a more modern wind generator??

[N74DV]

In rc gas powered RC helicopters we use small brushless motors connected to the engine crankshaft to generate power so small on board receiver battery packs can be used and flight time is limited only by fuel.

the entire setup with motor and rectifier/regulator is about 4 oz. Good for up to 7 volts and 10 amps.

so, I got to thinking... Instead of using the MAMMOTH original wind generators why not use a small brushless motor with a prop (maybe a 9x6) connected to a recitifier/regulator? With the proper motor and propped correctly It would be a simple task to get 14 volts and as much as 15 amps or more. Weight would be a whopping 6 ounces plus whatever it would take to mount it.

here's what we use in gas helicopters

http://mysite.verizon.net/vze49gsg/

can something like this be approved by he FAA to use in a Tcraft?????

[rcefird]

Re: a more modern wind generator??

Interesting. However, the RPM range is 4000 plus with really high rpm's to get the petter output. Can they be engineered to produce good output at lower rpm's. I doubt a propeller/wind driven device will reach any such rpm's, or will it?
Randy E.

[N74DV]

Re: a more modern wind generator??

it all comes down to using the proper motor.

a lower kV rating (volts per thousand RPM) would do it. It's not unconceivable to get 6,000-9,000 RPM at about 90mph on a 9" r/c prop. My guess is a Hacker

[flyguy]

Re: a more modern wind generator??

hello test
Ok, now it is working.
I was thinking a while back about some kind of generator using ram air and a vacuum or low pressure generating tube like a venturi to drive a high speed turbine instead of a prop. I think the generator mentioned here might be a good one to use with such a setup. One could either get a one-plane approval for an experimental test to collect data or just stick it on the plane for a test. Could also be tested on an auto. It would be a low torque high rpm device. Originall I was thinking about an internally mounted with vacuum and pressure tubes to the outside, but I think a small streamlined externally mounted one would probably be better.

I would be interested in discussing such a design and seeing what could be put together.
Darryl

[N74DV]

Re: a more modern wind generator??

I have several 3 phase AC brushless motors on hand that I use to power my unmanned aerial photo choppers. One I have is a ZPower Z50-600. capable of pumping out at least 45 amps at 15 volts.

According to my math if I could spin it at 8,500 RPM I could output about 15 volts which could then be rectified and regulated to about 14 volts. A 10" diamter, 8" pitch prop should get about 9,000 RPM at 80mph under load. I would need to do some testing with a car to check those numbers.

I'm positive this could be done and would be a great lightweight solution to the stupidly huge and heavy old school generator.

[flyguy]

Re: a more modern wind generator??

That is over 1/2 a kilowatt. I wonder if a small alternator would handle that type of heat/power for any length of time. Some percentage of that will be turned directlly into heat inside the alternator. Don't know the numbers, but it would be maybe 10% = 60 watts.
Anyway you want to email me on this?
Darryl

[midniteflyer52]

Re: a more modern wind generator??

Hi,
Some years ago I purchased plans from a fellow advertising in EAA's "Sport Aviation" who took a bicycle generator and mounted a model plane prop on it. With some other electrical components and modifications it was supposed to generate enough power to charge small battery operated devices like handheld radios and GPS's. The whole thing could be built for short money but mounting it on a certified aircraft could be a problem. A neat idea nontheless.
Regards,
Glen Brodeur
Putnam, CT
TF#42

[N74DV]

Re: a more modern wind generator??

That is over 1/2 a kilowatt. I wonder if a small alternator would handle that type of heat/power for any length of time.

for reference, the same motor in my helicopter is capable of putting out 50 amps at 42v, roughly 2kw and it only heats up to about 70° above ambient. The motors are about 85-90% efficient so your estimate of 10% wasted to heat is about right. They are designed to shed heat very efficiently though. The outer can of the motor has the magnets and is what rotates and has a fan on the end that pulls air through. The core (windings) do not rotate. I am not sure it could not run reliably at 2kw for hours and hours, but only putting out 700 watts should be something it could do 24/7, 365.

Anyway you want to email me on this?

message me your email and we can talk.

[cpirrmann]

Re: a more modern wind generator??

Seems a solar panel on the dashboard to trickle charge a battery would be easier. My concern otherwise would be the capacity of the motor to generate enough current to operate all the devices. In my case, I'd like radio, lights, gps, cd player, intercom and maybe even a portable transponder.

[VictorBravo]

Re: a more modern wind generator??

Several of us have been thinking about this issue for a while... there is indeed something there worth pursuing!

Take a smaller brushless motor and hook it up to one of the better R/C model planetary gear drives, so you get the RPM out of the motor to create more power, but using a lower "input" rpm from the propeller. Super high RPM on a spinning 9" propeller hanging under the airplane where rocks and gravel are flying around is not such a great idea IMHO.

Flyguy's idea of a ducted fan based system is good, and as you may know there are several very well made brushless EDF units out there.

IF you can find a good quality planetary gearbox that will run the motor at 10K RPM or so on a 4 to 1 gear ratio... then you can also seriously consider hooking it up to the stock Continental tachometer drive on the back of the engine. The brushless motor has less resistance than an old tach cable.

Make a weak link "shear" coupling, so that if the electric motor / generator seizes it will shear a purpose-built groove in an aluminum or plastic shaft and not impart any problems to the engine. THIS is what will make the FAA happy, a fail-safe situation where a catastrophic failure of the new part will not harm or impair the rest of the airplane. It's common sense too.

Mount the brushless generator on the rear of the engine at the tach drive, you'll have to make up some kind of adaptor with the shear shaft and the gearbox. Put some sort of a heat fuse on the back of this assembly so that if the motor, gearbox or wires get real hot it will melt something and cut the electrical connection... that's DOUBLE fail safe and the feds should like that too.

Then run the three wires inside a firesleeve tube back into the cockpit with a grommet at the firewall. Continue the firesleeve or at least a rubber tube for electrical insulation all the way to the brushless controller/rectifier, which IMHO should me Adel clamped onto one of the fuselage tubes some distance away from the fuel tank. Then finally you can run two plain wires (by now with only with 14 volts and a few amps) to your avionics bus.

You can use one of the STC / TSO electric tachometers because you used the stock tach drive for something else. Or there is a way to use the RPM/voltage from the brushless generator to give you a tachometer signal. That's how electric tachs work anyway.

In order to do this completely above boards you will have to get a temporary "flight test" airworthiness certificate, and have someone with an A&P license there within eyesight of you while you're doing all this.

When it comes time to have this approved, I happen to know there is an immensely talented, sincere and Taylorcraft-friendly FAA DER someplace in this sandbox, who also happens to be a specialist in engine and engine related modifications. He might be off someplace wingwalking on a Jenny in glorious black and white, but you can usually find him around here sooner or later

At the end of all this, if you manage to make it work safely and have the FAA approve it for an STC (which is a big project, do not underestimate the power of the dark side!), then you will have a product that will be very much in demand. All those thousands of 65 horse airplanes can now use a better radio, a built in radio, a built in GPS, charge their avionics, put in a transponder, etc. etc.If you can sell something like this for $499 and make a $250 profit on it, I'll bet your newly built hangar out there in beautiful Arizona will be paid for in cash.

[N74DV]

Re: a more modern wind generator??

interesting idea but with the aircraft essentially having an "engine driven electrical system" would cause those who live inside the 30nm vail of Class B require a transponder... no?

Or does the FAR read if the aircraft was "originally certificated" with engine driven electrical system.... does that mean you can add one later and still not need a mode C transponder? hmmm...

Or there is a way to use the RPM/voltage from the brushless generator to give you a tachometer signal.

yes, there is a sensor that I have on my helicopters which attaches to two of the three leads on the motor that sends pulses to my data logger that will read out rpm.

I could get my hands on a very low kV brushless motor, something like 200kv, and air drive it with a prop. The newer composite props are pretty tough. That would only require about 3,000 rpm to generate enough power for radios, intercom, and such. Brushless edf like this would possible work too but may be much noisier. I had two of these on a scratch built Cessna Citation I built and it was very noisy.





I'll still look into it further. I will for sure build one and test it hanging off the side of my truck driving between 50-100mph and see what happens. I've got a watt/amp/volt/rpm logger that I can hook up and gather some data.

Sounds like a winter project.

I'll bet your newly built hangar out there in beautiful Arizona will be paid for in cash.

I wish.... If I only had an extra $95,000 I could buy one.

[Forrest Barber]

Re: a more modern wind generator??

excellent thread I feel like a caveman when reading this stuff. OUR very own Balsa Bees Model airplane site at the rear of the airport has all these newest of the new motors, they are building me an electic RC model to paly with at the moment. I will approach them about coming up with a power sopurce, ari driven, We did this here a long time ago with an air driven, ducted fan alternator that had a strobe running on a gyro plane all the time Ultralites too. This was in addition to the induction one off the engine. Very interesting

[flyguy]

Re: a more modern wind generator??

It is a little early in the am to be thinking this much, but after thinking about it I believe I see my Idea of a enclosed turbine has a problem.

If using a "long" prop (compared to a turbine) the alternator is working from a high volume of air at a lower velocity to produce lower rpm X higher torque = HP= watts. If it is a turbine (smaller diameter) you are using less volume at a higher velocity to produce higher rpm X lower torque=same HP = same watts.

I'm not sure how to efficiently get the high velocity with adequate flow.

I think that whatever gizmo such as ducting, a venturi, or whatever, will have the same kind of problems as just sticking a alternator with a prop out in the breeze.

BUT--If area of high and low pressure that were close together could be found it might work by connecting the input and output of the turbine by short ducts (tubing?) to the outside and mount the turbine inside the fuselage.

Kinda fancy, but slick if it could be made to work. I'm going to kick it around some more.

That's all for now, my coffee cup is empty.
DC

[cpirrmann]

Re: a more modern wind generator??

Or you could have a 'pop-out' generator like the emergency ones on the big jets. Right next to your retractable machine guns. Or does most everyone just fire them out the door ?

[3Dreaming]

Re: a more modern wind generator??

Or you could have a 'pop-out' generator like the emergency ones on the big jets. Right next to your retractable machine guns. Or does most everyone just fire them out the door ?

Mine aren't retractable. I just mounted them on the jury struts with a string to the cabin. Sights mounted on glare shield and cowling. Tom