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Author Topic: Sundays Crazy Idea.  (Read 2736 times)
offthegridandy
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« on: December 04, 2016, 07:00:58 PM »

Hi bodgineers,

I have just been out rigging new guys on my WT lattice tower, up grading all main lines to 6mm, piccys to come on other thread. Any way adjacent to where I've been working I have a large 22,000 litre storage vessel.  Its super thick fibre glass and fitted with various take of pipes and lifting eyes.  The approx measurements are 3 Mtr high and similar height.

It  occurred to me that If I could attach a free standing WT mast to the tank, then filled it with water, the tank, would then weigh in at 22 tonnes and as such make a pretty firm base for the WT!

Now being a bit of a "bodgineer" I can already see how I might make the idea work here, but in all seriousness is there any reason why a tank full of environmentally friendly water doesn't the same job as 20 tonnes of concrete.

And if there's any money in it 10% is mine.

Thoughts peeps?

Andy
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« Reply #1 on: December 04, 2016, 08:06:10 PM »

Hi Andy,

sounds interesting. I guess if the fittings and flanges were 'man enough' it would work but I don't suppose it would have any where near the same 'damping' effect as 9 cube of concrete which would be around the same weight. The concrete would also be buried in the ground, do you plan to do that with the tank? If you filled the tank with water and could drop the level by 50M and extract 1lt/sec you'd get about 1.3kWh of leccy out of it over a 6 hour period or 100lts/sec would give you something like 2kW for 3 minutes, enough to boil a kettle I guess  Grin

Cheers, Paul
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« Reply #2 on: December 04, 2016, 08:10:31 PM »

I guess it comes down to the fixing between the tank and the tower, a tower buried through a blob of crete is intrinsically fixed whereas fixing a tower to a fibreglass tank is going to take some quality bogineering. There is going to be some serious force trying to pull the fixings out of the tank, the tower is effectively a lever with a ratio being its width at the base divided into its height. What sort of number is that? Maybe you could bond somehow a steel plate onto the top of your tank and bolt the tower down to that with some triangulation?? Or how about a cage that houses the tank which the tower bolts to??

Desp
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offthegridandy
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« Reply #3 on: December 04, 2016, 08:58:34 PM »

Hi guys,

My first thought was to attach mast ( dimension unknown) to a steel plate 3mtr dia that sits snuggly at bottom of the tank. Mast emerges through a precise hole the top of tank. Tank is then made air tight and completley filled with liquid. The the bottom plate is fixed by gravity, the weight of the water, plus the hydraulic resistance stopping the base plate from lifting off the base of the tank. Tank is currently set into the bank and could be completley back filed in and surrounded.
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biff
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« Reply #4 on: December 04, 2016, 11:15:43 PM »

It sounds doable Andy,
                      I once stuck a W/T on top of a cherry picker, Only 25ft or so up. It was a 600watt x 24volt Y/S. I had a short 8ft mast bolted to the cradle and sent it up say 20ft.
  My thoughts were,that ...It was an excellent idea and nothing could possibly go wrong. The controls were excellent and very quick to respond to the joystick.
  So the first decent breeze came along and the racket was that loud and jumpy that I could have sworn it was about to take off on it,s own..
 So I took it down that night (30 second job)and the following day I went and checked everything. I found that the prop was as near perfect that it did not matter. Everything seemed fine and up she went again. The next decent breeze a few days later had the same results, the cherry picker would wobble and clank all over the shop and I did notice that it mostly got the shakes when it was braking. So Down it came again and I attached guys to it, I sent it up again,checked the guys and tightened the lot by pushing the basket up against the guys anchor on the ground, so it was very well secured.
  The next decent breeze came along and the results were ok for the W/T, it was running fine and the basket was steady with the guys doing a good job,
 But there was a horrible knocking noise from the slewing gear at the base of the jib, every time the turbine braked, it was knocking hell out of the slewing gear. I lowered the W/T and sold the cherry picker to a happy owner.I learned that the guys that go to the ground do a lot more than just hold the W/T upright, They cover quite a wide spectrum of resonance or vibration and they pass it down to the ground,where it is soaked up and deadened.
  So I hate to tell you this, but you could become quite famous as the person who built the biggest musical instrument in Wales, because that is more or less what it will become. The tank above ground will become a soundboard for all the knocks and bangs,, hums and whizzes that your nice Hugh Piggott W/T produces and there is simply no way that you would ever be able to keep it quiet above ground. filling with water will change the pitch or note but it will still produce those noises. Guys are hard to beat.
                                                                               Biff,
     I don,t know a lot about tilting towers but I would not mind giving one a go.We have a member ,who stuck a 30ft+ tilting tower up in his back garden. I am not sure what happened but we got a post some time later, to say that he had moved into a bedsit. I recall that I was practically begging him to put guys on the lower half because the ground was dodgy, I think he told me he fitted 2. He was a good poster and a generous and helpful member. hopefully some day he will come back to us.
 
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MR GUS
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« Reply #5 on: December 05, 2016, 01:00:45 AM »

Everything has a resonant frequency, so the best counter to this is guys to the earth.

Look at all the traffic on a busy motorway, now tell me how much vibration you feel standing on adjoining tarmac!? precisely, . now go apply the same logic to your rig lest you have to do 2x the work to put it right.

airtight means nothing to sound, you'd still get resonance, this resonance, along with temperature differentials could potentially make short work of the chopped strands & glues finding a route of weakness to exploit (crack) as frequencies ramp up & down via a wt urbine under operation
« Last Edit: December 05, 2016, 01:08:39 AM by MR GUS » Logged

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todthedog
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« Reply #6 on: December 05, 2016, 03:44:54 PM »

I would love this to work Andy.
How would you fix the mast to the tank taking into account the vibrations and stresses that the turbine will transfer to the mast?


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« Reply #7 on: December 05, 2016, 04:53:06 PM »

If you are going to sacrifice the tank by drilling holes in it, do the job then fill it with rock/sand/soil. Water well in to consolidate, top the fill right up to the top and hey-presto, instant non-resonant foundation. fingers crossed!
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oliver90owner
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« Reply #8 on: December 05, 2016, 04:54:19 PM »

I would forget it as just a crazy idea.

The weight of water is nothing more than a force.  If you think the pressure of the water  (Pressure = force x area) will help anything, consider the pressure just beneath the flange, if the flange rises just off the bottom of the tank - the pressure below the flange will be amost exactly the same as just above (remember here that pressure in a liquid acts in all directions).  Unless the tower is rigidly fixed to that volume of water, the water can move; the material of the tank would need to be rigid (in which case it would work whether the tower was affixed at the top or bottom).  Hence the only real force holding the tower to the earth is gravity acting on the tower.  The only difference would be damping due to the viscosity of the water.  That is unless the top of the tank helped restrain the tower. 

Think here of a very long scaffold pole standing on a solid surface at the bottom of a deep pool.  It will not easily remain vertical, but fall over as soon as its centre of gravity is moved by only a small amount, the speed at which it falls being affected by the viscosity of the water.  So the water will not prevent it falling over, but just slow it down, compared to it being in air.

Simple physics equilibrium states for a solid block on a surface are (a) stable (block remains stationary on the surface), and (b) unstable (where the block will return to the stable position if the tipping/lifting force is removed.  These only apply while the centre of mass remains within the effective area of the base.  Moved any further and the item will assume a different stable equilibrium position (ie after it has fallen over onto another base)!

Sooo, if the tower was secured to the tank, it would be the material of the tank providing the mechanical strength and the water would be the ballast.  I don't think that a fibre glass tank would provide the same strength as a steel tank.

I somehow think you are not meaning transferring all the forces to the tank material?

Think here that guys simply increase the effective base area for a single pole tower.  More to it than that, but it is the simplest analogy -vertical guys (minimum 'base' area provide little or no stabilisation, but there is a practical maximum angle for distributing the forces sensibly).
RAB
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offthegridandy
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« Reply #9 on: December 05, 2016, 08:34:09 PM »

Thank you all.  I'd certainly not considered harmonics. A serious point to ponder but.

If we ignore for the moment my fibre glass tank. Think proper engineered solid tank,  using water not concrete. If the tank is bedded in the ground and completley filled with liquid and sealed it would withstand massive compressive forces wouldn't it? Lateral stability would be engineered into the tank strength and the surrounding ground . If it were feasable it could save 1000's on tonnes of concrete going to out of the way places for WT farms.

T easy, to obvious or me to stupid?

Cheers.

Andy
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8 KVA Lister TS2 Startamatic Genny
24 Volt 1000amp battery bank
Outback VFX3024
4.6 Kw PV array ground mounted
Outback Flexmax 80
2 X Flexmax 30 PV CC
2.5 Kw WT H Piggot design 4.5 Mtr Dia AC coupled
12 Mtr free standing Tower.
u/floor heating from oil boiler cross linked to 12 K wood stove
Scruff
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« Reply #10 on: December 05, 2016, 10:48:32 PM »

http://www.totalstructures.com/products/ballast_truss.htm
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MR GUS
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« Reply #11 on: December 05, 2016, 10:54:25 PM »

Not on any scale Andy, sorry, Its a nice idea & all avenues /options need considering when we look at what the environmental cost of pilings are, but no.

..don't let it stop you looking though, today's common availability commodity is tomorrow's drought.
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