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25th Aug 2017, 9:36 pm | #1 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Anemometer bearings
Hi.
When I can find the time, I hope to revisit a project that I first built when I was 14 back in 1980. It is the Everyday Electronics Weather Centre covered in the August and September 1980 issues of the magazine. The mechanical design of the anemometer and wind direction units in the original setup could be greatly improved by using ball race bearings rather than brass bushes. The problem lies in housing the ball race bearings which would need to be fitted in a flanged tube. I came across these linear bearings, http://www.ebay.co.uk/itm/1Pcs-LMF6U...53.m1438.l2649 but my question is, would these be suitable for a rotating shaft? I like the idea of it having a decent flange which makes mounting it more straightforward. If they are suitable then it should be fairly easy to install a pair of these in a weatherproof ABS box. Suitable rain protection covers could then be fabricated to shroud the bearing assemblies. Any suggestions welcome. Regards Symon. |
26th Aug 2017, 12:13 am | #2 |
Rest in Peace
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
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Re: Anemometer bearings
Not really an answer to your question but when I had cause to replace the bearings in an anemometer head a while back I used ball bearings from RS Components. They had quite a comprehensive range of really small types which fitted perfectly. I didn't even know you could get such miniature bearings before that.
Alan. |
26th Aug 2017, 2:22 am | #3 |
Banned
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
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Re: Anemometer bearings
That is a linear bearing!! In other words its for a shaft that can slide through the bearing rather than spinning in place.
Imagine a milling machine table! it travels ALONG an axis, rather than spins in place. Having said that, if the shaft is hard enough, it will spin very easily as linear bearings actually use the shaft as the "outside" race. You will find linear bearings in 3D printers and associated "engraving" type appliances Joe |
26th Aug 2017, 7:15 am | #4 |
Nonode
Join Date: Aug 2010
Location: Resolfen, Wales; and Bristol, England
Posts: 2,588
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Re: Anemometer bearings
It's possible to buy small races with a flange on the outer part, or a groove for a circlip. I have seen ball races as small as 2mm internal shaft diameter.
__________________
Richard Index: recursive loop: see recursive loop |
26th Aug 2017, 7:24 am | #5 |
Pentode
Join Date: Apr 2017
Location: South Coast, Western Australia.
Posts: 129
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Re: Anemometer bearings
I think that the product description has not been translated very well from the Mandarin- it appears that the bearing type is NOT a linear bearing but a standard ball race/s with a metal shield. I used to work on a lot of machinery that used linear bearings on pistons and actuators and their internals did not resemble ball races.
Coincidentally, I was looking at a Lutron hand-held anemometer yesterday and marvelling at the lack of friction/stiction in the turbine bearings. I recall, years ago, a colleague manufacturing an anemometer for a weather station (under the bench, so to speak...) and we washed the grease out of the bearings with Trichlor 1.1.1 so that the rotor would start in the slightest movement of air. We calibrated it by fixing it on a pole held out of the window of an NSU Prinz ! As far as I know the bearings were not replaced in the 10 years that I was in contact with him. Regards, BC |
26th Aug 2017, 12:19 pm | #6 |
Octode
Join Date: Jul 2008
Location: Gloucestershire, UK.
Posts: 1,043
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Re: Anemometer bearings
Hello,
These are linear bearings as you can see from the cross section on the data sheet (second picture). The picture below of a larger bearing from the same seller shows how they work. (The balls run linearly along the shaft then return back to the other end through a tube in the ball carrier.) Yours., Richard Last edited by Mr Moose; 26th Aug 2017 at 12:27 pm. |
26th Aug 2017, 12:25 pm | #7 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Anemometer bearings
Hi.
It looks like I'll have to err on the side of caution and not use these linear bearings. It would be a fair amount of work to construct the wind speed/direction units only to find that the linear bearings may not work properly or wear well. It's therefore going to be best to use conventional ball race bearings primarily intended for rotation. Finding suitable types with a decent size flange could be a problem. I suppose some sleeves could be turned on a lathe so that a good size flange will make it easy to fit to a box. Just a thought, I wonder if it's possible to use the linear bearings shown in my link in post #1 but remove the internal parts and fit suitable ball races. All that I require is 4 flanged bearings with a 6mm internal diameter. I might purchase a couple to experiment with. Thanks for all your replies. Regards Symon |
26th Aug 2017, 12:29 pm | #8 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
|
Re: Anemometer bearings
Thanks Richard for the pic of the linear bearings, very useful to know the workings of the bearings, something I've not seen in the flesh.
Regards Symon. |
26th Aug 2017, 12:35 pm | #9 |
Rest in Peace
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
|
Re: Anemometer bearings
Of course keeping drag down is very important, otherwise you may lose some low wind speed accuracy.
Alan. |
26th Aug 2017, 2:12 pm | #10 |
Banned
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
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Re: Anemometer bearings
Linear bearings are recirculating ball bearings. Not intended for rotation applications.
SKF can supply very small bearings. We used to wash the lube out of the bearings on go-kart axles, replace with WD40, it was worth a few tenths a sec on lap times! |