A120

DESIGN: Electrotor-SloMo ~ Concerns & Tasks (all)

Overview:

A listing of Tasks, Potential Concerns and Thoughts, regarding the Electrotor-SloMo.

Idea for Consideration:

Eliminate the CVJ & HS rotorhead and locate a 3-blade rotor on the same axis as the motor. Eliminate any lead/lag and flapping provisions in the rotorhead. Excluding the minimal bending of 'Absolutely Rigid Rotor' blades, the tip path plane and the motor plane will always be co-planer. Use conventional flight controls, running up the center of the 'mast' and use a gimbal head with the pitch and roll having a strong resistance to movement. Alternatively, substitute an ARR for this gimbal.

Concerns (general):

Perhaps a serious problem for Intermeshing and Interleaving configurations. The motor might offer a resistance to turning (cogging) during non-powered autorotation. Overrunning clutches between the rotors and the motors will only be valid if there is a means of interconnecting the two rotors.

If two rotors are located with only an airgap between them, would it be better to have the adjacent poles as having the same polarity. This will make the normal rotational location halfway between each other and the repelling force will increases exponentially as the rotors are rotated in respect to each other. The pitch? Between the magnets is

On this blade pitch concept; will a rotationally offset of the poles of the two rotors reduce the total torque?

Rotor Synchronization and Roll:

The addition of extra electrical power to one rotor, to maintain the synchronization of the rotors, will result in that rotor having greater pitch and therefore greater lift. A possible synchronization ~ roll coupling. A slight reduction in the power of the inside blade on the other rotor may overcome this concern.

Rotor-Rotor Synchronization:

It looks like the rotors must have their azimuths > 45º out of phase for them to clash. This includes the chord width. Hopefully, the electrical system can overcome any chance of rotor getting that much out of synchronization.

Downwash on Pilot:

No pilot in his right mind would go up in this thing ~ at least not until 10 years of testing had been done.

Flight Control during Autorotation:

Include capacitors and/or a 'low battery power' sensors. This should provide power for limited flight control and landing.

Stability of Teetering:

Re: small rotor & no paddle etc. Hub has delta3 (by Control System Geometry).

Rotor - Lead-Lag:

Could the rotor's desire to lead-lag during forward flight be large enough to cause the rotor on its electric motor to oscillate in and out of phase with the control+power phasing of the coils?

Would a rotationally flexible coupling, with damping, overcome the potential concern.

Perhaps a lead-lag hinge (delta-2) at the root will handle the concern.

Musings re a Concern below:

Rotor-Rotor Synchronization:

Torque [ft-lb] = 5252 * HP / RPM

If the rotational velocity of the two rotors and the power at the four motors is equal than the torque of the two rotors must be equal.

Theoretically, if the torque at the two rotors is equal and the pitches of the blades at the two rotors are equal then the thrust of the two rotors must be equal.

The potential concern is the accuracy of the torque-pitch coupling device.

Proposed method:

Hold synchronization ~ This is paramount.
Dissymmetry of thrust might cause a roll.
Because fuselage is tightly coupled to the two rotors in respect to roll, movement about the X-axis will result in the inertia of the fuselage resisting initial roll.
Then the off-center of the gravitational pull on the fuselage will tend to resist the roll.
Perhaps the above will sufice.

Concerns -All configurations:

Autorotation and Yaw control:

If the rotors and their motors are totally freewheeling, the pilot's application of differential collect will have little, if any, effect on the craft; other than perhaps rolling the craft due to a slight differential in lift.

Air Gap in Motor:

Consider using, large diameter, radial flux, Outrunner or Inrunner, gearless motors for bilateral and coaxial motors. Small amounts of un-coplanarness will not affect the air gap in the motor nor result in potential rubbing in a worst case scenario.

Concerns - Intermeshing specific:

Concerns - Interleaving specific:

Concerns - Side-by-side specific:

Concerns - Coaxial specific:

How to start rotor rotation with the blade crossings take place at 45º + (x*90º) azimuths. Could there be nylon gearing which maintain the relationship between the rotors during their initial startup.

2P vibration from the hub-spring? At a rotor speed of 666 RPM = 11.1 per sec * 2P = 22.2 per sec and that is near the bottom of the bucket, which is not good. OTHER: Aerodynamics - Vibration - Rotor Induced - Overview The fact that there is teetering at lower cyclical angles and weight-shifting at the larger cyclical angles may make this acceptable. Maybe only time will tell. 3-blade rotors (with smaller chords) will probably overcome the vibration, but who wants 2 more blades.

This is not the most aerodynamic efficient configuration and this is particularly important when considering electric drive. How efficient is a rotor (PM) - stator (windings) - rotor (PM) motor in countering the aerodynamic inefficiency?

Pilot induced YAW (by collective pitch differential) will result in one rotor having to deliver more drag and lift (torque) then the other rotor. The rotor that is requiring this additional torque will want to lag behind the other rotor. This may cause the lagging rotor in the motor to skip phases if the sensor is on the other rotor in the motor.

A potential solution might be to have sensors on both rotors in the motor and have the controller use the timing from the sensors on the lagging rotor. Hopefully, this will result in the leading rotor 'backing off' so as to be in sync with the control phasing.

Tasks (to do):

Xx

Same Page Different Craft: ~ SynchroLite ~ UniCopter

Initially displayed: July 23, 2006 ~ Last Revised: June 16, 2009