I can't help it...It's an illness I tell you...

I have clinical multi-projectitis.

It's incurable.

After seeing the GRASP lab video sof quads literally jumping through hoops, I HAD to make one of my own.

The beginnings:

Although everyone else seems to be going open-rotor, I want zero collateral damage to people, pets, and the living

room walls, so I decided on a ducted-fan design.

4 EDF combos from Hobby King

https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11166

Combined thrust of 4400g.

Combined mass of 424g.

The 5Ah 4S 40C LiPo from my currently grounded Swift Heli:

https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10307

Mass: 578g.

For testing, the initial fuselage is a chunk of extruded poly insulation.

5 Deans connectors and a new soldering iron later (the old 30Watt one couldn't make a decent joint for the wiring harness), this is the result:

I christen her "The Ugly Pink Quad."

At present, she's brainless. I just did a test with a little solderless breadboard sending the throttle signal to all EDFs simultaneously and, not surprisingly, things were learned:

1) With 4400grams of max thrust pushing 1220grams of pinkness, it only took about 1/3rd throttle position to hand-hover.

2) It wants to rotate.

Next issues: Basic landing gear (The motors are outrunners), basic brains, and an IMU

2) it will always rotate if you build it that way! That is a laws of physics on your build. All your motors spins same direction.

Let's say if your EDF motors spins to CW direction, your quad will rotate CCW and vise versa.

You have two ways to correct this yaw rotate issue:

1) Make 2 of EDF motors spinning counter direction, you also need to have propellers that are mean to spin counter direction. This might be a problem on EDF motors. I don't know do you have CW and CCW props for EDFs?!?

On normal quads/hexas/octos we are using identical CW and CCW propellers in groups of two. eg quad has 2+2, Hexa 2+2+2 and so on

2) To countermeasure rotation you need to tilt thrust from two of your motors 3-5° degrees and this way "kill" that rotation. This is a bit bad solution due it's not always symmetrical rotation force that motors are creating and also because two of the motors are "fighting" against two others, you are loosing some energy on it.

Jose from our group is using this method on his mini indoor quad and it works ok but with EDF i'm not sure.

Also one big problem with EDF is that you most like never get it stable. Reason is laws of physics again. To make quad stable, you need to control quickly rotation speed and thrust from your engines. That's why we are using rather low RPM engines with bigger propellers. Power of EDF then again is coming from small propeller and high RPM.

Controlling speedups/slowdown on EDF will be really difficult. Tho I have seen some EDF quads but they all also prove this point, they all fly a bit "lazy" and sluggish.

But anyways, good luck with the project and keep us posted on your progress :)

You need to be a member of diydrones to add comments!

Join diydrones

Comments

James Cann January 14, 2011 at 6:20am

Point form for now:

1) Didn't see matched counter-rotating EDFs, but I'd hoped the fan stators would counteract the majority of the torque generated by the fans. Not completely, so at present I am thinking a single micro-servo linked to small vanes at each fan. If I tilt the rotors to a static position, at a hover, I'll get a corkscrew effect with every throttle increase/decrease, while dynamically tilting the rotors would introduce a gyroscopic precession effect.

2) Ultimately I do want it to go outside, but for the cold weather season, indoor is fine and windless.

3) The choice of the fan was a combo of low price, and high thrust that I'll be able to grow into as I add other culture's technological distinctiveness to my own, and weigh it down with brains and sensors.

4) Yes, it's very noisy :-)

5) Ducted fans are props in a tube

6) The motors are outrunners and are in the airstream generated by the fan. By definition, even when hovering, they are air-cooled, so I don't think heating will be an issue... Efficiency is to be determined soon.

7) This is my first experience with anything VTOL, Quad, or Ducted Fan. (Much experimentation to come :-) )
Distributor

Martint BuildYourOwnDrone.co.uk January 14, 2011 at 6:06am

I always thought that the EDF's were not very well suited to this application due to poor airflow into the front of the fan unit?

Do they not need to be set in a “tube” to have a good level of performance over a normal prop?
Ritchie January 14, 2011 at 5:27am

I believe the rotation is the same as experienced by normal helicopters (hence tail rotor) and quads (hence two CW and two CCW). If you can get two fans that are the other way round you would have my dream quad.

Nice to see someone else wanting EDFs I only wanted them for thrust though.
Jim January 14, 2011 at 4:30am

Thats brilliant! I was trying a similar thing last summer with 3 gws EFD75s and some thick cardboard. Since then I've come by a 4th EDF75 so I plan to make a quad with it when the warm(ish) weather returns. Do you think that the distance between your EDF's was enough? It looks about the same as what I had with three units, but I vowed to increase the distance considerably on the next rebuild.

Jim
Distributor

Martint BuildYourOwnDrone.co.uk January 14, 2011 at 3:05am

That is an interesting design to get around the "open" prop issue. Indoor use only I guess ?
Marco Glattfelder January 14, 2011 at 2:38am

Should 2 of the EDF not be counter-rotating?
Developer

John Arne Birkeland January 14, 2011 at 1:28am

I like the spirit of it!!!

One question. To my knowledge there are no counter rotating EDF's. How do you plan to counter the torque roll when all the EDF's spin the same way?
Developer

Jani Hirvinen January 14, 2011 at 12:23am

2) it will always rotate if you build it that way! That is a laws of physics on your build. All your motors spins same direction.

Let's say if your EDF motors spins to CW direction, your quad will rotate CCW and vise versa.

You have two ways to correct this yaw rotate issue:

1) Make 2 of EDF motors spinning counter direction, you also need to have propellers that are mean to spin counter direction. This might be a problem on EDF motors. I don't know do you have CW and CCW props for EDFs?!?

On normal quads/hexas/octos we are using identical CW and CCW propellers in groups of two. eg quad has 2+2, Hexa 2+2+2 and so on

2) To countermeasure rotation you need to tilt thrust from two of your motors 3-5° degrees and this way "kill" that rotation. This is a bit bad solution due it's not always symmetrical rotation force that motors are creating and also because two of the motors are "fighting" against two others, you are loosing some energy on it.

Jose from our group is using this method on his mini indoor quad and it works ok but with EDF i'm not sure.

Also one big problem with EDF is that you most like never get it stable. Reason is laws of physics again. To make quad stable, you need to control quickly rotation speed and thrust from your engines. That's why we are using rather low RPM engines with bigger propellers. Power of EDF then again is coming from small propeller and high RPM.

Controlling speedups/slowdown on EDF will be really difficult. Tho I have seen some EDF quads but they all also prove this point, they all fly a bit "lazy" and sluggish.

But anyways, good luck with the project and keep us posted on your progress :)
simonl January 14, 2011 at 12:09am

Now that's one cool quad! I'll be followingyour progress.

One question: assuming all the EDGar are rotating the same way, how are you planning to counter the torque effect?
Alexander LeBrun January 13, 2011 at 11:11pm

It wants to spin cause you don't have counter rotating props, but you already probably knew that.I know what ya mean about protecting people and pets, I'll post up some pics in my blog of shrouded fan type quad Im making. Looks good though keep it up.

of 7

This reply was deleted.