[wiredfool]

Probably not, for the same reason that a quadcopter doesn't really scale to full size. The inertia effects of larger rotors make changing the speed of the rotors within a rotation much harder.

With full sized helis, it takes a long time to spin up the rotors to speed before the pitch is changed to take off.

[TaylorAlexander]

Well the critical difference here is that changing blade speed is not needed or desired. They just need to change blade torque, which would apparently immediately cause a change in blade pitch.

I don't see a specific reason why this wouldn't scale. I do wonder what changes in load do to the system though. If it can't handle changing loads without messing up the blade dynamics, it would only work for fixed payload systems like camera platforms.

[erobbins]

It won't scale because of inertia. Rapidly changing the speed/torque of a large combustion engine is nearly impossible.

It's a great solution for reducing mechanical complexity in mini/micro sized UAVs, though.

[TaylorAlexander]

You can use an electric motor. We can easily make extremely high power electric motors (see: CNC machines and Diesel trains), and power storage will continue to improve.

The added cost of batteries at even today's prices could be worth it for the decreased mechanical complexity of the rest.

If all we need to do is change the torque of an electric motor, that can be done essentially instantaneously even at high power levels.

[lambda]

> power storage will continue to improve

Power storage may continue to improve, but it will take a long time before you hit the energy density of fossil fuels; the difference between batteries and fossil fuels is something like a factor of 10 (actually greater than that, but electric motors are more efficient so let's say 10 for the sake of argument), and it's improving much more slowly than Moore's Law, doubling maybe once every 10 years. That means if those trends continue (and there's no guarantee they will), you're looking at 30-40 years before the energy density allows electric helicopters to be competitive with fossil fuel powered.

For cars, energy density isn't quite as important, as the weight of the car is not the dominant factor in its efficiency (it does have an effect, but the aerodynamics, engine efficiency, transmission efficiency, tires, etc. all make a big difference too). But for a helicopter, every pound you add to the batteries is another pound you have to lift, so energy density of your power source is quite important.

So, if trends hold on battery technologies, it will come about eventually; but I would put money more on the decades timeline than the years timeline.

[prbuckley]

I don't think scaling this up is a question of inertia it is more a question of weither a material exists that can be used in those flexural joints with much higher loads.

This is a material science question. A material may exist that has the right combination of flex, strength and lets also not forget durability. I am a mechanical engineer and crack propagation and cycle fatigue would be a major concern for a joint like that at large loads. There are all kinds of amazing tricks material scientists know how to play to combat these types of problem.

I think this could be scaled up if material to make those flexure joints exist.

[TaylorAlexander]

The joints looked like simple pivots, not flex joints. See how the blade is attached at a 45 degree angle? I think it just pivots there.

[dognotdog]

You could couple a high power combustion motor with a relatively low power electric motor via a differential, and have the electric motor do the 'high frequency' modulation the combustion motor is incapable of.

With a regenerative approach, you'd probably need very little net electric power.

[spacefight]

Not quad exactly but still worth following is this man lifting multicopter from Germany:

http://www.e-volo.com/

https://www.youtube.com/watch?v=CzP0Zqxam7E#t=76

[lotsofmangos]

Sure it would work. It only needs a variable clutch on a standard engine and the motion on the blades is very slight and mostly balanced, so the torque difference should be pretty manageable.