Fender Design Challenge

----------------- *** FENDER DESIGN *** ----------------

Objective:

To understand and design of Fender and its mounts such as Drip, Sill, Bumper, A pillar, Baffle using a Software design tool "NX CAD"

Introduction:

Fender is the American English term for the part of an automobile, motorcycle or other vehicle body that frames a wheel well (the fender underside). Its primary purpose is to prevent sand, mud, rocks, liquids, and other road spray from being thrown into the air by the rotating tire. Fenders are typically rigid and can be damaged by contact with the road surface.

Driving will be very messy if a car doesn’t have fenders that house the wheel wells. The tires of car spin fast when you drive. As they rotate, they catch moisture and debris from the pavement and spray them into the air.

The tire’s kinetic energy ejects these foreign matters into the air at high velocities. As this thing is happening, the moisture and debris that fly in the air can cause the following to happen:

• Get other vehicles or pedestrians on the road side dirty
• Hurt pedestrians
• Scratch the bodies of other vehicles
• Cause minor, and even major damage to other vehicles

There are  5 mounting regions on the  fender , they are

• A- pillar mounting
• Body mounting
• Sill mounting
• Bumper mounting
• Drip mounting
• 

Types of Fenders:

There are two types of Fenders 

1. Full bumper type
2. Half bumper type

• Presently we are using the half bumper type, the reason for choosing the half bumper type is that when we choose the full bumper type the blank used for creating it is very large and also has the lot of wastage, but in the case of the half bumper type we have the possibility to reduce the scrap. This is what we called as scrap management
• In half bumper type we reduce the usage of the steel material and uses the lots of plastic on the bumper which in term decreases the cars weight and increases the performance

The below figure shows Front fender and Rear Fender which are highlighted in red colour

 

Full Bumper type	Half bumper type

 

 

• Fender wheel arch is having some standard specifications, for example if you see the car from the front, if you see the wheel outside fender, it does more chipping and it causes lots of damage to the pedestrians and also to the car.
• In order to maintain the pedestrian’s safety, we have to position the tire wheel inside the fender
• For the European requirement the clearance between the wheel and the fender outer most skin is 5mm
• This requirement changes from country to country based up on the road condition.

Assembly:

There are two types of assembly, they are

• Bottom-up assembly
• Top-down assembly

Bottom-up assembly: 

The bottom-up assembly is the most preferred approach for creating assembly models. In this type of assembly, the components are created in part design work bench (As NX cad part) file. Parts are conceived in assembly design workbench using product structure tools. After inserting each component, constraints are applied to position them properly in the 3d space with respect to the other components. This assembly is preferred for large assemblies, especially those having intricate individual components.

Top-down assembly:

In the top assembly design approach, components are created inside the assembly design workbench. Therefore, there is no need to create separate part files of the components. This design approach is completely different from the bottom-up design approach. Here you have to create the product file first and then one by one create all the components. Note that even then the parts are created the product file, they are saved and opened individually one by one when they are needed. Here the construction and the assembly take place simultaneously.

Features/Tools used in NX CAD for designing process:

• SKETCH
• OFFSET IN FACE
• CURVE ON SURFACE
• BRIDGE CURVE
• EMBOSS
• TRIM SHEET
• LAW EXTENSION
• FACE BLEND
• EDGE BLEND
• DART
• THICKEN

 Data Given:

Master section for Drip Area mount for Half bumper type Fender

Drip Mount:

• It is the important mounting unit of the fender. It is connected with the engine compartment, therefore the lot of design constraints are to be followed while designing the fender
• While designing the drip area we have to initially leave 200-300 mm for cowl top
• For placing the headlamp we have to leave at least 150 mm at the front
• Cowl top part consists of wiper motor and its instruments

 The process of designing Fender mounts starts with drip mount, for our reference Drip mount master sketch given.

As per given master sketch, the dimensional parameters were followed

From A to C line B is 3degrees to vertical direction,

From C to E line D is 40deg inclined to horizontal direction, extended sheet 8mm

E to H line F  is 5 deg in vertical direction

H to J length 25 mm

And then, the end structure is as in below fig

 

             

 

Sheet metal operations for drip mounting:

Bending

Embossing

Punching

 

A Pillar Mount:

 The A-pillar is the structural pillar that combines the body to the roof, this make the sides of the windshield rest. front fenders are fastened to the A-pillar to form a robust structure

Sheetmetal operations for A pillar mounting:

Bending

Embossing

Punching

 

Sill Mounting :

Sill is the panel directly below the bottom of the door supporting the floor and may be used to combine the floor and the body. The bottom end of the fender is mounted on the sill body for reinforcement of the fender panel, thus the sill mounting position is designed with holes and emboss. 

 

Sheetmetal operations for Sill mounting:

Bending

Embossing

Punching

 

Baffle mounts:

Baffle mounting or mudguard are clip fit type of mounting on the inner side of the fender arch over the Tyre. It protects the car engine compartment and pedestrians from causing injuries from chip out debris on the road when the car is in motion. They are mounted on the fender using a special type of locking clips which are made up of plastics.

Embossments not given for baffle / splash mounts. only holes are given for fasteners to attach baffles

 

 

Bumper Mount:

Bumper Mount is fitted with plastic bumper using fasteners

Dart is given to add extra strength for mounting

 

Sheet Metal operations involved in Fender production:

Blanking

Bending

Embossing

Punching

Deep Drawing

First A sheet of metal blanked to required size and shape, then sheet is hydraulic pressed on the die to get desired curvature

The edges were bent to required dimension such as angle, length.

The formed sheet edges are then drawn for embossments

Holes for fasteners fitting are punched; dimension M5 or 5mm

Finally the sharp corners are trimmed to round corners to avoid risk of injury and damage

 

Final Fender: 

Note: Thickness given to sheet is 0.65 mm

n

 

Conclusion: Understanding the concepts of Different mounts, Design standards & Types of fenders and designed Fender mounts using "NX CAD" designing tool