Challenge 6 : Concept Modeling of Side Fender

DESIGNING OF CAR FENDER WITH THE HELP OF CONCEPT MODELLING TECHNIQUE USING ALIAS SOFTWARE

AIM

The aim of this project is to build a concept model of a fender of a car with the help of curves and surface generation technique using Alias software.

INTRODUCTION

Autodesk Alias (formerly known as Alias StudioTools) is a family of Computer-aided industrial design (CAID) software predominantly used in Automotive Design and Industrial Design for generating Class A surfaces using Bézier surface and NURBS modelling method.

The outside portion of the car which people can see from their naked eye is called the class A surface of the car. This surface needs to be designed with the help of concept modelling technique with the help of which the design of the car can be made and visualised. 

In order to make the surfaces smoother and realistic Autodesk Alias software is used. This software enables us to make surface as smooth as possible with the help of different continuities which can be given to the curves and surfaces.

FENDER

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.

Sticky materials, such as mud, may adhere to the smooth outer tire surface, while smooth loose objects, such as stones, can become temporarily embedded in the tread grooves as the tire rolls over the ground. These materials can be ejected from the surface of the tire at high velocity as the tire imparts kinetic energy to the attached objects. For a vehicle moving forward, the top of the tire is rotating upward and forward, and can throw objects into the air at other vehicles or pedestrians in front of the vehicle.

Purpose of fender:

Cleanliness: Protect the car, occupants and passsersby from items, water, mud, snow, ice, thrown off the tires as you drive.

Safety: Protects pedestrians from the wheel, e.g. its better to be it by a laterally moving fender than a rolling tire, keeps loose, streaming items from being wrapped up in a rolling wheel.

Aerodynamics: smooths the car profile so you don't get a lot of drag off the uncovered wheels. Some fenders are enclosed on the side for this.

General appearance: looks better with fenders, gives a finished look, looks more streamlined.

The position of the fender of a car is highlighted above.

DESIGN METHODOLOGY

PROCEDURE:

1. Importing the fender image into the alias workbench.

The first in this project is to import the image of the fender which needs to be concept modelled. The below image shows the fender which will be designed in this project.

The image of the fender will help us to build the concept model of the fender.

Steps for importing Image

File -> Import -> Canvas Image -> Go

Scaling the Image:

After placing the image in appropriate layer the blueprints of the fender will be scaled down to appropriate size so that it can be positioned accurately with respect to the other views. This will help in generation of curves at appropriate places and with desired shape of the blueprint.

Steps to scale the image:

-> Press ctrl + shift along with clicking and holding the left mouse button.

-> Select Pick object - Select the image

->  Press ctrl + shift along with clicking the middle mouse button

-> Select Scale

-> Hold left mouse button and move up and down to scale the image larger and smaller.

Steps to move the image:

Palette -> Transform -> Move.

The image is given some amount of transparency so that the curves can be traced easily on it at required positions.

Steps to set transparency.

-> Press shift + ctrl  along with clicking and holding right mouse button.

-> Select plane editor.

-> Set the value of the transparency level for the different views of the image in it.

2. Creation of different layers as per requirement.

Layers allow us to organize related objects into groups that you can pick, display, and edit individually or together.

Steps to create Layers

Menu Bar -> Layers -> New

The names of different layers mentioned in this project is shown below:

3. Generating the curves to trace the required shape of the fender.

After placing the image at required positions the curves are traced on it to give desired shape of the fender:

Cv Curve - It lets to create new NURBS on the scene by placing CVs.

In order to join curves at few places blends feature is used to give desired shape.

Steps for showing blends bar-

Palette -> Blend -> Blend Curve Toolbox -> New

Curve Trim

At few places the curves are trimmed to remove curves at certain places where it is not required.

Steps to perform curve trim:

Palette -> curve edit -> crvsct

-> Select the curve -> click on "GO" present in bottom right corner -> select the curve where you want the portion of the original curve to be removed.

The final view of the curve network which was build by using the features in curves is shown below:

Different views of the curve network:

1. Front view

2. Top view

3. Side view

4. Generating the surfaces on the curve to design the concept model of the fender.

After the file in which the model of the fender is being imported, the surfaces needs to be made with the help of these curves. For this purpose surface features are used which are present inside the palette bar.

 The steps to use the surface generation features are:

Windows -> Palette -> Surface

By following the above procedure the surface generation features can be used.

Few of the  surface generation features that were used in this project is listed below:

1. Square

2. rail

3. skin

4. ffblend

1. Square:

Steps to go to square feature:

Windows -> Palette -> Surface -> Square

Square feature creates surfaces by blending four boundary curves (or curve segments), while maintaining continuity with adjacent surfaces.

Square Control

Continuity Table

Continuity

Free Boundary – This edge is free to move if required by another edge’s continuity or by the Influence sliders (see below). This is the default.

G0 Position – Keep this edge exactly like the boundary curve that created it. In other words, do not let the edge move as with the Free option. This is equivalent to positional continuity.

G1 Tangent – Try to keep tangency with a surface that shares this edge.

G2 Curvature – Try to keep curvature continuity with a surface that shares this edge.

Implied Tangent – Try to keep tangency with an implied surface that shares this edge. The implied surface is the surface that would be created by mirroring the new surface. (The way the Square tool tries to keep tangency with an implied surface is by blending the slopes of the boundary curves.)

This is a powerful feature. It lets you model one half of a symmetrical surface (such as a car body), and maintain continuity at the seam. When you duplicate the surface to create the other half, the seam will already be continuous. For this to work across a symmetry plane, you must make sure the ends of the curves are tangent across the symmetry plane (that is, the tangents are perpendicular to the symmetry plane).

Implied Curvature – Try to keep curvature continuity with an implied surface that shares this edge. The implied surface is the surface that would be created by mirroring the new surface.

2. Rail

Steps to go to rail feature:

Windows -> Palette -> Surface -> Rail

Rail feature creates a surface by sweeping one or more profile curves along one or two path curves (rails).

The Rail Surface tool takes its name from its use of one or two “rail” curves. The generation curves maintain contact with the rails at the same points through the sweep, like a train traveling on a track.

The Rail Surface tool is similar to the Extrude tool, but has many more options and much more power.

The appearance of the Rail Surface icon depends on the Generation Curves and Rail Curves settings in the Rail Surface Options window.

3. Skin

Steps to go to skin feature:

Windows -> Palette -> Surface -> Skin

Skin feature is used to create a surface by connecting a set of profile curves.

4. ffblend - Freeform blend

Steps to go to ffblend feature:

Windows -> Palette -> Surface -> ffblend

Free form blend enables us to create a transitional surface by selecting two input contact lines. These input contact lines can be surface curves or free curves.

To edit the surface, surface edit tools are used to obtain desired shape.

The various surface edit tools used to give desired shape to the surface is shown below:

1. Project

2. Trim

1. Project

Steps to go to Project feature.

Windows -> Palette -> Surface Edit -> Project

This feature is used to create curve on surface of the existing curve which will be projected on the selected surface.

This is like shining a flashlight at the curve, and turning the shadows on the target surfaces into curves-on-surface. The line between the flashlight, the curve, and the shadow is the projection vector.