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Auto-gyro project.

Doctape

Junior Member
#1
Hey guys.

I have a few quick questions. In line with this post (http://forum.flitetest.com/showthread.php?528-RC-Gyrocopter). I'm planing to built one in my spare time. I only have rough sketches done and nothing definitive at the moment. So pictures will take a while to follow.

I'm going with a push configuration thrust wise. For the controls, should I go Throttle, Elevator and Rudder? Or Throttle, Elevon and Rudder? I also have 9g nylon servos for this built. Will they be strong enough? Should I think about going with metal ones to control the auto-gyro?

Thanks in advance for any input.
 

stay-fun

Helicopter addict
#2
Have you ever built or flown an autogyro before? If not, i recommend you start with the auto-g from hobbyking. I know how to fly helis and planes, but autogyros are a whole different story. I'm in the process of an ft-style autogyro based off the auto-g (keep your eyes open for the build log I'll be making).

I also have a lacie rotorshape, it has flown once for a couple of minutes, but i haven't invested much more time in it quite yet. The rotorshape has elevons only, no rudder.

Not to discourage you, but i find them hard to fly (and i consider myself a solid intermediate pilot - both helis and planes). I can tell you that if you start out, definitely go for a tractor style (prop in front). My auto-g has quite some flight time and flies pretty good.

As for your question, you need at least aileron and elevator control. The rotorshape has elevons, the auto-g has separate aileron (tilt rotor), elevator and rudder (both on the tail, so no elevon).

Whether your servos will be strong enough depends on the size and weight if your autogyro. The auto-g comes with nylon servos, but uses two of those on the aileron. You may compare your build to that to see what you would need.

Long story :) let me know if you need more info.
 

Doctape

Junior Member
#3
I did try 2 different ones over the years and yes they are difficult to pilot. The big problem is that, from my point of view, most models are too light compared to what they are supposed to be. The way I see it, gravity pulls down on the auto-gyro, the rotor spins freely because of the air flowing trough it generated by the forward momentum of the aircraft thus getting lift. If gravity has nothing almost nothing to act on, is the rotor doing it's job properly?

As a reference, I've look at the specs of an actual auto-gyro and just scale down. For example the Orion M-24 (http://www.magnigyro-canada.com/Aviasport/Details_M24_Orion_eng.html). As a starting point let's say I'm to use a 8x6x3 prop. Just because that's what I have beside me at this very moment.

The prop on the Orion is 1700mm, so roughly 67inches in diameter. That makes it a factor of 8.375. The scaled down weight should be around 34Kg (285Kg / 8.375) and that's insanely too heavy for a model. That's why in my opinion most auto-gyro models are to light. With that info what we ended up doing with the model I've tried was to just add more weight in form of batteries as dead weight just to start. We installed that at the bottom to keep the CG as low as possible and in the middle of the rotor. It improved a lot and he was able to perform a better banking turn. Added bonus, more flight time with a bigger battery.

Granted I don't have as much flight experience as the others people I know. Added to that I've started a short while ago to get re-equipped to fly again and there's a lot of new things around now. I totally agree with you that they are hard to fly. I find them too facinating and have to make one if you know what I mean. I just find that most of them are too light. In my opinion that's one of the causes that makes them hard to fly.

I'll post more as things move forward with this project.

Thanks for the info about the servos. I'll probably need more massive ones.
 

stay-fun

Helicopter addict
#4
There are problems with scaling down, because the rotor disc area scales down cubically, while the mass does linearly. The fact that from your calculation, the weight is way too high, confirms this. Typically, the (rotor)disc loading on a model is higher than that of a full scale.

I'm surprised you need a heavier autogyro... In fact, when I removed the pre-rotator (~90g) from my auto-g2 it suddenly flew a lot better! The only thing now is that I need a slight breeze to get the rotor going for launch (I always hand-launch).

The rotor will do it's job by forward momentum. If there is hardly any gravity, it just means it'll gain altitude if the lift is higher than the gravity :)

Are you going to use an 8x6 prop? My auto-g runs off a 10x8, and uses the nylon servos. So... Your autogyro is probably smaller.

RCgroups has a whole subforum on autogyros, and a sticky on how they operate. Interesting stuff!