Weight a minute - tail weight suggestions

[halfcrazy]

That is funny Bergey runs there turbines on MPPT

Anyways that is one of the finer features of the black box we can set an absolute amperage limit the stator can ever see. One of the issues with the standard turbine is not always the amperage coming down the wire but the heat in the stator from being over driven above battery voltage but yet clamped to battery voltage. I do realize that if you are handy and have time, Money and patience you can build a fantastic turbine that works very well like Chris has but not everyone has those resources a typical 10ft machine on a 100ft tower will probably cost most people $3-4,000 by the time they are done. Now if they can get 20% more power in average winds for $750 that seems like a good deal to me.

Another neat feature of MPPT is it allows you to wind a 10ft machine with a cut in voltage of say 75-100vdc and run it into the building on smaller copper and still charge a 24vdc battery. Lets say we have a typical install with a wire run from turbine to batterys of 300ft one way. A 10ft machine direct to a 24 volt battery we will be running 25vdc and 40A now that same machine running 100vdc will be 10 amps. I am not going to bother to figure the math but I am sure you can see already that the savings in copper would easily pay for the $750 dollar black box even if you programmed a straight curve at 100vdc so the turbine spun at its rated cut in RPM all day with no power gain you would be ahead.

So as you can see it is not really about peak Watts "although what guy does not like to brag" but the Mppt controller can offer a lot of other advantages Llike built in data logging that will include wind speed with charts and graphs available over the internet to the ability to use smaller wire also a pwm signal to do diversion on the battery bank and so much more.

[Volvo farmer]

For me.......... Chris is right. I can BUILD not buy... a decent mill for $400 including tower.  

Okay. I have to take issue with this statement. Maybe you could have done this a few years ago, maybe the AU dollar is trading 2:1 for the USD.. but I just looked up magnet prices.  Twenty four 1"x2"x1/2" magnets now cost more than $400 all by themselves.
http://www.ebay.com/itm//120771554771

How can you build a mill AND tower for less than the price of the magnets alone?

And Volvo, I urge you to read Flux's matching the load. If you design for the right part of the curve, you get a fair bit of the curve to play with. If you want good performance with minimal electronics, then  higher cutin with cap doubling as per Gwatpe (backshed) will give you your low and mid and high..... (or a booster.....but  seems less good than a good cap design)

GwatPe has managed to get as near as to perfect, the  cubic relationships between his mill and his batteries .... just with caps, and with very very good monitoring software to back up his claims.

So I don't share your all your views, and feel there is plenty of cause for the home mill builder to not despair and think he can only succeed with the help of your mppt solution..


Its all in the design..... and there are plenty of options around.

Well, if I understand matching the load, it requires extra resistance to be added between the turbine and the batteries.  It works because the improvement in performance is greater than the loss in resistance. It seems to me that MPPT has the ability to improve performance by the same margin without having to lose anything in resistance between the turbine and batteries.

I had pretty decent performance before MPPT. I don't think I have added more than 15-20% to my KWhr production.  I have my curve programmed so the thing does not get scary fast in high winds. The tips of my blades show significant wear, though I have zero battery-tied examples to compare to.  I also have a 5W parasitic load because of this controller 24/7.

Like you say, there are plenty of options. I just happen to like the whole concept of mppt for wind turbines. Five or six  years ago, it was an un-heard of concept and nobody could do it, it was practically impossible. Now somebody has done it and that tickles my funny bone and I want to try it. Thirty years ago, nobody ever had these things called Neodymium magnets. Then this guy named Hugh found them and figured out a nifty way to use them in a wind turbine.  Were they really "better" than the old magnets? or just "different"? I dunno.

I can appreciate the idea of keeping things simple and how that can help lead to an un-complicated  life, where we can fix all our own stuff and not be dependent on anyone else.  Personally, I look at the guys who have made this MPPT thing for wind possible, I look at their history and accomplishments, and I like what they are doing, so I invested in it, and them.

I think the real possibility for this technology is in reducing things like magnet and copper costs in future wind turbines. Maybe someday, we'll all wax nostalgic on the days we had to match loads to offset all the power we were making with 2" round magnets and still get good performance; much like a nifty old 500 cubic inch Cadillac V8 could roll a 3-ton chassis down the road in comfort and style.
 

 

[ChrisOlson]

How can you build a mill AND tower for less than the price of the magnets alone?

Use ferrite magnets.  I just built a ferrite unit no too long ago and it works good.  Oz straps'em together out of things like Seeley AC motors.  The expensive neo generator is not the only show in town.

Another neat feature of MPPT is it allows you to wind a 10ft machine with a cut in voltage of say 75-100vdc and run it into the building on smaller copper and still charge a 24vdc battery

That's definitely a factor.  I wanted to try a controller - I exchanged several emails with you about it - but I wanted to design a turbine from the ground up specifically for MPPT, instead of just bolting MPPT on to a turbine designed for direct battery charging.  But when I started looking at the details I ran into several issues.

• My turbines do not have this stalling problem.  They flat out freaking run.
• The controller does not handle enough amps.  I'd need two of them
• The controller does not handle high enough voltages.  I experimented with direct water heating some time ago and with the stock generator I was driving elements at 165 volts with the generator turning at 1,000 rpm.  The turbine was running way too fast - about 440 rpm.  If I bump the gear ratio up to .33 to put more load on the rotor, now the generator can go over 400 volts.  It would be operating on the raw edge and if your controller even had one single hiccup in it the voltage would hit 400 in the blink of an eye in decent wind and your controller goes "poof!!"
• To "fix" the above problem, now I need another device - a voltage clipper.

In the end I decided it's just not safe.  When you start pushing a turbine to the raw edge of its performance envelope, hooked to an electronic box that can't even protect itself from over-voltage without depending on an external device to do it, it's not if you'll have a disaster, it's when.  Things happen too fast with wind turbines.  I've had turbines running in storms that slammed the needle so hard against the stop in a 100 amp ammeter than it broke the needle off.  I had one bend a 2-1/2" diameter 18" long tower stub in a tornado once and the turbine looked like a 747 rotating to 45 degrees nose up for takeoff.  So I've learned to not trust any electronic box hooked to a wind turbine because I've blown rectifiers and melted wires that are a lot more robust than an electronic box.

After you fly turbines long enough you'll think you got it all figured out.  And then Mother Nature will throw a curve that you've never seen before just to remind you of who's really in charge.  You can only attempt to harness a small amount of the wind.  You can never tame it.
--
Chris

[birdhouse]

this should really be a new thread, as it has been hijacked so badly already, but... 

for a guy like chris, who is obviously very compitent at building very robust geared wind turbines with a very intense shop, and i'm guessing is retired minus the homestead  (chris, i mean this as a compliment), matching the load is not very hard. 

for the rest of us, mppt might be a very beneficial tool.  i think my mill cuts in too late for my 24v bank.   maybe some of you cut in too early.  it's all about hitting that sweet spot within the curve, for your wind area.  mppt may give the best of your mistakes.  it's kinda the fix for bad stators, or bringing the odd stator to life, or making your mill truely shine. 

if your like chris and are pushing 100+ amps @ 24v nom, maybe the midnite isn't for you, though i'm pretty sure you can program the unit to taper off mill power by decreasing voltage and heavily loading the mill in overload conditions.  or maybe it has some other functions, i don't know. 

chris, this is kinda a direct observation towards you:  you fought hell and high water that a 12v system works great in the past,  with high input mills, and SUPER high amps, then you switched to 24v without any regrets.  ...you may not always be right...

i just think that for the rest of us that can't cast 8-10 stators/year and test 4-6 magnet rotors per year, that is is hard to find the "curve" or even know where it is. 

chris is obviously ahead on most of us(compliment again), but for us others, mppt may be a very useful tool.   even if it is $700.  especially if you put alot of blood/sweat/tears into your turbine and it doesn't work quite like you wished it would, and building another would be a huge undertaking. 

just my thoughts...
adam

[Dave B]

  Lets say someone builds a book version 10' machine to the letter. I think some who have done this and have been unhappy with the results did not realize that the machine is only one part of the system. Maybe they have a poor wind site, maybe they have weak batteries, maybe they didn't understand what 300' of cable could do to performance etc. etc. etc. Plug and play, no such thing with a home built system.

  Now, this person might be frustrated enough to say forget wind or maybe this person decides to try to understand more of the system and work with it or maybe this person has more money than time or patience and decides that wind is still exciting enough to throw money at it to be more happy with the results.

  The first person gave it a go but now the machine is falling apart as well as the tower or maybe it's in pieces here and there, his or her spouse is a bit ticked off at all the money spent and or time out in the garage instead of paying attention to him / her and maybe fixing projects around the house instead would have been money and time better spent.

  This second person doesn't give up easily and figures there must be something wrong. Research is done here and there for a better understanding, questions are asked and different things are tried to better improve the performance of the system. If there is some success then this usually will keep this person interested enough to learn more, tweak some more and basically be happy with wind power and it's challenges as a hobby.

  The third person will not admit to doing anything wrong and or refuses to rework anything, the system should work as they assumed it should straight off the bench. Possibly there was enough money to begin with to purchase a self suppporting tower that they liked the looks of or maybe this was a code requirement (just money to fix that). Expecting never to really work on the machine much because it should just work this type of tower obviously becomes an issue for home built wind. You either now pay someone to climb and tweak and repair or do it yourself. That ain't going to happen, I did nothing wrong. If there are other money fixes then these options might be tried also. Enter MPPT or UASLC. $800.00 is not much money to save face if in fact the system can be tweaked with this tool enough to satisfy.

  Just a little math here. Lets say a 10' machine puts out 300 watts in a 12 mph wind straight off the bench. Lets call this average wind. Lets say a purchased UASLC box costs $800.00 and it's advertised to increase output 20% in average wind. This would be an additional 60 watts for 12 mph wind. If the wind blows for 24 hours straight @ 12 mph this would be an additional 1440 watts or 1.44 KWH. Lets say $.10 per KWH. this would earn $.15 cents per day. Lets see, dividing $800.00 by $.15 the wind would need to blow @ 12 mph 24 hours per day for 5333 days or 14.6 years to earn back your money spent on the box.

  I know this math can be done with all costs involved with making power. The point is that some boxes will sell, some will be on the fence about purchasing and some will flat out not consider it. IE: the types of personalities and money available will determine sales, always does.

  The next big marketing draw will be advertising the box as a smart box which just means that through algorythms, previous averages etc. etc. the box will work out the power curves for you. Woo baby, that's the one, that is until the next one.  Dave B.   

[Janne]

Very interesting thread overall.  As stated, it is possible to achieve quite a good load matching without any MPPT controller box. But having ran a DIY MPPT box for almost a year now I can easily see the benefits it gives you. First of all, it's the easiness of tweaking. Instead of making a new stator(or adding line resistance or whatever), just load up a new firmware to the controller the modify the load curve. If you value the effort put into it, the controller will "pay back" quite soon. Second, it let's you harvest the energy at peak efficiency right from cut in to the point of furling. My axial turbine is wound for quite a low cut in speed, it cuts in around 2m/s of wind. Probably not a good idea if you have decent wind, but in my site especially during summer months most of the energy comes from the slow 3-4m/s winds. With MPPT i can get the few tens of watts available in low winds, without having to sacrifice any of the mid-wind performance. Someone might say that solar panels would have suited me better, but I need power at winter too, and solar is no good here during winter months.

Overall MPPT best suits those, who build the system ground up with the concept in mind. Then all the benefits of it apply. If I were a contractor building these systems, MPPT would be the only sensible option with all the variables of the individual system in play. The biggest snag in them is of course the (un)reliability of the electronics.

If though all bits of the system can be controlled(each system built with same proven components), or there is enough time to tinker with it then MPPT probably is best avoided. I've also played with capacitor load matching (for direct heating), and they work great but it just takes more effort to find the sweet spot.

[oztules]

Sorry about your thread Dave, but it looks like I have a few questions to answer.

"Oz, can you expand on this?". Yes. As I understand it Flux was talking boost converters, and I'm not sure if it was in that post or another, but I recall him also talking of a more square function for the feedback loops........but not to put words in his mouth.... here's why I think that.

Notice I said impedance.... mechanical and electrical. Now we know the work the moving air can do will increase as a cubic function of it's velocity. So why less than cubic?

1. Velocity is a function of vectors, and the vectors at work are not the measured wind speed per-say.... because we have a gravity furling tail (cosine of the misalignment due to the gravity furling....the velocity the blade sees will be less than the measured wind speed, and it gets progressively worse as the wind speed picks up. If you have a straight tail (no offset for some reason), then this wont affect you... but it sure does on mine. I don't think I have ever had the furling anything near to my liking.... I need to try harder I know.

2. As we draw current from the stator, we generate the back MMF, which is in direct opposition to the magnet field. Now in axials Chris has shown that it cannot induce current limiting any where near to the degree of iron cored machines (think AWP). The neo's mask this effect much more than ferrites can, but the amp turns in the neo's is quite high
This allows the  back MMF to degrade the rotors flux  field as the current increases. This will probably exhibit as more RPM than we should have had for the incident wind speed....

3. As we increase RPM, we notice the effects of solidity start to come into the mechanical impedance. This is best seen on my pumper with 18 blades. It tops out at around 250 rpm, and no matter how hard the wind blows.... it does not seem to get faster. This obviously does not occur with three blades at the rpm in the average axial, but it does have a real and increasing effect as the wind speed drives the rpm up the scale.

4. The inductive reactance increases with RPM as the frequency increases. This will impede the current, making the rpm increase to get more EMF in order to overcome it. This will eventually result in current limit at the knee in the graph.... which for iron cored devices is very very much earlier than axials. ( I have not witnessed this in an axial) As the pole count increases, this becomes more and more prevalent, and of course as the rpm increases so the ac current will find it more difficult to make it's way through the inductance of the stator. I suspect that this will actually allow the TSR to be higher than we should have expected from the rpm: emf graph against windspeed, but the output will be down from where we anticipated for that windspeed. It won't add heat to the stator directly as resistance does.

5. As we increase the tip speed, the drag will increase. This will be more a problem with less than perfect airfoils I suspect..... but as a generalisation, as we increase the rpm, we increase the noise. This has to be paid for, and will reflect as lower available torque for the windspeed again. We should have had more power to overcome this drag (cubic proportion) but because of all the other things dynamically impeding our less than perfect wind transducer, the power to do this will lag the drag, and we will lose progressively more, as the wind speed picks up further.... it will run out of oomph eventually

So my  theory is that because of the dynamic nature of this inter-relationship, the losses are not linear. I don't believe that at "normal" speeds, that it will be an order of magnitude worse (squared), for air cored machines, but it won't be cubed either...... and it will tend towards squared as the wind speed picks up.... and as we get towards full furling it will be totally queer, but it will be warped well before that too. For iron cored machines I have been involved with, it is diabolical at even normal speeds. Nearly everyone with iron cores will have seen their mill run faster when they tried to brake it by shorting. The air cores are essentially resistance machines, so the mmf reactance and inductive impedance is less obvious, but the blade drag and furling problems will still be prevalent... and the furling misalignment will probably be the main culprit.


moving right along.....

"Okay. I have to take issue with this statement. Maybe you could have done this a few years ago, maybe the AU dollar is trading 2:1 for the USD.. but I just looked up magnet prices.  Twenty four 1"x2"x1/2" magnets now cost more than $400 all by themselves.
http://www.ebay.com/itm//120771554771

How can you build a mill AND tower for less than the price of the magnets alone?"

If I were where Chris is, I'd use those  ferrites he gets.... and I note Hugh has procured some for 60c/piece recently too (thebackshed.com today)..... As it is I bought 100 2"x 1/2" round N45 for just over $1000 (see them on anotherpower.com site) and just over 9 months ago, I bought 50 50mmX15mm N50 magnets direct from a manufacturer in China.... for $550) These are serious serious nasty dudes.

I bought 25kg 1.8mm wire for about $200  over 7 years ago (probably on another power as well havent checked for a while ) before I came here.

The 8mm steel for the rotors came from the side of a small ship that was built here some years ago (off cuts lying in the scrub) free. The mill head was from pipe scrap... free. The radial arms from power pole stays... free. The fibreglass for the stator from a local farmer (son in the business on the mainland)... helped with some fencing for a day or two... lots of beer and resin and glass..... free. about 30 liters of resin, and 10 meters of glass ......too much by a country mile. The resin I think was out of date, but 6 years on, still works fine.

Blades...... pine tree from the other side of the island..... $30.00 plus chainsaw fuel

2x12m x 8" galvanised pipes for the tower.... excess from a irrigation spray system... a farm 30 miles away.... free (delivery cost a few beers). The guy cables are 5/16" galvanised from a travelling irrigator......... hundreds of meters. No longer used, good condition..... free.
I own a drott (cat 955l 16 tons 4 in 1 bucket) diggs holes  etc etc.....
The 12m tower is free. If I were to use both pipes, for 24M.... still free. If I wanted another pole.... still free.

Don't  people over there even try any more to talk to neighbours and establish friendships? This is a very small island in the middle of nowhere....only 700 or so people. and I can find the makings of a turbine and a tower for nothing..... you people are on the most industrialised continent in the world..... and seem not to find simple scrap. I make solar for well under a dollar a watt.... for 900 bucks, I can easily do a 1000watt array. At this latitude (40) it will get 5kwh/day across the year....... on a remote outpost???

To add insult to injury, I have just finished the trial of my solar hot water system.... total cost ..... nill.  There is currently 320 litres of 65C degree hot water outside at the moment... and it is still only 2 days out of winter. Hot water cost over the last week 0 kwh.

Don't get me wrong, there is nothing intrinsically wrong with mppt. I just don't think the commercial version  is a sensible cost effective solution to anything really. It is easy to add an extra foot or so to the blades from what you thought you needed, and design it properly..... and blow the doors off the smaller mppt system. At least you got 15-20% improvement..... but if the neophytes listened to some folks here they would be genuinely expecting a 100% improvement...... and that will only happen if the machine was very poorly matched. Another more carefully designed stator would be money far better spent in my view. Just getting the furling right (I'm guilty) will yield probably more than your 20%.

Matching the load is way more than adding resistance. Gaps and resistance is when the horse has bolted. Better to build a new stator, and get it right.

I can't agree with your appraisal that Mppt will mitigate the cost of the mags and copper...... you can buy a lot of that for the kind of money being bandied about here

Just my thoughts from here..... and I'm not always right either..... but gee too much money for so little..... Solar panels (approved by CEC and CE etc) are down to $1.44watt now. At this price it is getting hard to justify building panels (I'm still half price DIY), but if you guys are putting out $4000 for a wind system of little consequence, I'd rather buy 3kw or more of solar panels. (government has destroyed the solar installation business in Aust.... plenty of bargains at the moment)

 I'm just not getting it apparently.
 .
And This :
"Another neat feature of MPPT is it allows you to wind a 10ft machine with a cut in voltage of say 75-100vdc and run it into the building on smaller copper and still charge a 24vdc battery. Lets say we have a typical install with a wire run from turbine to batterys of 300ft one way. A 10ft machine direct to a 24 volt battery we will be running 25vdc and 40A now that same machine running 100vdc will be 10 amps. I am not going to bother to figure the math but I am sure you can see already that the savings in copper would easily pay for the $750 dollar black box even if you programmed a straight curve at 100vdc so the turbine spun at its rated cut in RPM all day with no power gain you would be ahead."

Is all true................. but why stop there. On the AWP, we use up to 600v at the stator, and it comes down the big hill into the power shed..... where it gets transformed to 48v It is not voltage sensitive, it can't blow up, it is basically lightning secure (lets face it 1000 feet above the surrounding country with a steel tower..... looking for trouble).

The kicker is if you grab three microwave transformers, and rewind the things, it also costs next to nothing.... I just  have so much trouble seeing which part of DIY or built myself says ..........................buy something you wouldn't need if you had thought  about the problems and built accordingly.

There are other options, and as I have stated many times this darn thing does 24kwh and more ...day in day out  (and I'm not jealous.... hell no) for the last 5 years (I think it's that long)..... and the transformer is still perfect and will be for the next 100 years.


I'm just not on the right wavelength I know..... but why build it if you are not going to try to understand it. Black box may help the machine..... but not you.

Janne, just noticed your post. If you check thebackshed, some of the blokes are using cap doubling and tripling and getting up to 8 amps before cutin in the lighter winds. The cap banks look like starwars, but they are dirt cheap and allow for careful matching. Series caps for heating are only the start. Those fellows have taken caps to a new level by the looks. As an extra, they correct the power factor in the iron cored machines, and move the armature reactance up the scale, and mitigate the inductive components too.


Have fun, and I wish I had the chequebooks you blokes have got............. I would spend it wisely...... beer ,women... more beer......


.................oztules


Sorry again  Dave for messing your thread I will leave it there.................... I'll have to  retire shaken and beaten........ the big spenders can have the floor.... and whilst I can see their point, I just don't agree on the cost benefits involved.

[ChrisOlson]

On the AWP, we use up to 600v at the stator, and it comes down the big hill into the power shed..... where it gets transformed to 48v It is not voltage sensitive, it can't blow up

What he said.  When I put the trusty calculator to all this I figured out that clipping the voltage off at 200-250 is like wanting to climb the mountain but getting only halfway up and calling it "good enough".

Me sorry too, Dave, for messing up your thread here.  But OTOH your project is about extracting more energy and wanting a slower turning, more reliable machine.  I'd have to read back and see how it got going on the MPPT thing.  But it is important for folks who don't have the money, or want to spend it on beer, women, ......more beer, that a wind turbine is not a sorry state of affairs that needs an electronic box to make it run.
--
Chris

[12AX7]

Hello!

First of all let me state for the record that I don't have a horse in this race.  I'm in a location where I'd have to put up a 250ft tower to reach the wind.
So I haven't any comments on furling, MPPT, or any type of matching, whether impedance,mechanical or other.

However I would like to comment on a statement Chris made a few posts back.

------"After you fly turbines long enough you'll think you got it all figured out.  And then Mother Nature will throw a curve that you've never seen before just to remind you of who's really in charge.  You can only attempt to harness a small amount of the wind.  You can never tame it.
--
Chris"----------

A long long time ago I was helping an old ham operator put up a HUGE 40 meter beam.  I'm pretty sure it was on Halloween (end of OCT.)  We started early in the morning, a warm and humid day.  About noon we were both near the top of his tower (he was a few feet above me) and we felt a change in the wind,  temp dropped and from out of now where a fog bank rolled in.
With in a few minutes we couldn't see the ground.   We continued working and about an hour later the fog just fell.   We then saw that the clear skies had clouded over.  We had the gin pole mounted and one set of guy wires loosened when lighting struck a couple of blocks away, down the tower and into his shack.  In less than a 1/2 hour we had close to an inch of rain and it moved out of the area...  back up the tower.

Sun came out,  temperature jumped from the 50s to the 80s  Down the tower,  off with the coats and gloves..  back up the tower.
It took us longer than expected (rusted bolts)  to remove the 10 meter beam.   Another Temp drop.  and dropped some more.  Down the tower..  LONG UNDER WEAR..  coats .. gloves...hat..   Back up the tower.  Darker clouds...  hail... wind..colder..SNOW STORM   We had the 40m beam half way up the tower,  snowing so hard I could see only his feet a couple of rungs above me.  We lashed down the beam (to the side of the tower) and beat feet into the house.
Done for the day.
I said to the old man..  "sure looks like nature thru us a few curves!"    he said..   "boy,  just when you think you know what nature's ready to pitch she steps back ten yards and kicks a 60 yard field goal" 

Point being,  when it comes to nature..   she not only has all kind of pitches at her disposal,  she can change the GAME at a blink of an eye.

ax7

[Dave B]

  No apologies needed for such a good discussion. My own comments on MPPT got this going and at the time honestly was just an outloud thought confirming I was moving in the right direction. A large investment to patch my machine by running it faster is exactly the opposite of what I was working on. And as many of us familiar with how the components work together we know we can take that approach and dial in our machine to run faster where it makes the most sense for free. I keep saying it but I think it's helpful for some of the new and maybe uninformed out there to know that MPPT (user adjusted stepped load control) does not add any power to the system that isn't already there. (output potential for swept area vs. wind speed graph attached) These machines will scream already without it, try it you'll like it but be very careful.

  Here is a chart I graphed based on this link http://www.ndsu.nodak.edu/ndsu/klemen/Perfect_Turbine.htm It is loaded with great information and I go back to it frequently to keep myself focused on wind power. This clearly shows the potential of the monster's we have created. If you are running your machine any where near the ground for testing etc. please realize that you can be killed in a heartbeat, a run away machine or just plain carelessness, mother nature rules.

  Dave B.

  

[ChrisOlson]

If you are running your machine any where near the ground for testing etc. please realize that you can be killed in a heartbeat, a run away machine or just plain carelessness, mother nature rules.

Amen.  I got a bracket I can slide on the forks of my forklift with a pipe on it so I can mount a turbine on it and carry it around with the forklift.  I pulled it outside last winter with a 12 footer on it just to run the rotor a bit to make sure the balance was good.  After it got spinning at about 300-400 rpm unloaded I decided I had a problem because I had no good way to stop the confounded thing.  I had the yaw locked and tried to back the forklift up and turn it around to stop it, but the forklift just has smooth rubber tires, it was in the winter and the forklift got stuck.

I climbed up on the rollcage of the forklift and grabbed the output shaft with a leather glove on to try to brake it and all that did was get my glove really hot.  Couldn't find my jumper cables to short it but I found a piece of tester wire with alligator clips on it.  I hooked that up and it melted it off instantly along with fire and a bunch of sparks.  By the time I found some heavy enough stuff to short it and stop it I had to take a leak really bad.  I remember standing there peeing in the snow looking at that damned turbine and thinking to myself I'll never do that s&*t again.
--
Chris

[fabricator]

Mine is still on a 25 foot tower, the other day I glanced out there and saw the plug at the bottom was right up against the tower, meaning it was badly twisted.
So I stroll out there like hundred times before and unplug it and start letting it untwist itself, now, my turbine is scary quiet until it's spinning really, really fast, could be because I got 30% hearing loss but anyway I started noticing a noise and looked up, HOLY MOTHER OF PEARL, that summich was a blur, I completely forgot to plug the shorted out plug I got laying there to use for untwisting the cord.
So I says to myself, self, your head is 15 feet away from a runaway 17' turbine and if you plug this shorted plug into this thing your gonna end up lookin like a bacon wrapped appetizer with a giant toothpick stuck down through the top of you pea sized brain, lets get the hell out of here, so we did, fast as these 52 year old bad knees could run. Into the pole barn, up the stairs, into the shop, through the shop into the garage, to the stairs to the basement, down the stairs, plug in the compressor and apply the air brake.
By the time I got up there it was just sitting there like nothing ever happened, another "I'll never do that $#|+ again moments" too.

[niall2]

sorry this may be a bit off topic but as basic costs (sometimes hidden...or the scheme of things ?)... have been mentioned a bit with reference to mills i thought it might be ok to comment....

first time i tried to source some 6 mm guy wire cabling i was a bit shocked at the price from the local hardware ...kind of "take it or leave it " ...we dont really care ....i could,nt afford that kind of outlay, as i needed to think about all the other bits in some way ...just to get the thing up on a small mast

scrap yards are a god send....the guy just priced some cut off winch cable by the size of the boot of my car ... how much i could squeeze in there was up to me and i certainly fitted it in that day......

scrap yards are like that ....barrels of cut up steel plate from workshops , dumper truck axels , pipe , old electronics everywhere

later i was back to rummage around again and they were  oxy cutting huge spools of  elevator cable into 2 meter strips ,just to make it easier to get to the bailer.....what a waste

again sorry ...this has nothing to do with mppt or furling ......but economics do seem a base factor especially if the budget is tight