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9

At least at the small/model scale, the answer is no. There is significant efficiency loss due to the stacked propellers not receiving the same clean air as they would if they were horizontally separated. This is demonstrated experimentally in a Youtube video by rctestflight which compares the efficiency/thrust production of three different propeller ...


5

TLDR: The thrust would not double. You can get close but it won't be easy. There are a lot of factors affecting this but in my experience the distance between props dominates. I once built a push-pull RC airplane and got close to 180% the thrust of a single prop. The configuration is similar to the Dornier Do335: Dornier Do335 So you can get quite close ...


4

The usual way to calculate exact thrust is actually experimentally, through testing on a thrust stand. There are countless factors that may influence the performance of your particular motor and propeller combination, some of which are hard to measure and quantify, so the exact number has to be found out just by testing it. That said, if you only need a ...


4

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 issue is that pitch-speed is important - the prop needs to be producing thrust when the plane is moving, not stationary. Measuring static thrust only tells you ...


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

To fly above ground effect, you need thrust equal to the weight of the aircraft (or slightly more, as you want to climb). Ground effect doesn't hold aircraft down, it just makes it easier to fly when they are close to the ground. The exact amount varies quite widely depending on exactly how close the wing/rotor is to the ground. For a plane or helicopter it ...


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

Many common motors will come with a data sheet for a range of voltages and propellers, such as the data sheet at the bottoms of the description for these motors: https://www.quadcopters.co.uk/iflight-xing-e-2207-motor-2-6s This is the easiest way to check. Alternatively, you can build or buy yourself a motor test stand (like this: https://banggood.app.link/...


2

There are too many factors to be able to give you a precise plot. All the below have major impacts on propeller performance: Activity factor A blade with a thicker chord will generate more thrust, but have less efficiency Airfoil selection Prop airfoils change as a function of radius. Some airfoils are good (bad) at low Reynolds and/or low Mach, but are ...


2

The problem you have found is that you are trying to calculate the efficiency and lift coefficient of your fan, which isn't possible. There's no simple calculation to convert power to thrust because it will depend on the angle of attack of the blades to the airstream. The mass flow rate is calculated on the velocity of air through the fan, not the motor ...


2

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 these vectors using trigonometry to work out how much of that thrust is going to be effective in the downwards direction and how much will be horizontal.


2

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 airflow is straight down, all of the force is used for lift If the airflow is completely horizontal, none of the force is used for lift Aligning the motor at ...


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

There are a number of performance differences between open-blade quadcopters and ducted fan quadcopters and they may depend on the shape of the ducts. In theory, the most notable difference in performance is the increase in either hovering efficiency or increase in thrust. When a drone has the ideal shape of ducted fan, it could decrease battery consumption ...


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