[12many]

Thinking about multi-rotor concepts, a few ideas occurred to me:

Tri-copters, being inherently yaw-imbalanced due 2:1 CW/CCW rotation, use a servo to rotate the 3rd motor over to induce yaw to counter the yaw (torque) imbalance.

Would this servo be necessary if the frame had the ability to set a fixed but manually adjustable rotation from vertical on all three motors?  By monitoring motor throttle levels and experimentally adjusting rotational offset, tuning for balanced motor throttle, an optimal setting could be found.  Yaw could then be controlled by conventional means of varying CW/CCW induced torque balance.

Once a reasonable tilt is established, this motor tilt could be manufactured into the frame.  Has anyone tried this?  At a minimum it should save cost & weight.

Alternately, has anyone tried tri-copter with 2 CW : 1 CCW props where the CCW prop is a larger motor / diameter?  Again, experimenting with balancing prop diameters might generate good results.

Your thoughts?

[f5soh]

You can maybe compensate/stabilize the yaw axis but i wonder how you stabilize the Roll/Pitch axis at same time.

If you don't want servo on tail, try Y4.

[12many]

I think I see your point:  stabilization of all axises are connected.  Will think it though.  Thanks for the reply.

[nitromethane]

I did some superficial thinking and came to a conclusion that yaw would me more or lees impossible to decouple from the roll and pitch.
There may be a way to make it play together and produce a flyable copter, but control wouldn't be nearly as free and flexible as with classic tricopters with a servo for yaw.

[12many]

I experimented with rotor tilt last night on a larger vehicle I built (9 props, 5:4 or 1.25:1 rotation imbalance) and even a ~ 5-degree offset was too much - I saw the observed 20% FC CW:CCW throttle imbalance totally reverse.  Am going to try 2 degrees tonight.

A tri-copter, being 2:1 imbalanced might need more tilt, but from my initial results a guess is it's probably far less than 10 degrees.  Not sure at what  point rotor tilt induced instability would overcome attitude stabilization and where cost/benefit loses any potential benefit, but the required tilt appears to be pretty small.

I don't have a tricopter available - does anyone know what angle the servo typically induces on the prop when a tri is hovering?

Any thoughts on how a 2-small + 1-large prop scenario might pan out?