Item 0946

DESIGN: UniCopter ~ Power Train - Assembly - Lateral Engine - All Gear

For use with Hirth and Rotax 912 and 914.

Drawing:

 Possible Disadvantages:

The engine might have to be move to the side to get the primary reduction ( plus soft start and overrunning ) in.

Consider opening up the rotor stagger slightly. Done

Consider driving a central shaft, with flex couplings to the rotor.

The driven sheave will not fit under the mast bearing. Can lower the X-over shaft.

Is there room for the aft air cleaners?. Consider leaving the forward intake manifold as is, with the air cleaner pointing to starboard, but replacing the aft one with the opposite handed one so that the air cleaner point to port, aft of the transfer drive.

 Advantages:

Engines torque should offset some of the rotors" torque in pitch, with changes in power. The helicopter wants to pitch up with increased power, therefor the CW rotating crankshaft should be pointing out on the starboard side.

Only 1 spiral bevel gear and no belts will result in least loss of power..

The pilot and the engine can be closer to each other, longitudinally.

The width (rotor stagger) of 27" may have to be increased anyway.

 Notes:

Get engine as far forward as possible, for center of gravity and smallness of fuselage.

Can move the engine to starboard one or two inches, if required to give more room for the gears. The weight of the transmission will offset the side shift of the engine's weight.

Drive Train:

When standing on the starboard side and looking to port, the XZ plane of the rotors is rotating CCW and an increase it torque wants to drive the tail down. The X-shaft is rotating CCW when view from the starboard side. The engine's prop flange is pointed to starboard and it is rotating CCW when view from the atarboard side. The engines crankshaft is therefor rotating CW when view from the starboard side. Therefor there must be an odd number of gears between the gear on the prop shaft and the gear on the X-shaft. The distance is 10.5" so the center gear will be bigger than the propgear and the x-shaft gear.

Components:

Engine:

Torque absorption: In engine's std reduction

Soft start:

Reduction: Approximately 1.06:1

Overrunning clutch: Located between last gear and X-shaft.

X-shaft: Second pinion at rotor brake end should maybe float on shaft ???

Rotor brake: (on other end of X-shaft). Must default strongly to normally off.

 Notes re Primary Spur Gear Set:

These two gears are in addition to the two that come with the Rotax engine.

 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

 Center of Gravity of Engine:

 

X = 10.0"

Z = 14.37" or less

Y =

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Last Revised: January 6, 2002