UAV FRAMES & MATERIALS

UAV FRAME TYPES

Tricopter

Tricopter
  • Description: A UAV which has three arms, each connected to one motor. The front of the UAV tends to be between two of the arms (Y3). The angle between the arms can vary, but tends to be 120 degrees. In order to move, the rear motor normally needs to be able to rotate (using a normal RC servo motor) in order to counteract the gyroscopic effect of an uneven number of rotors, as well as to change the yaw angle. A Y4 is slightly different in that it uses two motors mounted on the rear arm, which takes care of any gyroscopic effects – no servo is therefore needed.
  • Advantages: Different “look” for a UAV. Flies more like an airplane in forward motion. Price is theoretically lowest among those described here since it uses the fewest number of brushless motor (and ESC).
  • Disadvantages: Since the copter is not symmetric, the design uses a normal RC servo to rotate the rear motor and as such, the design is less straightforward than many other multi-rotors. The rear arm is more complex since a servo needs to be mounted along the axis. Most, though not all flight controllers support this configuration.

Quadcopter

Quadcopter
  • Description: A “quadcopter” drone which has four arms, each connected to one motor. The front of the UAV tends to be between two arms (x configuration), but can also be along an arm (+ configuration).
  • Advantages: Most popular multi-rotor design, simplest construction and quite versatile. In the standard configuration, the arms / motors are symmetric about two axes. All flight controllers on the market can work with this multirotor design.
  • Disadvantages: There is no redundancy, so if there is a failure anywhere in the system, especially a motor or propeller, the craft is likely going to crash.

Hexacopter

Hexacopter
  • Description: A “hexacopter” has six arms, each connected to one motor. The front of the UAV tends to be between two arms, but can also be along one arm.
  • Advantages: It is easy to add two additional arms and motors to a quadcopter design; this increases the total thrust available, meaning the copter can lift more payload. Also, should a motor fail, there is still a chance the copter can land rather than crash. Hexacopters often use the same motor and support arm, making the system “modular”. Almost all flight controllers support this configuration.
  • Disadvantages: This design uses additional parts, so compared to a quadcopter which uses a minimum number of parts, the equivalent hexacopter using the same motors and propellers would be more expensive and larger. These additional motors and parts add weight to the copter, so in order to get the same flight time as a quadcopter, the batteryneeds to be larger (higher capacity) as well.

Y6

Y6 Hexacopter
  • Description: A Y6 design is a type of hexacopter but rather than six arms, it has three support arms, with a motorconnected to either side of the arm (for a total of six motors). Note that the propellers mounted to the underside still project the thrust downward.
  • Advantages: A Y6 design actually eliminates a support arm (as compared to a quadcopter), for a total of three. This means the copter can lift more payload as compared to a quadcopter, with fewer components than a normal hexacopter. A Y6 does not have the same issue as a Y3 as it eliminates the gyro effect using counter-rotating propellers. Also, should a motor fail, there is still a chance the copter can land rather than crash.
  • Disadvantages: This uses additional parts, so compared to a quadcopter which uses the same components, the equivalent hexacopter would be more expensive. Additional motors and parts add weigh to the copter, so in order to get the same flight time as a quadcopter, the battery needs to be larger (higher capacity) as well. The thrust obtained in a Y6 as opposed to normal hexacopter is slightly lower (based on experience), likely because the thrust from the top propeller is affected by the lower propeller. Not all flight controllers support this configuration.

Octocopter

Octocopter
  • Description: An octocopter has eight arms, each connected to one motor. The front of the UAV tends to be between two arms.
  • Advantages: More motors = more thrust, as well as increased redundancy.
  • Disadvantages: More motors = higher price and larger battery pack. When you reach this level. most users are looking at very heavy payloads such as DSLR cameras and heavy gimbal systems. Given the price of these systems, added redundancy is really important.

X8

X8 Octocopter
  • Description: An X8 design is still an octocopter, but has four support arms, each with a motor connected to either side of each arm, for a total of 8 motors.
  • Advantages: More motors = more thrust, as well as increased redundancy. Rather than using fewer yet more powerful motors, octocopters provide added redundancy in the event of a motor failure.
  • Disadvantages: More motors = higher price and larger battery pack. When you reach this level. most users are looking at very heavy payloads such as DSLR cameras and heavy gimbal systems.

UAV Size

UAVs come in a variety of different sizes, from “nano” which are smaller than the palm of your hand, to mega, which can only be transported in the bed of a truck. Although both very large and very small UAVs may get quite a bit of attention, they are not necessarily the most practical for hobbyists. For most users who are getting started in the field, a good size range which offers the most versatility and value is between 350mm to 700mm. This measurement represents the diameter of the largest circle which intersects all of the motors. Not only do parts for UAVs in this size range come in a variety of different prices, there is by far the greatest selection of products available.

Drone Size

Smaller UAVs are not necessarily less expensive than medium sized ones. This is largely due to the fact that the technology and time needed to produce small brushless motors or small brushless motor controllers is the same for small parts or for large ones. The prices for the additional electronics such as theflight controller, remote control, camera etc. tend not to change at all. The frame is normally one of the least expensive parts of a UAV, so although the frame for a small UAV may be half the price of a larger one, the overall price, with all parts needed, may still be very close.

UAV Materials / Construction

Below are the more common materials found in multi-rotor drones. This list does not include all possible materials which can be used and should be looked at as a guideline / opinion as to the use of each material to make the frame of a drone. Ideally the frame should be rigid with as minimal vibration transmission as possible.

Wood

If you want your frame to be as inexpensive as possible, wood is a great option, and will greatly reduce build time and additional parts required. Wood is fairly rigid and has been a proven material time and time again. Although the aesthetics may suffer, replacing a broken arm after a crash is relatively easy and “dirt cheap”. Painting the arm helps hide the fact that it’s wood. Ensure you use wood which is straight (no twisting or warping).

wood

Foam

Foam is rarely used as the sole material for the frame and there tends to be some form of inner skeleton or reinforcement structure. Foam can also be used strategically; as propeller guards, landing gear or even as dampening. There are also many different types of foam, and some variations are considerably stronger than others. Experimentation would be needed.

foam

Plastic

Most users can only access and work with plastic sheets (rather than 3D plastic shapes or objects). Plastic tends to flex and as such is not ideal. Used strategically (such as a cover or landing gear), plastic can be a great option. If you are considering 3D printing the frame, consider the time needed to print the part (versus buying a plastic frame kit), and how rigid the part will be in the air. 3D printing parts (or the entire frame) has so far been more successful on smaller quadcopters. Using plastic extrusions may also be an option for small and medium sized drones.

plastic

Aluminum

Aluminum comes in a variety of shapes and sizes; you can use sheet aluminum for body plates, or extruded aluminum for the support arms. Aluminum may not be as lightweight as carbon fiber or G10, but the price and durability can be quite attractive. Rather than cracking, aluminum tends to flex. Working with aluminum really only requires a saw and a drill; take the time to find the right cross section (lightweight and strong), and try to cut out any non-essential material.

Aluminum

G10

G10 (variation of fiberglass) is used as a less expensive option than carbon fiber, though the look and basic properties are almost identical. G10 is mostly available in sheet format and is used largely for top and bottom plates, while tubing in carbon fiber (as compared to G10) is usually not much more expensive and is often used for the arms. Unlike Carbon Fiber, G10 does not block RF signals.

g10

PCB

Printed Circuit Boards are essentially the same as fiberglass, but unlike Fiberglass, PCBs are always flat. Frames <600mm sometimes use PCB material for top and bottom plates, since the electrical connections integrated into the PCB can reduce parts (for example the power distribution board is often integrated into the bottom plate). Small quadcopter frames can be made entirely out of a single PCB and integrate all of the electronics.

pcb

Carbon Fiber

Carbon fiber is still the #1 sought-after building material due to its light weight and high strength. The process to manufacturer carbon fiber is still quite manual, meaning normally only straightforward shapes such as flat sheets and tubes are mass produced, while more complex 3D shapes are normally “one off”. Carbon fiber impedes RF signals, so be sure to take this into consideration when mounting electronics (especially antennas).

Carbon fiber

SOURCE : ROBOTSHOP

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