## Introduction: Begginner's Guide: 3D Printed Quadcopter

### Materials Needed:

• Motors
• Propellers
• Microchip
• Remote Control
• Safety Glasses
• Double Sided Tape
• Rubber bands
• Calipers (measuring tool)
• Solder and a Soldering Iron
• 3D printer Access
• 3D Modeling Software (Solidworks is used in this instructable)

## Step 1: Understanding the Science

### Scientific Forces

Before we start making our quad-copter it is important to understand the basic science that allows us to fly our quads. First we will go over the basic scientific forces that affect the quad-copter's ability to fly, maneuver, and hover. These are all essential to the design process. These forces include thrust, lift, drag, and weight.

### Thrust & Weight

Thrust is the mechanical force that drives our quads upward. Thrust is generated by the motors. Variables that affect thrust include propeller size, motor strength, and weight of the quad itself. Bigger propellers produce more thrust per revolution, however, they also add more weight. Stronger motors produce more thrust by spinning faster but may also require more juice (power). These are just a few examples of trade-offs that you should consider when designing your own quad.

Weight is pretty self explanatory. This is simply the downward force due to gravity and mass. This follows the simple physics equation of F = ma. Where "F" is the total force created (in this case, weight), "m" = the total mass of the object, and "a" is the acceleration of gravity which is -9.8m/s^2. "a" is negative because it is a downward force, and in our case, the desired direction is upward.

Weight and Thrust counteract each other. In order to calculate how well our quads will fly, we must understand the Thrust to Weight Ratio (F/W, F = force of thrust)

F/W = Thrust/Weight = (mass*acceleration)/(mass*gravity)

If F/W…

• = 1 - there is a chance the quad can fly
• > 1 - the quad can accelerate vertically
• > 2 - the quad will be quick and agile

### Lift

Lift is the ability to raise a given weight off of the ground. Lift is created by each individual propeller blade. Variables that affect this are propeller size, weight, and RPM (Revolutions Per Minute). Bigger propellers produce more lift than smaller propellers. RPM is a measurement of how fast the propellers rotate. Higher RPM’s are required with smaller propellers to provide the same lift as bigger propellers with lower RPM. Here is another trade off to consider when designing your quad.

### Drag

Drag is a reaction force created by the propellers, and design of the quad-copter.

## Step 2: Radio Frequency. What Is It?

Radio frequency is what allows us to communicate wirelessly with our quad-copters. Other examples are RC Cars and Video game controllers. Radio Frequencies cover a portion of the electromagnetic radiation spectrum such as Infrared (IR) and “radio waves”. These frequencies are measured in Hertz (HZ). For example, Wi-Fi uses radio frequencies that allow us to connect and communicate on the internet, these frequencies are typically 2.4 GHZ (gigahertz).

For a list of examples and and more detailed description of Radio Frequency, visit these sites…

## Step 3: Remote Control

The remote control is how we communicate with wireless devices such as the quad-copter. This communication is possible because of radio frequency. Remote controls typically have multiple possible inputs that enable us to create movements and responses in our electronics.

For quad-copters, the remote control’s basic uses include controlling the pitch, roll, yaw, and throttle.

### Yaw (Z-Axis Rotation)

Yaw is a little bit more complicated than pitch and roll. First, it is important to understand that the rotors (propellers) directly opposite from each other must be spinning the same direction, counter-clockwise (CCW) or clockwise (CW). The rotors that are next to each other must NOT be spinning in the same direction. For example, is we go around the quad-copter clockwise the rotations should be… CW --> CCW --> CW --> CCW. If the rotations do no alternate, your quad-copter will not fly and will most likely spin out of control.

Yaw uses these alternating rotations to help spin the quad-copter. By speeding up (applying more thrust) on a pair of rotors spinning in the same direction, it will cause the quad-copter to spin. The faster spinning rotors creates more torque (the force that causes an object to spin) than the ones spinning slower, causing to quad-copter to spin. Throttle Throttle should be another pretty self explanatory term. Throttle is how we control how much thrust we want from the motors. Controlling the throttle allows us the raise the quad up and down.

## Step 4: The Design Process

Here is the basic outline of the design process. Before you do any research or look at quad copters online, try to come up with some ideas and sketches. This will help you boost your creativity and may give you some extra ideas to incorporate into your final design. At the end of this instructable I will include pictures of my design process.

### Ideation

Be sure to keep in mind the scientific forces and the trade offs I mentioned before during your brainstorming and ideation. Try creating different sketches with their own unique strengths. This will allow you to take the best features of several of your ideas and combine them into one.

I created four sketches shown below and used some aspects of a couple to combine them into one. After creating my sketches I did some research. Before I started my project I did not have much background experience with quad-copters so I needed a bit more info to help me move along with the design process. After doing some research and looking at other examples of quads, I rated each of my sketches based on how I thought they would preform regarding the four basic scientific forces lift, drag, weight, and thrust. This is called a design matrix. Be sure not to skip this step, it is a very important part of the engineering design process and will help you identify the strengths and weaknesses of your ideas.

### Conceptualize

After deciding a final design (or possibly two) sketch a more detailed model. This is called a conceptual model. Be sure to include basic dimensions and small notes around your model explaining why you included features and how they would affect your design.

Note: Dimensions are very important. Most importantly, we need to take into consideration the dimensions of motors. Circumference, and Height. These dimensions are critical because we need to model "seats" for the motor with proper tolerances in order for the motors to fit.

Next is the mathematical model. A mathematical model does not have to be a detailed sketch like your conceptual model. It should focus on the math behind the (expected) performance of your final design. Typically, a mathematical model can be in the form of a free body diagram. Free body diagrams helps you map out what forces are involved and how each force affects your flight. Be sure to consider the Force to Weight ration from above. A mathematical model helps you come closer finalizing a design without building it. This model will help you recognize the strengths and weaknesses that you might have overlooked with your conceptual model.

Things to consider in your mathematical model

• Thrust
• Lift
• Drag
• Weight
• Total Mass
• Battery Usage
• Motor Strength
• Propeller Size

Calculating Estimated Thrust

Here are the specs for the Hubsan X4 H107L

• Motor (x4): Coreless Motor
• Frequency: 2.4GHz with 4 channels
• Battery: 3.7V/240mAh
• Flight time: about 9 minutes
• Motor Weight – 3.4g , Propeller weight – .3g, Chip Weight – 2.1g

### The Fun(nest) Part: 3D Modeling and the Prototype

Now hopefully your interest in this instructable is accompanied by your ability to use 3D modeling software such as Solidworks or Inventor. Explaining 3D modeling software and how to use it is another lesson in itself.

If you do have experience that's great! Now we can move on to making our 3D quad-copter. Based on your conceptual and mathematical models this part should be easier to do. Create your model and play around with some of the modeling features. In this step, we can make a few tweaks and leisure of simply hitting the "undo" button (probably the greatest gift from the software gods). See what features or tools can help you optimize your design, for example I used a fillet tool to hep me round some edges. Rounding the edges seemed like a good idea to me in regards of safety, aesthetics, and decreasing weight.

The best part about 3D modeling software is the ability to see the mass of your design before you print. In a way, this software is the extra step in the mathematical model stage. I am pretty experienced with 3D modeling software but I could still use a few more lessons on the more complicated features. Solidworks and other software give us the ability to also test our materials, by applying outside forces to them. This Finite Element Analysis (FEA) gives designers a huge advantage when it comes to the design process. Since I do not have enough experience with the FEA section of Solidworks (the software I use) I cannot give much advice on how to properly test the quad in the 3D environment. If you find a way, or already have knowledge on how to properly simulate the affect of gravity, drag, and other forces, feel free to let me know!

Okay, so now we have our 3D model and are ready to print. Print your model and examine it. Did it print properly? Are there flaws in the design that affected the print? What can you do to improve the design based on your prototype? Is it durable enough? Do the motors fit? Can the wiring reach the designated spot for your microchip? These are all questions you should ask yourself after your first print because most likely there will be some issues. After deciding what you want to improve, open your 3D file, make adjustments, and reprint.

*As I said before, I will include pictures of my sketches, 3D model, prototype, and final product at the bottom.

## Step 5: My Process - From Ideation to Final Design

Here are my ideation sketches, conceptual model, first iteration (Red) and Final design/print (White). For my conceptual model I tried to use some aspects from the four ideation sketches. As you can see, my first iteration (red) had some durability issues. The purpose of my first iteration was to test the general idea and design of my quad. I could tell immediately that the seats for the motors were too thin and would break easily. Seeing this allowed me to make some changes in Solidworks to improve the structure and durability. I also decided to cut down on weight by shortening distances and I also made small slots for the wiring (see close up picture of motor in seat). This small slot allowed for some wiggle room with the motor placement. Also, be sure to adjust the fill % of the print, to low will make your quad brittle and too high will add too much weight (Around 20% should be good).

Soldering Tips:

Blue/black - Negative ( - )

Red/white - Positive ( + )

Each motor has a set direction for this soldering configuration, either clockwise or counterclockwise. My quad was able to fly with all motors rotating outwards from the middle as opposed to inwards. In reference to the image with the motor directions my microchip would be facing northwest. Also, be sure to secure your microchip (uses double sided tape and a rubber band to secure the battery.) because it has an auto-balancing feature and reacts based on the tilt of the chip.

Good luck and happy flying.