[JoeAltmaier]

Having the center of mass under the blades is fundamental to helicopter stability. There's no mention of how he made this bike stable. I'm guessing, he didn't. Thinks he can work out the bugs by testing. It will work as well as software that's been 'tested to correctness' - after a lot of crashes and hacks, it will limp along.

[samlittlewood]

This is only true for teetering rotor heads (eg: Bell, Robinson) where the fuselage hangs freely by the mast from the centre of the rotor disk. (Under -ve G the rotor and fuselage don't stay nicely aligned, and mast bumping happens - not good).

If there is a rigid/semirigid rotor head like on models, then there is no problem having the center of mass above the rotor. I have sometimes found models to be more stable and perform better when flying inverted.

For soemthing like this 'bike' - the thrust vector rotates with the vehicle - it will stay lined up with the CoG. Like rockets - it may appear unstable to have the motor at the bottom, but it is actually stable.

[RickHull]

> If there is a rigid/semirigid rotor head like on [sic] models

Like on what models?

[ptomato]

Not sic. I believe he was referring to model helicopters, not a specific model of helicopter.