Tetrakaipentacontacopter
Phil Pilgrim (PhiPi)
Posts: 23,514
At least I think the title is right. I counted 54 rotors:
Or, if you prefer Latin prefixes, quattuorquinquaginticopter.
-Phil
Or, if you prefer Latin prefixes, quattuorquinquaginticopter.
-Phil
Comments
54 counter-rotation propellers, six grouped control channels with Hobbyking stabilization.
"Looks like as good away to commit suicide as any."
As Sir Henry Rawlinson said on seeing a hang glider passing over his estate. Shortly before bringing it down with his shotgun.
At this rate he should definitely get more padding in his seating as he is going to be very sore. And what he seems to have created so far is a ride-able leaf blower.
Much depends on his next generation including good stabilization and a way to recover from failures.
I read that it had a Hobby King KK controller running in 6 quadrants, (think hex copter matrix).
The youtube video seems to have been edited, as it had a post of a Hobby King Williamson? KK controller, but that link is gone.
Jim
I think this is why he gets airborne, then has a hard time climbing. But as he descended suddenly had more lift.
Those props don't look like they're much more than a foot across and it looks like they're about three feet off the ground. If the "one rotor diameter" rule applied, there shouldn't be any meaningful ground effect. I doubt the "one rotor diameter" rule does apply though.
Still, I bet the 'copter could fly higher than it did in the video. I think the pilot didn't want to go higher than he was willing to fall.
So I would expect the ground effect to be noticeable up to an altitude equivalent to the diameter of the whole machine.
I know nothing of flying copters apart from messing with a tiny contra-rotating prop machine. It seems to demonstrate ground effect up to about 3 times it's props diameter. When the battery is expiring it can float on a cushion of air at that height but not get any higher.
"...the effective diameter we should think about is the diameter of the entire craft." - agreed .... here is a demonstration of the "ground effect" or "Bernoulli effect" ....
http://www.seykota.com/rm/spool_card/spool_card.htm
...If you think about the "Bernoulli effect" for a moment and think about how a wing gets lift, by air traveling faster over the top than the bottom, then you can visualize that the ground is acting as a wing at close proximity where the ground is "lifting" towards the craft.... and since the ground can't usually move, the force is still there and ends up pulling the craft closer to the ground instead.
So ground effect should suck an aircraft down?
I think it's been pretty well proven that wings get lift from more than just the Bernoulli effect. I'm not sure how accurate this page's explanation is but it seems reasonable to me.
http://amasci.com/wing/airfoil.html
I agree with the rest of you ground effect likely is a strong contributor to lift but I don't think the pilot kept the 'copter low in order to stay in ground effect. I think the pilot wished to keep the altitude low for safety reasons. I'd be surprised if the 'copter couldn't have flown higher.
which if it is above the wing . Also wings deflect air downwards, which is a change of momentum, and this
varies with angle of attack. Vortex induced lift is especially powerful in flying creatures as flapping flight
can generate vortexes and then harvest the lift from them.
The old argument about air flowing faster over the top of the wing is of course bogus as the air
has no requirement to meetup again at the trailing edge, its quite possible for the air to travel slower on
top. What is needed is a pressure difference between top and bottom of the wing - the Bernouille effect
can contribute to that, but simple downwards deflection of air is a huge effect. Wing shape is about
achieving lift with as low a drag as possible, and in particular avoiding turbulence (which also destroys
lift mechanisms anyway)
https://grc.nasa.gov/www/k-12/airplane/wrong1.html
I agree with localroger that these people should be testing these aircraft by remote control , rather than proving the early 20th century adage about how designers test flying their own poorly conceived aircraft ensured they didn't live long enough to keep building them.
Does anyone know enough about this project to know if there had been unmanned flights or not?
I thought it was interesting to see each motor have its own power supply. I suppose this simplifies the wiring but it sure seems like this strategy would end up costing more.
It sure is a fun looking contraption.
I always have replacement propellers when I fly my quadcopter. They fall out of the sky.
This isn't the first manned multi-rotor I've seen, and in each occasion the operator seemed to have poor control over them. So even if they did test them remotely, they sure didn't appear to build enough experience before they hopped in the pilot's seat. Of course, I can see it being really hard to resist.
I'm pretty sure such a thing already exists for paragliders. I've definitely seen electric propulsion for hang gliders. They can take off from flat land and climb to altitude before cutting them off and the blades folding back. They're really cool!
Build an air frame, (having to think about where the seat should be),
install all the power plants,(how much power will i need?),
install all the electronic controls,(how will I steer this thing?),
Tighten all the hardware and propellers down, again!,(I hope nothing comes apart...)
Fire it up!, Test it with a couple of concrete sacks and a remote control setup, WORKS GREAT!,
Now, all you have to do is
Get in it....
That guy is a hero, a true pioneer, Those daring young men and their flying machines,
We need more folks like this, but, it's not gonna be me, I'm keeping my feet firmly planted on the ground.
-Tommy
That article certainly is an interesting read and the author has a serious downer on the traditional school text book explanation of flight. There is more of it here: http://amasci.com/wing/whyhard.html. Sadly it is long and poorly written and confusing itself.
And wrong!
He states:
"Two-dimensional airfoil diagrams depict an odd type of "venturi flight" situation, while genuine aircraft fly far from the ground and have no instantaneous weight applied to the Earth's surface."
None of the typical diagrams and explanations of lift I have ever seen require the wing to be near the ground or say anything about "instantaneous weight applied to the Earth's surface". They are generally two-dimensional and assume a infinitely long wing of equal section simply for simplicity, which is perfectly reasonable.
Further:
"To explain lift in high-flying aircraft, we absolutely require a 3D diagram with its vortex downwash wake."
This is just not true. Vortices are not required to explain lift.
Further:
"Real wings fly because of vortex-shedding, and they're lifted upwards as they fling a mass-bearing vortex-pair downwards. Yet introductory textbooks always use the misleading two-dimensional diagrams which depict only the regime of ground-effect flight: 'venturi-flight.-'"
No, vortex shedding is nothing to do with it. Yes, flinging air downwards is the key. No, two-dimensional diagrams to not imply ground effect.
This glaring incorrect statement seriously undermine the entire article. Which is a shame as it makes some good points.
Wow, it's surprising to see some so adamant while being so wrong. I guess I shouldn't be surprised. There are a lot of people on the internet adamant about being wrong.
It seems like he should also be arguing rockets don't work in space since they can't push against the ground.
Edit: To be clear (the person I was accusing of being wrong was the author of the vortex paper.
Somehow I thought my statements might lead to some objection. I'm adamant because I'm right
I quite happy to have one say that I'm wrong, I'd be happier if they would also offer a reason as to why.
Simply stated I believe:
1) One does not need to think about vortices to explain the lift of a wing.
As a clue I will say that clearly at the point where the lift is being generated, the wing, there is no vortex. Those beautiful vortices we observe, see the video on the page we are discussing, are somewhere else. In fact they are necessarily behind the wing, how on earth can they be responsible for generating lift on the wing when they are behind it? They are history as far as the wing is concerned. They are a consequence of the wing generating lift.
2) The "infinite wing" two-dimensional model used in explanations of lift is quite OK.
Clearly for an infinitely long wing there cannot be vortices spinning around an axis parallel to the aircraft's direction of travel. Those particular vortices are a consequence of having short wings.
"A two-dimensional diagram (also called the 'infinite wing diagram,') is misleading. It depicts ground-effect flight where altitude above a surface is always much less than one wingspan."
Can you spot the logical contradiction there?
Clearly if the wing span is infinite AND ground-effect flight happens when the altitude is less than one wing span THEN ground-effect flight can occur at any altitude less than infinity.
That is to say the lift of an infinite wing can happen at any altitude.
An infinite wing can have no vortices along the direction of travel.
Anyway that is not my reasoning, only an observation of one of the flaws in the article. Those infinite wing explanations have nothing to do with ground effect or vortices.
Any monkey sticking their hand out the window of a car while it is moving can determine that angle of attack can cause problems, but fail to see what happens if the air is moving straight down. Since in this "Tetrakaipentacontacopter" application, the bulk of the air flow goes straight down UNTIL it hits the ground. Then it follows a radial direction approximately 90 deg to the downward force, and unlike a helicopter the airflow would be relatively laminar because of all of the counter rotating propellers, otherwise you would have a spiraling downward air stream. The radial flow outward in all directions over the ground does cause lift only because the airflow needs somewhere to go. Once this "cushion of air" is established and flowing radially outward, it creates a low pressure region BELOW the high downward pressure which is inverted from a normal wing situation (angle of attack or not).... because it is inverted, the downward high pressure tries to perpetually maintain a balance distance from the escaping low pressure .... A feedback loop if you will ... In this situation it is the "GROUND effect" causing a problem, not a benefit to the overall lift. The more downward air flow the stronger the hold from the feedback loop, but at the same time the air cushion is proportional to this downward airflow. Eventually you break free, most commonly by a slight perpendicular imbalance or tilt in relation to the ground and direction of downward air flow, but any surface anomaly in ground features will cause a similar breakout. At this moment you will have a sudden acceleration which can cause a fish tailing effect due to over compensation in the controls from the operator.... thus the reason taking off and landing is ALWAYS the most difficult. Once you experience this first hand and realize what is actually happening it's like riding a bike and you can evolve past the 'monkey in the car with your hand out the window'. The link I posted earlier and once again below is what you have to deal with from any vertical takeoff with a multi rotor system. I encourage you to build it and physically have it in your hand.... experiment with it, and make your own deductions from there.
In the article link below, ignore the text, there are some discrepancies, but focus more on the actual experiment
http://www.seykota.com/rm/spool_card/spool_card.htm