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Forum Index : Windmills : VAWT Idea - input wanted
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| KiwiJohn Guru  Joined: 01/12/2005 Location: New ZealandPosts: 691 |
It is not necessary to gybe the sails if they are arranged so that they can rotate about their vertical 'mast'. In that mode they would never be turning their back to the wind and would be tacking instead of gybing. |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
John, I believe it could possibly work as you say, a diagram would help a lot to grasp your idea  .
I'm seriously considering adapting my non performing Lenz II to movable wings so some useful power can be got of it. At the moment its just a rotating bird perch  .Klaus |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Klaus, I am not very good on the diagrams for things that are really only a concept in my aged brain. 
The sails/blades would be arranged so that (considering a clock face with wind from 12 o'clock) when in the positions 9 through 12 to 3 the sail/blade is angled to the right and between 3 and 9 the sail is angled to the left. I am not exactly sure of the mechanism that could ensure this but I guess it would be like what there is on the front of a harvester machine that keeps those little tine things vertical! Maybe!
John |
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| skgtheblij Newbie  Joined: 14/10/2011 Location: EthiopiaPosts: 8 |
Thanks for all the replies and advice. For now, I have already ordered the gearmotor (which doesn't contain any worm gears) so we'll see how that works. I actually probably won't get to build it until I get home for winter break in December. I'm using a chain to drive the motor (partly because I want to put it in a shelter) so we'll see how that goes. I was going to use a belt, but I think belts won't work in such a high torque system. And you are right, this may not last very long; I'm not expecting it to really. This is mainly a proof of concept. If I can get it to work for a little while then I will have succeeded in my mind, because with the proper equipment a real gear system could be created (ideally one with an automatic transmission that changes based on wind speed) When I get around to actually building it, I will document it well, and post results. Caleb |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Yes, maybe might be right . The harvester 'tines' are being pushed against a stop during their power stroke I assume and gravity keeps them vertical on the return stroke.
My aging brain can better deal with a working model so I guess I'll build one. What you suggest might be done with a eccentric arrangement but that would make it way too complicated, I saw a special ship drive (Voight Schneider?) that works on that principle, its used on tugs. Klaus |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Crew Pardon my late arrival on this thread, but I thought I'd pop in anyway for my 2 cents' worth: I've tried using sails on a VAWT and found part of the total rotational pathway of each sail is wasted on the mast moving to such a position that the 'luff' is taken out of the sail and it actually pulls or pushes the rig. During this time period, the entire rig must "coast" using its momentum until the next-in-line sail fills and begins to gather power. There's also a whopping "bang" as the boom switches sides from one to the other and that tends to shake things a bit. This could be offset somewhat by running the sail "close-hauled" but then you give up on the length of the power stroke, as it were. If the entire pathway of sails is made so there are many sails and a very large rotational field (ginormous diameter), much of the banging could be lessened. Doing this would as well take more advantage of each sail's short window of opportunity; using many sails would "smooth out" the run. Having tried all the above, I built one VAWT that had nylon "pockets" sewn into a large sheet. The sheet was wrapped around a central cylinder, which was attached to a vertical axis. As the wind hit it from any direction, some of the pockets would fill and push, while the rest collapsed and coasted. This gave push on only one side and made it a truly "drag" machine. I found out also that the forward momentum tended to collapse somewhat even the "full" pouches and that action helped lessen the amount of torque produced. All in all, I didn't have enough positive experience using sails in a VAWT situation to continue my efforts. Using sails on a HAWT however, has been done successfully for years in the Netherlands. The ONLY successful VAWT I've ever built was one that housed a flat sheet of Styrofoam housed in a carrier mounted to a shaft all within a cylindrical housing that had short fins sticking outboard every few inches. The shape of the cylinder captured wind and caused it to spin (like a tornado) inside where the flat sheet of foam (in a frame) spun like crazy and had torque like you wouldn't believe. I never scaled it up, but if a fellow had the room, this would make a dandy high-torque VAWT. This was a case of spinning the wind and emersing a flat blade within the flow instead of spinning the blade in a flat plane of moving air. Merely a case of backwards thinking; I do a lot of that!
. . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I have played around with similar if not identical gearmotors, and I think you will find that the output shaft is just about immovable, without the motor being powered. Even if you clean out all the heavy grease from the gearbox and use light machine oil, it will still be hopelessly inefficient when driven in the reverse direction. Cheers, Tony. |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Yeah, I would second the above. Multistage spur gears of a high reduction ratio also have lots of drag. You could try a planetary gear, I have one with a 6.4:1 ratio in use and it has little drag. It has a light grease inside. You might find small planetary gears in battery powered drills, medium size ones (like mine) in some washing machine motors and hefty ones in automotive auto gearboxes. The latter may be difficult to adapt Klaus |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Yes, for sure that is a much better example of the principles I had in mind. For myself, I dont have too much enthusiasm for VAWTs, especially any of the schemes that have flexible sails. I think one of the ones that use symetrical airfoil section would be better but as far as I know they are not self starting. Of course the pure drag machines are easier to cobble together and can be built to withstand anything between now and the Opocalypse, but they are not at all efficient. |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Yes, I know all about VAWT efficiency . But, living in suburbia on a small block has limitations with regard to fast spinning HAWT on tall masts.
Its a turbulent wind location and anything that pokes much above the TV antenna is usually not permitted so having a HAWT would not be beneficial. To just mess about with wind turbines a VAWT does the job, mine spins at 60RPM on a windy day and if I get this thing to produce some power its a bonus. Solar panels are the real battery bank chargers here and with soon to be 1.2Kw on 3 trackers they deliver just about all the power I require. Klaus |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Tink More in keeping with the current topic of this thread, gears, I have the perfect project for you to while away the hours. Build a VAWT that spins a worm gear against a helical-cut down gear, which is coupled to a large mainspring. Make the spring trip out after one revolution such that it drives a small-ish ax-fx alternator. You could design your own simple alternator to be maybe a skein-wound, single phase unit. Single-phase would vibrate, but only for a few seconds each time the mainspring unwinds. Such a rig will give you small surges of battery-charging power with a small and hopefully unnoticeable windmill. You'll be the talk of the town! I'm living in a similar situation as you, in my land yacht in a small, seaside park with lots of neighbors. I may cook up one of these for myself now that I've mentioned it to you. When I do, I'll post the build. So many interesting little projects to do . . . the fun never ceases. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| skgtheblij Newbie Joined: 14/10/2011 Location: EthiopiaPosts: 8 |
Advice taken on the gearmotors. One more question though: if it's impossible to turn the gear in reverse, why not do a little surgery on the gearbox and turn it around so that input is output? And spring idea is good, I think I saw someone doing something like that with rope; I was thinking about a weight on a rope that is slowly lifted by the torque of the windmill, then released such that it gets an alternator going really fast for a short while. |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
With regard to small gearmotors, this is typical of the type of pinion you might find inside. Works fine driving a large gear. But almost impossible for a much larger driving gear to turn with reversed power flow. 
For reasonably good mechanical efficiency,the trick is to keep all the gear diameters large, for a speed increasing type of gearbox. Cheers, Tony. |
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TexAcoon Newbie Joined: 14/11/2011 Location: United StatesPosts: 8 |
There was a unique "V" rotor design a fella came up with on YouTube ... What was interesting if the wind became too high or the torque of the alternator became to much the wings would fold slightly allowing for constant velocity of the generator. Now if you would design a larger scale unit with preloaded springs on each wing, I would think you could have a heck of a unit that wouldn't be destroyed by high winds... Kind of keeping everything constant at a certain RPM so to speak. Allowing the wings to feather out horizontally to coast and allow the alt to maintain a constant velocity pending preloads of the springs of each wing. Check this YouTube video out and read some of the comments to give you some ideas. "V" wing rotor design Doug Cortland, Nebraska |
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