Davis anemometer cups not moving in light wind

[RayProudfoot]

Very lucky I would say Freddie. Perhaps being in the countryside helps. If it's just dirt as I suspect then as long as I can get access to it to clean it it's not a huge problem. The huge problem is getting access to the top of the roof.

[Super-T]

I just have the anemometer and direction mounted on a 6 metre aluminium pole and screwed to the fence with 2 screws. To get it down for the odd oiling I just remove one screw and walk the pole down.

[beteljuice]

6 metre aluminium pole and screwed to the fence with 2 screws.

Back when the beteljuice had a 30 ft aluminium pole it had to have two sets of guys to stop it bending / oscillating - the lady beteljuice was very pleased when she didn't have to duck walking around the garden anymore

[RayProudfoot]

Aluminium seems to have gone out of fashion for radio enthusiasts who need aerial arrays on top of poles. Fibreglass is the latest thing and a telescopic 40ft pole would make accessing the ane quite easy.

Fortunately my mate is an engineer so I'm sure he'll come up a suitable arrangement to keep it in place. My back garden isn't large so guy ropes are out of the equation. Bolting to the house wall seems the best solution.

Anyway, as long as a high pressure doesn't sit over my area the readings should be okay. Fingers crossed restrictions can be eased in 3 weeks.

@beteljuice, love that story. Important to keep the good lady happy.

[Super-T]

My pole is a square section which seems to alleviate the bending problem and doesn't seem to affect the wind gauges. Never put the rain gauge on a pole:-) No aerials required.

[RayProudfoot]

Well this is bizarre but relieving. Yesterday was quite a windy day so the strength of the wind made it difficult to assess if the ane was working correctly or not. Overnight the winds have dropped and going outside and watching it the cups seems to be rotating freely.

The console is recording speeds of 3mph and 1 mph which, if there was anything preventing rotation would not be possible. Fingers crossed it was just a temporary problem.

[Super-T]

The anemometer has munched up the spider that was having a ride on the bearing

[RayProudfoot]

The anemometer has munched up the spider that was having a ride on the bearing

If so I’ll take that!

[RayProudfoot]

The problem has returned with the last recorded gust just before 0600 this morning. I hope it is just cobwebs and nothing more serious because to have to swap out an expensive anemometer because of dirt ingress would be totally unacceptable.

[RayProudfoot]

Four pages of people with the same problem going back a number of years have convinced me this isn’t because of spider webs or anything of the like.
https://www.wxforum.net/index.php?topic=28845.0

Just a flawed design that lasts a few years before parts need replacing. If it was at ground level that wouldn’t be so bad but with my ane attached to a pole strapped to a chimney stack I’m not able to access it without professional help. And will that be possible under the lockdown?

[RayProudfoot]

Groan! Wind cups stopped rotating shortly after 09:00 today. There was no noticeable breeze at the time but there is now but they remain stationary although the vane is moving.

Maybe it’s another family of spiders using it as home. I won’t panic just yet because it’s happened before and generally they start moving with a decent breeze. Just frustrating that it only seems to happen to me and the anemometer is the new type with a magnetic sensor, not a reed switch.

@prodata, any ideas John?

[RayProudfoot]

And for no obvious reason they started spinning again around 30 mins ago. If it's dirt ingress why would they start spinning again when there's less wind than earlier in the day? It does rather point to insects blocking things but does anyone else have that problem in the British Isles?

I've had a chat with ProData and it probably needs a new cartridge costing around 35 GBP. Paying is the easy bit. Getting up there to change it is down to my good mate who doesn't return from holiday until the end of the month.

Fingers crossed it behaves itself until then.

[prodata]

@prodata, any ideas John?

Nothing apart from the obvious I'm afraid. Either there's some external friction on the cups like a spider's web or something binding somewhere; or the bearing has started to feel too much friction and needs replacing. It's obviously a relatively simple system so there aren't many options to explain it. Conceivably there's not enough clearance between cups and cartridge and in the recent hot sun (if you've had that?) both parts have expanded, but that's not very likely - the anemometers are obviously made to serve in California etc.So, subject to closer inspection, best guess is that it needs a new bearing/cartridge.

I have to say that it's not really recommended I'm afraid to locate the anemometer somewhere where it's really tricky to access - you never can anticipate all the reasons why you might need to do so. But I do also understand the temptation to get the unit as high as possible.

[RayProudfoot]

Hi John. Thanks for your reply. I’ve documented all the times the cups have stopped in this topic. The anemometer was replaced in Dec 2013 after the previous one purchased when I started in 2009 was broken in a storm.

The first problem occurred in Sept 2016 when it had been up nearly 3 years. But the cups started rotating again 24 hours later.

The next time it happened was on 26 March 2017. This time a friend replaced the faulty one with a spare I’d bought. That one was returned to you and you kindly replaced the cartridge FOC.

So the spare was mounted in late March 2017 and was fine until 16 April 2020 when the cups stopped. Two days later they started again.

On 9 May it occurred again. I didn’t post here but from memory they started again the next day.

Finally they stopped at 09:00 this morning and looking at the graph it wasn’t a sudden stop. There was virtually no wind this morning but by mid morning the breeze had picked up and it was then I noticed the cups weren’t moving. Nine hours later and they’re spinning freely. If there was dirt in the bearings I’d expect then to stop quickly but they don’t. They seem to be spinning freely. The most logical explanation seems to be insects or a spider spinning a web. Is that feasible?

When we speak tomorrow I’ll order a spare cartridge. It seems sensible to do so as any downtime can be minimised. I accept a chimney mounting isn’t ideal but it does ensure pretty good accuracy.

I had considered a telescopic fibreglass pole mounted to the side of the house above a flat garage roof. It would need to be offset to clear the gutters and would need a couple of guy wires to secure it. Not cheap but as long as I can get onto the garage roof the pole could be lowered making access to the anemometer easy.

That remains the only alternative I can think of. I’d appreciate any other suggestions to make access easier whilst keeping the cups at 30ft.

[The PIT]

My last two Davis anemometers failed as the plastic casing cracked due to the sun. Since getting anyone to go up on the roof is a real pain since most TV or Sky installers won't do it as they're not insured. Anyway I moved to Ultrasonic device mounted on 25 foot pole in the garden. Read slower than it did on the roof which I'm not surprised at although I think it's now too sheltered but then the trees to the west have grown as well and probably also blocking the wind somewhat. Before it used a almost clear run from the quarry. So the lower readings are probably due to a combination of shelter and additional tree growth on the quarry.