0925

Item 0925

DESIGN: UniCopter ~ Power Train - Assembly - 6º Crankshaft, All Gear

For use with the Rotax 912 and 914.

Drawing:

Possible Disadvantages:

The larger diameter of components behind the pilot's head necessitate that he sit further forward; but this may be necessary anyway for CG

Option:

If the CG and the aerodynamics of the fuselage will allow the engine to be moved aft 2.75" then the Rotax dog and disks on the propeller shaft can be included, in their standard location.

Advantages:

Total of 8 gears. Three gear sets between engine and each rotor.

Having the pilot slightly further ahead give more room for fuel or payload, at the center of gravity.

Arraignment of Components & their Design Pages:

Engine:

Primary Reduction: 2.43:1 ratio. Item 0945

Secondary Reduction: 1.24:1 ratio. Item 0945

Torsional Shock Absorber: Could use the one in the Rotax gearbox or can it be put into the larger Rotax gear and/or can in be part of the flexible coupling(s) between the X-tube and centrifugal clutch(es). Item 0942

Soft-start: SMC Axle Clutch, Item 0751 , or Zanzottera Item 0975

Overrunning clutch: Located on crossover shaft, outboard of centrifugal clutch. Item 0142.

Final Reductions & Rotor Synchronization: Two 81º (or 80º), 2.375:1 ratio, spiral bevel gears. Item 1017.

Rotors:

Rotor Brake: Consider locating it on x-shaft on opposite side from centrifugal clutch.

Notes:

This is designed for the Rotax 912 or 914 engine with custom gearbox. See 0945

Consider running the engine at a lower rpm, and decrease the power train ratio proportionately. In other words, de-rate the engine.

The engine's center of gravity is slightly to the starboard of the crafts centerline. Assuming there is clearance between the side of the engine and the fuselage, the engine might be shifted and inch or so to port to make room for the centrifugal clutch.

Notes re Final Spiral Bevel Gear Sets:

See B301. I think that these gears are applicable to Assemblies 0925, 0946 and 0999. Except the ratio has been changes to 2.66:1

Notes re Rotational Spike Absorber:

There must be a device for minimizing the rotational spikes from the engine since this will result in a considerable lengthening of the power train's reliability and life.

General Thoughts:

Consider if Rotax overload clutch assembly (or parts of it) can be located on the x-over shaft in lieu of current centrifugal clutch. This will reduce the size and the weight of the clutch.
Consider locating a sliding spline on the x-over shaft between the rotor brake and the mid gears.
Consider one large gearbox that encloses all.
6 degree slope may increase to around 8 degrees.

Center of Gravity of Engine:

X = -9.5"

Z = 9.75"

Y =

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Last Revised: February 19, 2002