I recall a disastrous video of several helicopters and a blimp from years ago; but still, why does it work so well on a small scale and yet, isn’t even attempted at full scale?
I’ll define full scale as a rotor diameter of ten meters.
How many rotors does it have to have to be a multicopter? The chinook has two horizontal rotors.
I see on wiki, the chinook (while looking for a picture) is called a Tandem Helicopter. The wiki page gives a list of others as well.
There was an English three rotor copter tested once. It had a triangular air frame. I saw a small clip of it many years ago, but otherwise I’ve never found any more info.
The main problem is that multicopters are uneccesarily complex. The single screw with tailrotor design has dominated the helicopter industry because of it’s simple, basic design. Counter-rotating co-axial rotors and intermeshed rotors have been used, but they are still more complex, and as a result have a higher failure rate than the simple single screw. Tandem rotors have been used with success, but they have the problem of transmitting power to 2 rotors space far apart.
For model helicopters multiple rotor systems are easy, and they are more stable than the single screw. But translating that into a full size helicopter is more difficult and costly, and introduces safety issues. The multi-rotor blimp disaster is an example of what can go wrong.
I’m pretty sure ALL helicopters have at least two; so, a multicopter would be one that has more than two. I’m happy to be educated either way.
It looks like most of those multicopters have fixed-pitch propellers. I suspect they’re controlled by speeding up or slowing down some of the props relative to others. At full size there’d be a lot more rotational inertia; maybe the control response would be too slow.
Some things don’t scale.
Not at full size. Rotor speed is a terrible way to control a helicopter. It just isn’t responsive enough. It works for light tiny models, but the only full size copters I’ve ever heard of that use rotor speed control are small tip jet models. All full size machines run their engines in a narrow operating range varying fuel to maintain that range based on load. The non-linear output of engines makes this a necessity.
Lack of need?
Too bad, those things look very cool.
I wonder how much an RC version would cost.
They start around $150 USD and go up from there. $200-400 would be a mid-range price.
Just my opinion, but if a multi-copter was to really be built full-size, it would be best if it had several units of dual, contra-rotating, coaxial rotors such as found on Russian Kamov military and civilian models. This would at least eliminate rotor torque strain on the assembly. But who knows. The only aero-stat to ever try the configuration (a blimp bearing a frame holding four h-34 helicopers) failed, apparently due to mechanical stresses on the steel truss structure holding it together, killing at least one of the H-34 pilots.
Another factor may be size needed for landing/takeoff and storing. Those things seem to need a lot more area which negates some of the versatility of a helicopter.
I wonder how many lights they smashed before they put that giant net in.
(Actually, I’m guessing it was more to keep them from hitting the wall)
I’ll bite. I believe there is a design that uses a jet exhaust instead of a tail rotor.
How about the Moller flying car;
Looks like it has 8 rotors.
Heck, Robur’s *Albatross * had dozens of 'em:
http://www.eccentric-cinema.com/reviews2011/master_world.htm
http://ohomemilustrado.blogspot.com/2011/06/albatross-sketch-from-robur-conqueror.html
Ever since the AR.Drone was released, there’s been a growing DIY quadrocopter scene.
Not a bad time to get involved, what with the technology (namely control interface and remote imaging) evolving so rapidly and the legislation on civilian UAVs still virtually non-existent. Who knows if they’ll still be legal in a few years…
NOTAR? (no tail rotor)
They should start their own nation.
They could call it the NOTAR Republic.
(d&r)