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__Wind direction meter__ </br>
## Generator Tower, shaft, bearings __Shaft tubes__ The diameter of the generator's shaft is 1.22 in. It's rated RPM is 360 at 12 m/s. The shaft consists of an 8 ft section and a 4 ft section of [1.5" OD x 0.134" Wall x 1.232" ID stainless seamless round tube](https://www.onlinemetals.com/en/buy/stainless-steel/1-5-od-x-0-134-wall-x-1-232-id-stainless-round-tube-304-seamless/pid/14789) made out of the 304 stainless steel alloy. The two pieces of the shaft are connected with a slightly wider tube that of [1.75" OD x 0.12" Wall x 1.51" ID](https://www.onlinemetals.com/en/buy/stainless-steel/1-75-od-x-0-12-wall-x-1-51-id-stainless-round-tube-304-welded/pid/483). __Bearings__ The shaft is held in place by two [Mounted Ball Bearing with Nickel-Plated Iron Housingfor 1-1/2" Shaft Diameter](https://www.mcmaster.com/6494K19/). ### Forces on the shaft[^ncyuMaterials]
## Tower
- averaging periods of 10 min are commonly used; 30 min period for turbulence studies; the larger integral time scale, the larger should be averaging period; sampling frequencies should be much smaller than the integral time scale
- you have to detrend the time series to get rid of high-frequency fluctuation
# References
[^ncyuMaterials]:http://web.ncyu.edu.tw/~lanjc/lesson/C3/class/Chap03-A.pdf
