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Forum Index : Windmills : wind charging system for Airplane
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| George65 Guru  Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Without knowing the amps, you are flying blind, pun intended. The fact you say you got 11.5V into a 12v battery makes me think the battery was driving the motor not the motor charging it. You need to know the amps and which way they are going. A shop vac would have an airspeed at least Double what your plane will do. It would also generate a far higher pressure. Sorry, I can guarantee you that would be a complete and utter waste of time and effort. Firstly, airspeed even with propwash is going to be too low. Secondly, running through a flex hose with all the corrugations disturbing the airflow will kill air flow and pressure. Next, a blower fan does not translate well into a driving turbine. It will spin but the inefficiency is huge. Been there, played with it, learned the hard way. The power you would get would be lucky to power a few incandescent Christmas lights with this setup. Another thing would be if you are even going to attempt something like this, you want a 24V motor not a 12V one. You will have voltage drop for a start with diodes or a controller to stop the thing using power rather than generating it when landing etc. You need to get the battery somewhat above it's rating in order to charge. You can get a small cheap charge controller to take the higher voltage down and that will be much more efficient that trying to take a lower voltage up or having a shortfall. Again, I think you are wasting your time and money and creating problems for yourself. I come back to what is the endurance of the aircraft? If it's say 2 Hours and your draw from the coil is 4A you could have a 12Ah battery and have plenty of reserve power. Have a 2nd cell to replace that one for the next flight and charge the used one up from your vehicle battery. Far simpler, infinitely more reliable and most likely cheaper than a questionable charger setup. Really, you need to know ( and tell us) what the numbers are. How much is your ignition system pulling? How long is the flight endurance of the aircraft? what size battery are you running now? Unless you know the numbers, you are just wasting your time guessing really. You have no clue if something is going to work or if it is working unless you know the numbers you are chasing. If you don't know if you are chasing 2A or 10A then you have no clue how much power you need a generator to make or if it's even possible to get one to do that output with any practicality. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Another crazy idea. If you only want a few watts, one source of considerable untapped free energy is the exhaust pipe. Some kind of crude turbine might work, and so might a stack of thermoelectric cells. Plenty of air cooling available for the cold side ! Cheers, Tony. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
The thermos are not such a crazy Idea I don't think. Looking them up,6 40x40MM TEG's would produce a bit over 1A @ 14.4V. 24 of them in series/ parallel would produce 4A @ 14.4V. A useful current. They only need 100oC temp diff to do this which should be easy to achieve on an exhaust. If a Bit of rectangular tube, be it steel or ally were grafted onto the exhaust pipe(s) and the Tegs secured and located in the prop wash which wouldn't be hard, this could actually be a very viable solution. Tegs should cost well under $100. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Might be pretty hard to beat for size and weight, and no moving parts. Just start out with one cell as an experiment, and see how it goes. Cheers, Tony. |
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Ronwend523 Newbie  Joined: 02/03/2018 Location: United StatesPosts: 7 |
Holy Cow you guys. You just got this ol mans brain shifted to something I didn't know existed. That is so intriguing. TEGS WOW!!! I love to think out of the normal box and find ideas to accomplish a same result. There are so many ways to produce electric energy and I want to find an idea that will produce enough to replenish what the engine coil uses when running. You guys are so knowledgeable with this stuff.  Here is a pic of the engine. The exhaust pipe idea would work I think. |
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| Ronwend523 Newbie Joined: 02/03/2018 Location: United StatesPosts: 7 |
Maybe this Post needs to go to another place. It's not Windmill any more. It's getting interesting though. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Thermoelectric cells are certainly interesting things to play with, and I suggest you just start out experimenting with just one. Excess temperature will kill them, and that might occur after landing and you shut down the engine. The cooling air stops, but the heat from the exhaust continues for quite some time. Might be best to mount the TEG on a heatsink and duct the heat to the TEG, rather than mount it on the exhaust and duct cooling air to the TEG. A couple of thermocouples will tell you what is going on temperature wise, and you can experiment with different layouts. Something pretty simple should work once you figure out a way to keep both the hot and cold temperatures within reasonable limits. There are two different types of thermoelectric cells. Peltier cells are used for cooling purposes only and are very low cost. In theory they can also be used as TEGs, but when I tried that myself they produced very little output and always failed fairly quickly. I think it has to do with the materials and construction. For cooling purposes the temperatures are never very high on either side, so crappy low cost materials work fine for thermoelectric cooling. A TEG on the other hand has to run at a much higher average temperature, and the devices designed for cooling just lay down and die. Beware of Cheap Chinese Peltier cooling devices, I think you will be very disappointed. Proper TEGS will probably cost more and be a lot less common, I really do not know. Never really looked into that side of it. I have a fair bit of personal experience using Peltier cells for cooling applications, but have never messed with the proper TEGS for power generation. You could probably start out with just one TEG and do some initial testing on the kitchen stove. Cheers, Tony. |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
In order to do that, you have to know how much power that is. Passing it onto up would be helpful if you want more targeted ideas and not just guesses. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The ignition points will be closed about 60% of the time. So the average of the (ramping up) coil current will be about 30% of peak. If the peak ignition coil current could be(?) about 6 amps, so the average running current might be about 1.8 amps. Could be a bit more or a bit less than that depending on the particular ignition coil and actual dwell angle of the points. But a rough as guts guess might be a couple of amps at 12v Cheers, Tony. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I guess it all depends what your skills are, I could build the pulley, bracket and shaft adapter from scratch in a day, maybe two for a serpentine belt and springloaded idler. With electronics every time I make a mistake it is another two week wait for bits to come from china. I find if I have a project with more than 10 unresolved issues the chances of it making it to completion is pretty slim. I'm confused, no wait... maybe I'm not... |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Personally Id look at a pulley behind the prop(ie take prop off, fit pulley and refit prop), something like an old ford 250ci steel pressed single belt pulley could be adapted, and fit that small 20a alternator. Very little work and well capable of supplying the coil power eta no need for a serpentine belt and spring loaded tensioner, just a simple vbelt and old fashioned slipping alternator bracket aka old holden/ford would be more than adequate, much less weight and much less fabbing required   woops was a little bigger than I thought, resized |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
And if the draw is a couple of amps, I cannot for the life of me see why it would be worth the trouble and expense of having a charging system in the first place. Seems like doing something for the sake of doing it rather than looking at the best solution. The likely endurance of the aircraft will be a couple of hours max and with 2-4A draw, just having a spare battery to change out would be so much easier and a better solution all round. Would also be easy just to put some thin film solar on the wings with a controller seeing this won't ever be night certified. 2 of these collectors, little controller, done. Thin film solar Cell Still easier just to do another battery though. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
I always by the 2 dollar items 2 or 3 at a time. A spare +1 to cover poor QC. Maybe another for future projects. That could all change if they decide to add $5.00 to every purchase. One of my Ali binges was around $15.00, 9 items. Add 9 x $5.00 to that.... Phil |
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| George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308 |
Pretty Much the same. I can't say I have had enough failures that I get extra for that, but rather I tend to find other uses for things when I get them. Tend to have one thing in mind and then discover they solve another problem or something new comes up. I did order some controllers in 12V and 240 a while back. Connected one up the other day powered it up and promptly blew the snot out the thing. I couldn't figure where I went wrong hooting it up and even why it did eject it's magic smoke. Put it down to the fact I got a dud but then when removing it realised I hooked a 12V version to the 240V supply. Bugger, almost $2 down the drain. would have been upset if I couldn't reach into the box, get the right one hook it in and carry on. :0) Other thing is, so much of this stuff is so cheap, I feel bad having 1 thing sent all that way for just a dollar. I want to make it worth my time ordering let alone theirs. That said, I am starting to get a LOT of this stuff saved up. Think I Od'd on relays but then again, last lot I ordered 4 relays and bases, got 8 relays and 6 bases. Bonus! I only actually wanted 2 but then changed my mind and only used 1. One thing I have stocked up on deliberately is MC4 Connectors. $12.50 a pair at jaycar, .74C on ebay from china. Been buying them 20 at a time with 20 in reserve. When I get to the next bag I order 20 more. Nothing wrong with the ones I have got either. Not like Jaycar's are made in Oz to higher specs. Another thing I have stocked up on is Jiffy Boxes. Got to put all this stuff I cobble together in something and they are so much cheaper ordered from OS. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I know the feeling, I needed a relay for my central locking, and it was so cheap, I ordered ten- was still under ten dollars with free postage... same relay from jaycar was $14 for one... |
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| greybeard Senior Member  Joined: 04/01/2010 Location: AustraliaPosts: 161 |
Saw this on ebay https://www.ebay.com.au/itm/CLIPPED-WING-J-3-Cub/323170262246?hash=item4b3e72dce6:g:BWwAAOSw3K1auJwI One of the pics has an image of a small windgenerator mounted on the undercarriage. Looks like a commercial solution but contacting the seller may give further info. |
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