Author Topic: Weather vane design considerations?  (Read 3125 times)

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Offline SLOweather

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Weather vane design considerations?
« on: November 04, 2015, 03:24:08 PM »
I've started thinking about the design for the weather vane for the top of my gazebo project.

I want the shaft to extend through the roof to a second indicator inside, under the ceiling, so an off the shelf one won't work.

As far as the part that blows around in the wind to show direction, I've thought about it and then studied a few wind vanes I have here and 2 things come to mind.

The center of rotation, or the axis that it turns on, should be coincident with the center of mass in that plane. (If you held it horizontally, it should balance.)

The center of pressure needs to be on the side of the indicator NOT pointing into the wind. :) IE: the area of the vane downwind should be larger than the ares upwind. I think these are terms from my model rocketry days, and may not be the correct meteorological terms. As a matter of fact, the term for what a rocket who's center of pressure is significantly lower than the center of mass does when flown in a crosswind is "weathercocking". It flies into the wind. (The term for one with the center of pressure ABOVE the center of mass is "lawn dart".)  ;)

Any other ideas?

Offline ACWxRADAR

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Re: Weather vane design considerations?
« Reply #1 on: November 09, 2015, 08:14:48 AM »
SLO,

I don't really know what sort of design (in the manner of décor) you desire, but a certain visual image comes to my mind. 

A really large, flat, round disc mounted on the ceiling and painted to represent a compass dial with the cardinal directions and degrees.  Then, an extremely lightweight "needle" pointer painted red on one end and black or green on the other.  Red end points to the direction of the emanating wind. 

The needle would have to be extremely lightweight, less than maybe 15% of the master driving wind vane atop the gazebo as to not affect the indication and sensitivity.  If the needle was made balanced and ultra-light, it would perform and look rather interesting.  It would serve the purpose of informing you of the wind direction and also be a conversation piece. 

A slat from a mini-blind might work for this, if it were rigid enough to hold its own weight with support only in the center.  To balance it lengthwise, measure nearest to center as possible, drill a hole and support it on a string, then add weight by spray painting one end or the other with more coats of the desired color.  Attach it to the master wind vane with a small diameter brazing rod.  The brazing rod would provide a long, yet sturdy axle.

Another idea, for an ultra-modern / sci-fi appearance... 

Fabricate and attach a small "hub" made from 1/2" thick HDPE plastic to the axle or shaft that protrudes through the roof of the gazebo.  Drill a hole through the outside perimeter of the hub and insert a (very small) neodymium magnet in the recess.  Drill other holes to insert nonmagnetic weights around the circumference to balance the hub.

Next, fabricate a ring to encompass the hub and attach Hall effect sensors around the inside perimeter to sense the neodymium magnet.  Use these sensors to activate LEDs set in a circular ring around the ceiling or walls of the gazebo.  If you are savvy with electronic circuit design, you could use multi-color LEDs and have the varying output from the Hall effect sensors produce a "range" of wind direction.  i.e.  Where the magnet is detected most strongly in the center (the output voltage/current being the greatest) the LED array would light up red, then diminish to yellow and then to green.  This would produce an arrow of "light" indicating the wind direction.

You would have to use Hall Effect sensors with raw, analog output signals and no digital switching circuitry so that you can take advantage of the varying proximity of the sensor to the magnet and create the illusion that the LEDs are POINTING to the wind.

If you desired to get really wild, you could connect an anemometer into the mix and engineer a sort of "generator" whose output would control a separate set of LEDs (different color - like blue or white) set in a ring around the gazebo just like the wind direction indicating LEDs.  Only now, the LEDs would pulse ON-OFF in a sequence so that the LEDS light up in rotating pattern to make a circle.  The faster the wind, the faster the LEDs sequence ON-OFF making the pattern appear like a "twister" going around the gazebo.

RADAR   



 
« Last Edit: November 09, 2015, 08:18:05 AM by ACWxRADAR »

Offline miraculon

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Re: Weather vane design considerations?
« Reply #2 on: November 09, 2015, 08:22:57 AM »
This sounds like basically a vertically-mounted "axle" with the wind vane above the roof on the top part of the axle hub, then a pointer under the roof surface with some kind of compass rose and a pointer on this "hub". The arrow would correspond to the vane tip.

Is this what you have in mind? It seems do-able to me. The tricky part might be sealing the axle shaft to prevent rain water from following the axle into the interior of the gazebo. You would want a good seal without creating a lot of friction for the vane movement.

Greg H.




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Offline ACWxRADAR

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Re: Weather vane design considerations?
« Reply #3 on: November 09, 2015, 08:35:31 AM »
This sounds like basically a vertically-mounted "axle" with the wind vane above the roof on the top part of the axle hub, then a pointer under the roof surface with some kind of compass rose and a pointer on this "hub". The arrow would correspond to the vane tip.

Is this what you have in mind? It seems do-able to me. The tricky part might be sealing the axle shaft to prevent rain water from following the axle into the interior of the gazebo. You would want a good seal without creating a lot of friction for the vane movement.

Greg H.

This could definitely pose a problem.  I expect that a gazebo would be more open to the elements than any living structure and a little rain water (minute) wouldn't bother it too much, but what about the rain finding a way into the roofing and starting rot up there?

I guess this would all depend upon how the gazebo is constructed and its ability to "dry out" in open air.  I have seen a few people create gazebos out of old grain cribs - all galvanized tin.  No worries there, mate.  But, I'd hate to mess up a wooden structure.

RADAR

Offline SLOweather

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Re: Weather vane design considerations?
« Reply #4 on: November 09, 2015, 01:14:03 PM »
Gee, radar, you are as, um, creative as I can be.  (In a good way)... Some of your ideas spoke into an "electro-punk" station I've been considering.

Y'all have no idea the iterations and schemes I have come up with.

I thought about the magnet and reed switches. I also thought about a 4 level Gray coded chopper wheel and 4 opto sensor pairs to give a coded 4 bit signal for the direction.

I did briefly consider a wind bird style propeller on the front of the vane arrow to measure wind speed. But that would entail some sort of take-off brushes or something the get the signal off the vane.

The most interesting one I came up with also included a traditional 3 cup anemometer, with a twist... Coaxial shafts... The weather vane would be the inner shaft so it could extend through the roof. That would be supported on an outer tubular shaft by bearings. That tube would have the anny cups and a magnet for speed. It wouldn't have to extend through the roof. That would be supported by an outer, stationary tube and 2 more bearings.

Ultimately, I decided that the bearing drag would cause interference between the 2 sensors, and that it was too hard to build.

I also thought about a laser pointer in the end of the weather vane. That would look cool in the fog. However, we are 4 miles LOS to the airport and under the terminal pattern, so the FAA would likely take exception to it. 

Offline SLOweather

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Re: Weather vane design considerations?
« Reply #5 on: November 09, 2015, 01:31:51 PM »
More good comments...

First, as to the name... Gazebos are open-sided, and this will be enclosed, so that's out. I happened on a Word Power in an old Reader's Digest in the er, reading room. It explained trellises, espaliers, arbors, pergolas, and gazebos. That's where I learned that gazebos are open sided. It ended with a "belvedere". (Italian for beautiful view.) I always thought a belvedere was either an old Plymouth or an M. C. Escher print.



So, now, it's a belvedere instead of a gazebo.

In any case... I'm making the thing out of 1/2' Type M copper water pipe for the vane and axle, and 1 1/2" copper for the support.



This is the parts assimbled w/out solder for checking and cutting to size. The drip cup to protect the top bearing is a 2" copper cap drilled for the 5/8" OD of the pipe.

Offline SLOweather

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Re: Weather vane design considerations?
« Reply #6 on: November 09, 2015, 03:21:35 PM »
I got the 5/8" x 1 3/8" ball bearings from Ace Hardware. The ID is perfect for the Type M copper pipe. However, the OD is a little small for the ID of the 1 1/2" pipe.

I cut a 0.5" ring off the pipe and cut a piece out if it to make an internal bushing. That was still not enough, so I added a 0.016" thick ring of hobby brass. That was good enough, so I assembled it all together with a sacrificial bearing that was bad but the same size, and sweat soldered the bushings in place. (The soldering heat bubbled the grease in the bearing...)



Below, inside the cupola, I shortened the steel pipe from the button hook support from the dish, and then made a plastic dielectric adapter from some PVC and another custom plastic bushing...



Now I need to mark the center of the steel bottom dish hub plate and hole saw a 1 3/8" hole for the bottom bearing.

Offline ACWxRADAR

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Re: Weather vane design considerations?
« Reply #7 on: November 09, 2015, 04:18:48 PM »
SLO,

I see now the general shape of the upper or super-structure and what you are working with.  The main drawback to such a design would lie in the friction that the bearings would induce.  Your wind vane atop the gazebo (or as corrected - the Belvedere) would be required to be engineered and sized to overcome the friction of the bearings you select. 

The term "Belvedere" arouses a fond childhood memory of a cartoon for me....  From the days of Bugs Bunny and Yosemite Sam and all the characters from the Looney Toons of the fifties and sixties with Mel Blanc doing ALL the voices.   "Oh Belvedere,  come here boy!"  \

https://www.youtube.com/watch?v=igMeotKsEEM

https://www.youtube.com/watch?v=6hX3VGZJwSw

https://www.youtube.com/watch?v=iMZfCar-Ks8

I cannot seem to find the "Belvedere" cartoon, but if you grew up in the era, you will know what I am referring to.

RADAR


« Last Edit: November 09, 2015, 04:21:10 PM by ACWxRADAR »

Offline SLOweather

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Re: Weather vane design considerations?
« Reply #8 on: November 10, 2015, 09:37:39 PM »
Well, so far, so good!

Today, I hole-sawed the bottom hub plate for the bottom bearing, trimmed a few inches off the standpipe, and assembled everything for a test.



The top and bottom bearings are in place, as well as the top vane and indoor indicator, both made from 1/2" copper water pipe. You can see both of them in the photo. The vane has a temporary 18 square inch cardboard tail taped on it for testing.



In the limited wind the driveway experienced this afternoon, it worked pretty well. Based on looking at the Davis anny above the roof, I'd estimate the threshold to be 1-2 MPH.

I don't think bearing friction will be much of an issue. If anything, that and the mass of the rotating assembly might tend to damp out some of the swinging that a Davis vane does.

At Ace, I had a choice of bronze bushings or radial ball bearings, and chose the balls. They are sorta sealed. :) If the drag is too much, I can always wash out some of the grease (about the viscosity of Vaseline) with a little solvent.

Also, the indicator weight... If the copper pipe one adds too much rotational mass, I was thinking about a big aluminum knitting needle. I like the red/black color scheme idea, like a compass needle...

The sheet copper from McMaster-Carr arrived today. I can start working on the final vane arrow pointer and fletching (at least double the 18 in^2 I have now, if not more), and the directional letters...

FWIW, I captured a little less than 30 seconds of "first wind) at https://youtu.be/JjuKGuX5V-w. It's not a wild swing, but you can see everything tracking.


Offline ACWxRADAR

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Re: Weather vane design considerations?
« Reply #9 on: November 13, 2015, 06:36:48 PM »
SLO,

Hey!  Looks like it works to me!

RADAR

Offline SLOweather

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Re: Weather vane design considerations?
« Reply #10 on: November 18, 2015, 02:07:44 PM »
I got to thinking too much again, out in the Think Tank the other day, about the various ideas for adding wind speed to the copper weather vane.

Radar had some interesting ideas that I tossed around. I also thought about leaving the pointer end of the vane open, thereby forming a sort of pitot tube. But, for low wind speeds, I didn't think it would be sensitive enough.

Then, I came back to my original idea of 2 rotating coaxial tubes isolated by bearings. I realized that I didn't really need the full length outter rotating tube. I only needed a short section supported on the wind vane tube by bearings.  That would then only need a magnet and reed switch to form a speed sensor.

After a stop at the 99 cent store for 3 4" plastic Christmas balls for cups, I fabbed up a proof-of-concept "add-a-mometer" from a piece of PVC pipe, 2 junk bearings, and 3 wooden dowels.



The add-a-mometer is just slipped over the vane shaft and spins independently.

The theory is sound and it kinda works, but the old bearings have too much friction or junk or old grease  in them to spin freely. I might have to get new bearings. :)

If I can get it to spin well enough, it would look cool properly rendered out of copper.
« Last Edit: November 18, 2015, 02:17:40 PM by SLOweather »

Offline miraculon

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Re: Weather vane design considerations?
« Reply #11 on: November 18, 2015, 04:00:40 PM »
I really like the oak leaf vane. It is taking on kind of a "steampunk" aura, which I like....  \:D/

Greg H.




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Offline SLOweather

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Re: Weather vane design considerations?
« Reply #12 on: November 20, 2015, 12:56:43 AM »
I really like the oak leaf vane. It is taking on kind of a "steampunk" aura, which I like....  \:D/

Greg H.

Thanks Greg!

Aw, you went and invoked steampunk... Now I gotta make it work.  :)

I found a better bearing and washed most of the grease out with Tri-Flow, and temporarily reassembled the proof-of-concept prototype. The dang thing works! The wind cups rotate independently of the vane shaft. There wasn't a lot of wind when I recorded this clip, but, clearly the concept is viable, and pretty cool to watch...

https://youtu.be/vc2bRXADhJQ

So, today, I received 2 freer running bearing from McMaster-Carr, (open and no grease) and I'm on the hunt for three 3"-5" copper hemispheres.

So far I these options:

Hammer out my own from sheet copper. This may be above my current abilities.

Use half of a copper tank float. These range from affordable toilet tank floats (new or used) to some pricier ones. The tank floats are corrugated, while the more expensive ones are smooth and probably thicker metal.

Use copper bowls or ladle cups. Some are already "hammered" in appearance.

Any other ideas?


Offline PaulMy

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Re: Weather vane design considerations?
« Reply #13 on: November 20, 2015, 09:37:51 AM »
Quote
There wasn't a lot of wind when I recorded this clip, but, clearly the concept is viable, and pretty cool to watch...
yes pretty cool...
Nicely done.
Paul

Offline W3DRM

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Re: Weather vane design considerations?
« Reply #14 on: November 21, 2015, 01:01:42 AM »
Hey Chris, did you see we have a new member (WindAndVane). Looks like he/she is another wind vane enthusiast!  \:D/
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Offline SLOweather

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Re: Weather vane design considerations?
« Reply #15 on: December 09, 2015, 05:54:52 PM »
I picked up more copper yesterday at a local sheet metal shop, and hammered out 3 almost-hemispheres for the anemometer cups, and soldered them to the arms.



Here's a youtube video of the whole thing running in a light wind.

https://youtu.be/ohFKBsH1T84

 

anything