hovering aircraft

Greetings,
I am contemplating building an aircraft which would have a fixed propeller pointing down, allowing it to move up and down. I have a
reasonable amount of experience with "grounded" robots, ie on wheels, but have zero experience with air robots. As a first pass at design I am thinking about having two propellers which rotate in opposite directions with each propeller's torque negating that of the other. Also, since the ability to gain altitude is a function of how much air can be shoved downwards, I assume that larger propellers at slower RPMs is the way to go since that requrires less power than smaller propellers at higher RPMs.
1. Does the two propeller design sound like a reasonable way to go?
2. Is my assumption about larger propellers at slower RPMs correct?
Any advice on propellers, DC motors, etc would be appreciated.
BEN
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There is a sourceforge project going on about automated flying RC helicopters. Solving the torque negating will be your smalest problem. A real helicopter (that's what I understood you are describing) needs a swasplate etc. to controll nick and roll axes or in other words to be able to control it at all. Said project should serve as a good point of information. What techniques are needed to make such an aircraft is best seen by examining an RC helicopter.
Markus
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Ben,
A counter-rotating rotor design is an alternative to coventional helicopters. There are two products you should look at:
1. Hirobo XRB (do Goggle search) 2. Wireless Vectron (e.g. http://www.hobbypeople.net/gallery/544028.asp )
The later is a toy (apx. $30 to $40) with a styrofoam body. The body rotates clockwise while the propellor within the body rotates counter-clockwise. One can only control up/down motion.
The Hirobo XRB is a helicopter featuring co-axial counter-rotating rotors. Its rotor design looks very much like a conventional heli (e.g. swashplates). It is tethered to a handheld controller. One supposedly can control all motions (vertical, forward, aft, left, right, yaw, pitch, roll). I am not a R/C helicopter pilot. Although Hirobo says this is a trainer, I found this vehicle VERY difficult to fly. I am looking for a R/C helicopter pilot to provide help.
Sincerely,
Paul Oh Boondog Automation
On Sun, 30 Nov 2003, Ben White wrote:

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Paul Oh wrote:

Vectron's slightly more expensive version of the Flying Saucer has three motors, and you can control vectored thrust and steer the thing around the room. It takes a while to get the hang of it. It's not the same type of craft the OP was asking about, but it offers another approach.
http://www.hobbypeople.net/gallery/544027.asp
-- Gordon Author: Constructing Robot Bases (Forthcoming) Robot Builder's Sourcebook, Robot Builder's Bonanza
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I've flown RC helis for years. Even still have a website up but haven't updated it in a long time.
http://www.geocities.com/CapeCanaveral/Launchpad/6328 /
Too busy with school and robots are kind of the focus of my attention now. But in the back of my mind I've been toying with the idea of a robotic helicopter. Although I can tell you from experience flying these things that it would be no small task. Have you possibly looked into RC heli simulator software? I learned on a simulator before flying the real thing. Good enough to learn the mechanics of flight to better understand what a robot would need to do.
I remember awhile ago in this group that someone had posted they successfully designed a robotic helicopter but I lost the link. I would very much like to see that again. Best regards.
-Dave

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"Dave" <blank> writes:

There's been more than one person to do this.     http://avdil.gtri.gatech.edu/AUVS/IARCLaunchPoint.html     
http://avdil.gtri.gatech.edu/AUVS/2000AerialRoboticsCompInfo.html/TheAerialRobots.jpg
--kyler
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I am working on a similar project for an upcoming article. Stay tuned, and I can probably save you $$$$.
Mike

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Blueeyedpop wrote:

Did you ever get the GWS turbo fans to not burn out so readily?
-- Gordon Author: Constructing Robot Bases (Forthcoming) Robot Builder's Sourcebook, Robot Builder's Bonanza
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No Gordon,
Alas I did not. The grit and heat were killing the bushings. The shaft would get hot, and the plastic of the prop would melt. The prop, free from it's press fit shaft, would fly skywared like an accessory from a Lionel Train set. I tried everything short of putting in expensive motors and water cooling.
Mike

and I

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Blueeyedpop wrote:

Too bad; the prices tend to be pretty attractive.
As a BTW, if you're having engineering problems with another GWS product you're wanting to use, you can always go to their Web site (www.gws.com.tw) and hit the Forum button. There you'll find GWS engineering, sales, even the owner, regularly answering user questions and comments. Not all of the GWS folks write complete sentences in English <g> but I think you'd be hard pressed to see the same of a Hitec, Futaba, or some other R/C company.
Let us know when your article hits the stands!
-- Gordon Author: Constructing Robot Bases (Forthcoming) Robot Builder's Sourcebook, Robot Builder's Bonanza
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I have a lot of respect for the folks at Grand Wing Servo. I was looking into importing their stuff some time ago, but I didn't like the quality of their servos.
As far as flying craft are concerned, if you do not go fuel powered, you are insane. I am unfortunately insane. About the only thing that makes it possible, is carbon fiber and NiMH and Li Ion batteries. Even then, if you get 10 minutes of good flight out of something, you are doing well.

would
it's
Train
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Great. I look forward to it.
And regarding some earlier messages, I am not really looking to build a RC helicopter. The aircraft does not need to be pilotable in the x and y dimensions, just adustable in the z dimension (altitude).
Any further advice from anyone on motors, controllers, etc?
BEN
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Well,
You might try the ducted fan units. They push more than their mass, and 3 or 4 of them, with Hitec HS-55 servos, and some very careful construction might do.
Consider foam and carbon fiber as your only successful material choices.
I would consider trying to build it R/C first, then add a microcontroller in the loop. Have it stabilize the various axis of motoion with inertial sensors, and accept imput from the receiver to direct it's flight. In fact, it would not be a bad idea to build a single rotational axis that can be clamped into a vise on your bench.
Once you have a platform that "stays where you put it" then you have a good start at a robot.
Bear in mind, that a little bit of tilt will result in translation. I do not think that gyroscopic sensors will do everything you need to do. I think you will end up doing the 6 DOF accelerometer/gyro thing.
Look up: Tramm Hudson Kalman filtering
Consider accelerometers and gyroscopes from Analog Devices.
Presently, I am in the built it, know I can lift my controller, don't know if I can lift my sensors, and trying to pilot this thing phase.
I have built and flown R/C helicopters for 2 decades, but what I am working on is a bit different than that. It truly should be a fly by wire device, before I kill a cat, or breake a piece of furniture. Since it is electric, I am testing indoors, much to the dismay of my wife and family), and I will likely destroy the first unit befor I get it autonomous.
Good Luck
Mike

and I

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Check out this toy: http://www.google.com/search?q=Vectron+Ultralite+Flying
It's almost exactly what you described and is self stabilizing (passive).
Ben White wrote:

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Ben White schrieb:

Once I made a flying thing like the Orka from the command&conquer pc-game. It fly, but was not able to carry the battery. You should take care that one prop rotates left way and the other right way, otherwise the flying thing will go in one direction. See aerodynamic symmetry on some helicopters.
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