WXforum.net
Weather Station Hardware => Rainwise Weather Stations => Topic started by: NCHighCountryWX on May 13, 2018, 12:57:23 PM
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I am considering a purchase of a Rainwise System over a Vantage Pro System.
One thing that concerns me on the Rainwise is if the prop blades do indeed stall in gusty variable winds.
Is this an issue?
Here is a video another forum member posted that validates my concern.
Thanks
https://www.youtube.com/watch?v=RQciYwaEyhU
NCHighCountryWX
Banner Elk and Denver NC
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Interesting, just looking at video its something I would stay away from. Glad you posted... =D>
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I have the Rainwise 111 rain gauge and two Davis VP2s. The VP2 is a great product except for the rain gauge. I think the reason for the better accuracy is the Rainwise has an 8 inch cone vs. the VP2 which is about 6.5 inches. One of these days, I am going to disconnect the rain tipper in my VP2s and connect it to the Rainwise. For example, my Rainwise recorded .48 inches of rain last night, one VP2 recorded .32 and the other VP2 recorded .28. My manual CoCoRaHS gauge (the “gold standard” in my view) had .48 too.
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I’m not sure that is the anemometer actually stalling. I’m leaning towards thinking it’s just the effect you get when the anemometer spins so fast it looks like it’s barely spinning at all on video due to a Video frames per second limit. Not sure if this has a specific name, and I could be wrong all together, but it’s a possibility.
I once took a video of my VP2 anemometer and when I viewed the video, it looked as though it wasn’t spinning at all at times. I know that it indeed was though, and very fast.
- Matt
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Good point, maybe others will chime in about whether its just a camera illusion similar to airplane propeller spinning sometimes it looks like it reverses.
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https://en.wikipedia.org/wiki/Wagon-wheel_effect
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Good information. I looked at the video again and in this case it sure looks like its stopping.
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Thanks for the link. I knew it probably had an actual name!
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I looked at the video again and in this case it sure looks like its stopping.
Completely agree. If it is still spinning, at that instance, you'd never know just looking. :eek:
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Kind of like this?
[youtube]https://youtu.be/yr3ngmRuGUc[/youtube]
Greg H.
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That's probably the best example I've seen. 8-)
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I have never noticed any condition such as you describe (and the video appears to show) in the 4 years that I have owned my rainwise. Not to say it can't happen, but I haven't seen it.
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I have a Rainwise MKIII LR and it definitely doesn't stall, but when I take a video it looks like it does.
Conversely, when I watch Baseball, I would never think the bat bends, but play it back in slow motion and......
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Absolutely NO question, so as Rainwise which is a fine instrument doesn't get any bad rap and because it is the truth, that the effect in the video is a camera effect. CCD cameras and CMOS cameras to a lesser degree, due to the way the image is read, make motion, especially rotating objects, seem goofy.
This illusion is even more amplified with the compression technology that stores the image, and then transmitted to UTube, and when there the 400 hours per second of video they get ingested gets compressed even further, no matter how pristine your video is when it arrives. Sampling time is a factor also.
I've given up on most attempts at showing much on their site, even though much of what I tried was of limited value and not important, it was clear that I had no control over what you think would be seen.
So don't worry, realize it is a faulty not real video, and the complex shape of the propeller is harder to encode than the simple rotating anemometers shown above.
But it is NOT a fault of Rainwise (which one of the respondents hinted at here). I maintain plenty of them and have 6 at home, so other than getting stopped by a build up of heavy wet snow in no wind conditions, they are as reliable as anything out there.
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Further thoughts, or perhaps even facts. As the Rainwise propeller spins it has inertia and angular momentum. If the blade stalled, there still will be rotation, not stoppage of the blade, since it would continue to rotate for at least a bit the same as you had flicked it with your finger and let it slow down. If you'd stuck your finger back into the spinning prop, of course it would stop, so if there were very variable gusty conditions that might impart an anti-rotational force on the blades there will be an unexpected change in rate of rotation.
That will drive the imagining system that deals with motion artifact (almost all non-film cameras which are the majority today) have a very hard time dealing with this, and the solution is very expensive) does the best it can but fails.
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While it is true that a camera does indeed have difficulty with rotation, I have personally seen propeller driven anemometers stall in cross winds. It is very rare, but would not stop me from employing the Rainwise MKIII. I will ALWAYS maintain a cup style anemometer which is hard wired for an accurate backup, much the same as having a manual rain gauge to complement a digital, tipping bucket gauge.