Hood design-Week 2

Challenge 3 - Hood Design

Introduction

Hood is a hinged door that covers the compartment that houses the engine and transmission components. An automotive hood also improves the aesthetics quotient of the car, so it is important for an automotive hood to be both functional and visually appealing. Car engine compartment is often accessed for service and maintenance activities; thus, it is important for the hood to be easy on its operator. Hood also is the component onto which the pedestrian crashes when the automobile undergoes an accident, thus it is critical to follow and implement design parameters that minimize impact to pedestrians as well as its occupants in case of any mishap.

Design considerations for automotive hood

Safety

The prime safety requirement to be considered while designing the hood is the Pedestrian Safety from frontal collision. Euro NCAP, a European vehicle and road safety organisation has developed test specifications and rating systems for assessing pedestrian impact during impacts with the front of vehicles. Such tests include a series of tests using impactors designed to mimic a collision at a speed of 40 kmph.

Thus, to avoid severe injuries to the head, the high impact area for adults and children are subjected to lesser thickness. Also, no reinforcement is provided in that area as during the head collision, the hood will absorb the head impact and collapse thus protecting the pedestrian from severe head injury.

Another important criterion for the hood design is the protection of the occupants inside the car during the front collision. The design of the hood should be in a such a way that the during the collision, the force should travel in a direction away from the its trajectory and dissipating impact energy in the process and thus no/minimum impact force to the occupants of the car.

Other considerations for hood design:

1. Aesthetics

Design of hood adds to the looks of the car. Hoods completes the flow to a car’s design; thus, it is important for the hood designer to work on aesthetic details of the hood.

2. Functionality

Hood is essentially a type of door that covers the powertrain and other vehicle propulsion system components such as drive belts, battery, fluid levels and lamp units in the frontal region of an automobile. As these components needed to be accessed often, so it is critical for the designer to work on hood’s weight, ease of use and hood mounting systems.

Subcomponents of hood:

1. Outer panel

The outer panel is the external cover the wraps over the inner panel. This component is styled to enhance the overall visual appeal of the car.

2. Inner panel

The inner panel serves as a structure for the vehicle to dissipate and channel shock waves at the event of a crash. Hence this part is designed with utmost precision to confirm to road and pedestrian safety norms.

3. Striker reinforcement

The striker is mounted onto to the car’s hood and latch is installed in the engine compartment. A striker reinforcement is designed onto the hood’s inner panel for enabling latching of hood to the engine compartment.

4. Hood stay reinforcement

A hood stay is an apparatus for an engine room of a car which can safely keep an engine hood in an open state. The support rod used is slightly bent intentionally, so that it adds strength & rigidity to the rod which can hold the hood. The positioning and type of hood stay differs from manufacturer to manufacturer.

5. Hinge reinforcement

The trajectory for opening and closing is maintained by proper positioning of hinges. Hinges are placed at the ends of the hood and are installed onto the reinforcements embossed in the inner hood.

Design procedure:

Given data:

1. Master sketch

2. Hood Thickness Information

• Outer Panel Thickness=0.75mm
• Inner Panel Thickness=0.75mm
• Reinforcement Thickness = 1.5mm

3. Hemming data

4. Corner reliefs data

Hood Designs:

        Inner panel design details

        The inner panel serves as a structure for the vehicle to dissipate and channel shock waves in the event of a crash. These design features helps in better              imfact force dissipation.

       Hinge and striker reinforcements

       The hinge position is first fixed and then to maintain the trajectory and striker position, the hood trajectory trace circle is draft with hinge points as axis.

       With the aid of trajectory circle the perfect position of striker is fixed and reinforcement for striker is embossed onto the inner panel.

       Mastic sealants are adhesive fillings that hold together the inner and outer panels. Mastic sealants provide thermal and acoustical insulation, and may serve as fire barriers.

      Outer and inner panel assembly

       The outer and inter panel are joined together by a process known as hemming. Conventional die hemming is suitable for mass production. In die hemming, the flange is folded over the entire length with a hemming tool. As hoods contribute substansially to a automobile's aesthetics, welding or riveting is not used for joining surfaces.

       Full hood assembly

     Full hood assembly - perspective view

   Conclusion

      All subcomponents of automobile hood were designed and assembled as per the given data. This project also helped me understanding various engineering processes and parameters in hood manufactring and assembling.

Checkout my hood designs by clicking the link below

https://drive.google.com/drive/folders/12sEeBvQig3AApFLgqcTdYlcNcbDjqTI6?usp=sharing