• Initially, and perhaps for some time, this might be one huge R/C rotorcraft, used for testing.
• Then, a back-pack helicopter
• Electric drive and collective. Gimbal cyclic control
• Low cost.
• Perhaps, somehow, FAR (part 103) compliant This craft is intended to be a low cost recreational helicopter not necessarily a homebuilt. Single 2-blade main rotor and no tail rotor.
• Large chords and low tip speed; to improve the craft's lift/power ratio. See Solidity Ratio section below.
• The rotor is powered by electric motor(s) and propellers, which are located at the widest location on both blades. Why the widest, particularly if the props can be moved further out the blade's span.
• Eventually, electric collective and cyclic control. This feature was originally developed for the Single-Bladed All Electric Rotor.

• This craft is little more than an electric powered and controlled Aircraft - Gyro/Heli - Non-powered.
• Also, this craft is only a little different from the Single Rotor - Simple Electric Ultralight. The main difference is that the rotor on this craft has a wide chord and a slow RRPM.

• All electric:

• Concern: The Speed-pitch coupling MAY not give a fast enough response. A torque-pitch coupling is required See methods 2, 3 and 4 in Item 1536. This is probably OK since the propeller's speed change, and thus torque change, will probably be quite fast.
• Both of the blades have electrical individual pitch control.
• Cyclic pitch change: Changes to the pitch of the blades is done by changing the power to the motors. This pitch change is effected by any or all of the following methods;

• Pusher propeller: If the propeller is at the trailing edge of the rotor blade and the propeller blades are moving upward when they are closes to the mast, then the propeller will attempt to pitch the rotor blade down.
• Motor: The motor is ahead of the rotors leading edge so that it contributes to the leading edge weight. Its rotation is the same direction as the propeller, therefore it will contribute a small amount of gyroscopic precession in opposition to the propeller.x
• Coaxial propellers: Coaxial propellers will give a greater induced velocity and reduced 0.75 propeller diameter. This means that the propellers can be further out the rotor blades, both propellers will contribute to pitching the blade down and there will be a smaller difference in the thrust and drag between the inner and the outer propeller. See method #6

1. Unequal induced velocity and drag by the propeller blades: When the propeller blades are closest to the root end of the rotor blades they will experience a lower free stream air velocity. They will therefore produce a greater induced velocity and induced drag (H-force) then when the are pointing toward the tip of their rotor. This difference of induced drag on the pusher propeller will attempt to push the blade pitch up (I think) and this is good. If coaxial propellers are use and rotate as mentioned in the above paragraph they both will be attempting to push the rotor pitch up. This #3/ may make no difference to performance during regular flight but it will contribute toward lowering the blade pitch for autorotation.

• Failure of power will result in the pitch of both blades dropping to the authoritative pitch angle. For more see [Autorotation] below.
• Rotor Hub:
• The two arms on the rotor hub are made from unidirectional carbon. This arraignment will strongly resist flapping and lead/lag while giving little resistance to rotation about the feathering axis.
• The rotorhub ring has a track on its inner diameter. The rotor and blades rotate around a 3-point bearing contact on the 'back-pack' (fuselage) portion of the craft.
• Absolute Encoder:
• For rotor speed [RRPM}.
• Joystick:
• xx

• Rotor overhead, as per conventional.
• Initially, use a gimbal rotorhead c/w teetering blades: as per conventional gyro. See Possible Future Enhancements ~ Item #3.
• Both blades and roots are made as a single item
• Spar made from spanwise unidirectional tape, from blade tip to blade tip.
• The skin of the two blades is built up from bias cloth.
• Root acts as Bell tension-torsion tube.
• Rigid hub, or teetering w/ hub springs.
• Hub spring will generate some 2/ vibration.

• Electric - Motor - Plettenberg - Predator 37
• The Predator motor will not require a reduction.
• Can the bearings in the motor handle the radial loading that is caused by the centrifugal force of the rotating rotor blades, plus the gyroscopic precession.
• The forces generated by the propeller will not affect the motor due to the shaft and coupling between the two.

• The propellers will probably have to have 4 blades so as to not effect the pitch of the rotor blades as the propeller turns.
• Plettenberg Propeller data

• CFK 28,5x12" has a geometric pitch of 12". At 12"/R * 6300 RPM this is 105 fps. The effective pitch will be 85% of 105 = 89 fps.
• CFK 29x12" has a geometric pitch of 12". At 12"/R * 5900 RPM this is 98 fps. The effective pitch will be 85% of 98 = 83 fps.
• Based on the Un-powered gyro belowa rotor speed of 180 RPM will have a speed of 89 fps at 4.75 ft, which is 4.75 / (25.77/2) = .37R. This may not be far enough out.
• The 28,5 diameter propeller will have a .75R of 10.7. this means that the .75R of the propeller blade closes to the rotor mast will be 46" from the centerline of the mast and the .75R of the propeller blade furthest from the rotor mast will be 68" from the centerline of the mast.
• The sketch above shows the propeller at .4R of the rotor.

Batteries:

• Perhaps the battery-pack(s) is the backpack.

• Tripod?.

• xx

• From Access.

• The battery packs could be dropped, thereby slowing the descent rate and presenting a larger area from which to select a landing site.

• The use of a propeller to provide rotor rotation will have an efficiency of 85%, at best. However, this is partially/totally offset by the elimination of the mechanical inefficiency and the lack of tail rotor.
• Both the American Helicopter XH26 and the McDonnell XV-1 Convertiplane tip jet helicopters required small tail-rotors. However, the McDonnell Model 79 did not.

• The aerodynamic inefficiencies of propellers mounted on rotating blades, combined with the intrinsic inefficiency of the rotating blades MAY make this idea unattractive.
• There is no flight-control once the electrical power is consumed. The good news is that the rotor goes into autorotative mode upon loss of power.
• Have a small capacitor and a switch for final flare.
• Alternatively, use a gimbal for the cyclic control and only use power for the collective.
• There should probably be a guard between the propeller blades and the pilot, just incase a blade brakes.
• Rick said that the propellers would be very noisy and they

• Folding blades on pusher propellers will reduce the drag on the rotor.
• The large chord - slow speed will result in a slow descent rate.
• The descent rate could be reduced further if the battery-pack is offload, at some point before landing.
• A lightweight capacitor could be incorporated to proved a short period of power for flare; assuming that the problem was only 'dead' batteries.

• Advantage: Only two blades.
• Bicycle seat; this allows the pilot to have a fairly upright position.
• The motor/reducer may be positioned ahead of the blade's pitch axis so as to give a balance about this pitch axis. A shaft will extend back to the pusher propeller.
• The reduction might be by 2 spur gears to lower the propeller shaft or by planetary gears where the plant holder does not rotate.
• Large use of composite construction.

• GW: 250 [empty weight] + 250 [35-pound fuel load + 215 pound pilot] = 500 pounds
• Blades: Rotordyne, 7 3/8 in. chord. (0.615 ft)
• Rotor Diameter: 25 ft.
• Disk loading: 1.02 lb/ft²
• Blade Loading: 32.52 lb/ft²
• Tip speed; 425 ft/sec.
• Rotor Speed: 325 RRPM; I am assuming that this is the Gyrobee's rotor speed.
• Collective Pitch: 7.9º
• Aspect Ratio: 20.325:1
• Solidity Ratio: 0.0313
• Power: Momentum: 16.8 hp, Blade Element: 20.6 hp ~ The blade element power is based on the use on a NACA 0012 airfoil.

• With the Predator 30 motor each propeller can develop 263 N = 59 lbs of thrust, maximum.
• The propeller centers are located at 4.75 ft radius on the rotor.
• Each propeller is therefore generating 59 * 4.47 = 263 lb-ft of torque.
• The rotational speed of the rotor is 182 rpm
• HP = Torque * RPM / 5252 = 263 * 182 / 5252 = 9/1 hp
• The total power of the 2 propellers is 18.2 hp.
• The thrust in the first line above was from the Predator 30 motor. The predator 37 motor is approximately 15 kw / 11 kw = 1.36 stronger. Therefore 18.2 * 1.38 = 24.8. hp.
• The above Blade Element calculation says that 10.76 hp is needed, at least.
• Therefore this looks OK.

• OTHER: Helicopter - Inside - Single Rotor - Simple Electric Ultralight
• OTHER: Aircraft - Gyro/Heli - Non-powered
• Single-Bladed All Electric Rotor

• Use four motors instead of only two, which could be smaller. Each blade would have a tractor and a pusher propeller.
• Reasons;
• Safety due to a redundancy in batteries, motors and electrical power and control circuits.
• The propellers would be coaxial and this should allow for small propellers, which means that the blades of the propellers will experience a slightly closer air velocity as they rotate through their 360º.

1. The addition of an electric paramotor Electric Paramotor Home. Rick said that they use Predator motor and belt drive for one of their designs.
2. Gyrobee seating etc. in lieu of backpack.
3. Consider giving the craft electrical cyclic flight control by varying the thrust of the individual propellers.

• Backpack thread on Rotary Wing Forum

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