1280

Item 1280

DESIGN: UniCopter ~ Pusher Prop - Configuration - Propeller - Twin

For UniCopter with two propellers.

Drawing of Side-by-side Configuration:

General:

For the same area of a single rotor the radius of the two rotors must be 70% of that of the large one. Check

The structure of the tail boom can start from three locations and meld into a single boom. The locations will be; just under the two rotor hubs and over the output shaft of the engine. The area between the three arms should be open for airflow.

The propeller unit and central gear unit at the engine output should probably be structurally integrated with the drive-train frame. The engine will float and be connected to the central gear unit by a flexible coupling. There might also be a clutch here for disconnecting the propellers from the engine, when the craft is on the ground or just hovering. The rear support legs will be attached to the rear bottom leg of the drive train A-frame.

The larger the ratio of the gears at the engine output, the smaller the cross shaft between the propellers and the smaller the gearboxes at the propellers.

Perhaps the propellers should be shrouded.

The thrust line of the propellers does not have to be parallel to the crankshaft.

Pros and Cons of Two Props over One Prop.:

Advantages:

Stronger tail
VS slightly further forward
Better yaw control
The engine will not be so detrimentally inclined as it currently is with the single propeller.
The airflow may be better than that of the single propeller configuration.
Higher engine and center of gravity
Could have shaft to rotor transmission lower and connected to engine via a gear set.

This will give better aerodynamics
The rotor and the props can be started by soft-start and therefore the safety on the ground will be increased

Disadvantages:

More gears. If the single prop is to be mounted on a single boom, this may not be true.
Probably heavier.

Idea: November 14, 2002

Two Counter-Rotating Propellers with Interleaving Configuration:

Consider having two variable pitch propellers, or ducted fans, located side-by-side. They would be interleaved by approximately 9 inches and because they are counter-rotating, they will be moving vertically in the same direction in the interleaving area. Just in front of and just behind this area are located static fins that are pitched in the opposite direction to the rotating blades. This area is devoted to exhausting engine-cooling air and the idea (or hope) is that even when the rotating blades are in flat pitch, the swirl will draw air past the engine.

The counter rotating blades will eliminate any torque-roll moment. If the propellers rotate up in the middle and the static vanes point down then the discharged air may help counter the rotors' torque - pitch coupling.

Idea: March 11, 2004

Two Counter-Rotating Propellers with Side by Side Configuration:

This will reduce the thrust in the center of the craft where there is little airflow.

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Last Revised: March 6, 2005