Wind Vanes

[Gina]

I was wondering if anyone had any ideas (or links) on how to make a better wind vane that the Fine Offset one. One that doesn't flap all over the place. I know of at least one apparently successful tail mod to the FO vane and I intend to try that but in the meantime I've been thinking of making my own vane, maybe with some magnetic damping. This is likely to be a spring or summer project but thinking and designing can go on indoors in the warm.

[mcrossley]

make the vane arm much longer than the FO?

[Orion]

Still using this one a bit of an improvement buy I am surrounded by trees and buildings so not sure will ever get very good readings
but I do agree that the vane arm needs to be longer and with a larger tail, how about oil damping rather than magnetic damping Gina
I did make one using the hub from an old 120mm PC fan after removing the coils and the magnets and that was very good

[Gina]

The problem with oil damping is that the viscosity of oil varies with temperature - as anyone with a car (or other vehicle) will know. Even multigrade oil changes viscosity with temperature though not as much. I don't know if there is any way to compensate for this (other than to heat the oil and maintain the temperature with a thermostat). I think a rare-earth super-magnet and aluminium (or copper) disc would be simpler. I don't think magnetic damping is affected by temperature.

I could certainly make the vane much longer and bigger. It could also have a longer shaft so that the "works" isn't in the air flow as it is with the F.O. one.

[sanramonrover]

You readin' my mind Gina? See the "Yet another Wind Vane Mod" just above.

[Gina]

I like having the wind vane and anemometer vertically in line and I've been working out some designs. It worked out the having the anemometer above the wind vane seemed easier. Now the F.O. anemometer with the added skirt (mentioned in another thread) is about as good as I'm likely to get but the vane wants to be much bigger. This is the start of one design I've come up with, without as yet the works of the vane sensor unit :-

New-wind-sensors.png

[gemini06720]

I was wondering if anyone had any ideas (or links) on how to make a better wind vane that the Fine Offset one.

I will try to be as 'professional' as possible and not put down the Fine Offset products...

I have found this link (through an other weather forum) a few hours ago: Fascinating Electronics Weather Instrument Kits

You could also peruse to this site: Hydreon Rain Gage - Model RG-11

You might also think of buying a fully built and tested wind vane unit similar to the one supplied with the Vantage Pro2 weather station, the Davis 6410 Anemometer - Archer Trading Post (according to many sources in other weather forums) have the best prices for Davis Instruments kits and replacement parts.

[Gina]

Interesting - thank you But I want to make my own - I like making things. And making cheap things work better without spending too much extra money. It all has to come out of my pension.

[Gina]

I've been investigating magnetic damping and a while back bought this ultra-strong magnet http://www.amazon.co.uk/gp/product/B003 ... ss_product. It certainly has a dragging effect on aluminium plate and copper tube. It travels quite slowly down a 28mm copper water pipe held vertically! It seems quite weird You put it in the top of the pipe then wait a while and then it drops out the bottom and quickly lands on the carpet (care taken not to let it drop on a hard surface). But linear damping is not what we require. Using one end quite close (1mm or so) from a flat piece of aluminium produces a noticeable drag. So a disc would be best for rotational motion.

I also thought of using the wall of a section of copper pipe but without specially made iron poles, the magnet would be further away from the metal on average and produce less effect. So I think I'll try to sort out something for a disc.

[Gina]

I've found an old aluminium saucepan lid - mainly just lacking its knob, otherwise reasonable. I'm not short of saucepan lids so I can use it for the damping disc. I checked it by suspending it in the middle, high enough to allow the magnet underneath. With no magnet it would spin for several revolutions. With magnet I couldn't get it to do even 90 degrees. Magnet was something like a couple of mm from lid. I might cut it down in size (tricky) or I might just leave it as it is, putting the magnet underneath with the lid the normal way up - it can act as a roof. Might need to add an extra ball bearing to allow for windage. I've found a source of ball bearings of all sorts of sizes at around a couple of U.K. pounds each (bit more for large, thin ones. Probably post another diagram tomorrow.

[sanramonrover]

Hi Gina, - Rollo has a nice description and photos in the thread "Yet another wind vane mod".

[Gina]

Hi Gina, - Rollo has a nice description and photos in the thread "Yet another wind vane mod".

Yes I have an apology to make - I should have acknowledged his contribution - it was that that gave me the idea. Thank you Rollo

I was originally thinking of having the damping disc attached to the vane with a stationary magnet but I think Rollo has a better idea with the disc fixed and the magnet rotating. For my system it could be the counterbalance for the vane. I was thinking of using reflective photo sensors and a gray encoded painted disc for reading the direction but the moving magnet makes reed switches a viable alternative (larger than the F.O. circuit board and feeding a 1-wire network). This would avoid needing a power supply. I expect my wind vane to be several times the size of the F.O. version.

[Gina]

Latest design.

New-Wind-Unit.png

[brassing]

Has anyone given any thought to increasing the moment of inertia of the vane? The response time would I think be directly proprtional to that, assuming the aerodynamics stay the same. I think I saw one photo of a modified vane with some lead? on the central hub but that is the wrong place to put it. You need to put the weight at the two ends of the vane in such a way as to keep it balanced (otherwise it becomes sensitive to any vertical misalignment).

It would help to have damping as well but damping only works after the vane starts moving.

[Gina]

Has anyone given any thought to increasing the moment of inertia of the vane?

Yes, I have. IMV it would only make it slower to respond to a wind change and once moving it would tend to move further before returning to the correct direction - the only result would be an increase in the time scale, with no improvement in overshoot. I plan to make my vane as light as possible to make it responsive. In fact the minimum weight will be determined by the weight of the magnet/counterweight.

It would help to have damping as well but damping only works after the vane starts moving.

Precisely, it stops it swinging too far before coming back to where it should be. The lack of damping is the main problem with the F.O. wind vane IMO.