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Author Topic: Anemometer pole / flex effects  (Read 6024 times)

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Offline James MB

  • Posts: 3
Anemometer pole / flex effects
« on: October 06, 2008, 12:21:54 PM »
Not wishing to Hijack the previous anemometer pole mounting thread I've created my own.

I've mounted my wireless VP2 on a pole attached to the gable end of my house. I got about a 10' lenth of galvanised steel pipe (1.5") (previously a compressed air pipe at my work) and a heavy duty aerial bracket (allegedly 9") that ensures the pole clears the end of the roof. My aim was for the anemometer to be 7' clear of the roof ridge. For safe keeping a put the rest of the ISS on the pole as well, offset down by about a foot.

Pleased with my handiwork I cleared the data from the console and left alone to see what the results were like. Of course every time I went outside I had to stare up in wonder! I'm not sure but there must be a little flexing of the pipe and / or the bracket - it's pretty heavy and there's a lot of leverage on the two bracket arms, I have a second bracket in case I want to add it. In looking for a description of the bracket I found an excellent UK website I wish I'd found before (aerialsandtv.com). (note to self - remember to swap out that galvanised pipe within the next 15 years)

Anyway - my question - does the flexing of the pipe/mounting affect the wind reading? I accept that a little sway back and forth would add to/subtract from the measurement but I doubt it moves that fast to make a significant difference. I was thinking more of the gyroscopic action of the rotor interacting with the sway?

Offline munrobaggins

  • Posts: 1,973
  • 38 mls NE Inverness UK
Re: Anemometer pole / flex effects
« Reply #1 on: October 06, 2008, 12:41:21 PM »
....I was thinking more of the gyroscopic action of the rotor interacting with the sway?
I must admit to frequently wondering about that myself....but as the mast has been up there for some 2.75 years now...I have come to the conclusion that the accelerations and decelerations probably have little overall influence....I say this as I have both a Vortex and a VP2 anemometer on the mast and they read substantially the same, although having different sample rates...But I still ponder...maybe the anemometer bearings wear more?.....!

I changed my original mast mounts (DIY sourced) to more substantial ones from a professional Ae erector..

Offline David W

  • Posts: 2,006
  • Isle of Skye, Scotland
    • 24 Elgol
Re: Anemometer pole / flex effects
« Reply #2 on: October 06, 2008, 01:12:46 PM »
UK website I wish I'd found before (aerialsandtv.com).
I was impressed by them too.

Pages such as http://aerialsandtv.com/polesandbrackets.html are packed with extra background details about poles and fixing.
Regards
David

Offline N7XSQ

  • Posts: 464
  • Phoenix, Arizona
Re: Anemometer pole / flex effects
« Reply #3 on: October 06, 2008, 10:30:18 PM »
Quote
For safe keeping a put the rest of the ISS on the pole as well, offset down by about a foot.

The pole flexing back and forth will have the greatest effect on the tipper in the rain gauge. If it flexes too much, it may cause false tips, and flexing less than that might cause the buckets to empty too early.

Steve

Offline Dujon

  • Cheers!
  • Posts: 391
  • La Crosse WS 2355
  • Blaxland, Blue Mountains (Nr. Sydney), Australia.
    • Blaxland, N.S.W., Australia
Re: Anemometer pole / flex effects
« Reply #4 on: October 07, 2008, 12:59:22 AM »

James MB,

I'm not a fan of using galvanised pipe for any vertical support, although a 7 foot length not guyed you might get away with - but only provided that the load (your gear) is light - meaning small mass - and has little wind resistance. In other words, move your ISS off the mast.

To be honest I find it surprising that Davis purveys such a combination when the requirements of its sensors conflict.


 

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