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Old Mar 20, 2010, 10:40 AM
Camflyer
Switzerland
Joined Oct 2004
35 Posts
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RC Harrier - my fist attempt to build hovering Jet

Hi all

The cold winterdays motivated me to start a new VTOL experiment. The goal was to build a really hovering Harrier.

This sea harrier has a weight of 1400g and is equiped with 4 lifting motors. The surface has been weathered. The wingtips have suffered hits from the the first unsuccesfull hover trials.

As soon as weather permits, I will upload a video of the first jumps with optimized settings of the IMU.

Ulrich
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Old Mar 20, 2010, 11:06 AM
Camflyer
Switzerland
Joined Oct 2004
35 Posts
Video of hovering Harrier

Weather finally permitted to go outside with the Harrier. A lot of fun, to hover something which reacts like a heli, but looks completly different than any helicopter.

Please, have a look at the first jumps of this new machine and enjoy.

Ulrich

RC Harrier hovering (2 min 25 sec)
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Old Mar 20, 2010, 11:14 AM
Jesus Freak
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Southern CA
Joined Oct 2008
3,209 Posts
very nice!!!
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Old Mar 20, 2010, 11:23 AM
LSF 004 - AMA 5055
bobandris's Avatar
Saratoga, CA USA
Joined Dec 2000
583 Posts
Hi Ulrich,

"Enjoy" is too weak of a description. Flabergasted would be closer to it!

Great job!!!

From what I could see in the video, it looks like a 'pusher' prop "quad-copter" similar to a tri-copter I've built and flown many times over the years. What type of control are you using? Do you have gyros for stabilization in pitch, roll, and yaw? We all would love to see photos of the underside and details of your control hookup. One final question, are you using the stock EDF(s) for forward flight or the four 'quad-copter' motors/props?

Thanks and details, details, details,
Bob
Quote:
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Please, have a look at the first jumps of this new machine and enjoy.

Ulrich

http://www.youtube.com/watch?v=gAAruGtX8bA
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Old Mar 20, 2010, 05:30 PM
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Quote:
Originally Posted by usr1 View Post
Weather finally permitted to go outside with the Harrier...
Nice job, I like it!

Not critical but it would be cool if there was some way to stop the props so that they end up parallel to the fuselage when the motors are shut down.

What king of IMU do you use? Is it gyros only or gyros and accels?

How much does it weigh?
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Last edited by RCvertt; Mar 21, 2010 at 03:04 AM.
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Old Mar 20, 2010, 07:04 PM
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United States, IN, Granger
Joined Jan 2003
3,098 Posts
very neat ... now get some pivoting on the two wing ones and do a transition !!!!!
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Old Mar 21, 2010, 01:13 AM
vtol fan
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Joined Jul 2009
627 Posts
very nice!

hi ulrich! you tell me please,how you connect the motors and if you use gyro?for the transition forward he tilt the 2 motors?and make a lot of photos!best regards
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Old Mar 21, 2010, 09:52 AM
Camflyer
Switzerland
Joined Oct 2004
35 Posts
Thanks guys for your positive comments

I'l try to answer your questions in this and the next posts.

Bob asked for details of the motor/propeller configuration. Have a look at the cockpit and inlet photo. I was looking for good places in the harrier to hide the lifting props. It was perfectly clear that they had to find their place under the jet. But - the uncovered surface of the propeller disk (white disk in the drawing) is an estimated 20%. The rest is covered under the huge inlets. I was almost shure, this would never work (!?). A propeller without airfeed cannot create thrust, isn't it? . Should I make cheater holes?
Then I found out, that a distance of an inch between fuselage and prop permitted airflow as shown in the second drawing.
Finally the Harrier lifted off, but then --- crash!!!

What was gone wrong? The rpm was so close to full throttle, the IMU could not add more power if the plane started to tilt the nose down.

So the next challenge was to create more thrust without adding larger props (which would not hide under the fuselage). Finally I was successful by modifying larger props and cut the diameter to 10''. These create more lift far away from the center than normal 10'' props.

If you want a self leveling construction, you need at least three or 4 motors.
There are more good places to hide brusless motors and props in a Harrier.... A good place is behind the main wing and in the drop tanks, that's what I chose. Again, the same principle of airflow can be used.


Ulrich
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Old Mar 21, 2010, 12:08 PM
vtol fan
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Joined Jul 2009
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hi ulrich!another question,i have for you...what tipe of motor you use in harrier and if you tried 4 edf instead of proppeller?!thanks for your time!!!best regards!
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Old Mar 21, 2010, 01:20 PM
Camflyer
Switzerland
Joined Oct 2004
35 Posts
Hi nadine

It's a modified Guanli Harrier with 4 Brushless MK2835/52 lifting motors. They are sold over the web in germany.
The weight of the Harrier is 1400g with Lipo 3s 2200mAh
3 gyros, 3 acc-sensors

A guy called christian in a german forum is trying to build a Harrier with 4 edf.

http://www.rc-network.de/forum/showt...?t=9716&page=6
Scroll down for pics.

There is no newer info, if he has come to success.

greetings to Italia
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Old Mar 21, 2010, 01:39 PM
vtol fan
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Joined Jul 2009
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thanks for greetings!

Quote:
Originally Posted by usr1 View Post
Hi nadine

It's a modified Guanli Harrier with 4 Brushless MK2835/52 lifting motors. They are sold over the web in germany.
The weight of the Harrier is 1400g with Lipo 3s 2200mAh
3 gyros, 3 acc-sensors

A guy called christian in a german forum is trying to build a Harrier with 4 edf.

http://www.rc-network.de/forum/showt...?t=9716&page=6
Scroll down for pics.

There is no newer info, if he has come to success.

greetings to Italia
hi ulrich!thanks for greetings!...and for the link,but tell me,this 3acc-sensors ,where do you buy it?you could make a foto in detail of that and a diagram of wiring do you make...i think,there is a lot of guys interested the diagram and foto!thanks...best regards!!
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Old Mar 21, 2010, 04:19 PM
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Quote:
Originally Posted by usr1 View Post
Thanks guys for your positive comments

I'l try to answer your questions in this and the next posts...
Very helpfull info. Thanks.

Do you plan to tilt the rear motors for forward flight soon?
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Old Mar 21, 2010, 10:08 PM
It's a really big number.
Brisbane Intl, Australia
Joined Jan 2001
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Awsomely well done! I can't wait to see the conversion flights.
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Old Mar 22, 2010, 03:16 PM
Camflyer
Switzerland
Joined Oct 2004
35 Posts
Inside the Harrier

For those of you who asked to see more of the electronics of this vtol project, here some pics of the wild jungle of cables and connectors.

The goal was to keep the the whole EDF-area free of cables and printed circuit boards to allow a later installation of an EDF for testflights with transitions from hover to full forward flight (and back of course). Yes, that will be a future challenge! As I have a lot of unanswered questions for this later phase of the project I will need your experience and advice, dear VTOLers. More of this later.

So on the left pic you can see the IMU (inertial measurement unit). I was so naive in the beginning to think, the Harrier would just hover with the settings I had optimized with a "flying bedstead". Indeed - for 2 seconds I felt a satisfaction to have it done - until the beast tilted uncontrollably to the side or the front or the back and hit the surface very roughly.

What had gone wrong this time?

The inertia of masses was completly different. What was perfect for the "bedstead" was absolutly unusable for the 1.4 kg Harrier with it's fuselage and wings.

So if you try your own Harrier chose an IMU which has a very wide range where you can adjust individual settings. Mine works with a PID controller (proportional integral differential). Only after increasing P and D to extrem values the Harrier started to lift off to a controlled hover.

On the right pic you can see the EDF in the front, wiring an parts of the 4 ESC in the middle and the IMU in the rear. Could be made nicer, I know. But you all know the feeling when you want to try your ideas, instead of spending even more time on the bench.

Ulrich
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Old Mar 23, 2010, 11:56 AM
vtol fan
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Joined Jul 2009
627 Posts
thanks for the pics!

thanks for the pictures,you are very kind!please tell me also,that IMU where i could find ulrich?and ,i forgot,you could send to me the link in germany for the motors!?best regards!!
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