Yeah, I've seen the Hiller platform at the Smithsonian, it's neat.
It's also unstable because of the high center of gravity. However, it has a specially designed duct that the propellers fit within which creates stabilizing aerodynamic effects, counteracting this instability. Also did you notice the Hiller's lip around the top edge? That's a carefully designed airfoil against which air drawn downward by the propeller passes, creating uniform lift underneath the whole lip edge, all 360 degrees around the outside of the platform! Very clever, but also prevents movement that isn't perfectly balanced upward lift, which is why they were hard to navigate.
The Chinese gentleman's aircraft does not feature either of these and will be unstable. But I'm glad you brought this up, because it's possible that the Hoverbike uses similar effects and is thus more stable, I suppose we'll find out more as Hoverbike prototypes make their way to market and are analyzed. I don't really see an airfoil lip of the same nature on the hoverbike though, but perhaps it's there. The general solution going forward with such things is likely not going to be the Hiller design but is to stabilize using automated flight control as has been mentioned elsewhere in this discussion. The high center of gravity is still a stability problem though that has to be dealt with. With the Chinese craft, there's no way it will be flown any distance untethered using its current design.
>Also did you notice the Hiller's lip around the top edge?
the primary purpose of [relatively wide] lips of ducted fans is this:
"Utilizing the Bernoulli principle, 40% of the vehicle's lift was generated by air moving over the ducted fan's leading edge. The remaining 60% of lift was generated by thrust from the counter rotating propellers."
It's also unstable because of the high center of gravity. However, it has a specially designed duct that the propellers fit within which creates stabilizing aerodynamic effects, counteracting this instability. Also did you notice the Hiller's lip around the top edge? That's a carefully designed airfoil against which air drawn downward by the propeller passes, creating uniform lift underneath the whole lip edge, all 360 degrees around the outside of the platform! Very clever, but also prevents movement that isn't perfectly balanced upward lift, which is why they were hard to navigate.
The Chinese gentleman's aircraft does not feature either of these and will be unstable. But I'm glad you brought this up, because it's possible that the Hoverbike uses similar effects and is thus more stable, I suppose we'll find out more as Hoverbike prototypes make their way to market and are analyzed. I don't really see an airfoil lip of the same nature on the hoverbike though, but perhaps it's there. The general solution going forward with such things is likely not going to be the Hiller design but is to stabilize using automated flight control as has been mentioned elsewhere in this discussion. The high center of gravity is still a stability problem though that has to be dealt with. With the Chinese craft, there's no way it will be flown any distance untethered using its current design.