Street lamp post for turbine towers

[JLB FAB]

I have recently acquired a few 30' - 35' traffic light poles that where damaged at the top where the horizontal pole bolts up. The poles are approx 3/16" thick have a 1/1/4" thick base 16" diameter to about 6" at the top. Does anyone see why these wouldnt work to mount 3kw turbines on. I plan on adding a small extension of 6' to 10' attached with a bolt flange. I have a cnc plasma table in my shop that will do up to about 1" thick so I can cut my own flanges. I live in a real windy area where all the trees show signs of flagging so I think its gonna be a good site. My plans are to eventually to have 3 or 4 turbines along a fence along one of our hay fields. We use alot!!! of electric with the welding shop, farm and greenhouse, I would love one huge turbine but I think more smaller ones are more affordable and accessible when maintenance  is required.

[PaulJ]

Some lamp posts are designed with a weak point near the bottom so they bend or break in the event of a vehicle collision, might make them unsuitable without reinforcing.

   Paul.

[JLB FAB]

One of the poles still has the remnants of a cast aluminum base that was sheared off. the post has a small dent in it that I was going to overlay will a piece of plate I will roll to fit. In an attempt to straighten one that has a bow in it I chained bow upward and drove a case 580e backhoe up it and nothing happened, I think that one is destined to the scrap dumpster.

[JLB FAB]

I forgot to mention the 3kw exmork produce 6500 lbs of force in a 110 mph wind, I have spoken to engineers on this and as soon as they hear what I am proposing they want no parts of it citing liability issues. The only liability is my property and if it works it saved me several thousand dollars!!!!!!

[SparWeb]

The Exmork tower probably has a base 12 to 16 inches in diameter.  A streetlamp post might have a 6" base.  The difference is a factor of 8x stronger, probably more.  No engineer will put those two together and for very good reason.  I've evaluated some of the Rohn free-standing towers myself and find that they can only take about 8-10 feet diameter WT's where I live. 
You also say that these have been damaged in some way...  Even more reason to STOP!

[Norm]

Well according to the ones replying sounds like good advice to heed and
stop but like you say it's on your property and no liability to no one else.
.....too bad it's always been a thought of mine....just a thought for me
it would never happen....still nice to know that it's not a very good idea,
thanks for posting.....
BTW  to all the guys that posted .....how good are wood "telephone"
post for this application?
Hmmm......but come to think on it I have seen a telephone post snap
when hit by couple tons of steel at 30 mph.

[Airstream]

Even with a 'turn-key' store-bought system leaping into ONE 3kw system for a first wind turbine is a little, umnn,  arrogant? (EDIT: missing the correct word, arrogant may be too harsh!)

The lamp poles sound like a good deal as your learner system - pick up the 1kw exmork or a Dan-Built 10 or 12-foot turbine and get the subsystems rung out, get your crew trained on operating it, etc....  sure it won't be a manly grid-tie from day one but if you want instant power find a deal on 3 or 5kw of grid-tie solar and let them pay for themselves then pipe a smaller turbine into the system for the hours the sun doesn't shine?

[poco dinero]

Before I made my tower decision I saw a Fieldlines post by Adobe Joe up in Wyoming in which he described how he had gotten some salvaged oil field pipe and built his own 60 foot free-standing tower.  He put a 10 kw Bergey ($$$$$) on top of it.  Even posted pictures.  I thought that was very cool, so I went down to Bakersfield, California (oil country) and found a place that had about 80 acres of salvaged pipe.  I bought five 12 foot sections, starting at 16 inches diameter at the bottom and sleeving down to 4 inches at the top.  The whole mess cost me less than $500 and a tank of diesel fuel.  Thought I'd skinned a fat cat.

Then I found out that my county building department, which had previously told me that I didn't need a building permit to put up a tower and wind turbine, changed their minds and now I needed a building permit.  And my homemade tower design would have to be wet-stamped by an engineer registered in the state of Utah.  Well, I'm a damn good engineer but I'm not registered in this state, so there went that idea.  Anybody need some pipe?

As some of you know, I ended up buying two Chinese hydraulically operated towers.  These towers are available directly from the Shenzhou factory for $3066, including the hydraulic cylinder and 14 fou dation bolts, but I got mine through Allen at Affordable Solar in Plano, Texas.  Cost me a little more to go through Allen, but he is Chinese and made all the arrangements, including clearing U.S. Customs.  I wasn't confident of my ability to buy directly from Chinese factories at the time, but have since found out that it works just fine.  Anyway, I got my towers and they are awesome.

Bottom line, if you are confident in your ability to use these lamp posts in a safe way, and nobody can get hurt, and the local authorities don't shut you down, I'd go for it if it was me.

[poco dinero]

Hello JLB, 

That advice from Airstream above is absolutely right on target--except I wouls have used the word "ambitious" instead of "arrogant".  Three kw is a pretty big machine to cut your teeth on.

poco

[JLB FAB]

I am not new to this I have a 3 kw solar array ,xantrex inverter and a homebrew windmill. I make washer plates and various stuff for a local wind turbine installer and simply thought the poles I have are the same size as his skystream poles but dont have as many holes in the base. I was just looking for some opinions . The skystream has a 13' rotor I thought the 3kw exmork was about the same. Below is the windmill I cut my teeth on built from scratch no plans just built it. It works to ,4 perm mag gennys a few sprockets and some stainless steel chain. 4 generators are wired in series to bring the out put up as I get about 65 rpm before the blades stall. I find the arrogant comment just that , I haven't been on this forum long enough to talk about what I have so people assume and what does that do but make an ass of u and me.

[JLB FAB]

Airstream,

"umnn,  arrogant? (EDIT: missing the correct word, arrogant may be too harsh!)   "

  I know you edited but it was initially thought or wouldnt have been said , how about asking what I have going on first I considered a manly 50 kw unit it was $290,000 after federal and state programs $160,000 cost to me well maybe next year. I can do a hell of alot of other stuff with that kind off money. I like to consider myself resourceful and thrifty with just a little smarts.

[DamonHD]

The problem is that quite a lot of people join up without the smarts that you have, but think that they do.  It's difficult to tell in the first few posts which category someone is in...  %-P

Rgds

Damon

[TomW]

I am not new to this I have a 3 kw solar array ,xantrex inverter and a homebrew windmill. I make washer plates and various stuff for a local wind turbine installer and simply thought the poles I have are the same size as his skystream poles but dont have as many holes in the base. I was just looking for some opinions . The skystream has a 13' rotor I thought the 3kw exmork was about the same. Below is the windmill I cut my teeth on built from scratch no plans just built it. It works to ,4 perm mag gennys a few sprockets and some stainless steel chain. 4 generators are wired in series to bring the out put up as I get about 65 rpm before the blades stall. I find the arrogant comment just that , I haven't been on this forum long enough to talk about what I have so people assume and what does that do but make an ass of u and me.

You need to relax. Not everyone has the same vocabulary.

Unless you want an argument take it as a lack of communication skills and move on.

Nice looking unit.

We get folks in here all the time with manly plans and no clue what it entails.

 We tend to discourage the jump into a huge one first idea because there is a LOT that does NOT scale on these units. Some folks get it some don't.

I know Airstream personally as in in the real world and he is not the type to say mean things and he did try to explain.

We only know you by your posts so how could we know you have  built stuff? Or have an RE system?

Remember, you came to us we did not come to you. All we know of you is what is in your postings here. I cannot tell if you are an idiot or a genius from a few posts here. So many instant experts online it is hard to tell a well read 12 year old from a 55 year old master fabricator from a handful of posts. See where I am going here?

Just a couple thoughts and I will leave it there.

By all means carry on. Please keep us in the loop.

Tom

[Harold in CR]

 I think the guy stated his situation very well, in his original post.

  He said "Traffic Light Poles", not street lamp.

  He said "16 diameter at the base, going to 6" at the top".

  He stated "3/16" thick tube".

  He stated " Drove a backhoe up on one to TRY to straighten it".

  I often read things into a post that are not there, or, miss parts of a post, just like most of the people online.

  I'm no Book learned Engineer, but, I see NO reason to not try, at LEAST, one set up. If anything, he loses the blades and tail in a crash.

[JLB FAB]

         Thats fine I tend to be quick tempered and as you say lots of know it alls with nothing to back it. I would love to share more pics of my stuff but it wont let me post more pics. Im the type that builds everything I am a fabricator by trade but do a little of everything. Ive got 5 hombuilt rigs under my belt 4 are bent and damaged and didnt work as planned, the one pictured came about on a slow day in the shop with lots off leftovers from a job. I built it in about a month of evenings and designed it with the old windmills in mind. Tons of torque, I didnt use as many blades thinking it wouldnt stall as quick. I started to build a asynchronous turbine using a 3 stage 10:1 reducer and a 25 hp 800 rpm 3 phase motor then couldnt afford the material for the tower and blades. 40 feet of 3' diameter 1/2" wall pipe is $3400 each and I wasnt sure it would work so its on hold for now. I would like to think I might be able to help some folks on here and vise versa.

[poco dinero]

Hello JLB,

I went back and read your original post, and have a few comments.

You said that the Exmork 3 kw wind turbine, which you are considering using, generates 6500 pounds of rotor thrust in a 110 mph wind.  I don't know where you live, but the building code where I live only requires structures to be designed for a maximum wind speed of 80 mph.  110 mph sounds pretty stringent.  If your house and outbuildings were designed to the 80 mph windspeed criterion, and a 90 mph wind blows them away, it won't matter to you whether your tower is still standing or not.  You got bigger problems.  My suggestion is to design the tower to the same wind speed criterion as your house, no more.

Secondly, the calculation of rotor thrust (which you stated was 6500 lbs.) is wrong.  Rotor thrust can be calculated as follows:

     RT = 2 * pi * (R**2) * rho * (V**2) * a * (1-a)

     where:

     RT = rotor thrust in pounds
     pi = 3.1417
     R = radius of the rotor in feet
     rho = mass density if air = 0.002378 slugs per cubic foot at sea level
     V = velocity of the wind in feet per second
     a = interference factor.  RT is at a maximum when "a" is equal to 1/2
     *  means multiply
     **  means  squared

For a side-furling wind turbine (such as the DanB 10 footer) that is set up to furl at 25 mph (37 feet per second), that is the correct windspeed to use in the above formula when calculating rotor thrust, not 110 mph or 80 mph, or whatever the structural windspeed design criterion is.  After furling is complete, assuming that the rotor is sideways to the wind, the force on the tower is strictly dependent on drag on the tower and turbine, not rotor thrust.  If the wind blows hard enough, the tower is coming down even with no wind turbine on it, so the drag of the wind turbine is essentially irrelevant.

However, you are considering the Exmork 3 kw wind turbine, and it is not a side furling  machine because the tail boom does not fold up when it furls.  It does yaw, however.  Even though I own three Exmork wind turbines, I haven't flown any of them yet, so I don't know the extent to which the rotor turns sideways into the wind, but I'd bet dollars to doughnuts that it doesn't go very far.  So I calculated the worst case scenario, a 110 mph wind with the Exmork rotor facing directly into the wind.  Using those assumptions, the rotor thrust comes out to 4236 lbs, not 6500 lbs as you stated.

You said that your lamp posts have a 1 1/4 inch thick base of 16 inches diameter, but to analyze the strength of the tower, an engineer would need to know the bolt circle diameter.  Let's assume that the bolt circle diameter is 12 inches.  You said that you plan to add ten feet to the lamp posts.  That would make the tower 45 feet high.  A force of 4236 lbs acting at a distance of 45 feet generates a moment of 191,000 foot lbs. (force times moment arm).  To keep the tower from tipping over, the foundation bolts have to generate an equal moment in the opposite direction.  You didn't say how many foundation bolts there are, but 12 bolts is not unusual.  The most effective bolt is the one farthest from the downwind edge of the base plate, since that edge would be the axis of rotation (giving that bolt the largest moment arm).

Assume for a moment that that bolt is the only bolt, because the nuts were removed from the other eleven bolts.  That bolt is 14 inches (1.17 feet) from the axis of rotation, and it would be subjected to a tension force of 163,000 lbs.  Assume that steel has a tensile strength of 50,000 psi; it would then require 3.26 square inches of bolt cross-section to keep the tower up.  A two inch diameter bolt would do the job.  Anchor bolts are usually 1 1/4 inch diameter, 3 of those bolts would do the job.

So, looks like your lamp post base would be okay under these assumptions.  That 3/16 inch wall thickness looks a little shaky though.  I'd want lots of  long gussets.

If it were me, I'd add the ten feet tower extension to the bottom of the tower, and use 20 inch pipe with a 24 inch bolt circle at the base, and at least 12 bolts, just to add some factor of safety.  My Chinese hydraulic tower has a 24 inch bolt circle.

Those so-called professional engineers you consult aren't afraid of liability--if they do their job right there isn't any liability. They're probably incompetent.  I have met lots of them who were downright stupid.  As an example, I once asked one of them to draw me a freebody diagram of a block and tackle, and he had some of the ropes in compression.  Ever try pushing on a string?

poco

[JLB FAB]

poco,

      I thank you for your opinion, you seem quite knowable and I like that. I got the 6500 lb from someone in Michigan and it was in kgs, I probably converted it wrong. I think what I am going to do is put up a 35 foot and 45' pcs of pipe 2" conduit (dont laugh too hard ) clamped to a hay wagon with a anemometer on top and see what kind of winds I get at the different heights. As I write this the wind is blowing about 25 mph the hay fields are laying flat. This is 300 days out of the year 2" of rain the past 2 days and now you cant even tell ,blow dried. As for my location Maryland just east of the Appalachian mountians, in an area that wind maps show as not real good for wind! Trees grow at a pretty good angle around here wind rolls off the mountains across 5 miles of flat farmland and were the first hill. Built my house about 4 1/2 years ago in the middle of one of the hay fields and the wind was relentless I was over at the neighboring farm daily retrieving construction trash from the fences, it was then I decided I cant stop the wind so I will put it to good use.

[halfcrazy]

poco,

  I decided I cant stop the wind so I will put it to good use.

Oh you can stop the wind and you will as soon as you put the turbine up. It works every time.

[TomW]

JLB;

You can always get a no hassle account to upload files over on pics.ww.com any size any number and it is free. Once they are on that server it is pretty trivial to copy and paste the location in a post here then highlight it and then click that 2nd icon above the smileys above the text window. The board will accept attached photos by clicking "Additional Options" below the text entry box. It keeps them with the story automatically.

Lots of ways to share photos and, frankly, we LOVE photos.

Tom

[poco dinero]

Hello JLB,

Since you said that you plan to mount some anemometers, I had to chime in once more.

What you really want to know is not instantaneous wind speed, but average wind speed.  If your site has an average wind speed of, say, 14 mph, you are in hog heaven.  You'll be cranking out lots of kilowatts, to be sure.  The average should hopefully represent a time period of a year or so.

To collect average wind speed data, you either need to sit in front of the anemometer readout for a year or so and take a reading every five minutes, and then average those readings over a year's time period,

OR:

You need data logging software.

A company called "Inspeed" sells anemometers with various length cables and they also can sell you their data logging software, called "Windware".  I bought their system, but you also need a PC to store the data, so my wife found me a really cheap, rebuilt  laptop on E-bay to do this job .  I'd like to end this post by saying that it works great, but unfortunately it's still sitting in my shop building, uninstalled, just like my three Exmork wind turbines.  Some day!!. 

I think it'll do the job though.  Check it out.

poco

[JLB FAB]

poco,

             You just got me thinking , a farmer west of us has a weather station thats been up for 2 years and he date logs, the wind hits him just before me so I could use his data. Also the catoctin orchard has the set up and is just before him. I am going to check it and let you know they are both on weather underground. I wanted to do the same but never found a $1000 for the weather station

[JLB FAB]

THAT WAS FAST!!! I found a 16-18 mph average every month this year, last years average 10.8 mph June - Aug like a 3-4 mph average .

[Perry1]

Secondly, the calculation of rotor thrust (which you stated was 6500 lbs.) is wrong.  Rotor thrust can be calculated as follows:

     RT = 2 * pi * (R**2) * rho * (V**2) * a * (1-a)

     where:

     RT = rotor thrust in pounds
     pi = 3.1417
     R = radius of the rotor in feet
     rho = mass density if air = 0.002378 slugs per cubic foot at sea level
     V = velocity of the wind in feet per second
     a = interference factor.  RT is at a maximum when "a" is equal to 1/2
     *  means multiply
     **  means  squared


Those so-called professional engineers you consult aren't afraid of liability--if they do their job right there isn't any liability. They're probably incompetent.  I have met lots of them who were downright stupid.  As an example, I once asked one of them to draw me a freebody diagram of a block and tackle, and he had some of the ropes in compression.  Ever try pushing on a string?

poco

Poco,
You must understand that yes, the thrust forces will be greatest when the axial induction factor 'a' is equal to .5 but that is a non  existent mathematical construct that does not exist in wind power. It indicates thrust on a rotor operating over the Betz limit. In fact the eqs you cite are the basis of the Betz derivation which points to the max rotor efficiencies that we all understand and obey under the axial momentum theory. Using a factor of a=1/3 would represent a rotor running right at the Betz limit by definition which would still be high. A more common value to use, at least for me. is a=.091 which corresponds to a rotor Cp of .30, probably a good value for the Exmork.

But then again, I'm just a PE trying to push on a rope 

Perry

[SparWeb]

JLB,
I have to apologize for almost getting this thread side-tracked.  I didn't read your original post as carefully as I should have, and missed the 16" bottom measurement.  By assuming it was a constant 6" all the way up, I decided to give you a reality-check.  As one member stated, I missed one part, then started to read the wrong message into it...   Ass of U and ME, all right.

I can't do much better than Poco's analysis: very knowledgeable.  You may have a 20" bolt circle on that tapering pole.  This does sound like the type of reinforced base designed to support large over-turning moments.  In that case, you have a contender.  I am still worried about the damage you mentioned.

Got any pictures?  Manufacturer's name + part number stamped on the side?

[poco dinero]

Hello Perry1,

Thanks for the clarification of the "interference factor" or  what you call the "axial induction factor" in the rotor thrust equation.   Using your value of "a" = .091 would reduce the rotor thrust on JLB's 3 kw Exmork from the 4236 lbs. that I calculated to an apparently  more realistic value of 1400 pounds.  We don't JLB to be running that turbine above the Betz limit; might get him busted by the wind turbine police.  But hey, if we keep working on this we might get it down to where he can weld two of those 35 foot lamp posts end to end and have one mean-looking 70 foot tower.

I didn't mean to imply that all PE's are stupid and run around pushing on ropes, but I'll stand by my statement that some are.  Some of them must have had a hell of a crib sheet at the exam.  Don't take it too hard, some medical doctors are quacks too.  Take out the wrong kidney, leave sponges in, etc.

If this isn't too personal a question, do or did you work for one of the commercial wind turbine companies like Bergey?

poco

[Perry S]

Ha! no prob Poco. I was just playing with you. I think your analysis was pretty good otherwise but I just wanted to clarify that point. When I took my exam there were no wind questions on it so having a PE doesn't mean anything with regards to understanding wind power.
I currently work at Northern Power and before that a couple years at GE Wind. Loads/systems integrations and lately PMA gen work. All multi-megawatt scale.
That background helps a lot but by no means makes me an expert in small wind. All my small wind stuff I learned from Hugh, the Dans and this forum as well as Backshed. Plus building my 10 footer and other small turbines as a hobby. After all, a guy that designs aircraft carriers probably couldn't design a very good ski boat.

Perry

[bob g]

here is my take on the subject,

i would go for using it, provided it (or any tower for that matter, even an engineered one) had a fall radius that was well away from
any person, animal or building i care about.

here are the critical points i would be most concerned with,

1. the mount flange at the bottom, how this is affixed is of critical importance as incredible forces are brought to bear on that interface
from flange to main tube.

2. i would not be concerned at all with the use of "undented" 3/16" wall material  with the OD and taper you are talking about.

3. there is nothing saying you cannot use guy cables as an added layer of safety.

4. if you are going to add to the top, i would not weld it, rather i would weld on a top plate, bored to fit the extention pipe or better yet
bored to fit a slip tube for the extension pipe to fit in, and use another disk that is of larger diameter to weld on the bottom of the slip
tube and slide the assy up through from the bottom.
then the extension pipe/tube could be slid it and there would be no weld at that interface on the extension pipe/tube.

5. i would "not" weld ribs to the base of the tube to the flange without some serious thought as to what the effects are, what generally
happens is one of two things, or worse both

   a. the ribs move the stresses up the tube, so have an engineer look into that, and

   b. the welds can provide a place for a crack to start, so having a professional welder do that would be in order

personally i think that with a little thought, and the use of some guys to add a level of added safety, and the slip tube/receiver
so that no weld is needed on the extension pipe at the top an you will be golden.

bob g

[wooferhound]

If you ever do decide to use a Lamp Post, You can build a ladder like this to put your turbine up with ...

[poco dinero]

Hello Perry S, 

Thanks for your response to my question about your professional involvement with wind power.

And your comments about the interference factor were most welcome and useful.  I personally have no professional experiennce with either small or large wind,  That equation that I posted came straight from a big, thick, book called "Standard Handbook for Mechanical Engineer's", Seventh Edition,, Page 9-8.  Just goes to show you how much you can trust those handbook engineers as compared to the ones with hands-on experience.

As for aircraft carriers vs. ski boats, I've been on some aircraft carriers (20 years in the Navy) that you could waterski behind, as long as you can hang onto the rope long enough, like at least five miles.  Those suckers could hit 44 knots----eventually.  Also been in  lots of skiboats--none of them could  launch an F-16, let along two at a time.

poco