Roof Design

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.

When it is seeing from outside of the car, it is just closing the top portion. But in design point of view, it is hard to create the design. Because of you have to create no of support rails for enough strength to withstand the load. Bow roofs are primarily fixed in flatter region to enhance strength.

Front roof and rear roof rails are fixed to the ditch area using spot weld operation. But front, rear bow roof and center roof rails are fixed to roof using mastic sealants. We don’t want so much gap between roof rails and bow roof area. So, we reducing the NVH issues.

DESIGN CONSIDERATION OF ROOF:

• Visibility criteria
• Head room clearance
• Bow roof position
• Heat distortion and Snow load criteria
• Draft analysis

Design Of Roof from Input Surface-

Roof is designed according to input styling surface and master sections for

1. Front Roof Rail and Rear Roof Rail –

They are created with reference to master section.

In order to provide more strength to front and rear rails, embosses are created with cut outs.

It will provide additional strength and also reduce weight too.

Design Of Center Bow roof and Bow roofs from Input Surface-

1. Bow roofs.- Positions of bow roofs are decided on flat surface of roof.

As height of bow roofs master sections is not provided, it is decided considering Head Clearance Criterion.

It is considerd as 20 mm.

Ditch Area Creation-

This is an extension to both the Bow Roofs and center roof rail.

Purpose- to provide sufficient space at least 10mm for spot welding with roof.

Draft Analysis- Is performed for all the parts created. This analysis is performed for the manufacturability of the part.

ROOF:

FRONT ROOF RAIL:

REAR ROOF RAIL:

CENTER BOW ROOF:

BOW ROOF RAIL 1:

BOW ROOF RAIL 2:

curvature study on the roof based on the Bow roof prediction calculation as well as the manufacturing techniques

Design is cheked for two criterion-Snow Load Prediction and Bow Roof Prdiction-

Bow Roof Prdiction- This calculation provide a guidline to decide position and number of bow roofs in a vehicle.

It W is < 2.7, design is accepted with postions of bow roofs.

in case , if required, number of bow roofs can be added to increase the strength.

Ideally, 2 bow roofs, and 1 center roof rail is sufficient, but depending upon curvature, it may be increased.

bow roof adds strength to the roof.

Conclusion-

W value for all sections is less than 2.7, hence heat distrotion criteria meets.

Snow Load Prediction- Performed for vehicles in cold regions.

Roof shold be strong enough to sustian the load of snow collected over it.

Qr value from the claculations is cheked. if it is gretaer than or equal to 3.1, design is acceptable. or else it needed to change.

Conclusion-

Qr value for all sections is greater than 3.1, hence snow load prediction meets.