Hello everyone, I have posted about this idea before in the form of an aircraft which could transition between vertical and horizontal flight. While I believe it is possible, especially in the form of a flying wing, the response I have received from this site as well as other sources indicates that most observers have serious doubts.
I have decided to focus on non-transitioning embodiments to eliminate that doubt for now, and hopefully get some feedback on the concept as a purely rotary wing airframe, the helicopter.
What is the point of this weird helicopter? The goal here is mechanical simplicity, turning a mechanical challenge into a software challenge. This is why multirotors are so popular. They are mechanically simple, and the rest is configured and reconfigured with code. The code can then be copied, altered, provided at little or no cost, and never wears out or needs replacing. The above concept would require eight moving parts.
This idea would require only three positioning sensors, one for the main shaft, and two for the rotors, and these can be simple rotary position sensors or IMUs which evaluate their position in relation to each other.
I would really appreciate any feedback or ideas anyone might have about this.
Thank You, and Happy Holidays!
Comments
extraordinary and impressive idea! hope realizing it soon
Hey Joe
I asked this in my previous post; what is the mission profile you wish to achieve for this bird? Or is it only an exercise to see if the mechanics work?
If you want a rotor assembly that is simple, I can do the same with one motor and one servo, that gives both cyclic and collective pitch control.
I have none of my own numbers to give you. My understanding is that prop driven rotors, which is not a new concept were actually fairly efficient, though having two per rotor instead of one reduces that. Here is an example:
http://www.dzynetech.com/rotorwing
I like helicopters, and I know that helicopter guys are always firm believers in them, then I also hear about how expensive they are and how maintenance can make them cost prohibitive...
My main question is about efficiency. One of the main benefits of Helicopters and Planes over multirotors is they are much more efficient due to a single large rotating rotor, or, having wings and a single motor to create "thrust". If you are now using 4 very inefficient means (Losses in electrical, mechanical, and aerodynamics) to turn another rotor system that has it's on losses in aerodynamic and mechanical efficiencies, what can be expected to gain over a traditional helicoper that has very low efficiency loses in the drive system? (Single motor with 1 gear reduction in most cases providing direct power to the mast)?
I am all few new idea's, but, what problem are we solving? The mechanical complexity of a traditional helicopter is not that much in most UAV systems, and, when built properly, the mechanical reliability is almost never the main concern.
I am not trying to put your idea down, but, what problem is this looking to solve? I have a hunch this will be far less efficient than even an octocopter which has the mechanical simplicity that is desired.
Great points Gary. Getting power to the props is definitely one of the challenges of this idea. I was thinking of the way monocopters seem to get away with it, but larger batteries would be an issue. There are brushless slip rings, I guess I should look into it. For communication between the rotors and fuselage I was thinking of optical slip rings or as you suggested a wireless link, or maybe nothing at all allowing the fuselage to operate separately.
Hey Gary tip jets would be nice, I have never thought of a good, simple way to precisely control thrust at the tips, also I pretty much always think of electric propulsion.
Hi Vladimir, I built a simple prototype with a 4s battery in the hub, and wires running along the spar to the motors, which are mounted on a wing rib that is spliced into an epp wing. It is actually super simple, strong and lightweight. I used a standard 450 rotor head minus most of the mechanics to connect everything together.
Hey Rainer, are you saying that this seems complicated? Not sure what you mean, but I was going for simple. This could be done with 8 moving parts or less.
Mateusz, yes like tip jets, except there are two so that they can control pitch of the rotor, there would be no swash plate and no servos.
Ouroboros, yes coax would be great, and yes they could be independent of each other but wirelessly or optically linked.
Hey Jerry, yes mostly because similar concepts have already been done, even with the motors mounted at the tips.
Hi JB, my original idea for this did in fact have the aircraft hovering only with this set up, then transitioning to forward flight. I imagine head speeds in the hundreds, not thousands, so the cyclic control should hopefully be quite possible. A long endurance hovering platform is a great idea and something I had not thought of. There is a market for that or we wouldn't see all these tethered systems. Ideally, it would pitch wings downward into a dive then pull up into forward flight for longer endurance. My imagined head speeds is low, and of course you would go with the highest that is possible, and at some speed, this concept should be able to function at the cost of performance. The trick would be to find that speed. I base this speed off of things like existing monocopter speeds, but much of my inspiration is drawn from concepts like the rotorwing by Dzynetech, which has head speeds as low as 60rpm. I believe speeds of 100 or 200 or more should be easily attainable.
Hi Chris, I really like their design and have referenced it many times. My concept would be similar, hopefully with the added benefit of not needing actuation for the wings, not cycling servos once per revolution and pitching the entire wing instead of just ailerons which should give better control.
https://www.youtube.com/watch?v=-cCoPBGq-iA
Hi Joe
It is a interesting layout that will probably hover, but how do you plan to propel it forwards/backwards/sideways with those rotor mounted quad motors that are unlikely to pivot fast enough through differential thrust to provide cyclic control? I'd imagine those motors will get a right workout trying to maintain the correct AoA to maintain level attitude, which in turn will expose the system to significant energy losses. What is your expected main rotor RPM?
What is this platforms intended mission profile? From my perspective this platform looks like a long endurance, nearly stationary VTOL hover platform. There are very few use cases that I can think of for this type of operation.
For long range aircraft, or for long endurance aircraft, a spinning wing (heli) can never compete with a fixed wing, simply because the "wing" only has an optimal angle to produce lift in the direction of travel (airflow) for a fraction of its rotation angle. A heli, is essentially artificially creating a moving wing by spinning it about an axis, that in itself is never optimal for any direction of travel, as it needs to return to it's point of origin to complete it's rotation. In contrast a fixed wing always travels in the direction of travel and can be optimised accordingly. Put another way, the heli "wing" needs to travel significantly further through the air than a a fixed wing would to lift the same weight, and even backwards for half of the time, yet the usable fuselage part of the airframe travels the same distance in both.
Considering this, I'd expect an airframe for range and endurance to be configured in such a way so that the wing/propulsion setup is optimised for the required cruise in forward flight, and reduce the fairly short period of VTOL flight into a secondary, much less dominate role. For example to make a plane VTOL adding a small quad setup for short period VTOL components of flight, like in a quadplane, would be most effective IMHO.
Regards JB
for a 2m diameter rotor for your design, you will need 2kw from 4 motors at least, and the centrifugal force on the four motors at 2k rpm, do you think it's possible to build such a rotor?
Would concentrating the hardware to essentially a battery rotor hub and joining 2 together (common payload shaft, functionally independent, but one slaved to the other wirelessly) to be a coax be another path?
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