0999

Item 0999

DESIGN: UniCopter ~ Power Train - Assembly - 12º Crankshaft, All Gear, (6 gears)

For use with Rotax 912 and 914.

Drawing:

Possible Disadvantages: & Thoughts

The pilot will be too far forward.

An axial load is placed on the crankshaft.

Consider addition of weight in tail to offset very heavy pilot (instead of adding weight in nose for very light pilot.

Advantages:

Total of 6 gears in the power train. Two gear-sets between engine and each rotor.

Arraignment of Components:

Engine:

Primary Reduction: 3:1 down to 2.58:1 ratio right angle spiral bevel gear. Item 1010

Torsional Shock Absorber: Could use the one in the Rotax gearbox or a flexible coupling located between the primary crown gear and the centrifugal clutch..

Soft-start: SMC Axle Clutch, Item 0751. Modify for greater horsepower.

Overrunning clutch: Located on crossover shaft, inside SCM axle clutch. Item 0524, if strong enough.

Secondary Reductions & Rotor Synchronization: Two 81-degree, 2.66:1 ratio, spiral bevel gears. Item 1007.

Rotors:

Rotor Brake: Located on x-shaft on opposite side from centrifugal clutch.

Notes:

This is designed for the Rotax 912 or 914 engine with new gearbox.

The gearing may be 2.66:1 on the secondary and 3:1 on the primary for a total of 7.98. 5000 / 7.98 = 627 RRPM. Consider making the mid-gearing with a ratio slightly lower and/or run the engine at a lower rpm. In other words, derate the engine.

The weight of the engine is 125 lbs. which might be slightly less with the modifications to its gearbox.

The primary/overrunning/soft-start/torque-spike-absorption portion of the power train are in the main frame. The two secondary gear units, c/w rotor hubs are bolted to this main frame. The drive shaft connections are floating splines. The engine will be bolted to this main frame also.

Notes re Secondary Spiral Bevel Gear Sets:

Two 81-degree, custom spiral bevel gears. 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

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 splines on both ends of the x-over shaft.

Alternatively, consider one large gearbox that encloses all.

Center of Gravity of Engine:

X = -9.8"

Z = 7.3"

Y =

Back to top | UniCopter Home Page

Last Revised: December 27, 2001