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Forum Index : Windmills : wind charging system for Airplane
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Ronwend523 Newbie  Joined: 02/03/2018 Location: United StatesPosts: 7 |
Now I know this will be off the wall from the normal post but I am trying to swim in an area that I know very little about. I am building an Ultralight Aircraft that has no charging system for the battery, on the engine. I have seen articles online, that wind generators have been used on aircraft, in the past. My idea is to use a small permanent magnet motor and somehow funnel propeller thrust and forward motion wind to spin this contraption. All the while keeping the weight and size to a minimum. An idea I had was to take a small squirrel cage fan and reverse the flow of air, using a flex hose coming from the front area behind the prop and into the exhaust outlet of the fan and spin the turbine. This all in place, I have not a clue as to the motor to use, how big to trickle charge the battery to keep it up, what items are needed besides the motor generator. Diodes, rectifier, regulator and the such. If any of this makes sense. Can anyone enlighten me? Thank you  |
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| electrondady1 Senior Member  Joined: 12/02/2009 Location: CanadaPosts: 208 |
it would be simpler to use the engine to generate power. there must be something like a magnet and coil on the flywheel to generate ignition voltage. perhaps another coil could be placed in there for your power needs. |
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| Trevorc Newbie Joined: 26/02/2017 Location: United KingdomPosts: 22 |
Hi, I don't know a great deal about this, but it may be worth exploring sites like this one:- http://www.aviationconsumer.com/issues/48_9/maintenancematters/Battery-Upkeep-Charge-It-Right_6974-1.html. It seems others have similar problems. Hope it helps. Trevorc |
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| George65 Guru  Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Any sort of "wind" system as you allude to will be horribly inefficient and create a lot of extra drag, reducing performance and likely affecting handling of the aircraft. There would also be the safety and airworthiness concerns that any inspector certifying the air frame is bound to have. You would be much better off to have a small alternator driven from the engine or as mentioned, add an additional coil. That is probably not even necessary. What sort of Motor are you using? Either there must be some sort of charging Circuit available or the thing is magneto ignition which is the likley bet and does not need electrical power. If you need the battery to power avionics, it should be a simple matter to work out the amount of current draw they have and size a battery like a Lipo to give you the power you need with a healthy reserve and just run from that. A battery with generous capacity is likley in the end to weight less than a charging setup and if your endurance is short, it's almost certain. Investing in a couple of batterys so you can swap one out while the other is charging on the ground from a vehicle for instance is probably a cheaper way to go in the long run as well and be much less complicated. The bottom line is a battery only has to last a bit longer than the fuel supply. |
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| greybeard Senior Member Joined: 04/01/2010 Location: AustraliaPosts: 161 |
Try this for some ideas. piper cub windgenerator |
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| Ronwend523 Newbie Joined: 02/03/2018 Location: United StatesPosts: 7 |
The engine is a Half VW aircool. There is no flywheel as the propeller does that job. It is running of the standard 009 distributer and would run for a long time on just the battery. I was just kicking around an idea of how to keep the battery charged using a small setup charging system. There are no opportunities to run anything of this motor as in belt driven alternator or generator. The reply by greybeard is the article that gave me the idea. |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Is there any possibility of glueing thin flexible solar panels to the upper surface of the wing? As for motors if you look at the motors used in RC aircraft now that have permanent magnets in them such as this one. They are a 3 phase device so you would need a 3 phase rectifier, some good things about these is they are very light at only 48 grams and being brushless could be more reliable. You would need to play around a bit with the size of the prop on it to get the current right. Older outboard motors had no regulation and just put 4 amps into the battery regardless of it's charge. But you are probably using a much smaller and lighter battery, a regulator something like this might be a very good idea. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Light aircraft use magnetos not the usual dc powered automotive ignition. There are usually dual magnetos (called right and left) and two spark plugs per cylinder (for reliability). A single magneto would be ideal on an ultralight.  The battery is only really required for engine starting, but once running the engine will keep going by itself without requiring external power. Agree with the others here, an engine driven charging system would be much better. Belt drive is going to be pretty much impossible to do because you cannot just slip a drive belt over the propeller ! How about friction drive through a spring loaded rubber faced roller ? Cheers, Tony. |
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| greybeard Senior Member Joined: 04/01/2010 Location: AustraliaPosts: 161 |
Not all aero engines use magnetos. Yes, most piston engine aircraft in commercial manufacture do but the OP is talking about an auto engine conversion that hasn't had a magneto added to it. In this instance ( half vw conversion running a coil ignition) it requires a battery. The engine would be hand started (ie swinging the prop by hand so no electric power needed for a starter motor. The trade off is the inconvenience of having a battery big enough to run the spark for longer than there is fuel in the tank and having to recharge the battery between flights. There are also potential weight issues but I'm not going into that as it's off topic. Choices are pretty much as others have mentioned, light weight flexible solar panels, wind generator or external charger between flights. The wind generator that I linked to earlier shows a couple of examples and gives a real life indication of how much drag it creates. Taking things back to the original problem, I'd be inclined to seek input from homebuilt aviation web sites. Recreation Aviation and search around vw conversion sites as it is a known issue with some conversions. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Run a magneto instead of a Distributor. I know they are made because I had a bit to do ( sadly) with VW performance nutters and have seen them. |
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| Ronwend523 Newbie Joined: 02/03/2018 Location: United StatesPosts: 7 |
Thank you guys for your input. I'm waiting for spring so I can work in my garage and continue my plane construction. I've been kicking around ideas like this one, in the mean time. I'll have to see what I can come up with once the engine is complete and on the plane. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Just had a crazy idea. Never tried this or seen it done anywhere, so its pure speculation. If you do fit a magneto, there will be a terminal on the magneto that is wired internally to the points and the primary of the magneto coil. The purpose of that is to fit a grounding (ignition) switch that is what is used to stop the engine. When the engine is running, there is very likely to be some fairly high voltage pulses and some severe ringing on that magneto connection whenever the points open, and the ignition fires the spark plug. You may be able to recover some small amount of energy from that, with some diodes and capacitors connected as a charge pump. Maybe even enough to charge a very small battery without reducing the ignition output, as its really free energy just going to waste. You would need to check with an oscilloscope to see what is actually there, and with a bit of luck it may be possible to recover some small amount of dc power from just the magneto. Even just a watt or two might still be worth having. EDIT ** If I get motivated enough, I might fire up my Briggs and Straton lawnmower, and see what the magneto is doing with an oscilloscope. See if I can steal some free power from it. Cheers, Tony. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I have seen quite a few rotax 912 engines running an external alternator, the kits bolt a pulley to the back of the prop flange. http://sportpilottalk.com/viewtopic.php?f=19&t=3004 there is a couple of photos if you scroll down. there is a thing called a small engine alternator, I have seen them on yanmar Kawasaki and John deere stuff around the 20-30 hp range. picture ride on lawnmower size, they are a 20 amp permanent magnet alternator and quite small, might be worth checking out.  I'm confused, no wait... maybe I'm not... |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Out of interest I looked up half VW engines and found that some people are running the normal aircraft maggys off the back of the engine. While I like the power from the magneto idea, I'm wondering if there is anything needing powering other than the ignition? If not and you have a maggy installed, then there will be no need for the power in the first place. I did see some pick where the backing plate behind the prop seems fairly large. Would seem to be an opportunity to screw some neos on there and have a coil mounted on the engine to make some power. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I just hooked up my oscilloscope to the lawn mower magneto. There is thee fifths of bugger all power there to be had. The capacitor across the points kills any ringing or excess voltage. So forget that idea. Cheers, Tony. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Seemed like a perfectly Feasible Idea! Any possibility to convert the HT to something useful? A VW ( or aircraft) mag will be 4 cyl and this engine is only 2 Cyl so there will be 2 spare outputs. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Maybe... But it would need to be tried, and I have nothing suitable here to test. If 100v to 450v of dc could be generated, then one of those small direct off line postage stamp sized switching power supplies might work. There should be more power on the spark plug side, perhaps 30 to 50 millijoules of energy per spark. Firing once per rev (using the two missing cylinders) that would be 33 pulses per second at 2,000 rpm. Thirty millijoules x 33 is 0.99 watt seconds per second, about 1 watt as a pessimistic guess, if that energy can be recovered. Its not going to be a vast power source, even if it works. But if it can be made to work, its power for nothing with zero added weight. Cheers, Tony. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Here is how one manufacturer fits an alternator to the crankshaft. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Ronwend523 Newbie Joined: 02/03/2018 Location: United StatesPosts: 7 |
Ok I'll try clarify some points. I have no room for a mag on the rear of the 1/2 VW engine. I am running a standard VW distributer which will run for some time on a small battery but when the battery is low it would need a charge up on the ground. There is no starter on the engine. It is prop started. I have thought of the small lawn mower alternator which is basically a permanent magnet motor. I'm not sure of how I could put a pulley on the back side of my prop hub. I have experimented with a 3" squirrel cage fan housing, attaching small brush type motor( not sure what it is) to it and blew air from a shop vac backwards thru it. It produces about 11.5 volts at unknown amps into a 12v lithium battery. Now my thoughts with something like this setup is to run a 2.5" flex hose inside the engine area to the front behind the prop, catching the prop wash and spinning the squirrel cage mounted inside the cabin area. No drag created on the plane. The charge would go to a charge control and to the battery keeping it topped off with charge. This plane is a Home Built design but the engine is up to the builders discretion as long as it is of a certain HP for the model being built. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Stupid question, is the prop on the crank pulley end of the motor or the flywheel end? either way there should still be access to the shaft, surely some system could be rigged up to get a pulley onto that shaft, or even mount something like that little permanent magnet alternator directly to the shaft with a custom made adapter? |
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