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Forum Index : Windmills : Power yaw, just what you need!
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| KiwiJohn Guru  Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Antenna rotator! They come from little wimpy things for Ham radio and TV antennae right up to huge things for ships radar and even bigger for airport radars! Here is one that might be suitable for a mill? http://www2.rohde-schwarz.com/product/RD130.html I have a ships radar one in my garage, it has a worm and wheel and a 2 HP motor. There are 8" (or so) pipe mounting flanges top and bottom. Of course the basic radar ones just go around and around whereas other move the antenna to a position which is just what we want with the yaw system. One thought that comes to mind with power yaw is that it requires the tower or mast to accept torque loads. |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
So, how are you going to control it? I have a ham antenna rotator (not exactly "wimpy"  ) but one needs to push buttons to get it to turn.
I suppose one could automate it by controlling it from the output of a wind vane. But I think it would react far too slowly in gusty conditions. For this reason I would not even consider this idea  .
Besides, the VAWT I'm building does not require a yawing device  .Klaus |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
[quote]For this reason I would not even consider this idea [/quote] Well if you ever change your mind you might consider something like this. It has a nice meaty worm and bronze gear in an oil bath and being a radar rotator it has a hollow shaft to take those cables down etc! 
(Yes, I have the cover that goes over the motor too) |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
KiwiJohn, I'm not questioning the "meatiness", of which there appears to be ample , its the response time of the worm gear what I consider the problem. I'm convinced that wind gusts from different directions will beat it every time. I guess its up to the windmill installation if it can cope with that in strong winds.Klaus |
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| Janne Senior Member  Joined: 20/06/2008 Location: FinlandPosts: 121 |
Tinker, isn't the power yaw's purpose just opposite of that? As to keep the unit from constantly yawing in gusty wind.. and just to keep it in the average wind direction. The good thing about power yaw is that it can be used to avoid lots of the gyroscopic forces that happen during rapid yawing. If at first you don't succeed, try again. My projects |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Tinker, I think radar scanners rotate at about 60 rpm. I notice the big wind turbines on the hills around here yaw at a very low, almost inperceptable rate. I assume the idea is to keep the turbine pointing in the average wind direction, as Janne mentioned. |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Yes, I agree with Janne and John, the units over here uses a time base to work out whether to yaw at all (user selectable). It senses the change in direction, and you can select from .5 to 15 seconds. If the direction sensor finds the wind is 15 degrees or so off the direction the mill is pointing, then it will change yaw ofter the consecutive time in up. This means that we need to be off the wind for the full selected time... contiguously. Any deflection back to current yaw will reset the timing to 0 and the whole thing sits and waits all over again. You need to be 30 degrees off the wind to begin to seriously degrade performance, so there is no point yawing for no good reason... ie the mean wind direction must have changed, no interest in gust direction at all. Good for the yaw mechanics, good for the blades and hub, good for power production. Am currently fixing some modules for these that do just that (electromatic's) plug in modules. ............oztules Village idiot...or... just another hack out of his depth |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
I think we need to distinguish between the components. The Yaw box has dual function in a normal side furling machine, allowing for rotor wind direction tracking, a relatively slowly changing event, and allowing the rotor to deflect away from the wind during furling action as protection from excess power in gusts damaging the machine, a relatively fast changing event. I do not think power Yaw will accomodate both functions. In the machines oztules has described, the mechanism is for wind direction tracking, as there is no tail. This works well on a big windmill [MW sizes], at a good wind site, with little wind turbulence and direction changes that happen slowly. Furling is achieved another way, usually stopping, or slowing the rotor, by mechanical braking, or blade tip adjustment. I don't think the power required to regulate a power yaw would be justified on a home windmill. Gordon. become more energy aware |
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