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Politics : Formerly About Advanced Micro Devices

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To: TideGlider who wrote (749435)	10/25/2013 9:27:50 PM
From: J_F_Shepard	Read Replies (1) of 1572901

FYI......do you think you're fast enough to run between the blades? You have 1-2 seconds.... How fast do wind turbines spin? In: Wind Power [Edit categories] Answer: We just timed the four turbines in Atlantic City, NJ. The tip of the blade will of course spin faster than the base since it has further to travel, so that is what we will calculate. Guesstimating that the blade is 120 ft. in length, we need to find the circumference of the circle described by the spinning blade tip. The formula for the circumference is 2¶r or two times the radius of the circle (which is the diameter) * pi (about 3.1415). So 2120ft.=240ft. for the diameter. 2403.1415=753.96ft for the circumference. Since the blade travels that distance in 4 seconds, the ft/sec traveled is (753.96/4=188.49ft/sec). To get that speed in miles/hour multiply (188.49 ft/s * 0.681818182). So the blade tip is traveling at about 128.5 mph! Which is a little bit slow... They typically (company statement) rotate between 15 and 20 rpm so: 60s/m / 15 rev/m = 4 s/rev and likewise 20 rpm corresponds to 3 s/rev. Measuring the blades laying flat on the ground in a construction yard in Google Earth results in an approximate length of 126 ft to 128.6 ft. HOWEVER, you also have to account for the hub that these are attached to. Measuring this is a bit more difficult as I couldn't find one where the perspective was perfect so I got between 3 and 4 feet for the radius of the hub. This results in an overall radius of between 129 ft and 132.6 ft. c=2pir gives 810.53 ft to 833.15 ft. Dividing by the time to travel this distance (3-4s) gives 202.63 ft/s to 277.72 ft/s. Multiply this answer by 3600s/hr / 5280 ft/mi. to get it into mph. Which gives a range of 138.16 mph to 189.35 mph for the blade tip. Which seems very, very fast when you stand directly under it with it swinging at your face!

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