Quad vs Hexa vs Octo -copter. (Radial and coaxial) Advantages-Disadvantages?

Hi everyone :)

Althought it seems to me it's the first question that comes in mind when building a multirotor, there's not really much interest in determining which is the best design (deppending on the use) on the net.

I only could find some tri/quad comparation, but nothing comparing the CPU-balanced ones.

Could you please tell me the main (relative) differences between them (including their possible layouts like raddial/coaxial). Just smack here what you now :P

Quadcopter

Skylens Aerial Photography

Hexacopter Radial

Holger Buss' MK Hexacopter

Octocopter (Radial)

Mikrokoopter

Octocoper (Coaxial)

www.robfrench.co.uk

Octocopter (linear?)

AscTec Falcon 8

Photo credicts go to their mentioned owners

Thanks in advance :)
Andy

>there's not really much interest in determining which is the best design (deppending on the use) on the net.

So not true :o) there's constant research in this field going on all over the net (usually known as "flamewars"). Here's my pick:

General rules
More engines means more power! and more lift. That means more batteries. That means more time in the air. Brushless electrics like to run slow (lower RPMs), so bigger means more efficient. Also, if efficiency is your goal, coaxial = evil.

The breakdown
Tricopters: cheap, easy to build, least stable, not as robust (tail servo and mechanics), low lifting power and flight time (because the motors have to run faster to hold it all in the air). No engine out capability.
Quadcopters: mechanically simpler than tris. While they weigh almost the same they have about 1/3 more lift, they are usually more stable (no servo issues) and are capable of staying airborne for a little while longer (they can either lift larger batteries or fly more economically because the weight is spread across 4 motors and not just 3). Still no engine out capability. If it fails, it goes down.
Hexacopters: All the good things that quads have, plus more power and more lifting capability. As a bonus they add limited engine out capability - a hexacopter can lose any single engine and still land (it will lose yaw control though), and if it loses one or both engines on the neutral torque bar it could even continue flying unaffected. Downside is that they are larger and a little pricier, especially if you're running high-grade motors like AXI.
Octocopters and heavier: All the good things from hexacopters, plus true engine out ability. Loses any single one and still flies fine. This is what you fly if you need horsepower and reliability in one package. This is what you strap that $1300 Canon 7D under :)) Even more expensive though. Also heavy craft are really power hungry and unless you have some serious chargers at hand they require a lot of work on the ground before a flight can be made (charging say 5 packs for 25 minutes in the air).

Replies

Dimitar Kolev August 25, 2010 at 11:03pm

Which page?
Andy Gongora August 25, 2010 at 5:36pm

Just found this page with lots of layouts.
But althought it's a wiki-like page, there's no extra info (at least when i click on them) about each.
Overwatch August 23, 2010 at 11:23am

>there's not really much interest in determining which is the best design (deppending on the use) on the net.

So not true :o) there's constant research in this field going on all over the net (usually known as "flamewars"). Here's my pick:

General rules
More engines means more power! and more lift. That means more batteries. That means more time in the air. Brushless electrics like to run slow (lower RPMs), so bigger means more efficient. Also, if efficiency is your goal, coaxial = evil.

The breakdown
Tricopters: cheap, easy to build, least stable, not as robust (tail servo and mechanics), low lifting power and flight time (because the motors have to run faster to hold it all in the air). No engine out capability.
Quadcopters: mechanically simpler than tris. While they weigh almost the same they have about 1/3 more lift, they are usually more stable (no servo issues) and are capable of staying airborne for a little while longer (they can either lift larger batteries or fly more economically because the weight is spread across 4 motors and not just 3). Still no engine out capability. If it fails, it goes down.
Hexacopters: All the good things that quads have, plus more power and more lifting capability. As a bonus they add limited engine out capability - a hexacopter can lose any single engine and still land (it will lose yaw control though), and if it loses one or both engines on the neutral torque bar it could even continue flying unaffected. Downside is that they are larger and a little pricier, especially if you're running high-grade motors like AXI.
Octocopters and heavier: All the good things from hexacopters, plus true engine out ability. Loses any single one and still flies fine. This is what you fly if you need horsepower and reliability in one package. This is what you strap that $1300 Canon 7D under :)) Even more expensive though. Also heavy craft are really power hungry and unless you have some serious chargers at hand they require a lot of work on the ground before a flight can be made (charging say 5 packs for 25 minutes in the air).

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Quad vs Hexa vs Octo -copter. (Radial and coaxial) Advantages-Disadvantages?

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