Setting up of pitch blocks and blade angles.

[asra]

Setting up of pitch blocks & blade angles.Question 1If your blades are set to there max A of A does this mean they will in turn create greater max lift, will they turn at a slower speed, will they be harder to start, and will they make your machine fly slower?Question 2Conversly, if blades are set at a finer A of A will the machine fly faster, will the blades rotate faster, will they produce less lift, and will they be easier to spin up ?My blades are currently flying perfectly at there max A of A, but could my machine fly better ?????????Regards Lazy Sam [?][?][?]

[asra]

Is no one prepared to pass on their experiences !!!!!! Well I have done some testing already, but need to confirm as weather was a little blowy at the time to make judgment.Sam............

[asra]

Hi Sam,Just saw your post today - been off the forum for a good bit.Question 1:If your blades are set to their max A of A does this mean they will in turn create greater max lift? Probably not - depends on a lot more variables - blade loading for one. And what precisely do you mean by max lift?will they turn at a slower speed? Yes, more AoA = less RRPM in normal rotors will they be harder to start? Almost certainly yes will they make your machine fly slower? Depends. Top speed is a function of drag, Mach and Mu. Cruise speed is mostly drag.Question 2 answers are mirror images - the flight speed one is tricky because the rotor efficiency depends on the rotor blade flying at a good L/D, and all the parts of the blades fly at different angles depending on RRPM, load, flight speed, and where they are around the clock face! So it's the sum of many parts, and hard to guess.Max speed (given infinite power) will be limited by Mu - the ratio of the tip speed to the forward speed. At a Mu of 0, gyro is stopped, at a Mu of 1, the retreating blade is flying backwards from root almost to the tip! Obviously won't support much weight, so this is impossible for regular gyros. A Mu of 0.4 is considered high, with a practical limit around 0.5 as rule-of-thumb. This translates into half the retreating blade having reverse flow, a bit more being stalled, and the bit at the tip keeping that side flying!Solution to high Mu, INCREASE the tip speedIF you have plenty of power, but not unlimited, you also need to worry about Mach - the speed of sound. At around 0.7 Mach, air starts to behave differently, and the drag rises fast as you approach the sound barrier. Solution for lower Mach drag, DECREASE the tip speed ! This catches the designer in a cleft between Mu and Mach, the only man to break free so far is Jay Carter, whose CarterCopter broke the Mu-1 Barrier this year. http://www.cartercopters.com/pr_2005-06-17.htmlRotors are great fun - good luck in seeking further understanding. I can recommend a flying model rotor (any flying model rotor) and a fan or air blower to help appreciate the reality, since it can be expensive to experiment with a real gyro. Failing that, a copy of the X-Plane simulator does a proper simulation of rotors and rotorcraft - free to download the limited version, and they have a special sale on Version 7 at the moment. http://www.x-plane.com/ The home pagehttp://www.x-plane.org/ The support groupWe use it to simulate our designs (www.BRAGgroup.com) and so does Jay Carter with the CarterCopter.Hope that helps, Ben

[asra]

That was good reading! So just for the heck of it what would be the ideal speed for a 30 foot rotor on say a 100 mph craft?Flying the right side up in Canada

[asra]

Hi Phil!Sorry for delay, we have been pretty involved lately. To work out a rotor configuration the aircraft weight would be handy, but may I assume that the address, rotor diameter and nickname is a clue? . [8D]So if we assume 1500 Lbs and a blade loading of 55 Lbs (for higher speed flight), a solidity of 0.039 gives you your 30 ft diameter near enough, with a chord of 11". This is an untapered untwisted blade of constant section with its section L/D max at a Cl of 0.4, blade L/D of 20:1 as installed and the computation is 'ballpark' rather than precise. The numbers run something like this....The blade loading sets the tip speed of the rotor, same way that the wing loading of a fixed wing sets things like aircraft stall speed and best cruise. Yes the foil section matters, but not as much as you might think - I assumed a standard gyro section like the 8H12.The 1500 Lbs and 30 ft diameter give you a disk loading of 2.15 psf, but this is too high for short takeoff and slow landing, so we will re-examine this below. Tip speed comes out at 490 ft/sec, so RRPM is around 310. This sets our Vne at about 130 mph using a Mu(max) of 0.4 with a tip Mach of 0.62 at that speedIf you prefer a lower Mu, you can lower the Vne... []...or raise the blade loading by reducing the chord.Disk loadingIdeally you are looking for 1.8 psf or below at MTOW, so 1500 Lbs calls for a larger rotor diameter, or at 30 ft diameter we should be considering a lower MTOW - say 1280 Lbs.Your rotor is still around 30 ft diameter, but the chord has shrunk to 9.3" to maintain blade loading at 55 psf. We still have 490 fps at the tip, so Vne is the same, and the aircraft will now fly off the runway more willingly and descend less rapidly due to the saner disk loading.If you want to examine it more closely I recommend a blade-element analysis of the rotor. I wrote a script for it a year or two back(recapitulating our PropDes prog from the 1970s) and a toe-rag lifted the Palm from my backpack before I could back it up to the laptop. Will get round to it again one day.X-Plane is a pretty good tool in our experience. It uses a blade element analysis (ten elements) and gives you a readout of almost anything you might want to know. I generally start with an untwisted untapered blade and look at the flow, which I then plug back into PlaneMaker and the twist is generated automatically. The taper should ideally be near square law, but practical requirements (and X-Plane) usually allow only linear tapers. It helps to maintain the same total blade area whilst tweaking the taper.For untapered, untwisted blades using a reasonable foil section the tip speed value is given by TS = 66 * (BL)^0.5That's Tip Speed equals 66 times the square root of blade loading in Lbs/Sq ft, with the result in ft/sec. Sea level, blah blah, clean foil surface, blah blah, your mileage may vary.[]Seems altogether too simple? It is! But it has a sound basis in theory, and gives a pretty reliable answer. Best regards, Ben

[asra]

Thanks for the Answer Ben. The rhino name just came over from another forum. I have one of those 660 Yamaha Rhino 2 seater quads and belong to a forum for them. I will post a picture of it all dressed up for winter! What I am up to is building a new sparrow hawk gyro. Its dry wieght is 830 pounds and maxes out at 1500 lbs full load. It has the 30 foot sport copter blades and 165 horsepower engine.Flying the right side up in Canada

[asra]

Here are the two toys!Image Insert: 80.63

[asra]

Phil, does the Sparrow Hawk use the Raf "magic" bush arangement or anything else for keeping the mast flexible to help with rotor shake?Aussie Paul.[]www.firebirdgyros.com

[asra]

Paul, Non of the RAF majic stuff here! I will throw up a picture of when the upper mast was still on the bench. You can see a horizontal pin that is is bushings. This pin is held in the center by a piece of spring steel on each side but still is allowed to move back and forth if the rotor tries to shake. The spring plates are not in this picture but I can take another pic up close of it all in place if you like.[]Image Insert: 78.33

[asra]

Ah ha, the slider head. Geez I saw a Sparrow Hawk head in NZ a month ago. I did not see the mast set up. A slider head with Sporcopter blades should be as smooth as.Do Sparrow Hawk give you an Anodized option?Aussie Paul []www.firebirdgyros.com

[asra]

I didnt notice anywhere on the order form for that option Paul. Not a bad idea though! I sprayed a clear insulating varnish made to do aluminum motor windings on mine. Hope it stands up good! Time will tell I guess!Flying the right side up in Canada

[asra]

Slider Head.This one was posted some time ago on this forum.Just shows how simple it can be !!!!Regards Sam.Image Insert: 79.97

[asra]

Chuck Beaty and Ernie Boyette initiated the idea for the Dragon Wings I believe.

[Des Garvin]

Observation question on Saml's picture. The spring fixing bolts are recessed on the inside of the mounting plates, so when the head is mounted between the cheek plates how does one hold the bolt heads for tensioning [V][?] May be a better option would be to not recess the heads. Des Garvin