My project wraps up.. but about that furling..

Discussion in 'Post Your Photos' started by AdironDoc, Nov 27, 2010.

  1. AdironDoc

    AdironDoc WindyNation Engineer

    Well, since last I posted, I've gone on to add a section of aluminum box channel with a plexiglass (love the invisibility factor) for the tail section. I'm not satisfied on the way the tail wiggles around constantly, and despite the furling set at 20 degrees, I've never seen it fully furl. Guess I'll need to wait until a super windy day. Some sites sell units that have no furling, some say the Delco Refabs are ventilated and as such don't need to be protected. Anyway, I'll post the links to the voltage test, and the amperage test below. I'm glad to be wrapping this up and have been very pleased with my Windy Nation Turbo Torques so far. I'm very curious how the PMA would behave with a set of 35" WindGrabbers compared with my 5 blade 24" Torques.


    Wind Project:
    Voltage without load:
    Deep cycle battery at approximately 30% discharge level:
  2. dlmcbm

    dlmcbm WindyNation Engineer

    Its funny that you posted about using 35" windgrabbers. I also Have a PMA from ebay Its the wind scorpion (wish I knew of windynation then). I am using windynation 28" hyperspin blades and the most I have seen out of mine is about 150 watts. In 9 hours today of 10-20 mph winds I only made .04 KWH of power with my grid tie. I would love to see what the 35" blades would do for it.
    Here is my video
  3. AdironDoc

    AdironDoc WindyNation Engineer

    Nice setup you have. That's a great mast. I'm intrigued at the relationship between the number of blades in determining speed vs. torque. More blades = slower but more torque. A conundrum for someone like me who lives in a low wind area. As they say though, the swept area of the rotor is very important so going up to a set of 35" blades seems like it would produce way more power. The radius increasing, however, means lower RPM's, which works against it too. That's why I'm really curious about torque vs. speed of a smaller 24" five blade setup vs. the 35" setup with just three blades. Diameter increase vs. losing 2 blades to up the speed. Anyone care to opine?

  4. Minnesota

    Minnesota WindyNation Engineer

    Hey Doc ...

    Nice to see it flying. Based on my analysis bigger and more blades do worst on a car PMA. Testing has shown that a 2-blade 60-inch rotor outperforms a 3-blade 81.5-inch rotor on the same "juiced" car PMA. The blade design is pretty important in both cases but I've not seen a very good description of how to really design the airfoil "best" for specific PMAs. Most people bend sheet metal blades so "it looks about right" rather than engineer it.

    Here is one of my vids on the subject of rotor diameter, RPM, and watts produced into a battery:
  5. AdironDoc

    AdironDoc WindyNation Engineer

    Great video, Minnesota. My project was really a cheap foray into the world of wind to test it's feasibility for my goals. Your assessment on delco style PMA's is spot on. I achieved on average 15W and on rare occasion up to 60W against a half charged 12 battery. I'm not sure how I feel about that. Disappointed that wind will not provide a large enough energy source to charge a bank of batteries drained of 1.5KW per day, but convinced a larger system such as the Windtura-500 will be well worth the money.

    Thanks for the data you've presented in your videos. It should be essential viewing for all newbies like me. I've been looking at some of the same BS ebay listings that you've debunked. No real data, just spurious claims and hype. In my world, clinical trials support EBM, or evidence based medicine. No shortage of snake oils on the market, however. In the world of e-bay sellers, I suppose it's a free for all. Precisely why it's nice to have some engineers out there! As such, I'd appreciate your thoughts on the following.

    As the power of a turbine is directly related to the swept area, which in turn relies on a square of the radius, the blade length is obviously a critical factor. For most PMA's, very little is said about torques but much is made about rotor speed vs. output. I understand there is always a trade-off on swept area vs. rotational velocity, but can the increased power of a larger rotor make up for the power lost by the reduced RPM's? If for instance, a light breeze would not be enough to rotate a 5ft rotor on a given PMA but a 9ft rotates, albeit slowly, then it seems the larger rotor is more consistently producing at least something. Secondly, can a larger rotor overcome energy losses of a simple gearbox to exploit both the greatly increased power inherent in the larger swept area and the increased RPM's the gearbox allows? It would seem to me that a 1:2 gearing would halve the torque, but the doubled radius would square the power, more than compensating?

    torque vs speed.. must we choose?
  6. Minnesota

    Minnesota WindyNation Engineer

    Hi Doc ... first, thank you for the complement on my videos, and thank you for subscribing to my channel.

    Like you I am in the learning process as well. You ask some good questions. I do know that it takes a certain RPM to get a specific PMA's voltage above the battery bank voltage - that's key. It is one thing to spin and another to spin fast enough to charge a battery bank. A related problem is getting the PMA to initially spin while the load (battery) is connected. It many times takes a gust to get the rotor turning. Afterwhich, the rotor's momentum helps keep it turning as long as the wind speed does not die off to the point where it comes to a stop again.

    The deep camber (sharp airfoil curving) near the root (center) of the rotor blades is designed to break the initial resistance but not interfere too badly drag-wise at higher RPMs.

    What's missing is a method to characterize the PMA under load and then use that data to design an optimized set of blades (length, shape, weight, number of blades ...). I'm still researching how this is done.

    There are also 2 blade types - drag and lift. These smaller units all use the drag style, including the WN units. The Pro units including the Bergey XL.1 that I covered use the lift style. The lift style are true "wings" that really ramp their RPMs once they get above "stall speed," just like an airplane. I know Jaybird has some "lift" blades on his WN500 PMA so perhaps he (and others) can chime in on this area

    I also don't have much to contribute on the gearing question. Let's learn together!
  7. AdironDoc

    AdironDoc WindyNation Engineer

    Thanks, Minnesota. I'm learning. I remember it being forever windy up in Rochester. I'll bet your PC is being run by a PMA at this moment! ;)

    Among the toys I've collected these last months is a hand held anemometer and laser tachometer. Now I wonder if there is a relatively cheap way of measuring torque at the shaft. I'd like to connect some PMA's to a full load and see just what kind of torque is needed to get them rolling. If I could rely on engineers for the formula on calculating predicted torque based on blades, swept area, and wind-speed, etc, we could more easily see whether a certain blade set would have a happy marriage to a particular PMA. Once the necessary torques are known, gearing should be a snap. Image the power of a 9ft swept area geared for 600RPM! I'm eager to explore that.

    Aside from some wind up on a ridgeline, I also have a creek (actually 85ft wide) running through my land. Unfortunately, despite a high flow rate, it hasn't the drop in height needed for most systems or the depth and volume needed for the rest. This PMA torque problem has been in the back of my mind for some time. Most PMA's are very large, or if small, have a high RPM. A simple bicycle wheel with paddles attached using the bicycle's gears could spin something small at least. Now, if I could just find a "mini delco" that could turn out even 20 watts with very little torque, that adds up to almost half a kilowatt daily. Wonder if someone in the wind community has some sources on small PMA's.

    Any ideas on how to inexpensively measure torques? Any small PMA sources?


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