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Tip Jet Helicopters. Hoyt Stearns' helicopter patents.  Cross flow fans. Pressure Jet helicopters.


Hoyt Stearns' latest helicopter page (Mosquito ultralight helicopter -- unfortunately it has a tail rotor :-(   )

This is a slide presentation I gave twice in 1986  to American Helicopter Society meetings in the Phoenix, Arizona US area regarding
my torqueless electric air pressure jet  tip propelled helicopter designs and an advanced high speed helicopter using the moments from an offset flapping hub and
shaft torque to unload the retreating blade.  I was delighted and honored that Ray Prouty, Bob Head and other notables attended.

I was granted  two US patents for these ideas:  4,702,437 and 4,720,059.
The patents are expired due to the high maintenance fees from the patent office :-(.
You're free to develop these ideas. Please keep me informed of any work you do in this area.

Email: hoyt-stearns@cox.net

Thanks to Eugene K. Liberatore, Bruno Nagler's chief engineer for some consulting on these projects.

My patent for the blade tip electric cross flow fan driven helicopter

My patent for using offset flapping hub moments to unload the retreating blades

Since there's no torque, there's no need for a tail rotor, however some means of yaw control is required.  In my design, a small
electric motor is coupled to the drive shaft.  For a conventional US left rotating from the top helicopter, envision it  thus:
To yaw left, just grab the shaft with a brake, for right yaw, power the shaft a bit with a small motor.  Practically, the motor is used
for both left and right yaw, acting as a generator for left yaw and motor for right yaw.

Since there's no tail and the rotor shaft tilts for rotor plane control, there's no chance for mast bumping or rotor/tail contact.

Since the main rotor shaft is free-wheeling,  pitch axis trim can easily be achieved by fore-aft movement of the shaft.

A backup battery could be used for about 30 seconds of  power at the end of an autorotation  in case of  engine-alternator failure or fuel exhaustion.

The tip fans could also be constructed to lower the pressure inside the blades allowing for boundary layer absorption, increasing the efficiency still further.

A chart showing how new magnetic materials are so much stronger that they, along with Metglas® amorphous iron, Kevlar®, and carbon
nanotube fibers allow for electric motors to be designed with up to 8 horsepower per pound of weight!
Not in the chart: Neodymium Iron Boron (NeFeBo) magnets are even better.  These new magnets are spectacularly strong.  
One inch cubical NeFeBo magnets are a real danger if not handled properly -- they can easily crush a finger.

The latest semiconductor technology including insulated gate bipolar transistors and power field effect transistors allow
for efficient electric invertors to drive these powerful motors.

Even for conventional shaft driven helicopters, motors of  such high power to weight ratio and efficiency could be used to
drive a tail rotor, avoiding the failure prone tail rotor drive shaft, gearbox and bearings.


New magnetic material parameters


An early Nagler torqueless helicopter

Nagler torqueless propeller driven rotor helicopter


Helicopter pioneer Dr. Bruno Nagler
See my Bruno Nagler web page

Helicopter pioneer Dr. Bruno Nagler


A torqueless pressure jet helicopter proposed by Nagler's company, Vertigyro Co.
Note the T-bar stick that predates the Robinson R22.

A pressure jet helicopter Nagler proposed to supply


Another view of the air pressure jet powered Phoenix helicopter




Advantages of tip propulsion

A typical cross-flow fan blade.

An example of an electrically driven cross flow fan rotor used at the blade tips

I t seems other engineers think cross flow fans are practical.

A Lockheed proposal for using cross flow fans in a jet liner


An example of how electrically driven cross flow fans may be used in a helicopter blade tip.

The speed of the fans can be modulated to inertially dampen blade tip pitch variations, allowing higher speed forward flight.

The rotation direction of the fans is anti-coning, about 50 pound-feet (68 Newton-Meters) of downward torque.  This should increase efficiency
somewhat.

According to motor engineer Peter Campbell, two horsepower (1.5 KW)  per inch (2.54 cm)  of lengh for a one inch diameter motor should be
achievable.  The fans spin about 200,000 RPM bringing the fan edge to the transonic region.

In a Nagler type pressure jet helicopter, most of the power is lost in the air ejected from the trailing edge blade tip nozzle, so the
efficiency is rather low.   With the fan-in-blade, theres ten times the air flow, exiting at a lower velocity so the efficiency is
much higher.

My proposed electric cross flow fan propulsion system

Some calculations about blade tip fan propulsion.

Calculations regarding tip propulsion

My three dimensional (spatial) extension to a Peaucellier mechanism to create a virtual pivot.  The idea is to simulate a spherical
bearing near the rotor hub, but keeping it well inside the fuselage and out of the airstream.  No swash plate would be required,
just tilting the rotor shaft as in a gyrocopter would work in a tip propelled helicopter.

Since fully half of the aerodynamic drag in a helicopter is due to the hub and associated structures protruding into the airstream,
the virtual pivot should minimize that.

A 3-dimensionl extension of a Peaucellier linkage for virtual hub pivot

Two dimensional drawing of how a Peaucellier mechanism may be used as a component of a perfect virtual pivot.

How to use Peaucellier mechanism to create a virtual pivot for the rotor hub


Parts you won't need in a torqueless helicopter.


The tail and tail rotor you won't need in a tip propelled helicopter


Images of a high speed tip propelled helicopter. The moments created by the offset flapping hub and some torque applied to the drive
shaft keep the helicopter suspended under the advancing blades.  This completely unloads the retreating blades.  As forward
speed increases, the rotor rotation speed is reduced to keep compressibility effects from occurring on the advancing blades.


Advancing blade concept helicopter using offset flapping moments to unload the retreating blades


Front view ABC helicopter


The colored sticks represent the moment components of this configuration: roll, pitch, yaw, and the sum, showing
how the helicopter can be maintained in equilibrium with this configuration.

As the forward speed increases, the hub is tilted more forward and right and the rotor RPM is decreased.

The hub position may be moved laterally for different flight regimes.

Since there are five more control degrees of freedom in this rotor configuration, it's likely a computer control system would
be required.

Another view of ABC helicopter showing moment vectors

Another view ABC helicopter