Roof Design

AIM : To design and assemble the roof of a car.

OBJECTIVE: We were given class A surface of the roof and our task in this particular project is to model the entire roof with the help class A surface and also model the roof reinforcements based on the master sections, dimensions and parameters given to us. Also I done calculations for heat distortion criteria and snow load conditions along with draft analysis.

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 carriage, early automobile roofs used similar materials and designs.

REINFORCEMENTS DESIGN:

• DITCH AREA : Ditch Area of the Roof is designed by taking the considerations from class-A surface. It is designed to have only 3 degree of maximum draft angle and 0.75mm thickness.
• The ditch area is the extended portion of the main roof concealed by other BIW panels. The rails of the roof were attached by using Spot welds and Mastic Sealants. Visibility Criteria, Head Room Clearance, windshield clearance and back door clearance was also taken into the design consideration of the Roof.

• FRONT ROOF RAIL : The front roof rail is located on the front of the roof where the wind shield joins with the roof. The visibility criteria and the head room clearance of the passenger are taken into consideration for the bottom flange. One end of the rail is joined using spot welding while the other end is joined with the roof using mastic sealants for increased strength.

• FRONT AND REAR REINFORCEMENT/BOW ROOF : Bow roof is an additional siffening member for the roof to increase the strength and so that it can satisfy the norms. Both the ends are joined together using mastic sealants to increase strength and also this would not affect the styling of the roof.

• CENTRAL ROOF RAIL/ CENTRAL REINFORCEMENT : IT is located at the centre of the roof. The cross section of this is more, since it needs to provide more strength to the roof. Here both the ends are joined together using mastic sealants.

• REAR ROOF RAIL : This joins with the back door and the roof. Inputs from the backdoor are taken into consideration for designing this roof rail. Here one end is joined using spot welding while the other end is joined using mastic sealants.

COMPLETE ROOF ASSEMBLY:

ANALYSIS / CALCULATION:

HEAT DISTORTION CRITERIA : It is the temperature at which the metal softens and deforms under a specific load. This study is done to check the ability of the roof to withstand high temperature with respect to the positioning of the reinforcements which contribute to increased strength.

SNOW LOAD PREDICTION : It is a type of study done to check the ability of roof whether it can withstand to different temperatures like cold weathers, and also bear the atmosphere where the snow falls and rebound to its original position when a load of snow load is removed.

• From the above results and the criteria given to us, we can understand that it does not fullfil/meet the criteria.
• In order to fullfil it we must make roof more stronger by giving embosses at required areas, improve the bow structures and also increase the thickness of the reinforcements as well.

SECTION MODULUS :

• BOW ROOF 1:

• CENTRAL REINFORCEMENT:

• BOW ROOF 2:

DRAFT ANALYSIS : draft analysis can be done after modelling so that we can verify whether the product is manufactured by pressing or not. One side of the surface is highlighted by green and other side by Red colour means that the model can be manufactured. Result of the draft analysis is shown in the figure below.

CONCLUSION :

Hence the ditch area and all the respective reinforcements are designed as per the input parameters given and also the respective analysis/calculations have been calculated using the input parameters from the roof that I have modelled.