Design of Roof of a car
Objective : To design a Roof of a car & do the curvature study to resist Heat distortion & snow load condition.
What is a Roof on a car ?
Roof of an automobile is that commodity which sits above the passenger compartment. Roof houses the vehicle as shielding part which safeguards the occupants from sunlight, heat, rain, wind, dust, etc.
Fig.1.1.
Types of Roofs
- Convertible roofs. Roof modules.
- Hardtops
- Sunroofs
- T-tops
- Targa tops
- Vinyl roofs
- Solar - powered rood tops
Components of the Roof
1) Front Roof Rail (FRR)
2) Bow Roofs (BR)
3) Reinforcement Roof Center (RRC)
4) Rear Roof Rail (RRR)
Front Roof Rail is present on the front of the car. To design a front roof rail we should have some basic knowledge of dimensions to accomodate commodities & trims used. The fig.1.2. shows the master section of the front roof rail and the roof.
Fig.1.2.
This master section shows the following featureS :
1) The windshield is accomodated in the front of the FRR which is of 3.70 mm
2) Below the windshield , mastic rubber seals are provided which is 8 mm thick . This rubber seals are provided to avoid breakage of windshields
3) Below the rubber seals 2mm clearance is given to accomodate the commodities provided by the Trim team
4) Rubber sealents are used which is of about 8.50mm thick to hold the windshield on the roof
5) 3 degree angle is maintained from the styling point to satisfy the deep drawing criteria. We cant be able to draw the parts if there is anything above 3 degree
6) The dimensions 80 mm & 32 mm is provided based on two factors :
a) Visibility Criteria
b) Head room clearence
Similarly master sections are formed for the Reinforcement roof center & the Rear roof rail as shown in figure 1.3. & 1.4. respectively.
Fig.1.3.
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Fig.1.4.
Roof
Fig.1.5.
The Roof along with the ditch area which are extruded or coextruded parts which functions are to ensure the sealing between the parts of the roof and to allow the mounting of the roof racks/rails.
Front Roof Rail (FRR)
Fig.1.6.
Bow Roof 1
Bow roofs are placed in much flatter area in order to increase strength in bigger curvature regions. These Bow roofs should not be positioned on the mastic regions. It should always be placed apart from the mastic regions.
Fig.1.7.
We should try to reduce the non mastic influence area so that we get a roof of better strength.
Reinforcement Roof Center & Bow Roof 2
Fig.1.8.
The fig.1.8. shows the cross section view of the the bow roof (Pink surface) placed inside the Reinforcement roof center(Brown Surface) itself as the curvature available on the roof is better. Below the reinforcement roof a slot for fixing the room lamp in the car is provided.
Rear Roof Rail
Fig.1.9.
Fig.2.0.
Bottom view of Rails along with the Roof
Fig.2.1.
Top view of Rails along with the Roof
Fig.2.2.
Importance of the Embosses in Roofs
- Embosses are given to improve the strength of the roof.
- Embosses are created in some cases when we cannot satisfy the curvature study criteria and the curvature needs to be modified. When there is a huge modification in the radius of curvature of roof, the styling team cannot accept it.
- Embosses also provided for styling purpose and to improve the Aerodynamics
Fig.2.3.
Fig.2.4.
Section modulus Report
Front Roof Rail
Fig.2.5.
Bow Roof 1
Fig.2.6.
Reinforcement Roof Center
Fig.2.7.
Bow Roof 2
Fig.2.8.
Rear Roof Rail
Fig.2.9.
Curvature study of the Roof
1) Heat Distortion Criteria
Fig.3.0.
Fig.3.1.
Table.1.1
2) Snow Load Condition
Fig.3.1.
Table.1.2.
Conclusion
Hence from the results obtained in the curvature study of the roof we can conclude that the design of roof is acceptable.
The link to the .prt files of the Roof & the Roof Rails :
https://drive.google.com/open?id=1GIzKYGX3BNTKW9xDuNojWSttEfMqiz-s