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25

With aircraft, there are 6 degrees of freedom (DoF) we want to control (roll-pitch-yaw, and x-y-z), but for hovering vehicles (i.e. rotorcraft) we can get away with controlling two degrees of freedom (x-y) by combining the 4 other degrees (roll-pitch-yaw + z). There are many ways of controlling those four DoF, typically: helicopters, which use variable ...


11

This is a very interesting question, and one that is always my favourite to answer. Firstly, rotary aircraft commonly need an even number of propellers (though not always) or another way to counteract the inertia of the props. Think, for example, why helicopters have a propeller at the end of their tail boom; they need to counteract the rotational forces of ...


11

It depends on what kind of stability you're after. Nicolas Petit wrote a paper on this several years ago, the graphics below are taken from Pages 4 and 5. The summary is that a higher CG is better for x-y position stability, a lower CG is better for speed stability. Background Before we begin, let's assume we're only talking about a drone flying purely ...


11

It should be possible so long as the aircraft has enough spare thrust and lift to counteract the drag and weight. Many model aircraft have good power-to-weight compared to their full size equivalent. For the banner attachment, you need a secure point to attach it to the aircraft, well away from any propellers or control surfaces. Usually this is on the ...


8

It is definitely possible to attach a banner to an RC plane. There are many people who have done it and It should be relatively simple. Some things to consider are: Use a very lightweight material for the banner. Make sure you have some support on the banner that prevents it from crumpling vertically. (you can use straws, a wire, or any lightweight rods) ...


7

I'm going to give you the answer first: Yes, it is worth calculating the approximate range if you're building a (very) long-range aircraft. However, theoretical calculations will usually be such a crude approximation of reality that you can't rely on them, and the actual maximum range will depend on a myriad of factors besides what you can consider in the ...


7

This design is to prevent unwanted yaw when moving, or vice-versa. Consider the following two actions: When a quadcopter yaws, it does so by creating a speed difference between the opposite-rotating rotors; creates a torque that rotates the quad. When a quadcopter moves left/right, it does so by slowing all the motors on one side of the frame and/or ...


5

As far as I know, it doesn’t make too much of a difference in regards to flight stability because of something called the Drone Pendulum Fallacy, which describes how the drone rotates about the centre of mass, not from the point at which the thrust is created as illustrated below in the photo from the Drone Pendulum Fallacy website: In my experience, it may ...


4

Most forces in aerodynamics are proportional to area, speed squared, air density and a 'coefficient' that describes how efficient your object is. There's also usually a 1/2 for obscure theoretical reasons. If you work in metric, the density of air at sea level is basically 1, which takes that out of the equation. The maximum lift coefficient of an average ...


4

I just want to add to FlashCactus's excellent answer... Depending exactly what you want, you can get some fairly good estimates on range on various range calculators online. You can get them pretty easily from Googling "Calculate FPV range," but here are a couple: FPV.lt MaxMyRange.com Of course, I concur with FlashCactus... it's not a perfect no-...


4

To me the only weight that matters is the total weight of the craft that is airborne. Or commonly referred to as All Up Weight (AUW). That is what performance depends on. That is what regulations are based on ( mostly ). Anything else is just the weight of individual components in my opinion.


4

I have a working theory for why this may be the case; some micro-quad designs support this theory more than others. Due to Newton's third law, the thrust force created by the propellers also has the effect of trying to lift the propeller up off of the motor in traditional multirotor designs where the propeller is on top of the motor. Aside from ensuring that ...


3

Microquads tend to be flown indoors, where the floor is relatively smooth but there are lots of other things to hit. Putting the prop under the frame provides additional protection when the quad flies into an obstruction. The direction of air flowing through a prop would tend to suck objects in from the top and blow then away from the bottom, so more ...


3

They don't necessarily have to spin in the same direction, but it gives the best results. This has to do with the mathematics of drone flight. Pulling from https://drones.stackexchange.com/a/419/46, and in particular the mixing matrix: (where ω is the motor speed, τ is the torque about the axes, and F is the vertical thrust. Furthermore, the +/- signs ...


3

Not very useful. If you're designing at the absolute limit of what a frame can handle, such that it's as light as possible, then maybe you'll want to know the maximum torque, but you should be designing for orders of magnitude more strength than that (It's not hard, small BLDC motors aren't very torquey). There are control algorithms that take into account ...


3

There are two possibilities, depending on how ducts increase efficiency, but the end result should be the same. It could reduce torque required to spin the motor at a given RPM and thrust, or it could increase the thrust per RPM of the propeller with a constant torque. In either case the torque required to spin the propeller for hover thrust goes down. For ...


3

Ducts and shrouds reduce tip losses; the reason we don't see them more often is that a well designed propeller should not have large tip losses. Tip losses are greatest when there's a large pressure differential between the upper and lower side of the blade. In other words, the blade is highly loaded. This question explains why large, lightly loaded blades ...


2

You can make your own using free software. Let’s take Fusion 360 as an example, in its simulation suite it has a Computational Fluid Dynamics study option. If you’re willing to design an accurate-ish model of the aircraft you want, or pay someone to design one for you, you can run the CFD simulation and get the results for yourself. This is obviously CPU ...


2

Short answer seems to be no standardization. Personally, I am only concerned with AUW and have no concern for individual groupings. If I'm all that concerned I can either weigh each component individually or check the product info. I can see where grouping components together would make sense, though. If a craft is being designed to be modular with ...


2

Capacitors come in various sizes and values, so one big capacitor could equal two smaller ones in value; I do not know for certain if this offers a weight saving, but can reduce PCB footprint size by being 'taller' (although, you can stack capacitors of the same footprint.) A reason to have more than one would be to adjust the frequency response, as a ...


1

You can make a small quad with relatively large props without the propellers being in the FOV of the camera. If you look at the quads you've mentioned, if you flip the motors and props over, you'd need to extend the arms or re-design the entire frame to be bigger. Pusher props can be under the quad and squashed together, making the wheelbase smaller.


1

The torque a brushless motor is capable of producing is particularly important when dealing with control loops. The torque is directly proportional to the rate of change of RPMs, which is directly proportional (though non-linear) to thrust. How quickly the motor-prop combination can make adjustments has a massive impact on overall stability. That may or may ...


1

I am a fan of "More information is better". I believe that torque can be used to calculate system efficiency. I just do not know what those calculations are. I have seen one commercial thrust stand like your concept/design that includes one or two load cells that measure torque. I do not believe that measuring torque would be included in that ...


1

Propeller tip losses are a function of, or perhaps we could say it is a side effect of the propeller design itself. The designer of a propeller can influence the tip losses, but a user is unlikely to find a practical way to accomplish it for a propeller they already own. So this question is theoretical. The overall size and geometry of a propeller can ...


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