Author Topic: Are Using Monopole Towers Taboo? (Read 39580 times)

ChrisOlson · « **Reply #66 on:** April 16, 2012, 04:26:00 PM »

The other thing with lattice structures is ice loading. You can spec them 70 or 90 mph survival, no ice. Then throw some ice on it and suddenly it takes two more weeks of FEA work.

Simply put, monopoles are a LOT more engineering friendly.
--
Chris

DamonHD · « **Reply #67 on:** April 16, 2012, 04:44:09 PM »

Monopoles also don't encourage birds to roost in them, then fly off drowsy and ***chop***

Rgds

Damon

fabricator · « **Reply #68 on:** April 16, 2012, 07:06:05 PM »

Quote from: DamonHD on April 16, 2012, 04:44:09 PM

Monopoles also don't encourage birds to roost in them, then fly off drowsy and ***chop***

Rgds

Damon

That's called natural selection, some Limey wrote a book about it a while back.

DamonHD · « **Reply #69 on:** April 17, 2012, 03:54:54 PM »

But it annoys the enviros, and gets them into a very unnatural rage...

Rgds

Damon

fabricator · « **Reply #70 on:** April 17, 2012, 05:09:25 PM »

That is known as an apocalyptic fit, it's really fun to watch. I was at a wind power conference once where a lady from the University of Michigan explained how they determine how many birds and bats are being killed by utility scale wind turbines.
They tie a 500 foot rope to the base of the turbine and then 5 or 6 people walk out 500 feet and start walking in a circle holding the rope, as it goes round the tower it spirals them in towards the tower.
they walk very slowly because they have to check every dried up leaf because that is what bats look like when they've been dead for a while.
They do this once a year at one or two turbines at every wind farm in Michigan, in 2010 they found one bird (common house sparrow) and one bat.
A lady in the audience stood up and basically had an apocalyptic fit, because two living creatures had been killed by these turbines, she was a total whack job, I badly wanted to ask her about the people who are killed every year mining coal and drilling for oil, how many hundreds of thousands of living creatures have been killed by oil spills in the last 75 years or by Chernoble or Fukushima.

SparWeb · « **Reply #71 on:** April 17, 2012, 11:41:30 PM »

Going back to my thing about the monopole towers a bit... (sorry to swing back on topic)

I don't want to give the impression that monopoles are "bad". Might have sounded like that, though. Much like the bird lady in Fabricator's last posting, there is no good versus bad, no hero versus evil. Just different degrees of suitability for this or that purpose.

I'd much rather have a monopole tower, with no guy wires at all, myself. All that space on the ground not taken up at the anchors, less threats of some dork getting a trailer wheel snagged on the anchor and pulling the whole tower down.... I have many other reasons besides. Aesthetics are pretty important around here, even though there aren't by-laws or regulations on tower types and sizes in this county.

Balancing that is that truss towers are so EASY to make, and so light, and so stiff. Such useful properties that appeal to the engineer in me!

Fabricator,

That's a funny variation of the term "apopleptic", because there sure are some folks who think it's the end of the world.

As a fun quiz, I like to ask "how many people died in the Fukushima accident?" You can get some pretty big numbers, depending on who you ask. Do some research before asking that question, so when you give the correct number, then ask "What did they die of?". More knee-jerk answers. Good clean snobbish fun for know-it-alls like me.

tecker · « **Reply #72 on:** April 18, 2012, 08:23:49 AM »

This is all a really expensive and it seems like service would put me in dire straits . I can 't even think about something I can't service . I don't think you guys can't either . unless you own or can get a lift . So if you make a 60 to 80 foot serviceable tower you'll have to spread out the base so you can work the head or guy it to lower the head to the ground .

SparWeb · « **Reply #73 on:** April 18, 2012, 10:50:02 AM »

Quote from: tecker on April 18, 2012, 08:23:49 AM

This is all a really expensive and it seems like service would put me in dire straits . I can 't even think about something I can't service . I don't think you guys can't either . unless you own or can get a lift . So if you make a 60 to 80 foot serviceable tower you'll have to spread out the base so you can work the head or guy it to lower the head to the ground .

Exactly why I *actually* have a guyed tower, instead of a free-standing one. The internet is great for talking about what I'd *like* to do... But if the point has been missed before, and your point is a very important one, then it must be admitted that free-standing monopole towers are much more expensive than trusses or guyed-monopoles. Not just in buying the tower in the first place, but in costs raising it, too.

fabricator · « **Reply #74 on:** April 18, 2012, 06:41:51 PM »

Three leg lattice towers can easily be made to tilt up and down with a gin pole.

defed · « **Reply #75 on:** April 18, 2012, 06:55:03 PM »

they make monopoles that tile up w/ a nice little hydraulic cylinder. probably not something most ppl would want to fabricate, but it is possible.

fabricator · « **Reply #76 on:** April 18, 2012, 08:54:44 PM »

Yes they do, the American made ones will cost you and arm and a leg, the Chinese ones ARE sells are more reasonable, unless you want them shipped over here then the cost doubles, I have watched an 80 foot Chinese hydraulic tower raised and lowered, they work great and are built like a tank, I was surprised, the guy had a little Chinese Honda engine clone close coupled to a small hydraulic pump with about a five gallon oil tank, quick connects on the cylinder on the tower and the pump.
He hooked it up and I figured it would slowly go up, nope, it was like pull the up lever and it was up in about five seconds.
The problem is if you need an engineers stamp for a building permit An American engineer won't touch it with a twenty foot pole.

ghurd · « **Reply #77 on:** April 19, 2012, 10:04:49 PM »

I agree with what SparWeb said, but he said it better than me.
G-

fabricator · « **Reply #78 on:** April 20, 2012, 08:09:20 AM »

Lets not forget that a large and constantly growing number of local units of government all over the country now require by ordinance, free standing monopole towers.

dinges · « **Reply #79 on:** April 20, 2012, 03:28:08 PM »

Building a monopole tower is technically perfectly doable - other amateurs have done it:

(His fundation looks smallish to me, but I may be wrong, and he may have actually done the calculations for the fundation, or had them done)

http://www.windmolensite.be/index.html
(click on 'mast' and 'fundering' for more information)

However... even the professionals make mistakes....

Also keep in mind though that the fundation is at least as important as the tower though. You don't want this to happen to your tower and turbine:

Building a monopole tower is not something I'd undertake before really studying up on tower design and fundation design. Keep in mind that I am a mechanical engineer who is (supposed) to know how to do construction calculations (no fundation calculations though - that's more civil engineering; but have no doubt I could learn how to do that). But designing towers is definitely something I wouldn't undertake without a lot of extra study. The stakes are too high to risk mistakes.

So no, monopole towers are not taboo. And I visually much prefer the elegance of a monopole tower (they look beautiful to me) over cluttered guyed towers. But the economics are definitely in favour of guyed towers.

fabricator · « **Reply #80 on:** April 20, 2012, 06:33:41 PM »

The big problem with building a monopole is if you live in a area that requires a state licensed engineers stamp on tower and foundation it could run into many thousands of dollars, most I have talked to wont touch it at all, it's their livelyhood they are putting on the line when they stamp a drawing.

just-doug · « **Reply #81 on:** April 21, 2012, 02:07:26 PM »

in doing construction projects,there are generally to ways of design approval.one is builders standard.the second is engineers stamped.the concept of builders standard is that every body does it this way and it mostly works well most of the time,so lets do it again!if a regulating body was to give me crap about a tower ,i think i would invoke builders standard and tell them to go to hell if they didn't like it.if enough people use the same basic designs and it works,it must be scientific ,no matter what the engineers say because it is proven to work!no engineering stamp needed.to require a engineer stamp on a proven method or design is just racketeering for profit.it might even be illegal depending on the particulars.

fabricator · « **Reply #82 on:** April 21, 2012, 04:02:10 PM »

Do that in most areas with an ordinance and they will slap a non conforming structure sticker on it and fine you 50 bux a day for every day it is non conforming, and they will be perfectly happy to defend themselves in a lawsuit with your money.

Ungrounded Lightning Rod · « **Reply #83 on:** April 22, 2012, 01:36:01 PM »

Quote from: fabricator on April 17, 2012, 05:09:25 PM

They do this once a year at one or two turbines at every wind farm in Michigan, in 2010 they found one bird (common house sparrow) and one bat.

Even if there were bird and bat corpses present that doesn't mean the windmill killed them. Animals generally die where they live, and they all die eventually. (Most have a pretty short lifetime by our standards.) I'd expect a few corpses of the local wildlife around a windmill from time to time.

Indeed, a LACK of corpses would indicate that the windmill was driving animals away and reducing the available habitat. On the other hand, an increased number in the region near the windmill could indicate the mill is PROVIDING habitat. There are lots of ways that could happen: A mill could provide shade, wind-shadow shelter, roosting sites, nesting sites, drinking water (from morning condensation on or running down the support), different edible plants from nearby areas (due to modified microclimate or construction soil disturbances), a visual reference for navigation and improved territory definition, and I could go on. An animal X habitat has a lot more X corpses than an area where animal X doesn't live.

A concentration of prey species (as around a waterhole) leads to a concentration of predator species. So you get more corpses: Prey fatally injured by predators, predators fatally injured by prey, predators dropping dead from other natural causes, predators fatally injured by other predators - in territorial or mating battles, or niche-competitor battles. (Many predators battle other predatory species with overlapping niches - fighting "like cats and dogs". Bobcats, for instance, try to eliminate ANY other predator in their territory.)

So it's not enough to count corpses found near a windmill. You have to examine each corpse to determine if the windmill actually killed it by a blade hit. Even if it did, you still need to do a LOT of other work to determine if the windmill is a net loss or net gain for the species in its area. (It might even be providing additional habitat for some endangered species.)

fabricator · « **Reply #84 on:** April 22, 2012, 02:40:50 PM »

Try explaining that all that to a screaming greenie, I personally can't believe a bat or a sparrow could be killed by blades spinning at 50-60 rpms, seems like they would have to fly into them at full speed, then you have to get into the whole thing about the top speed of a common sparrow.......................

JW · « **Reply #85 on:** April 22, 2012, 02:44:05 PM »

This also does not discount, how many birds also fly into stationary radio towers with the same end result.

Ungrounded Lightning Rod · « **Reply #86 on:** April 22, 2012, 08:27:58 PM »

Quote from: doubledipsoon on June 07, 2011, 10:59:22 AM

The wild and wonderful wierd forces on any tower would spook anyone into throwing in the "cost effective" towel, and blowing 10 grand on a Rohn tower, better known as paying for their engineering know-how.

Wouldn't spook me. This wouldn't be authoritative for a code approval. But if I was computing loading on a tower I'd do it like this:

- A theoretical mill spinning and running steady-state at the Betz limit slows the air passing through the swept area to 1/3 its original speed, dumping 8/9 of its momentum. Wind variations (where the mill is not matching the optimum speed) and less-than-ideal blade designs might raise that, but not quite to the point of bringing its downwind motion to a complete stop by deflecting all the air sideways. So calculating as if the mill is a solid disk gives you a small extra margin.

- Side forces from the mill not being aimed dead on into the wind are also close to (and slightly below) those of a solid disk.

- The gyroscopic effect take the forces the tail applies trying to turn the mill and shifts them by 90 degrees in the direction of rotation. This takes the torque of the wind working against the tail (a lever arm that's easy to calculate) and turns it into a torque on the yaw pivot as if the windmill were trying to "nod" up or down. This is mainly an issue for the bending strength of the TOP of the monopole, similar to (but much smaller than) that at the BOTTOM from the wind load against the mill. (It's much smaller both because the lever arm is shorter and because the tail vane has much lower cross-section.) Meanwhile the yaw pivot is free, so there's no torque on the top of the tower. (If you use a motorized yaw system rather than a tail, you do get a torque on the yaw axis, and a copy of it on the "nod" {pitch} axis. But both of those are limited by the torque of the powered yaw system.)

If you think about it, this means that (neglecting the various vibration loadings) a mill on a monopole has essentially the same load characteristics as a round or oval advertising sign of the same cross-section, only slightly smaller than those of the sign. There are plenty of those along major highways. Looking up their designs should give you a good idea of how to calculate for a mill. (Or perhaps you can purchase a retired giant rotating gas station sign. B-D )

Quote

But, for the rest of us in a build it-mode, all you can conclude is that it's builder beware. I would suggest eye-balling the Rohn SSV tower, and duplicating it as accurately as possible (specific parts are listed on some web-site), and for us angle iron-lovers, beefing up the sizes. The big mystery now is why there were so few cross bows on the old angle iron towers, as compared to the Rohn SSV's. With all the old wincharger towers still standing it makes you wonder what's really necessary for a Bergey XL-1, not exactly a large machine. That little voice keeps telling me that the jury will be out on this one indefinitely.....Any three-legged angle iron tower builders out there with an XL-1?

Edit: Oops! That was from the original post. (I'd intended to respond to it further but got interrupted and missed that it was unquoted when I came back and posted. I'm leaving it there, now quoted, to minimize confustion. Sorry, Fabricator. I did already see in a previous response that Rohn isn't selling to us hoi-polloi any more.)

fabricator · « **Reply #87 on:** April 22, 2012, 10:13:26 PM »

And BTW, Rohn does not sell towers to the general public anymore, they only sell to turbine builders and communications type companies, they have a long form with all the specs for your turbine that have to be filled out by you, and being in the business as long as they have been they can tell right off if your FOS.

Ungrounded Lightning Rod · « **Reply #88 on:** April 22, 2012, 11:43:23 PM »

Quote from: fabricator on April 22, 2012, 02:40:50 PM

I personally can't believe a bat or a sparrow could be killed by blades spinning at 50-60 rpms, ...

Sure they can. Figure a TSR of 6 or more (for efficiency) and wind speed at the rotor disk of 2/3 the undisturbed wind speed. That puts the tips at four times the wind speed, minimum. Call it 60 MPH in a 15 MPH wind.

(I've generally assumed homebrew wind turbines tended to be designed with a TSR of about 6 rather than, say, 8, to avoid supersonic airflow in a storm. Seems to me increased drag wouldn't be overcoming the increased efficiency by TSR 8, and you can get such a mill start turning before cutin windspeed.)

Quote

seems like they would have to fly into them at full speed, then you have to get into the whole thing about the top speed of a common sparrow.......................

Birds are quite capable of knocking themselves out or breaking their necks flying into a picture window. Some examples from personal experience:

- I watched a pigeon in a mall garden kill itself that way when a hawk was chasing it, and there were a dozen or more bird-shaped dust prints on the same windows to indicate this sort of mishap was common.

- When my Nevada place (with a big prow) was under construction, one of the upper panes of the prow windows was broken during installation and the window frame was left open for weeks while the replacement was on its way. One day (when escorting a visiting brother on a Nevada tour) we visited the construction site and found a wild bird had come in through the opening and become confused. I was about to sneak in and opened the sliding door for it to escape, but my brother ignored my instructions to stay clear while I did this and tried to grab the bird. Of course it took off and hit a window pane. This one survived, but it was knocked out for maybe 15 minutes.

One of the problems with the early stealth fighter prototypes was that they tended to be surrounded by dead bats every morning. Hangers in a desert area are popular hangouts for bats. The geometry designed to bounce the radar signal anywhere but back to the radar worked just as well for the bats' sonar. So the bats flew full-speed into the titanium (or whatever) aircraft, with fatal results.

And then there are all the birds hit by cars.

(Of course the animal leftists would be happy to eliminate cars and large glass-sided buildings if it would just save one bird.)

SparWeb · « **Reply #89 on:** April 23, 2012, 02:01:47 AM »

Quote from: fabricator on April 22, 2012, 02:40:50 PM

... they would have to fly into them at full speed, then you have to get into the whole thing about the top speed of a common sparrow.......................

The coconut would put a nick in the blades!

ULR, The way to defeat the bird-lovers is to tell them how many birds are killed by cats every year. Bird-lovers are often cat-lovers (though not all) so spreading that statistic around should shrink their numbers.
... Also, I think Fab knows about the blade speeds, it was all set-up for the joke.

But, if you don't know about the sparrows and the coconuts, there's this great movie you should watch...

fabricator · « **Reply #90 on:** April 23, 2012, 08:21:49 AM »

Quote from: SparWeb on April 23, 2012, 02:01:47 AM

Quote from: fabricator on April 22, 2012, 02:40:50 PM
... they would have to fly into them at full speed, then you have to get into the whole thing about the top speed of a common sparrow.......................
The coconut would put a nick in the blades!

But, if you don't know about the sparrows and the coconuts, there's this great movie you should watch...

I'm glad somebody caught it.

adobejoe · « **Reply #91 on:** April 24, 2012, 08:51:46 PM »

Here is a 10 KW Bergey on a tower I fabricated. The tower is from salvage oil pipe. Three sections each twenty feet long. 22" dia, 18" dia, and 13" dia. Turbine is about 55' above ground level. My tower cost less then 2k. System gets very high winds. I am sure it has seen 80-90 mph. REcorded a 70 mph at base in early March. August will be 8 years of install and I have NEVER climbed the tower. Oh, average daily output is 23 KW...not bad on "short" tower.

AdobeJoe

SparWeb · « **Reply #92 on:** April 25, 2012, 03:09:15 PM »

Nice tower. 8 years without servicing it - exactly why people still buy the Bergeys.
Did you make provisions for climbing it (as you imply)?
I assume a crane was used during the erection, though.

adobejoe · « **Reply #93 on:** April 25, 2012, 11:36:17 PM »

No ladder or provision to climb. if I need to I can rent a bucket truck. Yes a small crane lifted it up. The most nervous part was assuring the 6 holes on the base met and aligned the large J bolts. I am totally impressed with the turbine design, although the inverter trips occassionally at high gusty winds. Attached pic was a few days ago in 50-60 mph winds. Even with the tail folded it will crank out 10-12 KW. The tower I painted brown to match our landscape (wyoming) and also the tail boom is brown. I am much happier with this design then a guy-wired as is standard bergey recommendations.

AdobeJoe

equiluxe · « **Reply #94 on:** April 26, 2012, 01:26:36 PM »

I had the problem of reducing the foot print of a cable stay mast and at the same time keeping the cost down about 15 years ago. The solution that I came up with is what I called the rigid stay mast. The stays are made out of 40mm dia. tube the whole thing is mounted on a cross shape made from I beam set in concrete that is 8x8 foot X 6 foot deep. There is a bow running down one side of the tube in order to stop bending during raising and lowering of the turbine during maintenance. There is no vibration or wind noise from the tower which mounts a 1 KW Bergey wind turbine unit which has now been up for nearly 15 years without needing to come down for any maintenance.

SparWeb · « **Reply #95 on:** April 26, 2012, 11:06:08 PM »

Quote from: equiluxe on April 26, 2012, 01:26:36 PM

.... no vibration or wind noise from the tower which mounts a 1 KW Bergey wind turbine unit which has now been up for nearly 15 years without needing to come down for any maintenance.

15 years? Are you sure you don't want to take a peek, maybe change out the bearings, all in the name of getting another 15 out of it?
(that's the meddling nosy side of me talking).

Cool-looking tower, by the way! How does it lower/raise?

equiluxe · « **Reply #96 on:** April 27, 2012, 03:11:27 AM »

If it ain't broke don't fix it. The stays are tension'd with 30mm dia. studs at the lower end. To lower the stud nuts are undone one bolt is removed from the central pole and the whole let down with a two ton chain block attached to the lower end of the pole and one of the stay anchors. When erect the stays are tightened until the longitudinal compressive forces on the central pole are greater than any bending force that would be applied by the wind, that means in effect they are done up until there is no slack and then given two full turns on each nut.

dinges · « **Reply #97 on:** April 27, 2012, 11:12:22 AM »

Quote from: equiluxe on April 27, 2012, 03:11:27 AM

When erect the stays are tightened until the longitudinal compressive forces on the central pole are greater than any bending force that would be applied by the wind [...]

But obviously not so tight as to cause instability (buckling) of the central pole. That'd be my main worry, but it's hard to argue with something that has been working for 15 years....

equiluxe · « **Reply #98 on:** April 27, 2012, 12:26:52 PM »

As long as the force is taken down evenly withe force the bolts will develop you are very unlikely to buckle the pole.

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Author Topic: Are Using Monopole Towers Taboo? (Read 39580 times)