Thread: Discussion Japanes Ball Drone.
View Single Post
Old Aug 20, 2011, 05:51 PM
corocopter is offline
Find More Posts by corocopter
Registered User
Joined May 2010
436 Posts

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.

corocopter is offline Find More Posts by corocopter
Last edited by corocopter; Aug 21, 2011 at 11:02 AM. Reason: Spelling error: changed cleaver to clever, last Para.
Reply With Quote