Power Train

The set of parts known as the power train are responsible for generating power and transferring it so that movement can be produced. The engine in your car produces power that is delivered to the transmission that transmits it to the wheels, which move the vehicle, via the axle system. In order to move our quadcopter, we also have a power train system. Now let's have a look at those elements.

Propellers

The propeller, which is at the very end, is the ideal starting point. The propeller, or "prop," is sometimes compared to the tyre in car power trains; much as the tyre "grips the road" to produce movement for the car, the propeller "grips" the air to move the drone.

Props come in a variety of sizes and shapes, just like automobile tyres, and should be chosen in accordance with the rest of the power system that will be driving them. The three basic criteria you should consider while choosing props are direction, size, and pitch.

Direction

Examine your kit's props in detail. Take note of the two distinct shapes and opposing pitch angles of the propellers. These accessories are designed to be spun in opposition to one another. The official names for each type are tractor or pusher.

Pusher props, often known as left-handed props, produce lift when rotated anticlockwise. Tractor props, also known as right-handed props, produce lift when rotated anticlockwise. These two propellers work together to maintain the plane's equilibrium and level flight. Later in the book, we will go into more depth on how this operates.

Size and Pitch

The core of a propeller, which is mounted directly to the motor, is surrounded by two (and occasionally more) outward-extending blades. A two-blade prop is used to measure the size, which is fairly easily defined as being measured in inches from tip to tip. Props in the 5- to 6-inch range are suitable for the Little Dipper, however other drones can use props up to 29 inches or more!

Pitch is a little trickier to describe. The majority of people mistakenly believe that the angle of the prop's upward tilt from a flat surface is measured in degrees. In actuality, the pitch is a measurement of how far the propeller would advance in one revolution through a solid object. Consider the wood screw's threads. In comparison to a coarse thread, a fine thread travels farther per revolution.

Props work in the exact same way. Theoretically, a boat's or an airplane's back propeller with a higher pitch would move the craft farther with each revolution than one with a lower pitch. Like that coarse screw, it is likewise more difficult to spin!

We won't go into great depth because it is beyond the scope of this book, but we will remark that the pitch of a propeller is rarely met in real life (see Figure 3-1). The mismatch between the expected and actual movement of the vehicle is caused by a phenomenon known as prop slip. Many websites offer a plethora of information on the subject if it is something you are interested in.

Figure 3-1. Slip is the difference between the Geometric Pitch and the Effective Pitch.

More air will pass through the propeller with each rotation the greater the pitch. A higher degree of thrust is produced by moving more air through the prop. This is excellent if your aircraft needs more lift, but be aware that it reduces efficiency because the motors of the aircraft require more energy (in the form of battery power) to spin a higher-pitch prop. By acquiring greater lift, switching to a higher-pitched prop might shorten your overall flying time.

There are numerous sizes and pitches of propellers, each with advantages and disadvantages. While others produce more lift, some are more effective. Generally speaking, more lift is produced the higher the pitch and/or larger the prop. A high-pitch or huge prop would be appropriate if you have a hefty aircraft or one that has to fly at a fast rate of speed. But, something with a lower pitch will probably be better for you if your requirements are for a longer flying time with a lesser cargo. But more lift has a cost: it reduces the prop's effectiveness.

On the side of the prop itself, next to the hub, the size and pitch specification is often something like 0845P or 08X4.5P. (see Figure 3-2). The size, 8 (inches), and pitch, 4.5°, are the first two numbers. This propeller is a pusher, as indicated by the P.

Some businesses refer to pusher props as left-handed props and may label them by substituting a L or R (for reverse) for the P in the prop name. Tractor props just go by the designation 0845 and don't have a letter at the end.

Figure 3-2. Two pushers and two tractors.

Efficiency Versus Maximum Thrust

The props we are using on the Little Dipper are 6 × 3. These have the advantage of providing more power from a larger 6-inch design, yet higher efficiency from the 3° pitch. If you are looking for more speed for your aircraft, try a higher-pitch prop like a 6 × 4.5. Remember: the higher the pitch, the more air is passed through the prop, at the cost of using more power fro the battery.

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