Roof Design
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
Title- Design of Roof
Objectives-
1. For the Given Roof styling, Develop the essential flanges and reinforcements, provide appropriate dimensions and check for Draft analysis and also submit your section modulus report on the O-Y section.
2. Start with the creation of a roof ditch area the tool opening angle is only 3 degrees.
3. Do a curvature study on the roof and perform calculations to determine the position of the Bow-roof
Introduction
An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements. Because the earliest automobiles were designed in an era of horse-drawn carriages, early automobile roofs used similar materials and designs.
Types of Car roofs
• Convertible roofs
• Hardtops
• Sunroofs
• T-tops
• Targa tops
• Vinyl roofs
Safety point of view vehicle roof plays a very crucial role especially roll over kind of accidents, in which vehicle tips over onto its side of the roof. And vehicle rollover crashes are the causes of many fatalities and several heads, neck, and spine trauma around the world. Therefore, passenger safety is also a very important parameter in front of OEMs. It is not only a marketing strategy but also it is an obligation stipulated by international standards that are now placed in several countries, as well as a governmental requirement. Rollover crashes, especially in the country, are usually very destructive events. Vehicle damage often includes the deformation of the roof and its supporting structures. Head and neck injuries are common and associated with roof deformation. Strengthening of the roof is suggested as an appropriate countermeasure for such injuries.
Types of Rollovers
1. Tripped-NHTSA data show that 95% of single-vehicle rollovers are tripped. This happens when a vehicle leaves the roadway and slides sideways, digging its tires into soft soil or striking an object such as a curb or guardrail.
The high tripping force applied to the tires in these situations can cause the vehicle to roll over. E.g. Soft soil, Guardrail, Steep Slope
2. Un-Tripped -On-tripped rollovers are less common than tripped rollovers, occurring less than 5% of the time, and mostly in top-heavy vehicles. Instead of an object serving as a tripping mechanism, un-tripped rollovers usually occur during high-speed collision avoidance maneuvers.
Inputs Given From Styling Team
1. A surface with a railing Rack
Design of front roof rail
For designing the front roof rail we need to consider some parameters which are as discussed below
a. Visibility of the driver and passenger
We always keep in mind while designing the front roof we do not reduce the visibility available to the driver. While designing a front roof one must stick to the master section dimensions because little change in dimension will have an impact on the visibility of the driver (e.g. small change in angular dimension will lead to a large change in linear dimension)
Designing of Roof's Rails One by one as per Mastersections
1. Front Roof Rail
2 . Bow Roof 1
3. Center or Reinforcement Roof Rail
3 . Bow Roof 2
4. Rear Roof Rail
Creation of Roof Rails
Creation of Ribs on Outer Panel of Roof to strengthen the Roof Structure
Assembly view of Roof along with Roof Rails
Draft Analysis on Roof Rail's
Cross-Section View of Roof panel along with Rail's
Section Modulus
- Front Roof Rail
- Bow Roof 1
- Center Roof Rail
4. Bow Roof 2
5. Rear Roof Rail
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
Judgment Condition
OK< 2.7
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]
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)
Judgment 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 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
• From the above results, the last case failed to satisfy the judge's mental condition.
• Hence to increase the strength and stiffness over the roof from the center roof rail to Bow Roof 2 where the Qr
results were very low embosses were provided.
• The embosses over there will increase the strength and stiffness of the roof drastically.
As per Snow load criteria, we come to know there is improvement required so we forward this data to our styling colleague to improve and do changes on A surface.
Final Roof Design
Conclusion-
1. Using all input data we have successfully designed Ditch area flanges, Front roof rail, Bow roof rails 1&2, Rear roof
rail as per the requirement
2. As per heat distortion criteria we come to know all bow roof positions are OK
3. As per Snow load criteria we come to know there is improvement required so we forward this data to our styling colleague to improve and do changes on A surface.
4. All roof rails draft analyses are found OK