Roof Design
TITLE: Roof Assembly Design
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AIM:
To design a Roof with its components by following the master section of the Front Roof Rail, Center Roof Rail, two Bow Roof Rails and Rear Roof Rail with all the design parameter mentioned and to study curvature on the roof based on the Bow roof prediction calculation as well as the manufacturing techniques.
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ROOF:
What is Roof?
- 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.
- Roof is the structure above the wind shield glass having the reinforcements to provide the strength to the overall structure and to with stand the over head forces like snow.
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What material is used for Roof?
- The material is same to the rest of the body for the car, the material is High Strength Steel.
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Why is roof rails used?
- If the roof is flat it is very weak and cannot able to with stand the forces like snow, so in order to increase the strength of the roof these reinforcements like front roof rail, central roof rail, rear roof rail and the bow roofs are introduced and joined to the flat surface of the roof with the different joining process.
- The number of bow roof rails depends on the length of the car.
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Types of reinforcements in a car :
- Front roof rail,
- Bow roof 1,
- Central roof rail,
- Bow roof 2,
- Rear roof rail.
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DESIGN CONSIDERATION FOR ROOF:
- Visibility criteria,
- Head clearance,
- Curvature study,
- Heat distortion and snow load prediction criteria,
- Draft analysis.
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ROOF ASSEMBLY:
The roof assembly consists of Outer Roof Panel, Front Roof Rail, Bow Roof Rail 1, Center Roof Rail, Bow Roof Rail 2, and Rear Roof Rail.
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1. Outer Roof Panel:
Outer roof panel is the primary component to house the roof rails and attach on the top to the rest of the BIW of a car.
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2. Front Roof Rail:
The front roof rail attaches to the front of the roof panel, A - Pillar of the BIW and above the front windshield.
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3. Bow Roof Rail 1:
The bow roof rail (1) is actually a reinforcement component to support between the front and center roof rails.
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4. Center Roof Rail:
The center roof rail supports the center of the roof and attaches to the B-Pillar of the BIW.
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5. Bow Roof Rail 2:
The bow roof rail (2) is also a reinforcement component to support between the center and rear roof rails.
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6. Rear Roof Rail:
The rear roof rail attaches to the rear of the roof panel, C - Pillar of the BIW and above the rear windshield.
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ASSEMBLY PROCESS:
- Mastics are applied between the roof outer panel and the reinforcements for joining, wherever the mastic is introduced there is remarkable improve of the strength.
- Spot welding is done to join the reinforcements to the outer panel.
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DRAFT ANALYSIS:
1. Outer Roof Panel:
2. Front Roof Rail:
3. Bow Roof Rail 1:
4. Center Roof Rail:
5. Bow Roof Rail 2:
6. Rear Roof Rail:
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CALCULATION:
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Heat Distortion:
The Judgement condition is OK < 2.7
This design satisfies the judgement.
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Snow Load Prediction:
The Judgement condition is Qr ≥ 120
This design satisfies the judgement.
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CONCLUSION:
Hence the outer roof panel, front roof rail, bow roof rails, central roof rail and the rear roof rail is designed by following the master section given. The moment of inertia and draft analysis are carried out to check feasibility manufacturing.
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