The conquest of heaven has been one of humanity's greatest battles since ancient times. Our ancestors warned us that the sky could be a dangerous enemy. Let's remember the legend of Icarus, a boy who wanted so much to fly like a bird that his father made wings for him out of bird feathers and wax. He flew higher and higher until the sun melted the wax and he fell to his death. We can learn two important lessons from this story:
1. Always build mechanical or functional prototypes of your aircraft and test them carefully.
2. Try testing them without being in them. Or at least take a parachute.
Fortunately, modern manufacturing and aerospace technology allow us to do both. We can control our aircraft prototypes remotely and create prototypes in no time.
What are drones?
Drones have become the ultimate amateur aircraft. They are light, small, easy to fly and you can do it yourself, which attracts a lot of people who like tinkering with mechanisms. However, drones existed long before. The first mention of them dates back to the 1920s.
Early attempts to build drones were unsuccessful. There were many individual inventors who managed to build prototype helicopters with 4 to 6 rotor engines. These aircraft were too unstable, out of sync and placed too much pressure on the pilot, so their development was largely abandoned until recently.
With modern developments in aviation and electronics, previous technical difficulties with drone functions have largely been overcome. The drones were left unmanned because the only problem left was the pilot. However, a pilot is no longer required. You can simply equip it with a camera and use a remote control. Modern electronics make designing this vehicle very easy, which is why many people build drones as a hobby or buy them to make great movies or art, deliver things, or even spy on their neighbors, who knows. There is even a story about a man who decided to immortalize his cat by turning it into a quadcopter.
What does a drone consist of?
A typical drone has the following elements that determine its functionality:
- Frame. This is the main and most important part. It holds all functional objects together, determines the overall strength of the structure and influences the aeronautical properties of the device. I will mainly talk about this part because it is practically the only one that you will need to design and manufacture yourself or with the help of a prototyping shop (which is highly recommended if you do not have a technical background, as it is cheaper and faster, as manufacturers of prototypes create a high-quality frame, better choose materials and advise on design).
- Engines. Depending on how many helicopters you need, you may need 4 to 8 engines. The engine determines the rotation speed of the drone's rotor blades and therefore its performance capacity. There are many engine manufacturers that offer affordable and reliable solutions.
- Electronic speed control. These are the devices that synchronize your propellers and prevent your drone from going crazy. They are also very cheap and easy to find.
- Propeller. These are the main moving parts of the propeller. Its leaves have a complex geometry and their size and shape depend on the weight and size of the frame, so you will probably have to order them together with the frame.
- Batteries, connections and controls. Some smaller electronic parts are required for secondary operations. For example, connections, batteries and a receiver with remote control to fly the drone. You will probably also need a camera, as flying the drone without a camera is like walking with only one leg.
As you can see, modern industry offers many ready-made solutions for manufacturing drones. Since making electronic devices is a complex and expensive project in itself, I advise you to only buy the parts you have, whether you are a hobbyist or want to sell things. As your sales increase, you might consider making your own circuits. This leaves us with two main parts that are custom-made and essential to the drone's performance. Of course, you will need to make some additional connectors and battery boxes. However, its design is not a problem and can be produced quickly through 3D printing.
How to Create Custom Drone Frames
So frames are really important for the overall stability and structure of the drone. As you learn to fly your aircraft, you will certainly bump into things and damage the structure, so it should also be easy to replace or repair.
Currently, there are several possible designs of drone structures depending on the number of propellers desired. The more propellers, the more stable the drone, but also the heavier. The most important parameters are stiffness and weight. For this reason, the following materials are most widely used:
1.Wood. The cheapest material, easiest to process and can be shaped into a frame using the simplest tools. The optics and reliability of this drone are not high. Although it is easy to replace, you need to be prepared for it to break at the slightest impact. Basically, it is a good choice for amateurs. The frame is usually machined on a lathe or with a simpler tool and then glued.
2.Plastic. It's the most obvious choice. Many polymers are lightweight, have high tensile strength and – best of all – can be processed quickly using modern technologies. For example, plastic frames can be manufactured using 3D printing or urethane casting prototyping techniques. This makes it a really good choice for prototyping commercial drone models. You can easily make a small batch, assemble it and test it using PR techniques. And when you're ready, order an injection mold.
3.Aluminum. You should choose this material to create the most durable and stable systems that can withstand a lot of stress. It is also the heaviest material. Typically, this structure is CNC milled. You should use aluminum frames if you are only building professional industrial drones. Or if you've already tested and approved the design and want your drone to look and shine great.
Let's build propellers
Propellers are the most complex parts of drone design. In fact, you need to calculate your geometry depending on the weight of your drone to achieve the necessary thrust. Fortunately, there are many services to help you with this. If the geometry seems too complex for you, you can always order the blades from a prototyping workshop where competent engineers design, calculate and manufacture the perfect propellers.
Therefore, diameter is obviously important. The larger the blades, the more air the propeller can pump. However, you should note that the propellers must be synchronized so that they do not collide with each other. Therefore, maneuverability is worse with larger propellers. You should choose what suits you best: a larger drone payload or better maneuverability.
The angle of attack is another important characteristic of the rotor blade. Essentially it indicates at what angle the propeller hits the air and deflects it. The greater the angle of attack, the more efficient the rotor blade, but a larger engine is also required because wind forces are greater. For constant pitch propellers, the angle of attack decreases near the center. However, when the angle of attack changes, the propeller geometry becomes too complex.
Propeller blades are generally manufactured by 3D printing or cast with silicone molds as plastic frames, as these methods are the most efficient for obtaining complex geometries at low cost and in a short time. The blades are then reworked because a good surface finish reduces drone vibrations during flight.
You must also remember to balance the propellers. That's easy. You can do this with a pencil and a knife. Simply attach the blade to a horizontal pencil. The propeller will probably rotate on its axis. Then cut a little bit from the root of the blade, which is usually at the bottom of the pencil. Repeat until the blade stops rotating when you attach it to the pencil.
