Wind Generator...Shattered Blades

[artemis07]

More from Artemis07

The controller does have an " electronic break" which slows the generator. This is activated by a switch. As I understand it when the turbine speed increases and the generator is in danger of overheating the load is removed. In my experience this causes the turbine to increase in speed, this happens with winds over 40 knots.

We had no time to activate the electronic break or rig a mechanical break (a line). The controller's 20 amp fuse blew but not before the controller was burnt out. The turbine was spinning at several thousand rpm. The blade tips were travelling at speeds approaching Mach 1 where aerodynamic forces on the blade tips are extreme. The boat was heeling at up to 80 degrees at times, to say the airflow was turbulent is an understatement.

Marlec say the blades are tested but what does that mean? Are they tested in a wind tunnel with a steady airflow or in real conditions. Marlec say the blades are tested to 10 times the maximum design rpm, but don't say what that is and when it will be achieved. Their graphs only go to 40 knots. 10x maximum design rpm would put a huge load on the blades, 100x the design maximum load.

For those of you who think I am having a moan it is far from the truth, I love my 913 and will be using it for many years to come. I would just like to point out that they are not indestructible and if the blades shatter like ours did it could prove fatal.

 

[Scotty_Tradewind]

The controller does have an " electronic break" which slows the generator. .

Hi artimis
can I ask which controller?
S.

 

[little_roundtop]

I'd have thought that if one blade failed (for whatever reason) the vibration set up in the hub would break the others in a short time, especially at the wind speeds we're talking about. So it might not be a general failure of all the blades but rather a chain reaction set up by the (unusual) failure of one?

Tony C.

 

[Conachair]

I'd have thought that if one blade failed (for whatever reason) the vibration set up in the hub would break the others in a short time, especially at the wind speeds we're talking about. So it might not be a general failure of all the blades but rather a chain reaction set up by the (unusual) failure of one?

Tony C.

Well, you certainly know all about it if one goes I'd one go in 30 plus Kts off Tenerife. Thought the radar arch was going to shake to bits. Interesting trying to tie it off without broaching in some hefty seas. There are solar panels between the aero4gen and my head, which is nice The breakaway blade probably landed half way up Mount Teide, but the others survived for a few minutes 'til i got it tied off.

 

[RogerG]

The controller does have an " electronic break" which slows the generator. This is activated by a switch. As I understand it when the turbine speed increases and the generator is in danger of overheating the load is removed. In my experience this causes the turbine to increase in speed, this happens with winds over 40 knots.
.

My Marlec controller does exactly the opposite, when the switch is thrown the turbine immediately slows down as a short is put across the generator to make it slow itself down.

Roger

 

[catmandoo]

vortex shedding , failure when vibration hits natural frequency of structure . happens in chimneys , lamp posts . On a chimney they put spiral strakes at the top to kill the vortexes or play around with cross section / mass etc to stiffen or slacken the structure
even small probe instruments in a fluid flow have to be either tuned up or tuned down to avoid hitting the natural frequency

 

[Jassira]

I have an AirX wind gen, one day I found a dead bird on deck, pushed it over the side and thought no more of it.
Some time later I noticed the AirX seemed a bit noisier than normal, when I checked, it had lost about an inch off the end of two of the three blades. I replaced all three blades and all was sweetness and light.

 

[BlackSheep1]

rutland 913

I too have a Rutland 913 and have had no prob with it. We have been in gale and storm force wind with no adverse effects, although it does go like the clappers. On looking up the info supplied with the Windcharger I note it has a built in thermostat to prevent the generator overheating. In this mode the output will cease and the turbine will temporarily speed up. It may seem to cycle in prolonged high winds and they state if safely accessible temporarily secure the turbine. Not an easy task however in 100 knot winds.

 

[NormanS]

In normal use, the regulator will slow down the rotation when charging is nearly complete. This causes heat, and if the regulator has to keep on absorbing power, (because the batteries are fully charged), this heat has to be removed. In order for this to happen, charging stops, and the blades rotate at a terrific rate, until the heat has gone. We refer to "Hyperdrive". Fine if you are aboard, you can switch the controller to "Stop", but if you've left the boat to it's own devices, that's how it works.

 

[sailinglegend420]

We have a DuoGen, which has the same alternator as the D400, and it has survived some very strong winds. Twice the 35 amp fuse has blown and I was concerned that the off load voltages could get too high. The makers assure me that the components are well over specced and they now fit 40 amp fuses. They also suggest if you live aboard there is no need to have a regulator which could get confused by a solar regulator - just tie off the blades if high winds are expected.

We had a micro burst in the sheltered anchorage in Ucagiz Turkey three weeks ago with winds up to 60 kts. Boats dragged and we had the bowsprit of a gulet over our cockpit! The wind genny was screaming, but I was trying to save the boat not the blades on the genny. The 40 amp fuse survived - they say the output can go up to 400 watts!

 

[OldBawley]

“ Bought “ a Aerogen 4 from a sailor who had wreckt his boat on a beach in Rhodes. The cat was sitting on the beach with two holed hulls, the man wanted to stop sailing, had enough.
I gave him a very large sum of money for the windgen who had a broken propeller shaft, only so my friend could pay for a ticket home.
The propshaft had been broken and welded, totally useless. Made a new drive shaft out of bronze ( SS steel is a #### in the ### to machine ) Mounted the gen on top of the yawl mast, it works fine since 2006. In the Dodecanese with its strong winds, gave all we needed. Fridge, two laptops, and the rest. At noon I had to cut the currant coming from the solar panels, the small gen had loaded all night long. Slow but steady. Mounted that high up makes it deliver much more than most others of the same size, who are mostly mounted on a arch. On a arch, the windgen gets bad wind and delivers shade onto the solar panels. Bad bad.
Sitting on top of the 7 meter yawl mast has disadvantages. First I can not stop it in very hard winds. The diodes mounted on the inside of the back cover are getting hot, triggering a bi metal switch who cuts the field currant and then the blades start to free-wheel. The rpm`s get very high, ( no more load ) no problem but the high speed makes sometimes vibrate the tail and that is dangerous.
Second drawback is that I can not dismount the propeller. Sailing upwind the propeller creates quit a lot of windage. On our old heavy boat, the sail surface to take that one square meter of windage upwind must be about four square meters. ( Almost the size of the yawl sail )
Tim Carr took away unnecessary halyards or replaced them with 5 mm kevlar to reduce windage when racing his Curlew. A very similar yacht to ours. We do not race but I hate it to be slower then others.
Since my youth I was fascinated by the power of wind. My father made me a sailing cart out of our old pram, I learned windsurfing, delta wing flying and build a water pumping windmill to irrigate my organic garden.
Just as a wintertime hobby I am building a second windgen. Bought for 50 € a surplus AC motor on Ebay, the rest is made from scrap. We are moving slowly to places where the sun is less abundant. The two bladed ( Easy stowing ) 1, 5 meter gen is to be put on the port side of the bow. Only on anchor, only when I am around. No regulator, no furling. Keep it simple. Will deliver 7 amps in light winds, with 4 BF the thing gets to dangerous and then the small one takes over. Just playing.

 

[chinita]

Might be a good idea for the makers to come up with a gadged that puts a brake on when wind exceeds say 80mph? Our aero4gen has been fine for 10 yrs exept once losing a blade in very strong winds and mizzen topping lift came loose and hit it.

Brilliant idea.

The 'Csail Hurricane Brake'

Just stick an empty sealed plastic box on the generator and state that 'this Brake comes on in winds in excess of 80mph'

How many people are going to experience those conditions? Not many.

How many Generators are going to disintigrate? Not many. Even if they do, offer a full refund.

You could charge at least £100.00 each. I would think.

 

[Hugh and Brenda]

Broken blades

Yes, I have had blades break on my x Aero Gen 6 on 3 occasions, all in high wind, 83, 79 and 103+knots. It,s not just the wind, but the airborne water and flying debris. I have now fitted a D400, fingers crossed.
Hugh Scotia

 

[silver-fox]

103 knots.....hope you were cleared for take off

By the way ..... how many amps were you getting at 100 knots?

 

[Hugh and Brenda]

Killer storm at Levker

Our old gauge only went up to 30 amp. No idea at what speed the blades broke. We were to busy hanging on to look anyway. The supporting pole also bent, as did the tail fin.
The storm came out of nowhere, one minute we were sitting in the cockpit enjoying a pleasant evening, then 2 minutes later our mast was in the water. I only had time to run forward to let go our second anchor. Then when Scotia came upright I slithered back along the side deck.
Google <killer storm at Levkes> to see a video ,Scotia, our yacht, is just beyond the capsized cat, Not a pleasant experience being knocked down at anchor. 103 knots recorded by yacht Poo Bear. Hugh Scotia

 

[haydude]

The wind Generator is the Rutland 913. It is about 6 years old.

Good for you for naming and shaming them.

Did they offer at least to take the unit back for further analysis? If they did not, then it means they really are not listening. I believe this matter deserves a conversation with YBW editor to see if they are interested in analysing the unit and publishing an article.

 

[DipperToo]

Look at the latest 913 manual. I was very surprised to see that they now clearly state as a caution;

Mounting pole outside diameter MUST NOT exceed 48.5mm for at least the top
0.5m. Larger section poles must not be used as this will reduce the tower to
blade clearance. In high wind conditions this could cause damage to the
Windcharger by allowing the blade to come into contact with the mounting pole.
A broken blade will cause turbine imbalance with consequent damage.

Many people I have spoken to about various resonance issues have a 2" mounting pole.... which the blades could conceivably touch.

Not sure if this helps much.