This could be a game changer
- Thread starter DennyR
- Start date
enjoytheride
Member
Definitely the first variable pitch quad I've seen outside of a research capacity. Would love to get my hands on one.
I've seen experimental code for variable pitch multi setups on Kk and Multiwii boards. If I get really bored this winter I may have a go at building one. All you would need besides the board with firmware is 4 servos, a set of motors with long shafts, 4 appropriate RC Heli tailrotor setups, and a bit of design and build ability to get it all put together. Having a metal lathe and mill in the garage would certainly help with the fabrication and I have small modeling versions of both.
That said I'd really like to see a close up of the one in the video to see how it was built, it obviously is very efficient and not at all slow or clunky. I've seen one that utilized 4 Trex 450 tailbooms with tailrotors powered off a central motor but I think the best way to do it is 4 motors with 4 servos if you can find the right bits to build it, very curious to know how this one is setup.
Ken
That said I'd really like to see a close up of the one in the video to see how it was built, it obviously is very efficient and not at all slow or clunky. I've seen one that utilized 4 Trex 450 tailbooms with tailrotors powered off a central motor but I think the best way to do it is 4 motors with 4 servos if you can find the right bits to build it, very curious to know how this one is setup.
Ken
redridinghood
Member
As usual I cannot see the link. Can someone be kind enough to copy paste the link for me? Thanks
enjoytheride
Member
Efliernz
Pete
As a diy'r with heli aero experience... I would like to see the finer points. In theory, this has been possible for ages. It is the fine tuning / smooth transition stuff that was always going to be an issue. Hopefully we see some real details soon...
Pete
redridinghood
Member
Why it's important for AP is the fact that the stabilisation is performed with a constant motor speed and a reliable mechanical servo response (like a heli) The engineering behind that is well developed and affordable. Throttle and pitch curve technology we already have. We only need a collective pitch function like a heli tail rotor (No swash plate). It could be devised with only one central motor.
The total reliance on a ESC changing motor speed to effect a fast thrust change is probably now as good as it will get which is not good enough. It has been the single most unreliable and poorly designed part of the MR evolution. (No point in having 800 or 400 frequency changes per second if the motor cant respond at that rate). That is why these small fun machines fly better than the big ones.
The future VP multi for AP will probably be a tri-copter with a servo driven tail (Yaw and pitch). That resolves the issues with fast descents with yaw movement. Also the less motors/rotors you have the greater the effective thrust area and overall lift efficiency. Auto rotation is here at last.
I think it is a breakthrough that will take over
The total reliance on a ESC changing motor speed to effect a fast thrust change is probably now as good as it will get which is not good enough. It has been the single most unreliable and poorly designed part of the MR evolution. (No point in having 800 or 400 frequency changes per second if the motor cant respond at that rate). That is why these small fun machines fly better than the big ones.
The future VP multi for AP will probably be a tri-copter with a servo driven tail (Yaw and pitch). That resolves the issues with fast descents with yaw movement. Also the less motors/rotors you have the greater the effective thrust area and overall lift efficiency. Auto rotation is here at last.
I think it is a breakthrough that will take over
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I have that problem with one of my MAC's It's your browser.
The more one contemplates the better it sounds. Proper auto rotation and the possibility to use a standard Naza-H controller. A single central motor, almost stock tail rotor booms turned at 90 deg. with any number of available rotor sizes. It raises the bar in every aspect.
Everytime your MR ESC makes a sudden change to the power demand the temps. go up and the efficiency drops. Time to get rid of that and run smooth.
The problem is that the more you contemplate, the closer you get to one of these......View attachment 8344 7Kg auw with 22 amp battery. When you fly one of these you don't go back.
Everytime your MR ESC makes a sudden change to the power demand the temps. go up and the efficiency drops. Time to get rid of that and run smooth.
The problem is that the more you contemplate, the closer you get to one of these......View attachment 8344 7Kg auw with 22 amp battery. When you fly one of these you don't go back.
Attachments
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yeehaanow
Member
I would have serious doubts about the ability to autorotate a craft that has a central motor and relatively small blades with their inherant low inertia. With the required gearing/ belts there could be a lot of friction.
Also, as we go up in blade size, don't we just get back to the vibration problems of a SMR?
Also, as we go up in blade size, don't we just get back to the vibration problems of a SMR?
nicwilke
Active Member
I agree with DennyR, and we could also assume the introduction of direct drive adjustment to the rotors, similar to the gimbal technology zenmuse, halo and tagv are all using. DD for precision adjustments with a single motor would be very efficient, even opening up the prospect of gas powered multi rotors.
I have flown those and still have several gathering dust on the shelf. One of the big disadvantages is the inertia built up in those large carbon fiber rotor blades, takes a while to slow or stop and that could quite literally be deadly in the event something goes horribly wrong with people nearby. By comparison dropping the throttle stops the props on a multi in almost no time at all and while that doesn't eliminate the damage of a heavy object falling from a height it at least eliminates the Ginsu factor...
In a VP multi you don't need to vary the motor speed, just as with a heli you can run the motors virtually wide open and let the variable pitch mechanism take care of the thrust factor eliminating the central motor and retaining the current setup of a motor for each prop. Utilizing idle up and throttle curves just as you would for a heli you can start up with 0 degrees of pitch and as the motors come up to speed all you do is increase the pitch evenly across all 4 corners to create lift then let the flight controller take over and vary the travel of each individual servo to change the pitch/thrust as needed on each corner, effectively the same thing as changing motor speed but in this case the limiting factor is how fast the servo responds to move the mechanical bits.
As for autorotation, without that inertia that the big heli blades have it will never happen on a VP multi, there simply isn't enough mass rotating at each corner to do it unless you're talking about a supersized M/R with something like 500mm blades on each corner at which point you might as well go back to a single rotor!
Ken
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DucktileMedia
Drone Enthusiast
I seriously doubt auto rotation will ever work on amulet I rotor. Blades have too little mass and how does it work unless all motors are off?
Well who said the rotor blades would be light or small, and Yuri we are talking about a single motor. The typical 720 size of blade that I use on the TDR (and most other modern blades) have lead cast into the leading edge of the blade getting heavier towards the tip. As far as mechanical drag goes it is minimal because the drive shaft has a one way bearing that disengages once the inertia is greater than the drive torque. Ken if a heavy lift MR hits someone it will be just as potentially fatal as a SR Heli - But there is about a thousand times less chance of a proper heli failing in the first place. Every other factor from stability, endurance, high wind rejection lifting power etc. etc. comes down in favor of a well designed SR heli. A VP Multi could be the basis of a sound compromise that will keep the die hards happy. Vibration - what vibration.
As with a SR heli, autorotation requires at least 6 degrees of negative pitch angle so starting at 0 would be a non starter...
As with a SR heli, autorotation requires at least 6 degrees of negative pitch angle so starting at 0 would be a non starter...
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Yes, the weight factor in falling from a given height can be just as fatal regardless of the the number of props but an out of control 700 class heli with blades spinning at 2000 to 3000 RPM isn't going to just stop those blades instantaneously, they're going to keep spinning until the come in contact with something, hopefully it won't be part of someones body. There is far greater potential for a large heli to be lethal at low altitudes than there is with an MR.
As far as 0 degrees of pitch go, setup as any 3D heli you get 0 degrees at mid stick, that's where you would want the pitch to be on a VP multi on motor startup, after that it can go either way into positive or negative depending on what you want to accomplish. Regardless of what amount of negative pitch you put into it, small tailrotor size blades just aren't going to autorotate well enough to be effective and the only way I could see them having any effect is on individual motors where there is minimal drag in the bearings. Add shafts or belts from 4 corners into a central motor and there's no way any small to medium size multi is going to be able to overcome the drag of all those components to autorotate. Make it big enough so that it can and you'll likely be well beyond the size of a 700 class heli which pretty much defeats the idea of a multi being more useful for close quarters and places where it's not feasible to fly an SRH safely.
Ken
As far as 0 degrees of pitch go, setup as any 3D heli you get 0 degrees at mid stick, that's where you would want the pitch to be on a VP multi on motor startup, after that it can go either way into positive or negative depending on what you want to accomplish. Regardless of what amount of negative pitch you put into it, small tailrotor size blades just aren't going to autorotate well enough to be effective and the only way I could see them having any effect is on individual motors where there is minimal drag in the bearings. Add shafts or belts from 4 corners into a central motor and there's no way any small to medium size multi is going to be able to overcome the drag of all those components to autorotate. Make it big enough so that it can and you'll likely be well beyond the size of a 700 class heli which pretty much defeats the idea of a multi being more useful for close quarters and places where it's not feasible to fly an SRH safely.
Ken
KapteinKuK has done the auto rotation trick with one of those little mxq quads, I think it was an accidental discovery with this model. [url]http://www.youtube.com/watch?v=uFU4y2zGpjY[/URL]
Ken
Well, it's a trade secret but my TDR's run at only 900 rpm. Due to the dev. done on blade design. The tips also disintegrate before too much impact damage.
Starting up at 0 deg. would not work because your throttle needs to be at 50% at 0 deg. if you want to be able to autorotate or fly inverted. Normal start-up usually has neg. pitch as it spools up.
You can switch to a different flight mode once in the air. I have a hold switch that shuts down the motor power so I can practice auto rotations (which I do frequently). I do this for a living and I have yet to find a job that was more suited to a MR. I do many jobs that would stretch the limit of what I could safely do with a S800. I would not trust any MR over the city center above 200 feet. Visual orientation being the most common disadvantage at anything beyond 100 feet against the light. The guys I work with say the same.
Well, it's a trade secret but my TDR's run at only 900 rpm. Due to the dev. done on blade design. The tips also disintegrate before too much impact damage.
Starting up at 0 deg. would not work because your throttle needs to be at 50% at 0 deg. if you want to be able to autorotate or fly inverted. Normal start-up usually has neg. pitch as it spools up.
You can switch to a different flight mode once in the air. I have a hold switch that shuts down the motor power so I can practice auto rotations (which I do frequently). I do this for a living and I have yet to find a job that was more suited to a MR. I do many jobs that would stretch the limit of what I could safely do with a S800. I would not trust any MR over the city center above 200 feet. Visual orientation being the most common disadvantage at anything beyond 100 feet against the light. The guys I work with say the same.
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