Autogyros

[norup]

Here are a few simple autogyro designs:
The first one is stock, while the rest use hinges and bearings from Infernal Robotics (IR) mod.
The stock one is very limited in performance and realism, but I hope it manages to whet your appetite and try the IR ones.
There is a lot of room for improvement - I hope you will tweak the designs or come up with completely new ones.

AutoGyro (stock)

Autogyro (stock) kerbalx download

Guide to flying:
Engange SAS and engines. Set throttle to 1/3 and stage to free bearing. Wait for rotor to spin up while using rudder to keep straight down the runway. When up to speed, increase throttle to 1/2, and it should take off by itself at about 42m/s. Be prepared to correct roll. If there is a strong rolling moment, rotor speed was too low.
Use throttle to control climb - recommended 1/3 to 2/3. Cruise is around 1/2 throttle and 45m/s. Try not to go too fast or have too low AoA, as rotor will slow down. For power-off descents, keep a forward speed of 30m/s and a descent angle of 40 degrees. Some flare is possible, but landings are a bit firm. Landings with 1/6 throttle are much more gentle.
When you get the hang of it, try to remove the reaction wheels in the cargo bay or set the wheel authority to zero, including the one in the cockpit. With a bit of care, it still flies reasonably.
Considering that the stock autogyro has a rigid rotorhead, it flies remarkably well - maybe due to limitations in the physics model or play in the bearing?!

The bearing was snatched from ThatSaneGuy's Stock helicopter:
https://steamcommunity.com/sharedfiles/filedetails/?id=1541278290

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I have tried to make stock flapping hinges for the rotor blades, but they kept falling apart. For this reason, I moved on to using hinges from Infernal Robotics:
Infernal Robotics v3.0.0 "Next" Beta 3 Patch 7
https://forum.kerbalspaceprogram.com/index.php?/topic/170898-wip-infernal-robotics-next/
https://github.com/meirumeiru/InfernalRobotics/releases

Kierva (IR)

Kierva (IR) kerbalx download

For your convenience, Separatrons are provided for spinning up the rotor - simply set half throttle, stage, and off you go.
However, it is far more interesting to take off without the rocket boost:
Set throttle to 1/6 and let the rotor spin up. At low RPM the disc will have a lot of coning - wait until it flattens, then increase throttle gradually to 1/2. Take off should occur at less than 40m/s.
It flies quite well without SAS. Level speed is about 35m/s at 1/3 throttle.

AutoGyro Light (IR)

AutoGyro Light (IR) kerbalx download

This uses the FAT-455 aileron for rotor blade - they look better but appear inferior to the "Wing Connector Type E"
Flying:
Take-off with wind-milling speed up of rotor quite difficult due to poor ground handling.
Recommend full throttle and then engage Separatrons to speed up rotor.
Needs 2/3 to full throttle in flight and 1/3 throttle for landing.

 

Edited December 9, 2018 by norup
imgur links, spelling

[norup]

Here is a video of the Kierva in a feeble attempt to keep this thread alive

Notice the dropping of the blades when stationary, followed by coning at low RPM, then flattening when approaching flying speed. A gentle takeoff to avoid rolling, followed by a lucky landing.

Why, oh why?
I have long been fascinated by the complex aerodynamics of helicopters, including autorotation. R/C hobby shop owners have grown wealthy from selling spare parts for my 450-size helicopter from all the failed autorotation attempts. With this size, there is little margin for error. (Symmetric blades with radius about 41cm. Weight 800g). After upgrading to a 550-size helicopter (55cm blade radius, weight 3kg), autos became much easier, and I usually finish every flight by one.

In the mean time, I also got a couple of R/C model autogyros. With larger, asymmetric blades, flexible articulated rotor heads and lower flying weight, these can fly pretty well.

Edited December 16, 2018 by norup
youtube link incorrect