RC copter camera platform, scratch built

[jstuedle]

I am not positive this is the proper place for this topic, if not, CNCadmin, please move. (tia) I am in the very early design phase for a “heavy lift” RC chopper to use as a stable camera platform. There is a lot on the net about aerial photography, ranging from weather balloons to kites to model rockets. But all are lacking the stability I desire. This would strictly be hobby related, but one of my other interests is Simi-pro photography. Anyway, to the idea. It has been done before, for very low-end toys, but I want a twin-rotor craft, using counter-rotating rotor blade assemblies. Fixed pitch for simplicity and reliability. Both rotors would share a common axis, about the centerline of the craft. No tail rotor would be employed, but maybe two thrusters on pods extending from the main chassis that could be controlled independently. Forward and reverse thrust could spin the craft, or used in tandem made the craft to propel itself fore and back. Again, the concept has been used to steer RC blimps, and the lift system has been used to power cheep play toy copters. But I wish to use it with a hanging payload of high-end photographic equipment. I wish to use commercial, replacement rotor blades. How would we calculate the lift, stall and desired RPM at certain prealligned pitches? What would be the power requirement to turn a pair of 600 mm blades at say a 22 1/5 degree fixed pitch, and what size payload could I expect to lift? Oh, and another little requirement for this little toy, no fuel to damage the precious payload, we need to use an electric motor. If I cannot rely on a model motor to do this job, any suggestions for an alternative. Maybe the motor from an 18-volt Dewalt drill? Would most likely get too hot in near continuous use. At this early point in the concept, any ideas could be entertained.

[CNCadmin]

For electric power a dewalt would not be a good choose, but a hacker twin geared properly would be.
Fixed pitch main blades will not provide the need stability your looking for. It really would need to be collective, as for blades their are may types of blades one in particulate is a blade designed for high lift.

[jstuedle]

If I have the payload in a hanging “platform”, using it to help stabilize the craft like the tail of a kite, would I not be able to use fixed pitch blades? This is the concept used with many small (18 ft.) blimps and round weather balloons with payloads. But they typically lift 14 – 16 oz. I am looking for 4 to 7 lbs. of gear dangling about 36” below the airframe. (PS, after mentioning the dewalt, I realized the error in the thought.)

[CNCadmin]

The problem with fix pitch is that it can't react to cyclic and collective pitch change quickly, there is a delay. That is on reason that collective can be made to be allot more stable. A danging object on helicopter platform will do little to provide stability in fact to opposite may be true.

[jstuedle]

Would you build it with collective on both rotors, or just the upper rotor? I would think if both were setup, not only would it be a design nightmare, but a programming hassle.

[CNCadmin]

You would have a bell-hiller mix type head in that you would have the rotor collective and a fly-bar system for stability.

cherck this site out- http://www.bergenrc.com/Observer.asp

[foamcutter]

Just a thought, Do you know how to fly a model helicopter? I fly R/C airplanes and have been around the helicopters and watched several people learn (or try) to fly them. They are not for the faint of heart. They can also take some people a very long time to fly well and even longer to fly with enough confidence to hang several thousand dollars worth of gear off of. I would recommend you find a local R/C club and get to know several helicopter flyers and get familier with the equipment before starting to try and build one. Most flyers are happy to show off their models and give you information. They can be VERY expensive to repair or build. Just my .02 worth. Good luck it's a cool idea. Ron

[jstuedle]

Let me answer by saying that anything worth doing is worth doing well. If this gets built, it will be made to work and I will invest the time and talent to make it work right. I know I have technical problems to overcome. What I had in mind was a craft that would accelerate and climb vertically based on rotor RPM alone. Both rotors would turn in opposite directions at exactly the same speed on the same axis/centerline, locked by gearing and driven by the same motor eliminating the need for a tail rotor. If the craft needed to be tethered, so be it, and for safety reasons, that might be acceptable. My planned use was to be able to go on location, climb vertically 200 to 400 feet, get the shots and recover the craft. If what we are saying, is that stability after the technical obstacles are overcome will be an issue, any other ideas? As mentioned, weather balloons are a pain, a large balloon capable of lifting my payload would require several hundred cubic feet of helium each flight. Cost per flight would be in the hundreds of dollars and prep time per flight prohibitive. Fixed wing aircraft are limiting due to the space required to launch, recover, and loiter in the area. Also, the speed and motion of the craft would not lend to crisp and sharp images. Rocketry of out for similar reasons with a few additional concerns. If built, I will learn to fly it and fly it well as I have fixed wing craft. It’s the physics that I need to work out first. For this project to work, I need size and thrust data, motor requirements so that aprox. weights may be calculated. I have done a lot of groundwork on this concept, just would like some additional input. TIA.

[whiteriver]

Unfortantly I have no good input on this other than I just want to subscribe to the thread.
I have wanted to do exactly what you are trying except I want a wireless setup on it to beam back the video and to use as a wireless access point for long range use.

Donny

[jstuedle]

Does anyone have a feel for the total lift in lbs. of a typical .60 size rotor, and at what RPM rotor speed that lift is attained? This would give me an idea of the size electric motor and power requirements I need to factor into the design. Also, is there a line of high-end motors that have output shafts on each end? This will simplify my design. If I need to use a single shaft motor, as I think I might, I will need to include a jackshaft, and two more gears. While not a major issue, it will require 4 more bearings and the additional weight to consider.

[jstuedle]

“except I want a wireless setup on it to beam back the video and to use as a wireless access point for long range use.”

Donny, for your application, there are a few camera/transmitter packages that total only a few oz. And are well within the capacity of most .30 and up size copters and fixed wing. One that comes to mind can be located at http://www.blackwidowav.com/. For my use, I want to lift a gimbaled 35mm camera, motor drive and power zoom. I have considered using the video link to see “through the lens” attached to the viewfinder, but that is third of forth generation, well down the road. At this point, I need to get past the drawing board. As I get plans together, I might scan them and post if there is any interest. (Yes, I am old school and prefer pencil/paper to CAD)

[whiteriver]

Thanks for the link. I'm checking it out now. If you do build this and decide to publish the plans I would be very interested in them. I have a nice cad program but still prefer to draw by hand 99% of the time.
I checked it out and its not quite what I need. I will need a camera that zooms way in for candid wildlife shots etc. Also need to run a true wireless access point like a apple airport. Maybe a windows ce device running at 500mhz to control the Wap. Anyways. Will probley need much more power than a 0.60 chainsaw motor. Also would like electrical so that it doesn't desturb the animals.

Donny