail:
- Master Section:
- Part Views:
- Front View:
- Top View:
- Isometric View:
Bow Roof Rail 1:
- Master Section:
- Part Views:
- Front View:
- Top View:
- Isometric View:
Bow Roof Rail 2:
- Part Views:
- Front View:
- Top View:
- Isometric View:
Roof Outer Panel:
- Part Views:
- Front View:
- Top View:
- Isometric View:
Bow Roof Prediction on the Roof
Bow roof prediction formula :
`W = (1.73 xx 10^-3 xx L) + (1.85xx10^-8xx R^2/t) + (1.1xx10^-3xxl) - 2.68`
where
- `L = "Roof length in X-direction (mm)"`
- `"R = Roof curvature =" (2xxR_x xx R_y) / (R_x + R_y)`
- `R_x" = X Curvature"`
- `R_y" = Y Curvature"`
- `"t = Roof plate thickness (mm)"`
- `"l = Bow roof span (mm)"`
Snow Load Prediction on the Roof
Snow load prediction formula
`Q_r = (I_y xx t^2) / (alpha xx s xx ((R_x + R_y)/2)^2 xx 10^-8)`
where
- `"t = Roof plate thickness (mm)"`
- `L_y "= Distance between roof rails on the vehicle along 0Y (mm)"`
- `L_x "= Distance between left and right end of roof (mm)"`
- `"Y = Distance from Front Roof Rail to Rear Roof Rail"`
- `"s = Distance for which roof BOW bears divided load (mm) = " (L_1 + L_2)/2`
- `I_y = "Geometric Moment of Inertia of Roof BOW (Y-cross section)"(mm^4)`
- `R_x = "Roof panel curvature radius of the length "L_x" in front view"`
- `R_y = "Roof panel curvature radius of the length s in side view"`
Bow roof 2 will pass the snow roof clearance by giving embosses on the roof outer panel
Draft Analysis on the Roof with 3 degree tooling angle
CONCLUSION
- Automobile roof was designed according to the given master section.
- Heat distortion and snow load criteria checks performed for the roof, and passed the tests.
- Draft analysis performed at 3 degrees tooling angle.