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Old 03-23-2018, 06:46 AM   #31 (permalink)
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Originally Posted by samwichse View Post
This isn't true. They are inherently unstable. There is no self correction without constant corrections from the electronic gyro.
Self correction is called dynamic stability. Neither helicopters or quads have dynamic stability. They both require electronic or pilot intervention to return to center. On the other hand there is static stability, the tendency to stay where you leave it. Many airplanes and quadcopters are designed to be fairly statically stable. Helicopters are not.

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Originally Posted by samwichse View Post
Try flying one for 10 seconds with the gyro disabled and you'll discover this quickly. There is zero return to self level and it will be like trying to stand on a beach ball.
This is common in aerobatic or "3D" flying, not in a photo platform quad.
My point was that since a quad has all thrust parallel and in the desired direction for hovering, has torque negated by counter rotation, and "can be designed" to have "static" stability. it makes for a better hovering platform for photos.

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Originally Posted by redpoint5 View Post
Helicopters are inherently stable and require no electronics to fly. Having the blades above, lifting the chassis keeps everything upright.
Not true at all. Conventional helicopters are both dynamically and statically unstable. They require skill to fly. But gyros and electronics could be used the same way quads do.

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Originally Posted by redpoint5 View Post
Quadcopters on the other hand are inherently very unstable, which is why they weren't popular until recently. They all require computer controlled gyro stabilization as they would just flip otherwise.
It's not the stability but the complex coordination of thrust that made quads difficult and expensive to build. cheap and light motor controllers changed this. Helicopters can use mechanical mixing of controls and one motor. Money not stability was the difference.

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Old 03-23-2018, 01:47 PM   #32 (permalink)
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Originally Posted by redpoint5 View Post
Swash plate is a better control method than variable speed rotors.
It's really a matter of scale. Try making & assembling a heilcoper-like swash plate &c at the size of a typical drone. Then try repairing it :-) Where with electric motors, you can use electronic PWM to change rotation speed in microseconds.

But scale that up to a full-size helicopter, and try to find an engine which will respond quickly enough for quad-copter style control...
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Old 03-23-2018, 02:23 PM   #33 (permalink)
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Originally Posted by jamesqf View Post
It's really a matter of scale. Try making & assembling a heilcoper-like swash plate &c at the size of a typical drone. Then try repairing it :-) Where with electric motors, you can use electronic PWM to change rotation speed in microseconds.

But scale that up to a full-size helicopter, and try to find an engine which will respond quickly enough for quad-copter style control...
I've got this XK110 heli (collective pitch / swash plate), which can be purchased for about $60. It is more expensive than some drones, which I've paid as little as $10 for. It has a gyro for maintaining heading, so it should be a relatively simple matter for a computer to also control cyclic and collective to hover in place.

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Old 03-23-2018, 03:16 PM   #34 (permalink)
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Electromagnetic swash plate? Seven poles would give you a selsyn motor

Koenigsegg use an electro-pneumatic valve train
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Old 03-26-2018, 05:13 PM   #35 (permalink)
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I know the topic is electronic range. Forgive me.


He finds little difference between commercial and home-made rotors; and concludes with a preview of an APU.

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