I wonder if the idea of the balance required for two wheels was an impediment to invention and use.

for example, I think one-wheeled devices / unicycles are crazy and only someone with a lot of time, energy and motivation will to learn to balance and use one.

But nowadays computers make it possible for normal people to use them without as much skill.

We might have a "why did we wait so long for simple one-wheeled transportation?"

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another analogous musing -- why did we start with main+tail rotor helicopters?

Nowadays 4-rotor quadcopters appeared and have taken over.

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LandStander 5 hours ago | parent | next [-]

why did we start with main+tail rotor helicopters? Nowadays 4-rotor quadcopters appeared and have taken over

The quadcopter advantage is in it's mechanical simplicity, but having fewer longer blades is better for aerodynamic efficiency(at the expense of max airspeed). This matters less at RC scale, but at full size, even an all-electric helicopter will likely have more range than a quadcopter with the same batteries.

	▲	nerdsniper 3 hours ago \| parent \| next [-]
		4 rotors is also a much more difficult “controls” problem. Helicopters actually glide reasonably well if their engine cuts off. They’re not super insanely unstable. Quadcopters are basically obligate fly-by-wire vehicles which necessitate at least pneumatic PID controllers if not computer chips to fly. You can make a helicopter work reasonably well a lot earlier in a pre-computer “tech tree” than you can a quadcopter.
	▲	taneq an hour ago \| parent \| prev [-]
		Upgrade that 'maybe' to 'definitely'. The disc loading on a helicopter is typically much lower than on a quad (excepting crazy designs like the giant human-powered quad) which makes it significantly more efficient for the same overall size.

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bondarchuk 2 hours ago | parent | prev | next [-]

>another analogous musing -- why did we start with main+tail rotor helicopters?

In fact we started with autogyros.

Also the Fw 61 ("the first successful, practical, and fully controllable helicopter" though I don't know the history in detail) has two equal-size counter-rotating rotors similar to a quadcopter.

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koziserek 3 hours ago | parent | prev [-]

what works in 100g - 5kg drone does not work for much heavier machines.

- Small UAVs are mainly controlled by varying RPM of each rotor

- Full-scale machines keep ~constant RPM optimal for rotor aerodynamics and change angle of attack for each blade for control (collective and cyclic changes).

With big inertia and no alien materials technology, it isn't possible to apply 'quad' design for your average SAR helicopter.

	▲	rcxdude an hour ago \| parent \| next [-]
		Also, four points of failure isn't a particularly enticing feature for an already slightly terrifying aircraft if you're actually going to be in it.
	▲	mrheosuper 2 hours ago \| parent \| prev [-]
		There is quadcopter with variable pitch blade.