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Unicopter ~ Interleaving |
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Electric UAV ~ 1/4 scale |
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This project may be the design, development and possible construction of a 1/4 scale electric UniCopter for UAV applications
~ comprising ~
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The utility inventions on this site are openly and publicly disclosed on the Internet to negate an entity from patenting them, to the exclusion of all others whom may wish to use them. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.
Item 1512
OTHER:
Helicopter - Inside - Interleaving - UniCopter-UAV - 1/4 scale - Electric
To Home Page ~ UniCopter-UAV
Objective:
To consider an advanced electric Interleaving UAV
Note:
- For comperable helicopter with Intermeshing configuration see
OTHER: Helicopter - Inside - Intermeshing - Electric UAV - 1/4 Scale.
Sketch:
Four Blades per Rotor:
Three Blades per Rotor:
Note that in the above 2 drawings, the shafts form the ruselage to the rotors will be turning in the same direction therefore some more gears, or revised gearing or universal joints must be incorporated
If it is to be built, consider a single x-shaft and 90º gears to start with. See sketch below.
At Cruse:
Change this to 1/4-scale
- RRPM = 300 (1/2 of 600)
- Radius = 8.666 ft
- Tip speed = 544 ft/sec
- Air speed = 150 mph
- Tip + air speed @ 90º azimuth = 492 ft/sec
- Tip + air speed @ 270º azimuth = 52 ft/sec
- Zero air speed @ 270º azimuth will be at = 7.0 ft Radius
Power Train:
- Gear count: 12 (not including Speed controller and not including x-shaft coupler). Note that 6 gears can be eliminated if frame of the motor is allowed to rotate in addition to the shaft.
- How is the Variable speed between the rotors and the prop to be handled?
See UniCopter ~ Pusher Prop - Variable Speed Rotors and Prop
Fuselage:
High strength will be necessary to resist opposed gyroscopic precession form the two rotors since 'Absolutely' Rigid Rotors are implemented.
The spar/airfoil might be angled to contribute to lateral stability.
Features: (now or considerations for future)
Advancing Blade Concept (ABC);
- The model's blades and rotor will have a greater rigidity than that of a conventional helicopter. This means that as the forward velocity of the craft increases the advancing (outside forward) blades will assume a greater percentage of the lift and the downwash on the fuselage, which is under the retreating blades, will decrease.
Independent Root & Tip Control:
- This, in conjunction with a cyclic control that has a higher rate than 1/ revolution, and with the ABC, will result in a significantly improved thrust distribution about the total disk area.
Large Chord and Low Tip Speed:
- To allow for faster forward speeds.
Reverse Velocity Utilization:
- To improve lift distribution during faster forward speeds.
- At mu < 0.75 and with Active Blade Twist, reverse velocity may not have to be considered.
Pusher Prop Assist:
- To provide faster forward speeds.
- Option:
Tractor props or Pusher props.
X-Frame:
- Consider using a tube for the cross brace and then locate a loose rotateable airfoil over this tube. The intent is that the advantage of streamlining the cross frame during hover and forward flight is greater than the added weight of the airfoil sleeve.
- An alternative would be to give the actual cross frame an airfoil shape; at some optimal angle.
- Another alternative would be to have three much smaller x-bars, each with the shape of an airfoil. The drag in this situation would be from the 3 x-bars, the x-shaft and the diagonal bracing.
Advantages over Intermeshing rotors:
Flight Controls:
Consider electrical independent blade control.
Synchronization by opto-elecrical means.
Collective and Cyclic by electrical actuators, located at the ...blade roots ??....
Motor:
Plettenberg ~ HP 370/40 Heli: This will probably be the choice for this craft and the 1/4-scale Intermeshing
Electric - Motor - Plettenberg - Predator
Astro Motors: http://www.astroflight.com/e/env/0001QRb9JcOyK14XdU9d9k8/index.html?link=/index.html
Hacker Motors: http://www.hackerbrushless.com/motors.shtml
GoBrushless.com: http://www.gobrushless.com/ccp51/cgi-bin/cp-app.cgi
Power train:
For an understanding of the drive motor and drive train see; Inrunner+Outrunner_Motor
Put sketch and information in here
Propeller:
Could a special front mounted propeller be folding? See info on Intermeshing - Electric - UAV
Should a 3-blade or 4-blade propeller be used to raise the thrust centerline or will the loss in efficiency be too much?
Just a thought re the Interleaving with a single propulsor: The streamtube of a single, fuselage aligned, propeller (tractor and pusher) MAY add slightly to the free-stream air-velocity that elements of the retreating rotor blades are experiencing. This MIGHT mean that the area of reverse velocity is slightly bigger for a given craft airspeed. I.e. the craft MAY have to operate at a slightly lower mu than convention would suggest.
Portability:
Could the blades be removable?.
Notes:
Consider using the control of the two electric drive motors to phase the synchronization of the rotors: as an option to the X-shaft.
Questions:
Where does the prop(s) go ~ to clear other items?
Twin boom at tail or single boom and tail?
Will the large solidity ratio of the rotor disks plus the dihedral result in a slow and safe descent?
Will the craft require an overrunning clutch?
Will the blades initially (before incorporating some of the above features) require a 2-position pitch change for authoritative descent?
Would the inclusion of a separate electric driven push (tractor) prop (before incorporating some of the above features) allow for rotor blades with a single pitch?
Concerns:
Tipping the rotor's disk forward for cruise will result in the propeller pointing downward. Perhaps the propeller must generate all forward propulsion. Perhaps the propeller should be at the back, where it can be lower, larger, And perhaps have an upward angle.
The use of a tractor propeller may result in the propeller being in the way of mission specific equipment or tasks.
Control and UAV:
This is a small (25 employee) Canadian company. http://www.micropilot.com/. There is an article on it in the business section May 30, 2006 Globe and Mail.
Notes and Thoughts:
Since this is a UAV, two fuselages should be acceptable. The batteries, controls and payload can be divided between the fuselages.
Configuration options;
- Could go with very small diameter central fuselage w/ prop and motor in front and a simple set of tail feathers at the back
- Pusher prop at the rear of central small diameter fuselage and canard at front.
- Tractor and pusher prop on small diameter fuselage w/ canard and positive angle HS at back (both contributing to lift), plus VS at back.
The reason for 4 blades per rotor is to reduce lateral vibration at high speeds. An option might be to use 3 blades per rotor, and do something with the aerodynamic spars (such as flaps or spar skin pitch) to offset any lateral vibration.
Miscellaneous:
Raptor 90 SE ~ Largest R/C helicopter.
Somewhat related craft; the SNCASO Farfadet
Alternatives:
Some Thoughts re: If this UAV Interleaving helicopter had 2-blade teeter rotors:
There will not be a centralized fuselage being subjected to the downwash of the rotors.
Gyroscopic precession will generate minimal forces between the two fuselages.
It will probably be the most efficient arraignment that can be made with current technology.
- There are no tail-rotor losses.
- If the retreating blades are on the inside then their mutual downwash will have a better thrust distribution.
A low central canard and high positive-pitch HS will be outside the downwash of the rotors and will partially offload the rotor during cruise..
The bad:
A 2-blade teetering rotor does not offer strong control responses.
All/most RC 2-blade teetering rotors utilize paddles and these paddles will interfere with the blades on the other rotor.
The pusher props might be located on the tail boom with deep ducting serving as the HS and VS.
Some Thoughts re: If this UAV Interleaving helicopter had
Teetering Rotor with 3+ Blades, Constant Velocity Joint and Hub Springs (CVJ+HS);
- The good:
- Control will be better than the .2-blade teetering noted above.
- At some strength of the hub springs the paddles may no longer be required
- The bad:
- Time of flight will be worse than the .2-blade teetering noted above.
Related UAV Web Pages:
Related Interleaving Web Pages:
The Future:
Introduction Page | SynchroLite Home Page | UniCopter Home Page | Nemesis Home Page
Initially displayed: May 29, 2006 ~ Posted on PPRuNe: July 10, 2006 ~ Posted on Rotary Wing Forum: July 15, 2006 ~ Latest revision: September 4, 2007
The above utility invention is openly and publicly disclosed on the Internet to negate an entity from patenting it, to the exclusion of all others whom may wish to use them. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.
June 14, 2006
See revised drawing 1512.dc.
OTHER: Miscellaneous - Thoughtless Ideas - Root Jet Rotor
For drive of pusher prop see;
OTHER: Aircraft - Gyro/Heli - Gyrocopter/Helicopter (w/ 50/50 power split)
- 4-blade to consume a higher percentage of the total thrust (torque).
- A 3,000-rpm prop driven through a 4:1 planetary reduction would use a 12,000-rpm motor. The motor would be 24,000 rpm if the stator was driving the rotors and the armature was driving the prop.
- Could the high induced-velocity through the center of the rotor, from the propeller, help drive the rotor and thereby reduce the counter-torque on the fuselage from the mechanical driving of the rotor. Would this be inefficient?
Can a double or triple in-plane universal joint (CVJ) drive through 60º?
The sketches below are only previous thoughts.
_____________________________
Increase the size of the airfoils, which will also mean spreading the fuselages etc.
Alternative Configurations;
Two ideas; A single central fuselage that is horizontally split ~ and ~ two fuselages which are located at the rotors and they tilt.
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Single Central Fuselage:
- Split the fuselage so that half is below the rotor blades and half is above the rotor blades. There will be very little thrust from the blades in the area of the fuselage. This is because the independent tip and root pitch control, during hover and cruise. Plus, during cruise the blade speed in this area will be very close to the crafts forward speed,
- If there is little downwash on the lower portion of the fuselage then there should be little downdraft on the upper portion of the fuselage.
- The drag due to skin friction will be greater due to the increased surface area.
Twin Fuselages, Located At Rotors:
- The fuselages hang vertically when the craft is hovering. The port rotor depicts hovering and the starboard rotor depicts cruise.
- There might be a pusher propeller at the aft of both fuselages.
- Consider using rotors with three blades if there are no pusher props and high speed is not a prerequisite.
