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I always wondered why there are no "real life" sized quadcopters in use for manned flight. From what I understand the design is simpler and requires less mainte

I always wondered why there are no "real life" sized quadcopters in use for manned flight. From what I understand the design is simpler and requires less maintenance compared to "normal" helicopters. Are there any reasons why we're not flying quadcopters around instead?

kabouseng 13y ago
I wouldn't say less maintenance, you've got 4 times as much motors running than a conventional helicopter.
- jamesaguilar 13y ago
  For the hobby sized quads, it's simple enough to swap a motor. It is definitely easier to maintain since a spare is only 20 bucks and attaches in minutes with zip ties.
- kybernetyk 13y ago
  I'm by no way an expert on this topic. I just skimmed over the wikipedia article[1] where I read the following: > First, quadcopters do not require mechanical linkages to vary the rotor blade pitch angle as they spin. This simplifies the design and maintenance of the vehicle. As already mentioned I'm blatantly ignorant about this topic so it would be nice if someone who knows this stuff could chime in :) [1] http://en.wikipedia.org/wiki/Quadcopter http://en.wikipedia.org/wiki/Quadcopter
  - lytfyre 13y ago
    The advantage doesn't scale up well. small quadcopters basically speed up and slow down the motor itself to control how much lift is generated. As the size and weight of the blade increase, inertia makes that impractical, so you have to go to variable pitch for control.
2bluesc 13y ago
Lady Gaga flies with a hexacopter @ http://www.dailymail.co.uk/sciencetech/article-2499954/How-Lady-Gagas-flying-dress-works.html http://www.dailymail.co.uk/sciencetech/article-2499954/How-L... ... what the world is coming to?
- pygy_ 13y ago
  Morning coffee, this put a big smile on my face. She (or, probably, her team) has been hacking the entertainment scene for a while. Dubbing "a dress" what would otherwise be considered a nerd toy is genius. What's not a dress for her?
- sanoli 13y ago
  She will also fly with Virgin Galactic: http://www.vanityfair.com/online/oscars/2013/11/lady-gaga-first-to-sing-space http://www.vanityfair.com/online/oscars/2013/11/lady-gaga-fi...
exDM69 13y ago
> I always wondered why there are no "real life" sized quadcopters in use for manned flight. The explanation is simple: quadrotor physics do not scale up. The rotational inertia of the rotors is proportional to the length of the rotor blade to the fifth power. Double the rotor blade length and the inertia of that rotor goes up by a factor of 32. High inertia rotors are not suitable for quadrocopter because fast changes in the rotation of the rotors required for maneuvering them. Having one big rotor for lift and three (or more) small ones for control is a very good idea. Another idea that is being researched is having multiple quadrotor copters flying in co-operation.
- rpenm 13y ago
  The moment of inertia for a uniform rod pivoting on end is (1/3)ML^2 where M is mass and L is length. Assuming mass scales with length, inertia should be proportional to the third power. Where am I wrong?
  - exDM69 13y ago
    Mass is not linearly proportional to length, because a longer rotor needs to be a lot heavier to be structurally sound. A uniform rod is not a good analog for a rotor blade. It's not a far fetched idea to think that the mass is cubically or at least quadratically proportional to the length of the rotor. Unfortunately I can't remember the source where I saw the 5th power figure. In addition, the aerodynamics of a rotor don't scale up linearly either.
  - barrkel 13y ago
    Your assumption is way too simple. Mass increases with the cube of the scale, while cross section area increases with the square of the scale. The cross section will need to increase to cope with the extra mass, and that in turn will increase the mass itself, and this mass is specifically the rotating mass.
kashkhan 13y ago
there are :) human powered at least: http://www.youtube.com/watch?v=syJq10EQkog http://www.youtube.com/watch?v=syJq10EQkog
Zigurd 13y ago
There was some crazy man/scammer building a manned flying thing with six snowmobile engines powering six rotors. I remember this because I was working for Ray Ozzie at the time and he was telling people in the office about it because he had invested in it.
- rsl7 13y ago
  Moller?
  - Zigurd 13y ago
    Yeah! That's the guy! HOly moley moller.com still exists. EDIT: Wow, this has been going on since the '70s: http://www.downside.com/scams/moller/ http://www.downside.com/scams/moller/ The name "Discojet" is way more badass name than "Skycar." Just another sign of lowered expectations.
    - Pxtl 13y ago
      Yeah, the Moller Skycar has been an impressively long-running scam. It felt like he got his own article in Popular Mechanics on an annual basis. I wonder how much damage he does to the nascent industry if personal flying vehicles by sucking all the oxygen out of the room.

kabouseng 13y ago

I wouldn't say less maintenance, you've got 4 times as much motors running than a conventional helicopter.

jamesaguilar 13y ago
For the hobby sized quads, it's simple enough to swap a motor. It is definitely easier to maintain since a spare is only 20 bucks and attaches in minutes with zip ties.
kybernetyk 13y ago
I'm by no way an expert on this topic. I just skimmed over the wikipedia article[1] where I read the following: > First, quadcopters do not require mechanical linkages to vary the rotor blade pitch angle as they spin. This simplifies the design and maintenance of the vehicle. As already mentioned I'm blatantly ignorant about this topic so it would be nice if someone who knows this stuff could chime in :) [1] http://en.wikipedia.org/wiki/Quadcopter http://en.wikipedia.org/wiki/Quadcopter
- lytfyre 13y ago
  The advantage doesn't scale up well. small quadcopters basically speed up and slow down the motor itself to control how much lift is generated. As the size and weight of the blade increase, inertia makes that impractical, so you have to go to variable pitch for control.

2bluesc 13y ago

Lady Gaga flies with a hexacopter @ http://www.dailymail.co.uk/sciencetech/article-2499954/How-Lady-Gagas-flying-dress-works.html http://www.dailymail.co.uk/sciencetech/article-2499954/How-L... ... what the world is coming to?

pygy_ 13y ago
Morning coffee, this put a big smile on my face. She (or, probably, her team) has been hacking the entertainment scene for a while. Dubbing "a dress" what would otherwise be considered a nerd toy is genius. What's not a dress for her?
sanoli 13y ago
She will also fly with Virgin Galactic: http://www.vanityfair.com/online/oscars/2013/11/lady-gaga-first-to-sing-space http://www.vanityfair.com/online/oscars/2013/11/lady-gaga-fi...

exDM69 13y ago

> I always wondered why there are no "real life" sized quadcopters in use for manned flight. The explanation is simple: quadrotor physics do not scale up. The rotational inertia of the rotors is proportional to the length of the rotor blade to the fifth power. Double the rotor blade length and the inertia of that rotor goes up by a factor of 32. High inertia rotors are not suitable for quadrocopter because fast changes in the rotation of the rotors required for maneuvering them. Having one big rotor for lift and three (or more) small ones for control is a very good idea. Another idea that is being researched is having multiple quadrotor copters flying in co-operation.

rpenm 13y ago
The moment of inertia for a uniform rod pivoting on end is (1/3)ML^2 where M is mass and L is length. Assuming mass scales with length, inertia should be proportional to the third power. Where am I wrong?
- exDM69 13y ago
  Mass is not linearly proportional to length, because a longer rotor needs to be a lot heavier to be structurally sound. A uniform rod is not a good analog for a rotor blade. It's not a far fetched idea to think that the mass is cubically or at least quadratically proportional to the length of the rotor. Unfortunately I can't remember the source where I saw the 5th power figure. In addition, the aerodynamics of a rotor don't scale up linearly either.
- barrkel 13y ago
  Your assumption is way too simple. Mass increases with the cube of the scale, while cross section area increases with the square of the scale. The cross section will need to increase to cope with the extra mass, and that in turn will increase the mass itself, and this mass is specifically the rotating mass.

kashkhan 13y ago

there are :) human powered at least: http://www.youtube.com/watch?v=syJq10EQkog http://www.youtube.com/watch?v=syJq10EQkog

Zigurd 13y ago

There was some crazy man/scammer building a manned flying thing with six snowmobile engines powering six rotors. I remember this because I was working for Ray Ozzie at the time and he was telling people in the office about it because he had invested in it.

rsl7 13y ago
Moller?
- Zigurd 13y ago
  Yeah! That's the guy! HOly moley moller.com still exists. EDIT: Wow, this has been going on since the '70s: http://www.downside.com/scams/moller/ http://www.downside.com/scams/moller/ The name "Discojet" is way more badass name than "Skycar." Just another sign of lowered expectations.
  - Pxtl 13y ago
    Yeah, the Moller Skycar has been an impressively long-running scam. It felt like he got his own article in Popular Mechanics on an annual basis. I wonder how much damage he does to the nascent industry if personal flying vehicles by sucking all the oxygen out of the room.