(ver_1_2410230727)
Intro
We are comparing the characteristics between different airframes for our initial commercial drone, which is currently unnamed.
The following content is based on various quick theories and long experiences.
I will summarize the key points and try include some miscellaneous points at the end.
All characteristics ratings are shown as + or - numerical values, a standalone - minus sign indicates average level.
Basic Environment
- Propeller: 22 inch / 56 cm (May change in futher development)
Basic Concept
| Quadcopter | Hexacopter | Octocopter | Coaxial-Octocopter | |
|---|---|---|---|---|
| Propeller Count | 4. | 6. | 8. | 8. |
| Friendly Description | Regular shaped as 99% of drones and our test bed | Similar as PT3 | All propulsion units are on the same level | Each arm combines 2 fully overlapped propulsion units spinning in counter-direction |
| Known Configuration | X H 工 田 O | ❆ 王 | ❉ # O 圭 | X H 工 |
(Landing gear or arm folder not included in the photo or configuration)
Weight and Power Efficiency
| Quadcopter | Hexacopter | Octocopter | Coaxial-Octocopter | |
|---|---|---|---|---|
| Structural Weight | +1 | - | -1 | - |
| Compact | Extra arms | Extra, Long arms | Simple, Compact | |
| Load Capacity | -2 | - | +1 | +2 |
| Limited | Entry level lifting | Performance balanced lifting | Heavy lifting dedicated | |
| Flight Efficiency | ||||
| Hover | - | - | - | -1 |
| Cruise | +1 | - | -1 | -2 |
| Climb | -1 | - | +1 | +2 |
| POS + | + Simple aerodynamic + Minimum air drag |
+ Good performace while small payload | + Lower current draw for propulsion | + Low weight structure + High structural density |
| NEG - | - Less redundant thrust - High current draw for propulsion |
- May generate excess torque while in high thrust | - Higher air drag factor | - Low aerodynamic by overlapped propeller |
| Weather Adaptability | (Experienced) | |||
| Front Wind | -1 | -1 | - | - |
| Side Wind | -2 | - | +1 | -1 |
| Instant Wind | -2 | - | - | +1 |
| Hot Weather | -1 | - | +1 | +1 |
| POS + | + Side redundant thrust | + Isotropic redundant thrust | + Smooth, high-ratio thrust + Narrow center of gravity |
|
| NEG - | - Less redundant thrust - Unstable trust |
- Wind can interfere lower propeller | ||
Control Performance
| Quadcopter | Hexacopter | Octocopter | Coaxial-Octocopter | |
|---|---|---|---|---|
| Stability | - | +1 | +1 | +1 |
| Smoothness | - | +1 | +2 | +2 |
| Turn stability | -1 | - | +1 | +1 |
| Agility | +2 | - | -1 | - |
| Brake | +1 | -1 | - | -1 |
| POS + | + Light total weight | + Balanced stability and agility | + Isotropic thrust | + Large thrust-to-weight ratio in each arms |
| NEG - | - Less redundant thrust | - Less brake effect by side propellers | - Wide spread of mass | - Less propeller airbrake capabilitiy |
(This table is based on flight experience with high speed, low speed cruising and precision maneuvers, within practical and test flight conditions. Different FCU configuration will strongly affect the control feedback)
Flight Safety
| Quadcopter | Hexacopter | Octocopter | Coaxial-Octocopter | |
|---|---|---|---|---|
| Propulsion Redundancy | (Theoretical) | |||
| Non-Neighbor | 0. | 2. | 4. | 2. |
| Neighbor | 0. | 1. | 2. | 1. |
| Structural Integrity | (Experienced) | |||
| Vibration | -1 | - | - | +1 |
| Deflection | - | -1 | -2 | -1 |
| POS + | + Gain confidence for beginner pilots | + Manageable vibration | + Manageable vibration | - Less vibration generated by propeller vortex |
| NEG - | - Lose confidence for customers - Lack of vibration compensate - Can’t make soft land while propulsion failure |
- Long arm may cause deflection to arm connections | - Extra long arm - Larger safety distance |
- Heavier stress at arm connections - Higher clearance between belly and ground |
Sample Size and Space
(All dimensions are in Centimeter and sorry for the inconvenience)
| Quadcopter | Hexacopter | Octocopter | Coaxial-Octocopter | |
|---|---|---|---|---|
| Sample Frame Size | 90 | 120 | 160 | 90 |
| Sample Board Size | 32 | 50 | 90 | 32 |
| POS + | + Good for carry and manage | + Large free space | + Maximum free space | + Large space in vertical dimension |
| NEG - | - Limited free space | - Lower size-space ratio | - Super large and hilarious looking from the side | - Limited space on surface area |
Misc.
| Quadcopter | Hexacopter | Octocopter | Coaxial-Octocopter | |
|---|---|---|---|---|
| Maintainability | +1 | - | -1 | -1 |
| POS + | + Less structural conncetion | - | + Balanced vertical size and space | |
| NEG - | - Excessive space utilization | - | - Extra screws - Extra connection points |
- Extra maintenance required for propulsion unit - Extra operation |
| Wiring | -1 | +1 | +2 | +1 |
| POS + | + Less cables | - | + Large sufficient space + Good anti-interference |
+ May routing at different layers |
| NEG - | - Easy to catch interference | - | - More propulsion cables | - |
| Upgradable | -1 | - | +1 | +2 |
| POS + | + Cheap structural components + Ducted propellers + 3 Blade propellers |
+ Foldable arms | + Almost all kind of payload | + Foldable arms + Ducted propellers + Propeller protector |
| NEG - | - Sensitive to center of gravity | - Nearly impossible to design foldable arms | - Limited pylon space due to propeller clearance |
Extra
- Simple cross-check with ChatGPT-4o (Chinese original).
- This document is writen by human and before the cross-chrck.
- The Onshape link to my sketch of all pictures in this post.
- More ideas, corrections, experiences in-needed,
please hate me immediatly. Vote the Project POTATO- Request to upgrade the permant editing permissions in the forum.
- Sorry for my ULTRA bad sleeping quality these days
FIN