Final Product

Below is the final 3D-printed model for my project.

Notice Anything Odd?

 The 3D Printer needs to build an interior support structure to apply layers that don't have anything underneath them. This is why the wheelhouses and the roof have plastic underneath them. Otherwise, the filament would just fall to printer bed below.

The support structure is very efficient, to allow for easy removal and to minimize wasted filament.

After pulling the support structure out with pliers, my model was complete.

Hooray!

The surface is full of ridges because the 3D printer cannot replicate the model with complete precision. I would have produced a smoother model by decreasing the layer height. (see previous post on 3D printing)

Sadly, this concludes our journey into the fascinating world of car design. I learned a lot in the past few months, and I'm sure you did too.

The next time you are on the road, I hope you see cars a little bit differently!

PS

To view my project's PowerPoint presentation, please click here.

CAD Model

After lots of trial and error, my surface model is finally complete. Surface models, as the name suggests, are two dimensional -- they have no thickness. To make a 3D printed model of this, I needed to add thickness to it. This was harder than I first expected because different parts of the car intersected each other when extruded outward, producing computer errors. I spent a lot of time correcting these errors to make 3D printing possible.

Here it is!

Preparation for 3D Modeling

Before I start developing my model in 3D, I need to make my initial sketches more precise. There are several key dimensions used in the Computer-Aided Design workflow that need to be identical across the sketches, to avoid any discrepancies. This includes the ground clearance, total height, and belt line height. It is also important that the height, width, and length have the correct proportional relationship, so the 3D printed model is to scale.

After making the necessary adjustments to the sketches, I am now ready for 3D modeling!

Below are the finalized sketches.

Design Considerations

After further reviewing my sketches, there are some design complications that I will have to address.

Firstly, the air intake system on the body side creates an impression on the doors. It is important that the side glass has enough room to drop into the door structure. This means I cannot add too aggressive indentations to the door's exterior surface, because it would push the interior trim inwards, cramping the occupants.

The side glass cut lines are not defined within the door profile. There are also no door cut lines. Fortunately, car doors are flush with the exterior surface, so door profiles will not change the final, 3D printed product. By contrast, side glass is slightly offset from the adjacent door surface, so cut lines are necessary to make changes to this surface.

A two dimensional model is not good at communicating the variation in depth along the vehicle surface, even with sketches from different views. I will have to wait for the 3D modeling to add more detail.

Occupant Packaging

To set up the occupant package, I must establish some key dimensions and position the SAE 95th Percentile Manikin. Before I can do that, I need to keep these factors in mind:

On a high performance car, the front and rear spindles are positioned to provide optimal weight distribution. I cannot change these to accommodate the occupants.

Crush space is behind the driver for a rear engine vehicle, because there are no hard components in front of the driver. Thus, there must be more room than for just the engine behind the driver's seat.

The dimensions below correspond to the diagram.

1. H-Point to Ground: 325 mm

2. Chair Height: 150 mm

3. Back Angle: 28 degrees

4. Forward Vision Angles: 8 degrees up, 5 degrees down

5. Effective Headroom: 955 mm

6. Shoulder Room: 1350 mm

7. Lateral Location: (from center line) 340 mm

Size and Proportions

In this phase of the design process, I will look at some key dimensions of the model, derived from my sketches, and compare them to similar vehicles. This is known as benchmarking.

The Ferrari LaFerrari is a modern rear engine, RWD supercar. I chose this vehicle for comparison because of the similarity in side profile view to my model.

Exterior Dimensions:

LaFerrari

Length: 185.1"

Width: 78.4"

Height: 43.9″

Wheelbase: 104.3″

Front Track: 66.9"

Rear Track: 64.4"

My Model

Length: 181

Width: 72.

Height: 47

Wheelbase: 105.5

Front Track: 65.

Rear Track: 63.

My Model

LaFerrari Front (not mine)

LaFerrari Side View (not mine)

Package Ideation

Before settling on one design, it is important to explore every possibility at the beginning. After the initial ideation phase, it will be too late to introduce different ideas and start from scratch.

There are two ways to complete the ideation phase for cars.

In one method, the exterior design is developed first to inspire the package layout. The package consists of all of the elements driven by function not appearance, such as the engine, fuel tank, wheels, seating, etc.

It is also possible to start by sketching different layouts for the cargo, occupants, tires, and powertrain. Then ,a loose sketch of the body profile will provide a medium to analyze how different package configurations change the exterior proportions.

Either way, the goal is to explore as many options as possible that satisfy the functional objectives.

I will use the latter method in my ideation phase.

For a high performance vehicle, a powerful engine is a necessity. This effectively eliminates the transverse engine layout, because the engine is constrained by the frame rails. I will consider front and rear-mid engine layouts, FWD and RWD, and also electric motors.

At this stage, exact dimensions are not important. The purpose is to evaluate the resulting proportions of each layout and then chose one or two to develop further.

I chose to continue with the mid-rear engine, RWD layout, which will be the focus of the remaining posts.

Next, I will work out the key dimensions and set up comparisons to similar vehicles.

Model One: Setting Functional Objectives

After spending the past few months studying car design and CAD software, (more to come on that) I will now create my own car! 

In the next ten posts, I will complete design exercises from H-Point, which outline the steps required to build a conceptual vehicle package. My concept will be called the Model 1. 

In the first exercise, I will set out clear functional objectives for the customers, manufacturer, and the market. 

Customers

• Power, speed, and handling are a priority. Comfort less important.
• Two occupants
• Targeted towards car fanatics that are comfortable driving a high-performance car. 
• Modern, Aggressive Vehicle Image

Manufacturer / Brand

• Primary Vehicle in Product Lineup 
• High Investment and Manufacturing Costs
• Annual Sales Volume: 300 (based on competitor's sales volume)
• Internet Marketing and Small Storefronts

Market/Driving Environment:

• All weather driving, only paved roads. 
• Uncompromised engine size, minimum height and front profile for reduced drag.
• Fuel economy won't inhibit performance. 

Up Next: Package Ideation

Exterior Lighting Requirements

There is a wide variety of lights that vehicles must have in different parts of the world.
This post will identify and explain them.



Headlights:
This consists of a high and low beam to illuminate the area in front of the vehicle.
Required in the US and Europe.


Daylight Running Lamps:
Consists of two headlamps that make oncoming vehicles more visible in daylight.
Permitted in US, required in Canada and Europe for some vehicles.


Front Fog Lights:
Two forward-facing lights mounted symmetrically about the center line.
Required in Europe.

Park and Turn Lights:
Parking- Indicate the vehicle's position during parking if the headlights fail.
Turning- Flashes to indicate the drivers intent to turn or for an emergency.
Required in US and Europe.


Side Marker Lights:
Indicate the overall length of the vehicle.
Required in US and Europe


Side Repeater Lamps:
Work with turn signals to show intent to turn or change lanes.
Visible to vehicles travelling alongside.
Required in Europe




Center High Mounted Stop Light:
One rear-facing red light mounted on the vehicle centerline, activated with brakelights.
Required in US and Europe

Back-Up Lights:
For illumination behind the vehicle and to provide a warning signal.
One required, two optional.
White in color.
Required in Europe.

License Plate Lamps:
Used to illuminate the rear license plate to be legible at night.
Required in US and Europe



Taillights:
Brake lights - Red - Indicate the vehicle is slowing down.
Turn Signal - Red or Amber - Flashes to indicate the drivers intent to turn or for an emergency.
A specified portion of the taillight must be mounted on the fixed body (not the trunk lid/hatch).
Clustered into one light assembly.
Required in US and Europe.

Rear Fog Lights: Red- make the vehicle more visible in fog.
One is required, mounted on the driver's or vehicle's centerline. Two are optional.
Not allowed in US, required in Europe.

Thanks for Reading!

Aerodynamics Basics

Aerodynamics is a very technical, in-depth subject, but I will cover the basic principles in this post.

Every package should be set up to allow the vehicle to travel through air as efficiently as possible.

The importance of aerodynamic soundness depends on the type of vehicle. Sports cars need high airflow and downforce improve top speed, handling and engine/brake cooling. Trucks, however, usually have drastically compromised aerodynamics because of their large frontal surface area and underbody structure.

The two most important aerodynamic factors are the drag coefficient (Cd) and total drag. Analogous to the coefficient of friction from AP physics, the drag coefficient (Cd) is an intrinsic property that measures the "slipperiness" of a particular shape, regardless of its size. The total drag is the product of this coefficient and the cross sectional area of the vehicle. This product is a force, which describes the amount of force needed to propel the vehicle.

Airplanes obtain "lift" when the air pressure below the wings exceeds air pressure above the wings. At high speeds, this phenomenon starts to influence the handling and balance of cars too. Spoilers are often applied to maintain consistent down force on the front and read tires, improving traction as well.

Vehicles also need air intake systems to perform several different functions. Engine cooling requires substantial air flow for the cooling modules to work. Cars and trucks usually have very pronounced breathing apertures for this purpose. It is also common for cars to have openings for airflow to cool the brakes. The HVAC (heating, ventilation, and air conditioning) system takes in air from the base of the windshield (aka cowl/plenum), called the cowl screen. Spanning between the a-pillars, the plenum chamber filters the incoming air.

Below are illustrations from H-Point depicting good and poor aerodynamics.

This car's small front reduces drag. The gently contoured roof line, sharp rear-end cutoff, and fared-in rear wheels also contribute to a low drag coefficient.

It doesn't take an aerospace engineer to notice the inefficiencies of a Hummer. The body is large in all dimensions, causing it to push through a lot of air. The sharp changes throughout the body's exterior and the exposed underbody components will create additional drag.

Thanks for reading!

Body Structures:

A car's body structure and the exterior surface have four main functions:

1. Protect the occupants and cargo
2. Connect the major components and manage stress between them
3. Provide an appealing product image
4. Make the car aerodynamically sound for efficiency and reduced wind noise. 

Below are the types of body structures used in a variety of vehicles.

Unibody: this is the most cost-effective option for mass-produced cars, minivans, and SUVs. It is made from steel and aluminum panels that are stamped into shape and spot-welded together. Exterior panels are made form metal or plastic, depending on the impact requirements.

Body on Frame: This is common in trucks and SUVs, where heavy loads and rough terrain require extra strength. The engine, suspension, and main body are all attached to the frame on rubber mounts. This improves ride quality, noise and vibration. On the other hand, this increases the vehicle weight and step-in height. This also gives trucks poor torsional rigidity, which is important for good handling.

Main body (above) and Steel Frame (below)

Space Frames: In low-production high performance cars, high stiffness and low weight are critical. The space frame acts as a skeleton to which the mechanical components and exterior are attached. These can be made from steel/aluminum tubing, extruded aluminum, or plastic composites.

• Extruded Aluminum: The thick sill sections (the sections beneath the doors) add a lot of rigidity to the frame, improving handling. This is ideal for mid- or rear-engine cars that don't need a tunnel across the length of the car for drive shafts. 

Audi Concept Frame

• Carbon Fiber: This "tub" is used on some exotic sports cars for high strength and very low weight. Additional metal structures are attached to the front and rear to complete the frame. 

• Steel or Aluminum Tubing: This is a "backbone" frame that looks similar to the body-on-frame layout used in trucks, but there is an important difference. There is a tunnel structure running across the center of the frame, improving torsional rigidity. Additional panels close off the floor and stiffen the structure. Exterior panels are made of plastic. This is used in front-engine Rear-wheel drive cars that need a tunnel for the drive shafts and transmission. 

Thanks for Reading!

Cut Lines

Along with the wide variety of closures, (covered in the previous post) there is also a diversity of door profiles. These are determined by the door's cut lines, which establish its perimeter. Below we'll take a look at how these cut lines are made for different kinds of closures.

Conventional Hinging: The cut lines need to be adjacent to the hinge axis line so that the doors can swing open freely. The cut lines must also be sympathetic to the rear view, side surface contour. In other words, cut lines should look natural from all angles. They should yield to the exterior shape of the car. The leading edge of the doors will rotate inwards, towards the car, while the door swings outward.

Toyota Yaris

Unconventional Hinging: There are many kinds of unconventional hinging, but consider gull-wing doors. With the hinge axis on the roof, there is a lot of freedom for the side cut lines.

Pagani Huayra

Frame-less, Conventionally Hinged Two-Doors: The front cut lines are still restricted by the hinge axis line, and the rear cut lines usually curve rearward, beyond the rear edge of the glass. This provides room for the latching mechanism and the glass to slide into the door.

Mini Cooper (cut line highlighted)

Exposed Structures: Sometimes the door cut lines will yield to the body structure, which displays strength in the exterior design.

Smart Fortwo

Large Two Doors: Large two-door cars need long doors to maintain good proportions. However, door length should not exceed 1400mm to reduce stress on the hinges and minimize the outward swing.

Dodge Challenger

Rearward A-pillars: The A-pillar lower is the structure behind the front wheels used to mount the front door hinges. The A pillar upper tracks around the windshield and supports the roof. In cars like the one shown below, with a long hood profile, the A-pillar upper is pulled back to improve cornering visibility. The A-pillar lower cut lines are moved forward to improve foot swing when entering/exiting.

Dodge Viper SRT

Commercial Vehicles: The driver is typically pushed forward to maximize the area for cargo or occupants. Thanks to the high floor structure, there does not need to be a lot of horizontal leg room. In other words, the driver's H-point is high relative to the pedals. To improve foot swing for ingress/egress, the front cut line tracks around the wheelhouse. The cut line for the sliding door is completely straight, which is not possible for a conventionally hinged door.

Ford Sprinter

Cab Forward: This is essentially the opposite of Rearward A-pillars. The upper A-pillar is pulled forward, beyond the lower A-pillar. In order to fall behind the front wheelhouse structure, the front door cut line passes through the upper A-pillar as it approaches the roof.

Honda Concept Car

Forward Control: This is when the A-pillar is at the very front of the vehicle. This is not common today because it has frontal impact issues, compromising driver safety. This setup forces the driver's feet between the A-pillar and the front wheelhouse structure. To accommodate this, the door's front cut line is dramatically different.

VW Type 2

Thanks for reading!

Exterior Design

The following posts will cover a wide variety of topics relating to the body and exterior trim. I will start by discussing the closures and cut lines.

Closures are parts of the vehicle's body that open for access and close to complete the exterior shape. This includes the doors, hood, trunk lid, and sliding glass windows. In particular, closures need to provide access to the occupant compartment, engine bay, and cargo area.  There are many ways to accomplish these objectives, which are introduced and explained below.

Lets start with the doors:

Front Hinged: Inexpensive and intuitive, this traditional layout is used in almost all cars. This requires a pillar in between the front and rear doors, called the B-pillar.

Mercedes Concept Car

Front and Rear Hinges: This setup is sometimes applied to vehicles with a small occupant compartment or wheelbase (distance between front and rear wheels) to reduce the length of the rear doors. Without, the B-pillar, access and foot-swing (aka leg room) are improved. It is also frequently used in high-end luxury vehicles. These are also referred to as suicide doors.

Rolls Royce Ghost

Scissor Doors: Not only do these doors add flair to exotic cars, but they come with some practical benefits. In tight parking spaces, wide sports cars with scissor doors will have easier ingress/egress (enter/exit) than out-swinging doors.

Ferrari LaFerrari

Gull Wing: This has similar advantages to the scissor doors. However, in the open position the doors add considerable height to the car, so it is mostly seen in low sports cars.

Mercedes SLS

Sliding Doors: These are used in minivans and commercial vans, where out swinging doors can be impractical. It is essential that the vehicle has enough room behind the door to Today they are usually electrically powered.

Now lets look at systems that provide access to the engine and cargo areas.

Access Covers: These are used in performance and race cars, where fast, easy access to the power train and suspension components is important. These covers have cut lines (the perimeter) on the side of the car, providing large apertures.

Pagani Huayra (also has gull wing doors)

Lift Gate (hatch): This is common for minivans, hatchbacks, and SUVs. They provide cover for the rain and won't interfere with traffic or nearby parked cars. Sometimes these are electric powered.

Porsche Panamera

Tailgate: This is mostly used on pickup trucks to extend the bed floor, and it can remain dropped when driving. Some are removable to assist in loading process.

Ford F-150

Some vehicles combine the lift-gate and tail-gate.

Lift and Swing Gate: This is often used on vehicles that carry a spare tire on the rear gate. One example is the Hummer H3 (couldn't find picture).

Rear Swing Doors: These are often used in commercial vans. They are designed to swing at least 180 degrees to provide easy access from all angles.

Ford Transit

Hood and Trunk Lid: Most cars use this simple system for access to the engine and rear cargo.

Pontiac Solstice

Thanks for reading!

3D Printing

As promised, this article will be a step-by-step guide to 3D printing.

1. The first step is to have something to 3D print. This is usually something created using CAD software.

2. The next step is to import the design to a 3D printing program. For this, I used Cura. Here is an example of the Cura interface from the internet--I did not make this design.

Cura 14.07

The panel on the left-hand side has adjustable settings for several variables. The most important ones are circled and explained below:

• Layer Height (mm): 3D Printers create 3D objects by adding one small layer on at a time. If you have taken Calculus AB, a good analogy is the step size of a line created with Euler's method. The smaller the step size, the closer the estimate will be to the real function. In 3D printing, a smaller layer height produces smoother, more natural surfaces, like a playground slide compared to a flight of stairs. The drawback of this increased quality is increased print time, because the nozzle must go over the same surface more times. 
• Fill Density (%): This is probably the most important feature, because it determines the 3D print's durability and how much plastic it uses. For example, objects that will be under high stress need a higher fill density for added strength. To make a hollow object, set the fill density to 0%. For a solid object, set it to 100%. Anything in between these extremes will fill a percentage of the volume within the 3D print in a uniform lattice structure.  

3. Then, once the variables are set to the desired values, it is time to print! This is the 3D printer I will be using.

Note the blue "string" sticking out of the print head. 

The red part is the nozzle, where the plastic filament is applied to the 3D print.
The blue lever on the side of the print head disengages the rollers that keep the filament in place.
The bed on the bottom moves left, right, up and down to position the nozzle.
The white piece at the top holds a spool of filament, allowing the user to choose the color and quality of the filament.

I need to remove the leftover filament shown in the previous picture. Right now the nozzle is at room temperature, so the filament is stuck inside. I need to heat the nozzle to 208 degrees Fahrenheit, the filament's melting point. To do this, I use Cura's printing interface, which is, unsurprisingly, very different from a normal printer's.

Only a few of these controls are necessary to set up and operate the printer. 

First, I change the Temperature from 0 to 208 and wait for it to heat up. Then, I use the rightmost cluster of buttons to remove the filament. The EXTRUDE buttons will push the filament through the print head. Once enough filament is pushed through, I can hold down the blue lever and pull out the remaining filament from the top.

Now I can put my filament into the print head.

My algae-based, smelly filament

Fed into print head opening

The last step is to hit the print button and watch the design materialize!

Soldering

Last week I learned how to use the soldering iron and the 3D printer at CREATE. I am going to dedicate the next two posts to explaining these in detail, and then I will continue covering my research of H-Point. Today I will show you how to solder.

What is soldering? Soldering is the process where a low-melting metal alloy is used to fuse together metals that have higher melting points. This metal alloy is called solder. Typically it is 60% tin and 40% lead, giving it a low boiling point of 188 °C (370 °F).

Solder

This is the soldering iron. When plugged in, the tip of the pen-like part gets very hot. This melts the solder from the spool onto the metals you are fusing.

(hopefully) Unplugged soldering iron

The tip of the soldering iron gets rusty over time due to oxidation. The copper mesh shown below is used to remove rust from the tip. This is known as "tinning".

I will be soldering wires from a battery holder to a motor, to make a complete circuit. The metal in the wires and the copper pads on the motor have very high melting points, but with soldering these can be joined together easily. For the motor to work, the circuit must conduct electricity, which is why you can't just super-glue the metals together.

This is the motor I will be soldering. Earlier I completed soldering the lower copper pad.

Note: Small hole for wire in copper pad

Next, I use these wire strippers to rip off the wire's plastic sleeve and expose the metal.

Then, I put the metal wire through the hole in the copper pad and twist to secure.

I have to melt the solder to close the hole in the copper pad. However, molten solder sticks to the hottest object it touches, which would be the soldering iron. To make sure it sticks to the copper pad, I must warm it up first.

Heating up copper pad/wire

Now I can introduce the solder. It will melt onto the copper pad, and some of it will vaporize into the air (probably best not to breathe in). 

Then, when I remove the soldering iron, the solder will quickly cool, creating a solid connection. 

Voilà!

When building my car, I will likely use soldering to connect motors like this to the rest of the electrical system. It's a very useful--and fun--tool!