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Sunday, August 18, 2013

Thrust test

One of the differences between a normal hexa copter and a Y6 copter is the thrust efficiency. 

On a hexa copter motors are placed side by side. They do not interfere each other and deliver maximum efficiency.

On a Y6 copter the motors (props) are mounted on top of each other (in sequence). The prop wash of the top motor/prop causes the bottom motor/prop to perform less. This setup is less efficient. The exact efficiency loss can only be tested in practice and depends on prop size, distance between motors, …


On my Y6 copter I use 9x4.7 inch props. The distance between the top prop and the bottom prop is also 9 inch. As you can see on the graph I got a 10% efficiency loss for this setup. That is an acceptable result.


Setup:


10 comments:

  1. How many percent lighter is the Y6?

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    Replies
    1. For my project a Y6 isn't lighter than a normal hexa.

      If I would build a hexa for this project i would/can equip it with very little or even no landing gear. Just some foam arround the arms.

      As for the Y6 this type of frame needs a high and strong landing gear. So the weight you lose buy having only 3 arms is added by the bigger landing gear. So weight loss is zero.

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  2. I’m interested in our project, I want to build a Y configuration system but wonder if ducting the fans would improve efficiency? I recognize putting a shroud around your system would add complexity, but would the ducting efficiency? What is the largest fan system you have seen used in a Y configuration? My thoughts are on a tilt rotor, one fan set on each wing and one in the tail.

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    Replies
    1. A ducted fan will increase efficiency. But I can't give you values for that. Keep in mind that this will add a lot of weigth to your configuration. So to be usable the efficiency gain needs to be a lot.

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  3. Hi, how do you get the graph result? I'm interested to run mine as well.Thanks.

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  4. Hi, here is an example of my test stand: http://ax2210n.blogspot.be/2013/09/test-setup.html.

    If you need more information you will find hundreds of simular motor/prop benchmark setups on the net (search google). Another example http://www.1001copters.com/en/content/6-motor-propeller-test

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  5. 10% loss is very good, almost too good to be true. coaxials with H/D =1 have around 28% loss as seen from some study papers. Are you really sure you got such a high efficiency?

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  6. No doubt about,these are real benchmarks. But notice that it depends on how you compare thrust efficeiency at the same power. Or you can compare power efficiency at the same thrust. This will provide different value. And at last, efficiency for coaxial mounted motors/props depend on a lot of values (rpm/distance/prop size/prop pitch/rotation/...) thats why you should Always run a praktical benchmark before applying it to your project

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  7. But what if you switch out the bottom props to more pitch than the top props.....
    I'm about to build a dodecacopter. I was doing a discussion with a guy. I'm using 14" props. Gonna run a 4.5 pitch on top and around a 7 pitch on bottom. All the props will be 14".

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    Replies
    1. All depends on your setup. motor, hover rpm, distance between props. On my setup I tested 10x45 top, 10x60 bottom. At hover thrust it performed equal to 10x45 x 2. So you should do a pratical test. If you can not do this, then just keep the same prop on top and bottom.

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