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Aug 15, 2011, 04:48 PM
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Originally Posted by corocopter View Post
Heli Halle / Gary,

Thanks for posting those two videos; they demonstrate the affect of the stability created by the spinning prop. The upper single motor craft is much more stable, the lower twin motor craft cancels out the gyroscope stability making the attitude guidance system work much harder to reduce the oscillations in the pitch and roll axis.
Actually, not quite. A counter-rotating setup will be slightly more stable than a single rotor setup, because the two rotor precessing moments will cancel each other out, while their inertia will still oppose the tilting moment. I think that the second, smaller counter-rotating twin had more trouble taking off because the control surfaces will be sitting in a cushion of air when it is on the ground. Indeed they become much more effective once there is some distance from the ground, and I bet that it would be easier to control if it had some form of stub feet. Or, seen the topic, if it was sitting in a lightweight carbon rod cage in the shape of a sphere
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Aug 15, 2011, 06:11 PM
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I agree with everything you said, with one exception. Please help me understand.

I agree that the twin will cancel it precession out, and the added inertia will oppose the tilting moment, but would not some precession from the single prop work much like the Turboplane disk (ring wing), or weights that were spun for the express purpose of creating gyroscopic stability, and thus precession? This should help to create some stability.That is the reason I brought the Turboplane into this subject. The Turboplane spun the disk and or the weights in the same direction as the spinning prop, thus adding to the gyroscopic forces.

I agree that the craft is flying too close to the ground and thus is being affected by self created turbulence. Also the control surface moments are very small as compared to the single motor craft. There is a Hugh difference between the two crafts with respect to control surface area, and placement. I suspect that it is a combination of these factors also that are involved. Perhaps my comparison was not valid for several reasons. Let use know our thoughts please.

Last edited by corocopter; Aug 15, 2011 at 06:28 PM. Reason: spelling
Aug 16, 2011, 04:21 AM
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Well, precession shifts a tilting moment along the rotation of the disk. This can be used to stabilize a device, for example a spinning top: as the top tilts, precession makes it tilt sideways rather than in the direction of the initial balance. this moves the contact point on its shaft sideways, meaning that the shaft will contact the ground off center and pull the top upright. On an helicopter the precession on the flybar plane of rotation is used to change the incidence of the rotor blades so that the rotor plane of rotation will compensate. But with a fixed prop the precession will only send the prop moving in a conical path. This also happens with the turboplan, but the spinning mass is large enough and the conical path is so wide that the pilot has plenty of time to compensate, while a smaller mass would tilt much quicker
Aug 16, 2011, 10:41 AM
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Your explanation makes perfect sense, I'll agree with your observations. Thank you.

Back to the Japaneses Sphere:

Thanks to a lot of great posts by other forum members, I was able to gleam a great deal of information about the sphere that I'll post over the next few days.

In brief; I ran the patent application into several on-line translation sites, looked at the posted videos and capture some stop frames of the device in flight and on the ground.

This craft has many novel features that are worthy of further discussion on this thread.
Some of the more interesting features are the fact that this craft is intended to take-off from any surface or obstruction that it may fall into will investigating a wreckage of a building etc. Thus it has a canard configuration of the flight controls, the CG is placed at the meridian of the sphere, and it also has those very interesting perimeter flaps, that one article called spoiler. I'll post some of the claims from the patent application which is 31 pages long too. I'm short on time now, but expect this date over the next few days.

Aug 16, 2011, 04:36 PM
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Here is some basic data, clipped from a web news sight. Please note that I've been able to identify only 8 spoilers (not 16 spoilers as mentioned, perhaps the translation to the news service as in error), and 8 so called maneuverable rudders. The patent application does not make reference to the spoilers or show then on the illustrations from the patent. Perhaps the spoiler are on a separate patent application? The spoilers are the most interesting feature of this craft in my option. More later.......

Clip from the web:

The radio-controlled black spheres are meant to fly in and out of structures weakened by earthquakes and other natural (or unnatural) disasters. It's equipped with an on-board camera that transmits live video footage back to the person controlling it, and boasts eight maneuverable rudders, sixteen spoilers and three gyro-sensors powered by lithium batteries. The frame is made from lightweight carbon fiber and styrene components, with a total weight of 12.3 ounces.
Aug 20, 2011, 04:57 PM
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Patent Application Claims

Here are some of the details from the patent application dated March 11 2010,

Please keep in mind that many of claims and descriptions in this application may not be represented in the device that we’ve been looking at on the web. One very interesting fact I noticed is the complete absence of the perimeter (spoiler) flaps. I’ll get back too that after I give a brief description of the claims in the patent.

The crafts is laid out in a canard configuration, so the upper control surfaces coincide with the elevator and rudder and as a combination are refered to as the Tail in the patent. The lower section is called the wing and has ailerons. The area in between is called the ladder.

The CG is adjustable and has a servo actuator. This allows the craft to be stable in both vertical flight and high speed sprint (horizontal) flight. The CG is forward for high speed horizontal flight is shifted aft for hover flight.

The CG is close to the center of the device to allow it to fly up to walls and gently tip the upper end of the sphere inward thus directing the thrust of the craft in such a manner to make for stable observation into windows or trace along walls looking for openings. The CG is also at the center so that it will roll like a ball across the ground to land and take off.

The craft can reverse its output thrust direction (reverse) to allow it to escape from holes or other obstructions with the use of the elevators and ailerons.

The craft is designed to land and look, and I presume listen and maybe smell for gases. My guess on the last two items. It can land and look to save power. It is designed for search and rescue missions.

The canard configuration allows the craft to rotate by directing propeller thrust and also allow for the ability to slide along walls and peek into windows. The canard allows the craft to tilt the upper half of the sphere always from the wall. If it was a normal tail configuration it would have to rotate the craft from the lower end thus dragging its outer circumference along the wall to make the pitch change. Those are my words. I’m trying to put meaning to the very poor translation. If you look at the photos you’ll see what I’m trying to explain. Tilting comes for the top of the craft not the bottom.

The next post I’ll talk about the spoilers that are missing from the patent. It is my option the spoilers are used to eliminate the complex adjustable CG mechanism. Perhaps they put the spoiler on a second application, we will require further help to try and find this other patent application. Can anyone out there lend a hand on this matter?

Last edited by corocopter; Aug 20, 2011 at 06:06 PM.
Aug 20, 2011, 05:31 PM
Gary Mortimer's Avatar
Well done Kelly!

I look forward to the rest of your report.
Aug 20, 2011, 05:51 PM
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The spoilers are hinged from the outer cage of the craft. The spoilers are capture so that they cannot tip outward, only upward, horizontal (into the plain of the propeller, or downward. There are 8 spoilers that I can identify and if you consider how they work it only allows for the spoilers at the top, placed just outside of the plain of rotation of the propeller(s). If it has counter rotating propellers then we might expect to have 16 spoilers. One claim in the patent was the fact that the craft could have counter rotating propellers.

The spoilers are passive devices that respond to the relative wind. In a hover the inflow of air into the propeller disk draws the spoiler into a horizontal position. When the craft gently tips, let say to the left, the relative wind changes, the spoilers on the left stay in the horizontal position, but the spoilers on the right side drop down, but cannot swing outward since they are block from rotating any further by the outer cage of the sphere.

The slight rotating motions of the sphere disturbs the inflow of air into the prop. The spoilers are placed at the exact location (distance from the outer edge of the prop) that will allow for the release from the horizontal position with a very slight change in relative wind. The drooped spoiler now act as air brakes/spoilers to slow down the rotation (tilting) of the craft to the left. They are aerodynamic dampeners.

When the craft is flying in the horizontal mode, (sprint mode) the relative wind drops all of the spoiler, reducing this drag. It is completely automatic and adjusts itself accordingly. In sprint mode you don’t need the dampeners. When you return to hover mode the relative wind pulls the spoiler back into the horizontal position, deactivating them until the craft is tilted in some direction.

Here is my take on this matter. By employing the spoiler the designers could eliminate the heavy and difficult to implement adjustable CG mechanism. They could set the CG forward for stable horizontal (sprint) flight and use the spoiler to dampen the oscillations that are created by have the CG forward (further ahead of the center of pressure) thus creating a solid stable hover platform. These devices could be implemented on other VTOLs to reduce oscillations.

It is very easy to see how these spoilers work by simply holding a few sticks of burning incense up to a spinning prop, or hold a sheet of paper up to the side of a prop. They will be drawing directly into the plain of the propeller. If you back away for the prop you see the paper drop vertically just like the spoiler. This is a very clever device! They are a passive stability system.

Last edited by corocopter; Aug 21, 2011 at 11:02 AM. Reason: Spelling error: changed cleaver to clever, last Para.
Aug 21, 2011, 01:59 AM
Gary Mortimer's Avatar
My hat that's clever
Aug 21, 2011, 09:39 AM
Registered User
Gary, thanks for pointing out that spelling error. I fixed it.

I hope this write-up was of some interest to forum readers. I find these spoilers very interesting. I'm wondering what made some person think of such an unusual concept of the passive spoiler system.

Last edited by corocopter; Aug 21, 2011 at 11:04 AM.
Aug 22, 2011, 07:12 PM
Registered User

CG vs CP

One more thought regarding the spoilers.

The use of the spoilers raise the Center of Pressure above the CG in hover making it much more stable in hover. This affect disappears in high speed horizontal flight since all 8 of the spoilers are in the drooped position allowing the CP to drop downward. This greatly improves high speed flight stability.

Of course this is just one more way of saying "adjustable CG", but in this case it really "adjustable CP".

I have to thank Brandano for helping me to get a handle on the CG/CP relationship regarding VTOLs. Thanks Brandano.

Aug 23, 2011, 02:58 AM
Registered User
hmm, so the idea is that those surfaces will deflect if there is significant sideslip and tend to cancel it out tilting the "nose" away from the direction of movement, towards the vertical in a hover. Won't this fight the inputs when the plane moves to make an horizontal flight conversion?
Aug 23, 2011, 09:54 AM
Registered User

Well, yes to a certain extent, while the craft transitions form vertical to horizontal fight. There will be resistance to tipping into horizontal flight. The canard has sufficient power to overcome this counter force. Also I need to add that the upper and lower flight control vanes work together in harmony. From examination of one of the posted videos on this thread, you can see that all 8 control vanes (rudders) can move to control pitch, roll and yaw. But we’re talking mostly about the spoilers right now. I need to make another post regarding the action of the flight controls later. This device is jammed full of all kinds of surprises and I’m trying to examine one thing at a time. First I had to describe the craft in its basic form and now I hope to examine a few of the most interesting features, for now I’ll continue with your question.

Here’s another way to look at the problem.

Consider these three different flight modes:

1, Hover: craft is in a steady hover, and all 8 spoilers are in the horizontal position, the pilot jams the throttle wide open and the craft dashes upward. All 8 spoilers will droop to full downward defection. They line up with the relative wind, reduce drag, and move the CP aft.

2. Tilted at a 45 degree angle, hover horizontal fight,: the forward spoilers will meet the incoming air at approximately 45 degrees, which coincides with the relative wind. The aft spoilers will droop creating drag as you mentioned resisting further tilting of the craft. Now if for some reason the pilot lets go of the stick the craft will immediately right itself. This is a powerful stabilizer. You must hold stick pressure to hold an angle of 45 degrees. One of the posted videos shows a clip from a movie taken by the onboard video camera. The craft is flying down a hallway and is tipped to about 45 degrees. You can see in the upper part of the images the forward spoiler tilted back with the relative wind to an angle of about 45 degrees.

3. Horizontal fight: This is exactly like the example in #1 above except the craft is now tilted onto the horizontal plain. All 8 spoilers will droop completely back out of the way, they line up with the relative wind, this reduces drag and moves the CP aft, which makes the craft stable in horizontal fight.

The CP will automatically shift from the top of the craft towards the bottom of the craft as the sphere tilts and accelerates into horizontal fight.

The spoilers eliminate the need to have an adjustable CG. It would take too much time to adjust the cg upward and downward, the CG servo(s) would waste a great deal of electrical energy too. This makes the craft much simpler to mass produce. I suspect the spheres are disposable crafts. If exposed to excessive radiation for example the craft is abandoned on sight.
Last edited by corocopter; Aug 23, 2011 at 10:47 AM.
Aug 23, 2011, 02:23 PM
Would those spoilers make something like the CrazyBall perform better?
Aug 23, 2011, 04:46 PM
Registered User


I would imagine that the spoilers would help. You'd need to move the cg aft from the current position, but with the spoilers correctly positioned you'd have a much better hover, and it should fly well in horizontal fight too.

When the craft was in hover mode it had troubles with the yaw axis, well maybe it should be called the roll axis depending one your point of reference.

I'd say this would be perfect craft to try the spoilers on, and maybe one of those OpenPilot CopterControl boards, at the very least a hk401b gyro to control that yaw axis in hover.

You may want to add and extra set of cutout flaps just below the opening for the prop for the yaw axis control. You could try the canard configuration with this setup. You'd only need 2 flaps for yaw control, I don't know if that would limit other areas, but you sure could tell a lot form that setup.

Best of luck, let us know if you have any success.

By any chance can you read Japanese?
Last edited by corocopter; Aug 23, 2011 at 04:57 PM.

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