23
votes
Accepted
Why are quadcopters inherently unstable?
A stable system is one where there's a force that pushes the system back towards it's original state when the system is moved from its balance point.
For example, when the driver gets into a car, ...
- 7,418
10
votes
Accepted
How does frame stiffness affect a quadcopter?
Background
Stiffness, oscillation, and vibration damping are separate concepts but all somewhat relevant to the question. Each affects flight dynamics, and each is (somewhat) a function of material ...
- 1,892
10
votes
Accepted
What is antenna gain?
Gain, as a general term, is a measure of how large or strong something (a voltage, a radio wave, a sound wave, or whatever else) is relative to some baseline value of the thing being measured. A gain ...
- 2,997
6
votes
Accepted
Does the performance of a brushless motor decrease over time?
Like most things, it depends on how you treat it.
As far as I know, you should never need to worry about a brushless motor wearing out, especially for our purposes where we will likely demolish them ...
- 4,432
6
votes
Accepted
Does the sharpness of a propeller blade affect efficiency?
Rounded leading edges are better for subsonic aerofoils.
Props and wings have to work at a range of angles of attack. The airflow has to split to pass either side of the aerofoil, and a rounded ...
- 7,418
6
votes
Accepted
Is there an advantage to having more LiPo cells in a low-power drone?
The advantage of running at higher voltage is that you can use thinner wires and lower current (i.e. cheaper) ESCs, as power lost to resistance is proportional to current (squared) and not voltage.
...
- 7,418
6
votes
Accepted
How does the center of gravity affect a quadcopter?
Altering the location of the CG (center of gravity) also changes the CM(center of mass) because the force of gravity acts roughly on the CM. Normally, the motor arms are equally sized so that all ...
- 6,063
5
votes
For custom multirotors, what is the most useful method of collecting flight data?
If you're using a flight controller running either the Cleanflight or Betaflight firmware, you can make use of the builtin "Blackbox" logging features. These firmwares rely on the flight controller to ...
- 6,063
5
votes
What is antenna gain?
'Antenna gain' gives you the power transmitted by an antenna in a specific direction, when compared to a theoretical antenna that radiates equally in all directions (this is known as an 'isotropic ...
- 599
5
votes
Accepted
Would it be possible to perform a manual flip with my camera drone?
To my knowledge, ATTI mode only disables GPS, optical, and other positioning sensors. Your drone would still be actively stabilized with the Gyro and would still be limited in how far it can roll or ...
- 5,802
4
votes
Accepted
How does a propeller with more blades create more "grip"
Aside from fancy material science which can result in propellers that interact with air more cleanly and is highly proprietary, the primary way a propeller could gain more "grip" on the air is by ...
- 6,063
4
votes
Accepted
What is the performance difference between a brushless motor with a wider vs taller stator?
The simple answer is "more width equals more torque".
More torque let's you drive a higher pitch or larger diameter prop effectively. Given the same size prop, it will drive it with more ...
- 525
4
votes
For custom multirotors, what is the most useful method of collecting flight data?
There are also some external logging devices that are available if you have a free UART on your flight controller.
For example the OpenLager project which is a fast serial attached SD card logger, ...
- 629
4
votes
Accepted
How to determine the minimum thrust to weight ratio for a fixed-wing aircraft?
I'm afraid it's not that simple. As you mention, planes can fly with a fairly low thrust to weight ratio. Obviously gliders can fly with no power at all, so there's no critical lower-limit.
The other ...
- 7,418
3
votes
Is there an advantage to having more LiPo cells in a low-power drone?
Other than running high cell count batteries on low-power drones for the lols, there isn't much point in doing this, which will result in the throttle being SUPER twitchy and ultra-responsive to small ...
- 6,063
3
votes
What is the performance difference between a brushless motor with a wider vs taller stator?
To simplify this discussion, it's easiest to focus on a single size class for these motors - 22XX-24XX motors on 3.5-6g propellers (5"-6"). It is also incredibly difficult to decouple effects of ...
- 846
3
votes
How to determine the largest LiPo I can use in a quadcopter?
I've heard that you want to keep your battery weight no heavier than 1/3 your drone weight.
- 291
3
votes
Accepted
What is the difference between a patch and helical antenna?
tl;dr: In terms of radio performance, they're almost identical if you compare similar-gain models, so choose based on dimensions, durability, maintainability and other practical considerations. If you'...
- 2,997
3
votes
What is the difference between a patch and helical antenna?
It is my understanding that in general a helical antenna will perform better than a patch antenna. I should really find a source for that though. However a patch antenna is flat or nearly flat and ...
- 1,160
3
votes
How can I run 2207 2450Kv motors on 4S with 7” props?
7" props have a disk area that is almost twice as large as 5" props, so the motors will be heavily overloaded. (7 squared is 49, 5 squared is 25, the other terms in the equation for the area of a ...
- 7,418
3
votes
If AUW is 90 grams, will 4500Kv motors be better than 7500Kv?
Lower kV motors will spin more slowly but with more torque. Spinning more slowly (with the same prop) will give you less thrust and less power (and thus lower current) at full throttle.
However, a ...
- 7,418
2
votes
What is antenna gain?
Antenna gain is a measure of how effectively an antenna sends or receives a signal. It is a relative measurement and is usually a comparison to a simple antenna design called a dipole antenna (dBd) or ...
- 6,081
2
votes
How to determine the largest LiPo I can use in a quadcopter?
I don’t think there are diminishing returns, if the propeller+motor+controller efficiency stays the same regardless of overall weight.
Imagine a drone where all the weight is in the battery and the ...
- 121
2
votes
How does frame stiffness affect a quadcopter?
TL;DR:
Yes, a semi-rigid frame will cause vibrations while flying because it alters the nature of motor and propeller oscillations as the frame parts move around. This will cause a drop in efficency ...
- 6,063
2
votes
How does frame stiffness affect a quadcopter?
I am going to jump in here with more than comments to other answers and I am going to answer this question in my own unique way. First, I have a similar related question, and I recently posed it to an ...
- 415
2
votes
Do propellers at different angles work the same? And do intersecting flows of air work the same?
The amount of force generated remains the same, however it is applied in a different direction; you therefore get an effective reduction in force for a given axis. To use the two extremes:
If the ...
- 6,081
2
votes
Accepted
Do propellers at different angles work the same? And do intersecting flows of air work the same?
The motors would still generate the same amount of thrust, however it would be aimed in a different direction.
Think of the thrust as horizontal and vertical vectors. You can work out the ratio of ...
- 4,432
Only top scored, non community-wiki answers of a minimum length are eligible