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Sep 09, 2011, 01:52 AM
DIY Mania from Taiwan
I must say your last 4 postings are quite educational,it inspired me a lot on the captioned subject.
simple is the best as you mentioned,that's how my drone were created.
Japaness spent 2 years to have the craft in public,and they are still continueing modifying the drone.....
some feedbacks:
1.Japaness patent mentioned that they have reversable switch/pitch on
propeller to extricate itself if it trapped in a hole on the ground.
2.one motor is better for cutting weight & spoiler effects,this would be my
next task.
3.switch back to my original design? I would like to challenge myself to
have two control surfaces mixed, thus, both surfaces react to 3 axis
with 3 gyro sensors installed like Japaness one,it may takes time.
4.compare to your Tower Hobby .75 engine project,Im convinced the drone
is an easy one.
BTW could you make a comment on my flying swan thread,I have something new there.
have a nice day
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Sep 09, 2011, 10:05 AM
Registered User
Good morning Sam,

Thanks for the feedback on the Japanese ball patent. That all makes sense what you said. I agree that if you went back to your original design you would be very close to having an ideal setup.

If you have a few days to wait until you start your new project I'd like to give you a few suggestions that maybe helpful. It will take several postings in a number of simple drawings on my part to illustrate these ideas.

What I would like to outline in these ideas are.....

Item 1. Utilize a configuration like your original craft with carbon rods wrapped around the outside.

Item 2. Utilize the least number of components, including servos.

Item 3. Utilize a three axis, or a six axis controller board.

Item 4. Concentrate the design of the craft on having a very stable hover and a secondary objective of moderate high speed flight.

Item 5. utilize a single electric motor and a tractor configuration with the addition of spoilers as required.

Item 6. Illustrate how to determine the Center of Pressure of your sphere.

Okay that's kind of what I like to go over in the next couple of days with a few drawings on how to visualize the Center of Pressure.

I have a few PDF files that I can also attach that may help you design your next craft.

Let me know if this sounds like a good approach to you.

Now I'm off to your swan thread.
Sep 09, 2011, 10:57 AM
Registered User

Ducted fan documents


Here's a couple of PDF documents that describe a tractor configuration ducted fan VTOL. One of the documents shows the difficulties that arise when VTOL aircraft have a duct. The duct interacts with crosswinds to tip the craft in the direction of the crosswinds making it more difficult to hold a stationary position. This is not this is major concern for what you're trying to do but I thought I'd give you a overview of this document. It is helpful to study this one because it would be useful to have this idea later when we discuss the spoilers.

The second document has a few details that are somewhat interesting to evaluate. Both of these documents show the relationship of the tractor VTOL and the control vanes set at a significant distance from the center gravity. The center of gravity on these craft generally is close to the propeller back plain.

Sep 09, 2011, 11:18 AM
DIY Mania from Taiwan

it sounds great to me,looking forward to the new info.
we have a VTOL contest game here on 2nd Oct.2011,I wish I could finish
this ball drone by end of this month and go for the game.
the drone reminds me the twincopter project I've done last year,
it's hard but it's fun.
have a nice day
PICT0158 (1 min 8 sec)

Sep 09, 2011, 11:29 AM
DIY Mania from Taiwan
just got your 2 PDF, I'll read the document carefully,it may take a little time to digest.
best regards
Sep 09, 2011, 11:32 AM
Registered User
Morning Gary,

I need some help please. I've been trying to find the URL listing that you posted on the Open pilot thread many weeks ago. I think it was the Fossy report 148. In this report they talked about the Open pilot flight controller for about one hour in length.

Would you please post again here,

Are they selling the Open pilot controller as well as the Copter control at this time?

Does the Copter control have a magnetometer or is it just the Open pilot controller?

Thanks Gary
Sep 09, 2011, 11:44 AM
Registered User
Hi Sam,

That's a neat little twin copter.

I'm hoping Gary can point us to the open pilot video that was posted on the Internet, it shows some absolutely amazing footage of quad copters being stabilized. I was simply amazed to watch these quad copters actually perform various aerobatic maneuvers like a simple loop and stick on the wall like Velcro.

I think the sphere is relatively simple as you said in components, yet I think the real secret is a very sophisticated or least high quality flight controller. It's virtually impossible to build a self stabilizing VTOL from my research. Unlike an aircraft that has a great deal of airflow over flight controls and wing area to stabilize the device, a VTOL has only the control surfaces in the slipstream of the propeller for stabilization.

Unlike a helicopter which has enormous control authority of the changing pitch angle of the rotor blades, the simple VTOL has to rely upon a relatively small amount of surface area of the controls for both control and stabilization.

Okay all start working out my simple drawings and try to get all of this to you as soon as possible so that you can enter the contest. Have you thought of what other type of flight controller you may use such as a KK controller?
Sep 09, 2011, 11:57 AM
Gary Mortimer's Avatar
Shameless plug for my blog coming,

If you trawl through this page there are lots of multirotor videos


These might be the videos you were thinking of

The Floss Weekly interview

FLOSS Weekly 148: OpenPilot (1 hr 2 min 7 sec)

Aggressive Maneuvers for Autonomous Quadrotor Flight (1 min 27 sec)

Dance with Three (2 min 51 sec)

CopterControl does not have a mag
Sep 09, 2011, 02:03 PM
Registered User
Thank you Gary,

That is exactly what I was looking for, and the dancing with three was spectacular!

Can you tell me if it's possible to purchase the Open Pilot controller or the Copter Controller now?

What kind of flight controller was used in those quad copters in those videos? I presumed that they where from the Open Pilot program, perhaps a Copter Control.
Sep 09, 2011, 04:06 PM
Registered User

Japanese ball physics

Hello Sam,

Here are three rough sketches I made, please excuse my poor penmanship as my right hand is still very sore, but I think you’ll get the idea.

Plate number one, shows three rockets, the first rocket has standard size fins with the center gravity head of the center pressure, the second rocket has fins that are approximately twice as large, and you'll notice that the center of pressure moves aft. Of course the center gravity would move at the little aft too since the larger fins has some mass, but I'm just trying to illustrate the concept of the center pressure.

The third rocket has equal amount of fin area ahead of center gravity as well as aft and it is completely unstable, in some respects this resembles the current configuration of the Japanese sphere.

Plate number two, shows four aircraft with varying configurations of horizontal and vertical tail volume's. The first two aircraft illustrate how the center pressure moves aft with an increase in tail volume, thus increasing stability.

The lower two aircraft show various configurations of vertical and horizontal fin area. You will notice the center pressure moves ahead of the center of gravity and the craft becomes unstable, once again this represents in some respects the configuration of the Japanese sphere.

Plate number three, shows two spheres, the first one representing the Japanese sphere, and the second one representing what I think would work best for you.

On the first sphere, please notice that the center of pressure and the center gravity nearly coincide, this represents a marginally stable if not unstable aircraft without the use of a very sophisticated flight controller.

Let's take a look at the second sphere. Please notice that the second sphere has only two small Yaw control vanes. These two small Yaw control vanes would be connected to the flight controllers Yaw Gyro.

To make the craft Yaw to the left or right on its axis you would use the upper two small Yaw control vanes to initiate this movement, after this movement has been achieved, the Yaw vanes would return to a vertical or neutral position. This would represent the least drag above the center gravity

Down below you'll notice 4 pitch and roll control vanes.

Next please notice that the pitch and roll vanes are offset to compensate for all of the Yaw while the craft is in a stable hover. This off-set would be controlled from the transmitter trim only.

Once again the lower pitch and roll vanes would hold this Yaw off-set at all times and it was set by you from the trim tap, this would take a transmitter mix to facilitate this offset. This offset would not be controlled by the Yaw Gyro, it is simply a fixed set trim that you set one time and forget about.

The lower 4 control vanes are for pitch and roll and each has its own Servo. Each Servo would be connected to the flight controller Gyro's for pitch and roll control.

The idea with this craft is to have the very minimum amount of control surface area ahead of the center of gravity, just like in the drawings I showed you about the rocket stability and airplane stability, you want to see the CG ahead of the CP.

Please note that the skirts are directly below and slightly inside the very tips of the propeller where the air velocity is at the maximum. Please notice that the skirts are parallel to the airflow, that is, they are not offset any way. That way the angle of attack of these skirt plates are set to zero. It's very important that the skirts be the within the air stream of the propeller, you want to a surround the skirts with a blast of air from the propeller on both sides of the skirts.

Please note that the small Yaw control vanes at the top are also within the air stream of the propeller, as close to the tips as possible. The velocity of air is the highest just slightly inside and below the tip of the propeller. The optimum size for the Yaw control vanes in my opinion would be quite long and narrow, that way they require very little deflection through a very low angle. This creates less movement of the center of pressure.

Keep in mind, you always want G. before P., center gravity before center of pressure. Just remember when you say the alphabet the letter G. comes before the letter P.

I hope that was clear enough, please let me know if I can add some more details.

Please note, when you open up these photos Sam, if you double-click on the images they will upload to you a very large version of the photograph for you to look at in detail.

Last edited by corocopter; Sep 09, 2011 at 05:57 PM.
Sep 09, 2011, 04:13 PM
Registered User


I left out the spoilers on this craft for the time being just so I didn't have to illustrate too many things at one time, I'll come back and add in spoilers at a later date with a new posting.

All of this data should get you started on your new project, I think I managed to cover everything in one day. Let me know if you have any questions.
Last edited by corocopter; Sep 09, 2011 at 05:58 PM.
Sep 09, 2011, 04:14 PM
Gary Mortimer's Avatar
@Corocopter, yes CC is available but out of stock everywhere at the moment, the main Pro/INS board is still coming. They are not OpenPilot Project boards in those videos.

The multirotors are inside motion capture rigs that are tracking them in 3D space most of the processing is being done on computers sat in a lab. Big cheat really!
Sep 09, 2011, 05:54 PM
Registered User

Japanese ball patent


There is the Japanese Ball patent in the Japanese language

Edited later today:

Well, Well that just did not work, you have to have the Japanese Language files from your Office XP etc. disk loaded to work. I have these files loaded on my PC. So sorry. It looked like it worked when I upload it but I failed on this one.

Last edited by corocopter; Sep 09, 2011 at 07:57 PM. Reason: Noticed it did not work correctly:
Sep 10, 2011, 12:41 AM
DIY Mania from Taiwan
good informations coming up from you.
we have 3 days of moon festival here in Taiwan,will continue digest the info
right after family outing tomorow.
my pc can read Japaness,I'll check that too.
have a nice day
Sep 10, 2011, 03:33 AM
Gary Mortimer's Avatar
Wow, that underlines how international this forum is, no moon festival ahead here, instead the remains of a hurricane crossing UK on Monday time to bring all the garden furniture in!

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