Effect of airfoil camber on small autogyro rotors
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- เผยแพร่เมื่อ 5 ต.ค. 2014
- A gyroplane rotor is pneumatically driven and extracts power from an airstream. That power extraction is seen as a reduction in the speed of the air behind the rotor disk.
This video demonstrates the effects that airfoil camber have on that airspeed reduction. It also shows how the camber affects the lifting efficiency of a rotor ( lift to drag ratio ).
The lift to drag ratio is determined by the angle the rotor takes relative to the oncoming air ( angle of attack ). As a rotor produces force roughly perpendicular it's plane of rotation, at very low angles, most of the force it will produce will act vertically. The larger the angle, more of the force is redirected backwards, making the rotor harder to push through the air.
For the purpose of a gyroplane, the rotor should be as level as possible, as it reduces the force needed to counteract rotor resistance to keep the machine flying. - บันเทิง
After watching dozens of videos to understand the lift, with yours I did it. Thank you!
Fantastic video...brilliant
Great experiment 👍
ya what he said! Nice to see some good detailed study!
nice video..
Awesome!
brilliant!
wow! that was very smart
This is fucking awesome!
I have seen beautiful videos in my life but this, this is amazing
You're a genius. :)
Thanks!
Thank you. Great video. What was your blade pitch angle?
yak55x I can't say with certainty. It was slightly different for each rotor as I adjusted it for maximum lift. From what I recall on average it was about -2 to -3 degrees of pitch.
Thank you, that's very helpful. I've been collecting as much data as I can on auto-rotation blade pitch angles.
This may also help you. Recently I played around with twist on these small blades. By adding approximately 12 degrees of washin to the tip, then reducing the twist in a approximately linear fashion towards the root, the 4% camber blades increased rotor rpm by 16%. Without twist their rpm at 90deg to the airflow was ~2820 rpm. With twist it increased to 3270 rpm.
yak55x The tips, while with washin, were kept at around -3 degrees of pitch. The pitch near the root of the blades was reduced as a result. Closet to -14 degrees at the 30% rotor radius. Interestingly enough, with lower twist, of around -9 degrees, rotor rpm only decreased to 3240 rpm. A very small change for a relatively large pitch change. Hope this helps!
Sorry but that's not exactly how it works, the blades should be on a hinges or you gonna create ''critical''(deadly) accident. th-cam.com/video/mQieKnglzj4/w-d-xo.html
I’m trying to conceptualize why is it it creates better lift than a fixed wing? Putting flaps on a fixed wing increase lift correct? What about comparing to a parachute?
Why are gyro propellers so wide?
Does the lift increase from the length or the area of the propeller?
I really want to make one I can fly. Any thoughts anyone?
I used to have minus 6 degrees on the powered rc helis I used to fly. I never bothered with minus 12 etc for inverted flight. Minus 6 was ideal for that dreaded moment of engine stoppage in flight (well it wasn't that bad...I practiced a LOT on rc sims) very interesting subject though...was doing a similar experiment a few weeks ago with some old wooden Trex 450 blades on a homemade hub. Doesn't the reduced radius of the advancing blade also add energy to an Autogyro setup? (manifested by the higher plane of the 'disc' when seen from the side) so advancing blade, flys higher...but gyroscopic precession meaning the action is 90 degrees later...thus the higher plane in front of the Machine)
I'm not sure what effect the rising and falling of the blades with respect to gravity has. I've honestly never thought about it! Maybe there's some interplay between potential and kinetic energy going on. I don't know. If there is, I think its very little due to the blades balancing one another (mostly) as they spin. Although the radial changes you describe may change that drastically.
Food for thought! Such is the land of rotary winged madness!
On many full size helicopter rotor heads there is a lead/lag damper for each blade. Retreating blade (ie in forward flight) will increase in pitch, and begin to rise...its total rise will be at the rear (so the precession result) as it rises the diameter will reduce...which results in that blade speeding up...the damper takes this adjustment as the blade leads....then as that blade becomes the advancing blade ie heading towards the front/into the airflow it will slow as its diameter increases. The way I see autogyration is the opposite of this. Very interesting subject btw and thanks for sharing such an interesting video. I take it you build working RC models?
Would 3 blades result in a better lift/drag ratio?
It's hard to say. It may not increase the lift-to-drag ratio, but it will increase the force generated by the rotor for a given airspeed. In general, increasing the blades on a wind-turbine will increase the power you can get out of the air (which for an autogyro translate into rotor force). Since you can fly slower with 3 blades, you can likely expect the aircraft to use less power.
@@XXXmags thanks.
Unfortunately cambered rotor blades have bad moment coefficient which is not suitable for rotor blades. They are long and thin (high aspec ratio) which they twist at high airspeeds which leads to an uncontrollable gyroplane . this was well known back in the 20s and 30s.
@Christos Psaras - agreed! The solution here is to control the twist aerodynamically - the Kaman synchropters use "Servo-Flaps" to control torsionally soft blades very successfully. Improvised thin cambered steel blades are super flexible but fly true and will self-start normally.
BS again 🙈
I bet an umbrella would have even better efficiency.
minus 4 degrees?
A slight negative angle built into the blades, such that they would push down if spun like a helicopter rotor.
I read some truth, but also a lot of BS. Sorry for that.
For starters, check out chapter 15ff in the
"FAA-H-8083-21, Rotorcraft Flying Handbook - Federal Aviation Administration"
Look it up in Google and download. It's free.
NACA has done wind tunnel tests on various airfoils for AGs.
A flat airfoil works fine in Gyros but properly shaped airfoils like the SG6042 work best on model AGs. It generates the most lift and low drag plus stable tracking.
Btw. to reduce retreating blade stall, chamber doesn't help. There is other tricks, such as flapping hinges and more needed.
bs