Multi rotor size vs stability

[sausageroll]

Hi Everyone,

Most you will have seen the hexcopters ive built, they are great, stable, but big. I tried removable arms, to help pack them up to make them more portable. This worked from a mechanical point of view but its a pain in the arse from a connection side, connectors that can handle the current and are small enough and not very expensive (x6) are hard to find. The only ones I have found are normal XLRs, and they are only rated at 16amps, and they are quite heavy. There is also the concern that I may one day put the wrong arm in the wrong socket and the thing may spin backwards....

Im now wondering to make the thing easier to transport, I might make the arms shorter. I can probably chop a good four inches off each arm, save weight and negate the need for removable arms, which again saves weight. What im wondering though, will the smaller ';footprint'; reduce its stability? Presumably the further from centre the rotor is, the more leverage it has? If I make it smaller it will have less leverage, will this mean it cant react as quickly to wobbles? Maybe it works the other way, maybe it will be more stable with shorter arms?

Any advice would be great, if anyone has any insight,

Pete.

[teslahed]

Smaller arms will reduce stability. I';ll copy and paste a youtube comment (youtube comments - lol) I wrote on the subject;

If everything else is equal then longer arms = more stability. The motors have more leverage to adjust roll / pitch with and you get more angular momentum as a result of the heavy motors being out on the ends of the longer arms which will resist changes knocking the quadcopter off course.

The result is the quadcopter will feel less jittery and unstable and be happier just sitting straight and level in front of your nose, but you';ll flip and spin more slowly and loose maneuverability.

I';ve messed about with a bunch of home made PVC quadcopters, all very similar except with slightly different arm lengths, and i';ve had 2 different flyduino frames flying with different length arms, but otherwise very similar hardware, all of which seem to support this hypothesis (Even if my second flyduino frame failed in the end as a result of my attempts to use cheap carbon fibre to make my own arms). So i';m pretty sure it does work like this.

Although with the naza flight controller i expect you';ll get a decent amount of stability with any kind of sensibly built multirotor.

[sausageroll]

Ok what if I stagger the height of the rotors so they overlap? lol.

[teslahed]

I bet you';d get efficiency losses where the overlap was, and an interesting noise from the turbulence.

Other than that, no idea - sorry.

There is also the concern that I may one day put the wrong arm in the wrong socket and the thing may spin backwards....

Number the arms and arm sockets?

[Gaza07]

If its not broke don';t fix it springs to mind