Hood design-Week 2

A car hood, also referred to as a bonnet in some other countries, is the hinged cover that rests over the engine of a front-engine vehicle. Its purpose is to provide access to the engine for repair and maintenance. ... Hoods sometimes also contain a hood scoop, wiper jets, power bulge, and/or hood ornament. It is used for resisting areodynamic force as the air flows around the car

Types of hood

1 INLINE HOOD (if the side reference line falls on fender , the the wrap around distance will be more , so impact zone will be lesser)

2 WRAP AROUND HOOD (if the side reference line falls on hood , the the wrap around distance will be less, so impact zone will be higher)

note : side reference line refers to measuring some part of the roadway with a point on your vehicle , thus giving you an accurate picture of your vehicle's position.

During the times of frontal collitions , the energy from the front end of the hood is dissipated out the car body rather than sending it inside the car

Factors to be considered before designing the hood

* Head zone criteria

*Opening and closing angle for support rod ?

* Where the support rod is going to get mounted and dismounted ?

* Hinge axis

* Hymming rules and regulations

The hood must be desingned in such a way that it meets all of the below following criterias

*gas stay mounting

Whenever preparing for support and layout for hood while designing , designer must also make arrangments for placing the gas stays for holding the hood in its opening position

* latch and striker placements

This is used to lock the hood to the frame near engine compartment , proper space for locating latch and striker must be made .

* NCAP regulations

The European New Car Assessment Programme (Euro NCAP) is a five-star safety rating system for comparing cars, and helps consumers judge the crash-safety of different makes and models. ... Cars with good test results and good safety equipment receive more stars

The rating itself is based on the Adult Occupant Protection and Child Occupant Protection scores resulting from the crash test.

DEEP DRAWING PROCESS

Deep Drawing the sheet metal is forced against a die that has been cut into the three - dimensional or often curved shape that the sheet metal is to take on . In effect , the die is used as a mould for the metal . This technique can produce relatively complex shapes Once again , pressure is applied to the workpiece using a hydraulically or mechanically operated punch .

HEMMING PROCESS

Hemming - It is a sheet metal forming process in which sheets are by bending it usually to 180 Automotive body panels and automotive parts such as deck - lids , trunk - lids , doors , hoods and tailgates are formed by hemming process . the hood outer panel is bend inside the inner panel to wrap around its boundary to house it , then both the panels are get attached by a roller which rolls on the panels outer surface with pressure to make them bind togeather tightly

HOOD OUTER PANEL

Hood outer panel - Outer panel provides the aesthetic look for the hood of car . its is designed in such a way that incase of any collision with the predestrian , the outer panel must not injure the predistrain so badly but at the same time it must also serves it purpose (covering the engine ) perfectly . By hemming process , the outer panel is made to attach with inner panel . Mastic sealants are provided between outer panel and inner panel to reduce vibration .

HOOD INNER PANEL

It provides the strength and rigidity to outer panel . The emboss is done in order to give strength to the inner panel , cut is done on the inner panel to reduce the weight as well as to reduce the impact when the car front hits pedestrian . Edge blend and face blend is done on the corner and face to remove sharp edges / corners . reinforments are given to provide strength to the hood .

HINGE

hood hinge acts like a door hinge and allows the hood to pivot open and closed

hinges on the both sides of the hood must lie on the same axis so that the hinges mid point will be perfectly perpendicular to the trajectory path of the hood

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latch trajectory

The hood latch which keeps the hood closed until it needs to be raised . Latch Trajectory The latch trajectory is obtained by drawing the circle taking reference of hinge connecting line midpoint . After drawing circle , a tangent line is drawn on the circumference at require angle , and a mid - line is drawn to striker latch . The tangent line on circle at an angle and the mid line of striker latch are made coincident by applying constraints

EMBOSSES

Emboss Definition Emboss are provided on inner panel to give stiffness for the sheet metal The emboss design decides how the force is dissipated when the collision has happened with the pedestrian of any object at front To reduce the impact force the force is made to go sidewards

FINAL HOOD DESIGN