 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Windmills : First Catch
| Author | Message | ||||
| pntrbl Newbie  Joined: 12/07/2008 Location: United StatesPosts: 32 |
I got the mechanical portion of my anemometer done and and out in the air today. There's been numerous times in the past when I've "caught" the wind with objects big enough to almost blow me over, lol, but this is my first intentional catch and man, it's a joy to watch 'er spin. Here's a pic. 
The cups are 2" and the total dia is 9". .005 endplay. I'm very proud of holding the runout at the tips of the cups to .020". I don't know why tho! I seriously doubt it needs to be that accurate but I can't seem to help myself .... It's running on miniature Class 5 bearings. 5/16"(8mm) shaft. Just a puff will send it around a couple of times. 8 pulses per revolution from a rotor out of a 350 Chevy distributor that will be switching a hall-effect sensor. I am having trouble with the sensor tho. Nothing electrical. In fact, all mechanical in that I keep breaking the leads off at the body. I'm probably being overly fussy about the way the wiring lays in there but them little leads sure won't take much. There's a minimum order at Mouser where I'm buying them so we have 8 arriving on Friday. THAT oughta be enough! Until then I'm working on the pole. Plan A is a 15' pole on top of the 16' peak of my house so I'll be up around 10m. I plan on leaving this up for at least the next year so I've done everything I can think of to insure long term reliability. The cups are stainless as is all the hardware. Body, hub, and arms are 6061 Alu. I figure there's 3 ways for the outside to get in and muck up the works. Top, bottom, and the split between hub and body. The top has a Viton rubber sealing washer under the acorn nut. The bottom's hard to explain so perhaps a pic will do better. You can also see the Chevy rotor in this one and a soon to be dead hall-effect. 
Any dirt, moisture, etc. will have to get past the lip and UP a 2.75"x20 tpi thread that's hard to see in the pic. I suppose I could use some sort of sealer on the threads but I'm not thinking it'll be necessary. Opinions are welcome tho .... The hub extends down to .015" above the fat part of the body and the top bearing is located just under the arms. Any contamination from there will have a labyrinth to contend with. Under the .015" gap at the split, up 1.375" thru another .015" gap, and finally over the top .015" gap to reach a double shielded stainless steel bearing. I do get carried away sometimes .....  .
So there it is. Any comments, advice, or general slaps about the head are as always, welcome. SP |
||||
Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5117 |
Now that is one sexy looking anemometer! 
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
||||
Gill Senior Member  Joined: 11/11/2006 Location: AustraliaPosts: 669 |
But Bill, You haven't painted it...and it spins the wrong way. In the Northern Hemisphere they have to go the other way, just like hurricanes. 
Sorry mate, just pulling your leg. It really looks great. I am envious. Well done. 
For the leg breakage, I can only suggest to try finer wire. I wouldn't suggest anything bigger than you have in the pic. For mine I've used wire that size also wire about 1/3 that. At least with the 8 you have coming, Murphy's Law says you'll be successful fitting the first one. Guaranteed. Will be listening for the cheering when the first data comes through.  was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
||||
Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Interesting to see somebody else's solution to a home brew anemometer. I have on up my roof for about 20 years now, it took a while to sort out teething problems .
I ended up mounting it upside down (cups rotating BELOW the sealed body) as that was the only long term low friction solution that actually excluded rain ingress. Its the water that will ruin the bearings, not dirt. I too use miniature bearings on a 1/4" shaft, took off the seals to reduce their friction. Cups were made from plastic towball covers, I'm amazed how long these things last (they're black). For the sensor I use a home made ten slot disk and an optical sensor - far simpler (IMO) than the hall effect gizmo's and very reliable. I calibrated the unit in a home made wind tunnel against a borrowed anemometer. The display is a 30LED string (1 knot per LED) whit a doubling switch. The unit also has wind direction (mounted on top of the anemometer), the vane drives a precision servo potentiometer with a 360 degree range which is connected as a voltage divider. A 16LED circle provides the readout. Klaus Klaus |
||||
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi pntrbl, Hall effects do have thin leads. This is true of Alegro current sensors as well. Make a support from an old piece of PCB. Drill 3 holes for the leads, and bend at least 5mm from the device body and cyano the device to the board. Solder to the protruding legs. You could also find a ready made pcb from this type of component in an old VCR. Gordon. become more energy aware |
||||
| pntrbl Newbie Joined: 12/07/2008 Location: United StatesPosts: 32 |
Thanx for the responses and encouragement guys. And Tink, wow, 20 years and still flyin'? That's fantastic. I can only hope ..... Again hopefully, rain might not be much an issue as I live in a desert. Annual precipitation is 5.51" inches and I swear, some years it don't rain at all. Sitting up there in the sun means it's gonna get HOT tho and that may be more of an issue. The sensor's good to 150C and I'm using JB Weld for epoxy that's rated 600F, but I'm wondering what's gonna happen to whatever light lube there is in those bearings. Hmm. Time will tell. Tinker brings up another good point in that I've got to calibrate this thing. Eventually I want to use the data to build the ultimate dual rotor axial for my area so I'd like to be reasonably accurate. I've got access to a buddy's handheld but all I was gonna do was put them both in front of a fan at various distances. Should I knock a box together for a tunnel? Are there any other tricks or ways for a dummy like me to get fooled into false readings? As always, any advice is greatly appreciated. SP |
||||
SparWeb Senior Member Joined: 17/04/2008 Location: CanadaPosts: 196 |
Wind Tunnel? Hey just put it on a pole, stick it out the window of your car, and go for a long, lazy sunday drive. Helps to have a companion to scribble notes from the multimeter(s) as you maintain reasonably constant speeds. I brought a GPS because the spedometer on my truck isn't very accurate. Test on a very calm day, and when you can, drive one way, then back the other, and compare the readings in opposite directions. Even a small breeze can throw the numbers off, so the average of a South, North, East and West set of headings will fix that. The companion also comes in handy because other drivers will pass you going 10 mph, they will lean out and make silly remarks, such as "you'd go faster if you use the engine of your car, instead of that little fan to push you along!", and a sharp-tongued wife will put the oafs into line, while you just get red-faced. Steven T. Fahey |
||||
| pntrbl Newbie Joined: 12/07/2008 Location: United StatesPosts: 32 |
Well there ya go. I never even thought about GPS. That stuff is deadly accurate. I can see me hanging out a window ...... SP |
||||
| pntrbl Newbie Joined: 12/07/2008 Location: United StatesPosts: 32 |
I drug this thread back up because I've done some preliminary GPS calibration on my anemometer, (aka the UFO), and I'd like to run some numbers by you guys. 9" rotor and in the pure mechanical respect, think 9" disc, it would have to turn 37 rpm to go 1 mile in an hour. I realize the wind's not gonna do that but I'm so far from there it makes me wonder about the numbers I am getting. 1st of all I'm using some software called WinScope that makes a PC act "sort of" like an oscilloscope, and it has a maximum sweep of 50ms. That will measure 20hz and up, but even with 8 pulses per rev the UFO's gotta be turning 150 rpm just to get a full pulse on the screen. At 10 mph that doesn't happen. At 15mph it's good to go tho and that averaged out to 198 rpm. At 20 mph we got 260 rpm which is roughly linear. If I extrapolate that back to a 1 mph windspeed I get 13 rpm, 260/20, and that's where I'm getting the big disconnect in my brain. Long way from 37 .... I suspect I've ran right smack into into Betz's Law, but I'd sure like to know what you guys think ..... SP |
||||
| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
SP, You seem to be constantly referencing your anemometer back to a theoretical TSR. Why? Who says an anemometer MUST have a TSR of 1? Reading the history of the anemometer on Wiki I see the original inventors assertion of a set TSR was found to be in error. Now no one will give a value only a large range of possible values. If your equipment is linear and calculates out to a TSR of 0.4 , so what, could this not be attributed to bearing friction(drag) and how about the drag of those thick spider arms? What coefficient do you allow for them? If your readings are consistent and linear you have a successful anemometer. Another thing, are your magnets N, S, N, S, N, S, N, S? Whilst this is 8 poles, the hall sensor will only pulse 4 times. Will this bring your 13 up to 26 and somewhat closer to your theoretical 37? Or your theoretical value should really be 18.5 and within that practical range for anemometers? Why not confirm the exact pulsing per rev with a voltmeter when turning slowly by hand? I hope that gives something to look into and maybe resolve what appears odd.  was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
||||
| pntrbl Newbie Joined: 12/07/2008 Location: United StatesPosts: 32 |
Thank You for your response Gill. This wouldn't be the 1st time I've made mountains out of molehills!
I've knocked some more numbers around, got a TSR of .34, and after your response and re-reading that wiki article I am more than happy with that. The original inventor may have been wrong in thinking "all" anemometers moved at 1/3 the wind speed, but he got mine right ..... SP |
||||
 Print this page |
 |
The Back Shed's forum code is written, and hosted, in Australia. | © JAQ Software 2025 |
