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Fine Offset anemometer repair

For discussion of DIY weather equipment - sensors, accessories, improvements to existing kit etc
kimis
Posts: 4
Joined: Sun Aug 26, 2012 4:01 pm
Weather Station: Elecsa (Fine Offset)
Operating System: Win7
Location: Klaipeda

Re: Fine Offset anemometer repair

Postby kimis » Mon Aug 27, 2012 5:58 am

Hi Daniel, and thanks

Yes, ball is for about 1mm larger, but I think length of "arms" is more important factor for anemometer. and of cource it is better to have such one than no at all :)

As Klaipeda is on the coast of Baltic we do have stronger winds here if compare to lets say Vilnius, which is 300 km away. But as Klaipeda is quite far away from Atlantics, only stronger depresions are pushing through Europe and reaching us. I have restored my anemometer just few weeks ago and not placed it well yet. So it doesn't show recent strong winds. right about 2-3 weeks ago we had very strong storms/squals here. even small kids (2-3 years old) were reported flying. biggest unofficial numbers I've seen were reported from S/Y reaching more than 70 kts in gusts. and the strongest huricane was Anatolij as far as I remember, reaching same spead as well.

I plan to place anemometer on the roof of house (about 10m above ground) as now it is partialy covered by house and bushes in the yard :)
Kimis
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Gina
Posts: 1885
Joined: Sat Feb 21, 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Fine Offset anemometer repair

Postby Gina » Tue Aug 28, 2012 8:25 am

Half ping pong balls make excellent anemometer cups. That's what I used for my home made anemometer with small pieces of dowel for the spokes. A half ping pong ball makes a good centre hub too in conjuction with discs of plastic. I used the same size ball bearing as in the FO units.

Yes, it's the spacing of the cups from the centre that decides the ratio of wind speed to revs. The size of cups is relatively unimportant.

And yes, it's important to have the anemometer (and vane) high enough to avoid the effects of buildings if possible. Ideally you want at least 2-3 metres above the roof.

P.S. My FO weather station (supplying my sig data) is no longer working.
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.

AllyCat
Posts: 1045
Joined: Sat Feb 26, 2011 1:58 pm
Weather Station: Fine Offset 1080/1 & 3080
Operating System: Windows XP SP3
Location: SE London

Re: Fine Offset anemometer repair

Postby AllyCat » Tue Aug 28, 2012 9:22 am

Hi,

Yes, certainly the height and (obviously) the length of the arms are major factors (in the speed of rotation), but one shouldn't overlook the "Anemometer Factor". It's not obvious why the FO version appears to be right at the "slow" end of the typical range (AF ~ 3.3), the cups moving at only about 30% of windspeed. Some professional anemometers seem to prefer conical cups.

See Wikipedia which in particular says: "When Robinson first designed his (4-cup) anemometer, he asserted that the cups moved one-third of the speed of the wind, unaffected by the cup size or arm length. This was apparently confirmed by some early independent experiments, but it was incorrect. Instead, the ratio of the speed of the wind and that of the cups, the anemometer factor, depends on the dimensions of the cups and arms, and may have a value between two and a little over three".

Cheers, Alan.

Gina
Posts: 1885
Joined: Sat Feb 21, 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Fine Offset anemometer repair

Postby Gina » Tue Sep 18, 2012 9:52 am

Yes, I think the wind speed readings are definitely on the low side - my measured speed always seems lower than the Met Office reported values for this area. There is a reporting station just a few miles away on a similar height hill.
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.

AllyCat
Posts: 1045
Joined: Sat Feb 26, 2011 1:58 pm
Weather Station: Fine Offset 1080/1 & 3080
Operating System: Windows XP SP3
Location: SE London

Re: Fine Offset anemometer repair

Postby AllyCat » Tue Sep 18, 2012 3:33 pm

Hi,

It's puzzling why many people (including Steve) consider the FO anemometer to under-read when its Anemometer Factor of 3.3 is already right at the high end of the "expected" (multiplication factor) range of "between two and a little over three". In an urban location, my own "real" measurements are inconclusive (certainly lower than expected), so I have tried a few artificial tests but haven't yet managed to confirm any error.

Another possibility is that the Console does not count the revolutions correctly, and this appears to be slightly true, but not to a large extent. The Console "truncates" the count every two seconds (rather than averaging over 48 seconds and then rounding) but this only represents an average under-read of 0.375 mph (each half-revolution in two seconds indicates 0.75mph on the Console).

For some time I've been independently counting the revolutions of the (same) FO anemometer and the daily wind run consistently (assuming there is some wind) exceeds the value calculated by Cumulus (from the FO logger data) by the expected 8 - 10 miles (i.e. 24 x 0.375).

I guess the only answer is sometime to attach a long mast and anemometer to my car and do some driving around with a GPS on a still day. ;)

Cheers, Alan.

Gina
Posts: 1885
Joined: Sat Feb 21, 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Fine Offset anemometer repair

Postby Gina » Tue Sep 18, 2012 5:01 pm

Yes, I guess that's the only way to be sure of your calibration.
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.

Gina
Posts: 1885
Joined: Sat Feb 21, 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Fine Offset anemometer repair

Postby Gina » Tue Sep 18, 2012 5:05 pm

ooops - posted in error
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.

gonk
Posts: 1
Joined: Fri Feb 07, 2014 2:09 am
Weather Station: WS1081
Operating System: Raspian
Location: Australia

Re: Fine Offset anemometer repair

Postby gonk » Fri Feb 07, 2014 2:17 am

DanielF wrote:Just a follow-up to my anemometer repair...

A few months back my wind direction vane became stuck. Unlike the anemometer, which just had a 'sticky' spot, but would still turn in a moderate wind, the direction vane was stuck fast – couldn't even move it by hand! It was rusted solid (remember I live right on the ocean!).

Getting it apart is the same process as for the anemometer, and its construction is identical for the top half. I prised the bearing up off the post, and found no numbers on it (it's pretty small - where would they fit a number? ;) ), so I measured it with vernier calipers.

I found a stainless steel sealed bearing with the same dimensions, bought online and fitted it, and now everything's working well again. The supplier listed below is in Australia, so postage would probably kill this source for those of you overseas, but it may be of use to other Australians experiencing this problem, and others might find the same part number overseas somewhere. I'm assuming (but haven't measured) that the anemometer bearing would be identical.

Supplier: http://www.smallparts.com.au (sales@bearingshop.com.au)
Bearing part number: SMR105A-ZZMC3
ID: 5.000 mm
OD: 10.000 mm
Width: 4.000 mm

They were $5.36 each incl. GST (I bought 4), with $9.35 total postage (within Australia), though the current price seems to have risen slightly since then.

I'm glad others have found my article useful, and hope this additional info is also of use to somebody.


Old post but still very handy. Thanks. I will try the Hybrids with the ceramic balls... Part Number: MR115-CSN-ZZS-AF12. Lets see how long they last.

wswat
Posts: 9
Joined: Wed May 20, 2009 10:57 am
Weather Station: Altronics 1081

Re: Fine Offset anemometer repair

Postby wswat » Wed Aug 20, 2014 11:19 am

Hi Folks,
The anemometer wind cups on my old FineOffset have become very weathered over the years and realising that some day in the not too distant future I would check the weather pole and the cups would be AWOL so I decided to have a go at making replacement cups.
I made up a female mould and a male plug from timber and set them up in the drill press after coating with wax as a releasing agent and placed a disc of ABS plastic from an old scanner over the female mould and carefully applied heat from a hot air gun and when the plastic became wobbly I pressed the male plug downwards.
So I now have 3 replacement cups but would like to know if anyone knows what type of plastic the original anemometer arms and cups are made from. And yes I do realise that the accuracy of the anemometer with these replacement cups will be blown out the door.
Cheers,
Darcy
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kevinlufc
Posts: 9
Joined: Wed Dec 28, 2011 2:35 pm
Weather Station: WH1090PC
Operating System: Win 7
Location: Leeds

Re: Fine Offset anemometer repair

Postby kevinlufc » Sat Jan 03, 2015 11:02 am

Just out of curiosity. Would this work as a replacement?

http://www.maplin.co.uk/p/maplin-replac ... 96fy-n82nf

I only ask as its a very cheap fix for me. Rather than going down the "getting my hands dirty" route...lol

water01
Posts: 1460
Joined: Sat Aug 13, 2011 9:33 am
Weather Station: WH1081
Operating System: Windows 7 64bit HP SP1
Location: Somewhere in the USA
Contact:

Re: Fine Offset anemometer repair

Postby water01 » Sat Jan 03, 2015 11:12 am

Just make sure you match your Fine Offset weather station as Maplin's has replacement parts for N25FR/N96FY/N96GY stations.

kevinlufc
Posts: 9
Joined: Wed Dec 28, 2011 2:35 pm
Weather Station: WH1090PC
Operating System: Win 7
Location: Leeds

Re: Fine Offset anemometer repair

Postby kevinlufc » Sat Jan 03, 2015 11:25 am

water01 wrote:Just make sure you match your Fine Offset weather station as Maplin's has replacement parts for N25FR/N96FY/N96GY stations.


Thanks for the quick reply. I will pop down and have a chat.

AllyCat
Posts: 1045
Joined: Sat Feb 26, 2011 1:58 pm
Weather Station: Fine Offset 1080/1 & 3080
Operating System: Windows XP SP3
Location: SE London

Re: Fine Offset anemometer repair

Postby AllyCat » Sat Jan 03, 2015 3:36 pm

Hi,

Yes, there are several types available, some are even "black" (dark grey), but AFAIK they are all electrically compatible. One even has a much longer cable (for the station which doesn't have a wind vane).

Some of the spares are kept in stock in some shops, and I think you can order as "click and collect" to save postage, if they are not in stock.

Cheers, Alan.


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