Item 1097

DESIGN: UniCopter ~ Pusher Prop - General - w/ Lycoming Engine



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 Sequence of Drive Components:

See; DESIGN: UniCopter ~ Power Train - Assembly - General Arraignment

Engagement clutch:

The shaft to the transmission is driven by belts.

Consider using as many Robinson R-22 components as possible, initially.

Note: "... selection of the number of belts may be made on the basis of approximately 1.75 times the rated belt capacity for light duty (helicopter) operations." [Source ~ MDD p.79]

The clutch for the rotor is engaged by raising the shaft and tightening the belts. (similar to Robinson)

There is a overrunning clutch in the propeller?


Much of the air-feed to the blades at the top of the propellers disk will come from above the engine, between the two rotor hubs.

Information on Accessories etc. for Lycoming Engines:

Van's Aircraft ~

Comparison with Cessna 152:

The Cessna 152 was built between 1957 and 1982. It uses a Lycoming O-235 engine. [O-235-L2C, (118 HP, 2800 Takeoff RPM) & O-235-N2C, (116 HP, 2800 Takeoff RPM)] The maximum diameter prop is 69". The prop has two blades. The cruse speed is 105 KTS. The Sensenich give a prop number of 72CKS6, Maximum takeoff weight 1670 lbs.

Note that the engine proposed for the UniCopter is the Lycoming [O-320-B2C, (160 HP, 2700 Takeoff RPM). It is to be run at 2400 RPM.

From a 69" diameter prop turning at 2400 RPM

Fuselage & Sheave:

Allow additional room about the driven sheave to the rotor so that a large sheave can be used in the future if there is a desire for a lower RRPM to be used with a higher forward speed. Alternatively, just increase the ration of the miter gear set.

Pros and Cons:


The shaft to the transmission belts is simpler than the Rotax reducer.

The free space above the engine could be used to incorporate a baffle for removing rain from the cooling air, which is coming from the hubs of the rotors. (If this will not cause a problem because the incoming air will be very turbulent.)

An aerobatic helicopter would have little practical value but it might be advantageous for testing and it would be awesome for display purposes.


The thrust from the single propeller, as shown, may be below the centers of mass and drag.

Attaching the propeller directly to the engine will probably not do since the engine's rpm will be too low for the required rpm of the small diameter propeller. Check this out.

Additional Thoughts re Propeller:

Rough Thoughts re Two Seats:

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Last Revised: January 4, 2004