1535

Item 1535

OTHER: Helicopter - Inside - Principal Assembly - Electrotor-Plus

The Means of Obtaining this Additional Cyclic Control Authority:

Axes of Rotation:

The craft's rotor and its motor (c/w reducer) are located on the mast. The rotor being at the top of the mast and the motor being slightly lower.

The Z-axes is the vertical axis of the mast: about which the rotor and the motor rotate.

The X_R-axis is the horizontal axis about which the rotor blades teeter.

The X_M-axis is the horizontal axis about which the motor teeters.

The Y-axis is a horizontal axis that is normal to the X-axes.

The teetering portion of the rotor is mechanically linked to the motor below. The aerodynamically generated teetering of the rotor therefore imparts a teeter to the motor; by the same amount at the same azimuth.

In other words, both the rotor and the motor will teeter on the mast, about their respective X-axes, at a rate of once per rotor revolution (1P).

Rotational Inertia:

The revolving of the aerodynamic-rotor about the Z-axis has a significant amount of rotational inertia due to its long moment arms.

The revolving of the motor's rotor about the Z-axis also has a significant amount of rotational inertia due to its very high rotational speed. The motor's stator does not rotate about the Z-axis.

Gyroscopic precession:

The rotor and the motor will be subjected to gyroscopic precession. Therefore the maximum teetering (tipping) angle of both will be located 90º beyond the azimuth where the maximum tipping force is applied.

This means that to tip the rotor disk plane down at the front of the craft (180º azimuth) the maximum tipping force must be applied at 90º azimuth. It also means that to tip the motor down at the front of the craft (180º azimuth) the maximum tipping force must also be applied at 90º azimuth.

Phase Angle between Motor and Rotor:

Assume, for a moment, that the aerodynamic rotor rotates at a speed of 600 RPM and that the motor's rotor rotates at an infinitely fast speed. Now, if a teetering force was applied to both rotors at 90º azimuth the motor would immediately tip down at 180º azimuth where as the rotor would not tip down until it had completed its slower 90º of rotation.

In other words; in this hypothetical example the forward tipping of the motor and that of the aerodynamic rotor are exactly 90º out of phase with each other.

To use a more practical example; consider the aerodynamic rotor rotating at 600 RPM and the motor's rotor rotating at 12,000 RPM. This is a ratio of 20:1 and this means that when the motor is tipping at 180º azimuth the rotor's blade is only at 90º + (90º / 20:1) = 94.5º. In this practical situation the phase angles are very close to the above hypothetical example.

The Additional Cyclic Control:

The inclusion of a Hub Spring (or a Teetering Hinge Offset) provides an additional control moment to a teetering rotor. However this additional moment creates a sinusoidal two/rev vibration. The gyroscopic moments creates by the electric drive described above also create a sinusoidal two/rev vibration. However, the two sets of sinusoidal vibration are out of phase with each other by approximately 90º and this will smooth out the vibrations while providing the additional control moment at the top of the mast.

For More Information:

See: DESIGN: Electrotor-Plus ~ MRGA - Gyro - General Perhaps some of the material on this page and the linked page should be combined.

Drawings:

For the general arrangement of configurations under consideration see the links on this page.

Description:

This teetering rotor behaves in a basic conventional manner, in that when tipped it applies a constant horizontal component of the rotor's thrust force in the direction of the downward tipping.

This basic teetering hub, is modified as follow;-

The hub of the rotor is equipped with a hub spring, or with a 2-blade offset teetering hinge. These two devices apply a moment at the top of the mast and fuselage when the rotor disk is tipped (teetered). This moment is in addition to the horizontal component of the thrust force at the top of the mast. It is in the same vertical plane as the component force vectors.

Both the hub spring and the 2-blade offset teetering hinges will create cyclical moments at a frequency of twice per rotor revolution.

The yoke of the rotor has two arms that extend out to the blade grips.

The above assemblage will now be referred to as the Rotorhub.

A connecting rod extends downward from each of the two arms on the Rotorhub to the Motor/Reducer/Gyro assembly (MRGA).

These moment-arms transmit a percentage of the moment, which is created by the teetering of the blades, down to the MRGA. In other words, the teetering of the blades applies a moment directly to the top of the mast, and a moment to the MRGA via the moment-arms.

The MRGA is located on the mast just below the Rotorhub

The motor has a relatively large diameter and a relatively large mass.

The motor's rotor (armature) rotates at a speed that is a multiple of the rotor's rpm.

The motor' rotor will have a high rotational inertial.

The motor might be of the axial flux or radial flux type. The preference will be a radial flux outrunner.

Between the motor and the rotor is a one, two or more stage (planetary?) gearbox, which has a ratio of perhaps 20:1.

One method is to have a pair of coaxial knuckle joints connect the rotating portion of the motor and the gearbox to the rotating rotorhub.

A universal joint connects the motor's stator to the stationary lower mast.

The yoke of the Rotorhub is connected to the MRGA by two vertical connecting rods, which are located at 180º azimuth to each other.

This causes the teetering of the Rotorhub and the MRGA to be in unison. The tipping angle of the rotorhub and that of the MRGA may or may not be equal, (until determined by experimentation).

The swashplate might be located below or above the MRGA.

Method of operation:

The two connecting links between the Rotorhub's yoke and the MRGA are at 180º to each other. The teetering of the rotor will create a downward force on one connecting link and an upward force on the other connection link. This will create a downward force on one end of the coaxial knuckle joint and an upward force on the other end of the knuckle joint.

These two forces result in a moment on the mast.

Gyroscopic precession with result in the above moment being in the same direction as the teetering of the Rotorhub and MRGA except that the azimuth of the moment will be up to 90º ahead of the azimuth of the teetering rotorhub. (See page xxxxxxxx)

The result is that the gyroscopic moments will be located midway between the Rotorhub induced moments.

The greatest moment on the mast from the Rotorhub is when the blades are at their position of greatest teeter.

The greatest moment on the mast from the MRGA is when the MRGA, and the blades, are experiencing their greatest rate of teeter change.

Therefore about the mast, the azimuths of greatest rate-change are 90º offset from the azimuths of greatest teeter.

Therefore about the fuselage, due to the gyroscopic precession, the azimuths of greatest rate-change will be the same as the azimuths of greatest teeter.

For graph of activity see; DESIGN: Electrotor+ ~ MRGA - Gyro - General

Load Pathways: Review these because the layout has changed

X designates bearing.

a/ Motor rotor ----X----> Planet holder ---X----> Hub ---X---> Mast
b/ Motor stator ----X----> Planet holder ----X----> Hub ----X----> Mast
c/ Motor stator ----X----> Mast

b/ or c/ must 'float.

c/ is only transmitting torque, however it must rotate about X-axis and Y-axis and slide on Z-axis.

What about having the primary pathway of b/ changed to Motor stator ----X----> Motor rotor. (re maintaining motor's air gap)

Thoughts:

Consider the pros and cons of substituting the 2-blade offset teetering hinge for the hub spring.

Consider the possibility of having both on the same rotor. The hub spring might operate by resisting the lateral travel of the tie-bars.

Fuselage:

Consider buying all or most of the peripheral assemblies from John Uptigrove.

Related Pages:

Gyrocopter:

Some unthoughtout thoughts regarding the applying of this idea to a gyrocopter;

The Good: A small electric MRGA will provide partial power to the rotor. This should give better cyclic control and safety. It may increase the efficiency of the craft. It may provide greater rotational inertial for take-offs and landings.
The Bad: This will require a swashplate or spider type of blade pitch control.

Just an Alternative but Somewhat Related Potential Idea for the SynchroLite:

OTHER: ~ Rotor Concepts - Gyroscope for 2-blade Rotor(s)

Just for Consideration ~ Scale - Overview:

	Full Size:	Ratio:	1/2 Scale:	Ratio:	1/4 Scale:
Rotor Radius:	104" (8'-8")	2:1	52.0" (4'-4")	4:1	26.0" (2'-2")
Chord:	0.4375' (5.25")	2:1	0.219' (2.63")	4:1	0.11' (1.3")
Single Disk Area	40,844²" (284²')	4:1	2,553²" (17.7²')	16:1	2,553²" (17.7²')
Total Disk Area	(331²')	4:1	(20.6²')	16:1	(20.6²')
Effective Disk Area	(407²')	4:1	(25.3²')	16:1	(25.3²')
Total Gross Weight:	550 lbs.	8:1	69 lbs	64:1	8.6 lbs
Power (Hover):	30 hp. ⁽²⁾ 15 hp/rotor??	8:1	3.75 hp.^{(2) (3)} 2 hp/rotor??⁽¹⁾	64:1	0.47 hp.^{(2) (3)} 0.25 hp/rotor??
Motor Speed:			13,000 rpm		13,000 rpm

Close to household current.

This is only hover power, plus it maybe too little for even hover at GW

Use the equation in 1474.html p = (l /L)^7/2 x P: p is power. l/L is the scale of the model. P is power of the full-size craft ETC. It will show a lower power requirement.

MGRA Assemblies Being Considered for this Principal Assembly:

See; ElectrotorPlus ~ MRGA - Arraignment

Same Page ~ Different Craft: ~ Electrotor-Simplex ~ Electrotor-SloMo ~ SynchroLite ~ Dragonfly ~ UniCopter ~ Nemesis

Same Concept but with Combustion Drive: ~ OTHER: Helicopter - Inside - Single Rotor - Tip-Jet and Enhanced Flight-Control

Last Revised: March 24, 2009