Wondering how much thrust a drone propeller generates

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  Nick Nowaczyk

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  Jul 5,

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  Airflow Drone Propeller

In summary, the faster the propeller spins, the more force it can create. The rpm of the propeller also affects the force of the airflow it releases.

• Jul 5,

• #1

Nick Nowaczyk

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TL;DR Summary

Basically I&#;m wondering how to calculate how much fast a drone propeller or fan spinning affects the amount of energy that it releases. I can&#;t find any information and I&#;m sorry if this is in the wrong spot I&#;m new to the forums.

I was wondering how fast you would need to spin a drone propeller to lift x amount of force and mostly how the rpm of the propeller affects the force of the airflow it releases. I&#;m incredibly new to physics in general and you can take everything I say with a grain of salt.
I have no actual device but for a hypothetical the question would be something like:
&#;I have a fan/drone propeller that is .8m in diameter and the propeller is made of carbon fiber. How fast would it or how many at what speed would it take to release a force of N?&#;
Again, sorry if I&#;m going about this all wrong, I&#;ve never taken a physics course and may have no idea what I&#;m talking about.

 

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• Jul 5,

• #2

Baluncore

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Welcome to PF.
If you look at the blades of a propeller, you will see they have an airfoil profile like a wing. It is that wing moving through the air that lifts the drone propeller upwards, pulling the drone up by the motor mounts. The air that goes downwards is a reaction to the lift of the blade section.

The lift force will depend on the RPM and the number of blades on the propeller. It will also depend on the blade profile and the twist along the blade. That makes it complicated.

A rotor of 0.8 m diameter will have an area of 0.5 m2.
The rotor disc loading will be / 0.5 = N per square meter.
I think that is a bit high, and you may need a bigger prop or less weight. Look for specification data on a similar size drone. Find the rotor diameter and calculate the swept area. Find the total drone weight in kg, then multiply by 9.8 to get the hovering force in newtons. Divide force by area to compute a realistic rotor disc loading. Compare that with your example.

 

• Jul 6,

• #3

A.T.

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Nick Nowaczyk said:

&#;I have a fan/drone propeller that is .8m in diameter and the propeller is made of carbon fiber. How fast would it or how many at what speed would it take to release a force of N?&#;

Estimating the thrust just from propeller geometry and RPM is not a simple computation. One can use numerical methods, but it's much more reliable to look at the datasheets from the propeller, which are based on experimental measurements.

Estimating the thrust just from propeller geometry and RPM is not a simple computation. One can use numerical methods, but it's much more reliable to look at the datasheets from the propeller, which are based on experimental measurements.

 

• Jul 6,

• #4

russ_watters

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From the other direction, though, is fairly straightforward: force (thrust) is rate of change of momentum of the air. The propeller just accelerates a disk of air. Larger propellers mean lower velocity to generate the same force -- and less power.

 

• Jul 7,

• #5

Arjan82

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https://nar-associates.com/technical-flying/propeller/cruise_propeller_efficiency_screen.pdf

With some good guestimates you can come a long way. But you would need some more details of the propeller, the most important ones are diameter and pitch. You've already mentioned diameter, for most propeller performance data this is also just a scaling parameter. This means you can say something about a 0.5m diameter propeller if you have data of a 1.0m diameter propeller, as long as the propellers are mostly geometrically similar.

But pitch is the other important parameter, you can not scale performance data for that. I don't know what the typical pitch is for the propellers you are talking about. If you have the pitch you need to find a performance curve for a propeller roughly of similar shape but most importantly of similar pitch.

The rest are 'second order' effects (I mean, based on the level of detail you are asking for). Yes, the number of blades is overrated, it hasn't got that much of an influence on the performance... (the difference between 2 and 3 bladed propeller is largest, and diminishes rapidly after that, but by large I mean <10% thrust difference at equal RPM or so)

Maybe this document helps, it's a good explainer (unfortunately imperial units...):With some good guestimates you can come a long way. But you would need some more details of the propeller, the most important ones are diameter and pitch. You've already mentioned diameter, for most propeller performance data this is also just a scaling parameter. This means you can say something about a 0.5m diameter propeller if you have data of a 1.0m diameter propeller, as long as the propellers are mostly geometrically similar.But pitch is the other important parameter, you can not scale performance data for that. I don't know what the typical pitch is for the propellers you are talking about. If you have the pitch you need to find a performance curve for a propeller roughly of similar shape but most importantly of similar pitch.The rest are 'second order' effects (I mean, based on the level of detail you are asking for). Yes, the number of blades is overrated, it hasn't got that much of an influence on the performance... (the difference between 2 and 3 bladed propeller is largest, and diminishes rapidly after that, but by large I mean <10% thrust difference at equal RPM or so)

 

• Jul 7,

• #6

A.T.

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Arjan82 said:

https://nar-associates.com/technical-flying/propeller/cruise_propeller_efficiency_screen.pdf

Maybe this document helps, it's a good explainer (unfortunately imperial units...):

The OP sounds like it's about a copter-drone. Static propeller thrust is more relevant while hovering than cruising efficiency for fixed wing aircraft propellers.

The OP sounds like it's about a copter-drone. Static propeller thrust is more relevant while hovering than cruising efficiency for fixed wing aircraft propellers.

 

• Jul 9,

• #7

Lnewqban

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Nick Nowaczyk said:

I was wondering how fast you would need to spin a drone propeller to lift x amount of force and mostly how the rpm of the propeller affects the force of the airflow it releases.

Welcome, Nick!

The pitch of the propeller is important as well.

Please, see:
https://rcplanes.online/calc_thrust.htm

Welcome, Nick!The pitch of the propeller is important as well.Please, see:

 

Related to Wondering how much thrust a drone propeller generates

How is thrust generated by a drone propeller?

Thrust is generated by a drone propeller through the process of converting rotational motion into linear force. As the propeller spins, it moves air downwards, creating a difference in air pressure above and below the propeller blades. This pressure difference produces an upward force known as thrust, which lifts the drone.

What factors affect the amount of thrust a drone propeller can generate?

The amount of thrust a drone propeller can generate is influenced by several factors, including the propeller's diameter, pitch, shape, material, and rotational speed (RPM). Larger diameters and higher pitches generally produce more thrust. Additionally, the efficiency of the motor and the density of the air (affected by altitude and temperature) also play significant roles.

How can I measure the thrust of my drone propeller?

To measure the thrust of a drone propeller, you can use a thrust stand or test rig. This device typically consists of a mounting point for the motor and propeller, as well as sensors to measure the force produced. By running the motor at various speeds and recording the thrust readings, you can determine the performance characteristics of the propeller.

What is the relationship between propeller size and thrust?

Generally, larger propellers can generate more thrust because they move a greater volume of air with each rotation. However, they also require more power to spin and can create more drag. The pitch of the propeller blades also plays a crucial role; higher pitch blades move more air per rotation, increasing thrust but also demanding more power.

Can changing the propeller improve my drone's performance?

Yes, changing the propeller can significantly improve your drone's performance. By selecting propellers with the appropriate size, pitch, and material for your specific drone and its intended use, you can optimize thrust, efficiency, and stability. It's important to balance the propeller's characteristics with the capabilities of the drone's motors and the overall design to achieve the best performance.

I&#;ll be honest: I love my drone. I mean, I always had remote-control vehicles back when I was a teenager. And of course the most impressive RC vehicle was the gas-powered helicopter. But it was expensive and hard to fly. Now, with a quadcopter, it's a breeze. On top of that, it takes pictures and videos.

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Video: Rhett Allain

On the Ball

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Video: Rhett Allain

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