Besides the danger of flapping and hitting one against the other, the other drawback is the autorotation capability it's the last feet which are the most important ones to store the rotational energy. It increases with the square of the diameter
I think ti would helo to reduce the disk diameter, but I would be very worried about blade flap in bad weather. This could lead to the two disks hitting eachother.
What's the purpose of a 4-bladed design? Is it just to distribute the mass load across more rotors? If so, then why isn't this more commonplace? Also, why can't there be a 6-bladed gyroplane? Or an 8-bladed one?
@@manofsan Hi! Well, there _could _be. but . . . Inter-blade interference is the problem with more blades - like one aircraft always flying in the turbulent wake of another. It reduces efficiency. Broader blades (wider chord) add the same area increase much more easily. Three blades is almost always smoother than two, the cyclic rotor drag variation is greatly reduced. Biplanes are less popular for new designs these days, and more than three blades on an autogyro is rare too.
@@bmull81 Is that so? Gee, I've heard different things and don't know who's right. I'd read somewhere that more blades enables similar thrust at lower RPM, and that lower RPM allows more efficiency. I guess there must be tradeoffs due to higher number of blades producing more shockwaves at a given RPM.
@@manofsan Heh! It can get confusing, can't it? ;) One of the hardest barriers to overcome lies in the serious differences between a helicopter rotor and an autogyro rotor. Anybody with an electric cooling fan can demonstrate propeller and helo rotor dynamics, sorta. The gyro rotor is kinda like a windmill. But to work well in an autogyro it has to be almost perfect. This is because when flying, the 'windmill' is turned to an angle where the air arrives from near the edge of the rotor disk. The flow vector is changing constantly. Not good for windmill efficiency. If the gyro blades are tapered/twisted (like most propellers) the twist has to go the opposite way to a prop, because the air is flowing up, not down - but - there is not much benefit to twisting a gyro blade, especially at higher forward speeds. Twist works best in a vertical drop. And . . . The root of the retreating blade sees reverse flow when flying forward, and the faster you go, the further out from the root this happens. So a vanilla untwisted un-tapered blade works well enough, and it makes the calculations a lot easier. To make all this work well, gyros usually have much lower blade and disk loadings than a helo. This is partly why autorotation after an engine failure is non-trivial in a helicopter... Often the impact wrecks the helo. Be careful to separate Helo rotors from Gyro rotors in your mind!
I expect with dual rotors, the circumference can be reduced allowing the blades to spin faster. The faster the blades the faster the gyro can fly. Gyros are different than helicopters with the limit being retreating blade stall but rotor speed and drag are still directly related to aircraft speed. I’m guessing here.
No.😅...4 Rotor blades simply flesh out the Rotor disk... distributing the Rotor workload amongst the 4 blades...also vastly reduces the adverse effects of blade flapping/coning.. ALL Rotor blades are limited by rotation speeds...faster you go= faster you enter retreating blade stall.
Ok great: What are the advantages of dual rotors? What are the disadvantages? Why a two cylinder 4 stroke engine as opposed to a 4 cylinder 4 stroke engine? Would a dual rotor be capable of carrying more load than a single rotor gyro for a same size cockpit? Nice to see it fly, however, I think we all like to know more of why the decision for dual rotor and precisely its benefits, if any?
You can shorten the length of the rotor blade, and make it more rigid and aerodynamically efficient (rigid rotor technology) and less susceptible to 'rotor slap'. However, the blades would then not create a shallow cone shape which - according to some - aids with the stability inherent with autogyro flight. This might be overcome by adding anhedral (or is it dihedral that points up ?) at the axis.
@@LessAiredvanU How about an twin intermesh rotors in a 'V' shape. Each rotor would be about 7 feet in length, the mast could be shorter, it would be easier to balance. No rotor slap at all. Of course the intermesh mechanism would make the mechanics a little more complex, however, in my opinion, the craft would be much more stable, be able to carry a heavier load with better efficiency. I am not an engineer but I have seen dual intermesh copters and when I inquired about them, the answers were. Lighter craft, better efficiency, carry heavier loads.
@@ew4096 You would have to regulate the rotors in some way, otherwise they would collide when one rotor was under more stress owing to manoeuvres. Once you do not have a freely pivoting rotor head the autogyration becomes difficult. The Russians. long time experts on intermeshing rotors, have returned to contra-rotating blades. This would, on a autogyro, make for a tall mast to allow both sets of rotors. Pre-rotating would be an issue then, but a bonus would be that the centre of gravity becomes higher and then engine installation is a lot easier to manage. If you can move away from hydraulic pre-rotation to electro-magnetic methods then you could have a very stable aircraft with a narrow rotor radius.
Of course, intermesh rotors would create a somewhat more complex, however, a light, non-slip differential between the intermesh rotors would still allow free play and maintain the intermesh without rotors colliding with each other. Another benefit I see, is reduced length of rotors and as I mentioned earlies no rotor slap. I have seen those contra-rotating blades, the mechanism much too complex for an autogyro, and no real benefit. As you mentioned the CG too high. CG should be as low as possible. There is not need for a prop engine, there are enough small jet engines which would fit the bill for propulsion quite well. Why is everyone gravitating to ROTAX engines, when converted automobile/outboard engines seem to be a much better and less expensive alternatives. Gyro manufacturers are not willing to let go or buck the ROTAX monopoly. Gyro are suppose to be simple uncomplicated flying machines, however, they are used within a small geographical area due to its inability to carry enough cargo. I am willing to hop three hours from airport to airport, however, I am not leaving my underwear behind. (LOL)
Looks like they are doing what the AH64 (and other helicopters) did with the tail rotor configuration. (increases tail rotor authority) More blades means more lift for more weight carrying or same original weight but more maneuverable. Mounting two semi-rigid rotors next to each other makes for a simpler system then making a rotor head to attach four blades. Semi-rigid do not need drag hinges and drag dampers. Whereas rotors using 3 or more blades either need drag hinges and dampers or a flexible blade that can absorb the forces. As blades rotate around they flap (move up and down) to balance out the difference in lift between the advancing and retreating blade in forward flight. This flapping causes each blade to speed up (when flap up) and slow down (when flap down). The semi-rigid two blade system hinges (under slug) so that center of gravity does not move as much when the blades flap which reduces the blades wanting to speed up and slow down. Eliminating the need for drag hinges and dampers (complexity).
@@singinchicken Not during powered flight; however when practicing or experiencing power loss, you are taught to apply opposite rudder so that the body does not counter rotate against the rotors. This would not occur with contra rotating blades (although then you get into the issue of ensuring there is sufficient distance between each set of blades so there is minimal turbulent air for each set to work with).
Mounting two semi-rigid rotors next to each other makes for a simpler system then making a rotor head to attach four blades. (check my Jamal Rey reply for more details)
Any first-year freshman rotorcraft engineer will tell you that the higher the center of lift of the rotor disk is from the gimbal axis, the harder it is to change the angle of the disk to maneuver the gyroplane. If you want a four-blade rotor, this is the worst way to do it. I guess it might make sense as a proof of concept before going ahead with a more expensive hub, but as a practical rotorcraft this gets a D-.
@@cameronlapworth2284 Thanks, What sort of cracks, to what sort of blades? Searched but can't find any information. Web site appears to be very limited. does not look like it actually exists.
@@ramjet4025 there were two that tried it here in Australia on was a blade manufacturer Gerry Goodwin was test flown by my instructor. Worked well blades ran up very quickly probably due to on set always being into wind at any moment and the power required to lift two people was very low. Very low take off speed too. Gerry was going to build very narrow chord and shorter rotors. He didn't pursue it further than a few tests because he knew it would need lead lag hinges. Another club member who'd build a few nice gyros experimented too. He flew them for a few hours until cracks started forming at the root end of the blades where they attach to the hub bar (from memory) this was about 16 years ago so not likely to be on the web. The two per rev vibration is designed to be absorbed by the flexible mast - see the bensen design manual. If you put lead lag hinges on problem solved but starts to get more complicated.
