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wallablack Senior Member Joined: 10/08/2011 Location: AustraliaPosts: 164
Posted: 07:45pm 07 Jul 2013
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Good Afternoon,
This will be the first gin pole tower I have built and I would like to draw from experiences from other people regarding the connection made between the gin pole and the bottom of the tower. I have a few ideas but experiences are always best.
Firstly, a quick drawing of the tower...
Basically the main tower is 100Nb and the gin pole is 90NB pipe, both medium.
Rule of thumb is generally to keep all guy wire anchors level wit the base of the tower so hence the above high ground gin pole, this is ensuring "B" is level.
The first guy rope is at 5m and the top guy rope is at 7.5m.
The VERTICAL tower is constructed from two pieces of pipe, 1 @ 6.5m (standard length) and the top piece being 1 @ 2.5m.
These two pieces of pipe will be fixed together using an AS2129 slip on steel plate flanges welded to the end of the pipe, each flange has 8 x M16 bolt holes.
The guy cables are 6mm 7 Ton BS flexi rope cable (Steel, Galvanized) and to AS0607196 regulation.
So all this is up to specification and strong as an ox my main concern is the base.
Scavenged pictures....
This above picture is an idea I like the most, easy to build as there is no welding involved. Now, with the gin pole not being fixed to the main tower causes an issue of the gin and the tower going away from it's 90 degree placement. At the other end of the gin pole though it is secured very well to the ground and also to two sections of the tower so it "shouldn't" go out of square. The main tower however would have to have a STOP on it to stop the tower going past 90 degrees during the standing process. And I don't see the point of having the gin pole fixed to the tower as you only use the other end of the gin pole for leverage.
The above image is another one I semi like. Nice and solid but totally relying on bolts to keep it all together. has the advantage to be checked very often and any maintenance can be done at ground level with zero fuss. I guess it also had less part really as it is only two plates exactly the same and a pole from the ground for it to swing/mount on.
And above is the third one. I like this idea but there is a hell of a lot of fabricating and you would need very good welds. it just looks like too much to go wrong.
I would love to have some input as to what to do with the base as these three can't be "the best"....
Foolproof systems do not take into account the ingenuity of fools.
brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548
Posted: 09:51pm 07 Jul 2013
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Yes, I like the middle one ,second one ... You can disassemble it for re-painting ,etc.
Easy to make, fairly adjustable if the holes are a wee bit larger ..
Cold Gal everything inside and outside (if possible) then use Epoxy paint on all steelwork... Guys --get your top ends Swaged onto gal thimbles (those heart shaped things ) . Bottom .,leave a bit of slack for adjustment and tighten with "crosby" clips (those things with a u bolt and a saddle ) .
All looks good to me...
How big is the blade diameter ?
Bruce.Bushboy
Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1344
Posted: 10:55pm 07 Jul 2013
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OK I'll be the devils advocate....
Looking at the first pic,
Look at the very small foundation and what is that a M12 or M16 soft bolt that does the pivoting and it looks like a bolt wleded on the inside to take the major stress of the raising of the tower.
Looking at the second pic,
Using bolts to secure a tower is asking for a failure as tower vibrations can and will loosen bolts....
Looking at the third pic
No gussets for the welding and look at the plate where the hole is cut, welds around a pipe causes stress's that can and do fail and as the pipe is welded @90 degrees it would of been easier to bring the wires out where the sun glass's are.
------------------------
Just remember Murphy(that great guy) is just around the corner and ANY bodgy work will give him a reason to come around. When welding pipe towers it is OK to weld ALONG the pipe but to weld AROUND the pipe is asking for trouble down the track if that weld isn't properly supported using gussets or a clamp that goes around the pipe, then that said clamp is welded on one side ALONG the pipe and guy wires can be attached to that point.
Now as I scored a heap of 75mm nom bore new hyd pipe 6.5mm wall thickness they will be my next tower or towers. There's several ways I can go as I got 6 x6 metre lengths, go 12 metres with a 6 metre gin pole or got 18 metres with a 12 metre gin pole and the last pole can be used for cattle yards.
If I can score some thick cable as my best spot for wind is 140m + away I could go several 6 metre towers and just use a ladder as a gin pole.
Now for a tower foundation, notice how guys throw old motors, car bodies etc in tower foundations is to give a firm SOLID base for the tower. I drove past a foundation I made and the concrete is dated 2005, that one is 900mm deep then I hit solid rock so I bored several holes and chemical anchored some M24 grade 8 all thread in the rock then welded the frame to them before concreting( it did take a 6x4 trailer load of ag to fill the hole). Thats the site of my 4kw motor conversion and I'll be using my lattice tower for that one. As the area is close to solid rock more chemical anchors will be used and more road base(as I use now for concreting).
Just remember that great guy is waiting to come around so do EVERYTHING to avoid the visit.
Cheers Bryan
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 03:04am 08 Jul 2013
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Just remember that the gin pole too requires side guys (C&D) and these *must* remain taut during the whole raising process.
I nearly lost a 12m lattice antenna mast once by thinking the hinge part was stiff enough to resist side loadings. But a small wind gust as the mast was halfway vertical convinced me it was not.
If you are playing with the gin pole method for the first time it is a good idea to make a scale model (make the pipes rather flimsy) and then study the effect of slack side guys as you raise the mast.Klaus
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 12:04pm 08 Jul 2013
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That diagram in the first post is a bit misleading, It does say A B & C must be level but the diagram looks like A is higher up on the slope.There are only 10 types of people in the world: those who understand binary, and those who don't.
wallablack Senior Member Joined: 10/08/2011 Location: AustraliaPosts: 164
Posted: 01:36pm 08 Jul 2013
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Thanks for your input Bruce.
I am using 3 swages (copper/nickel coated) per guy rope end at the top, it is also necessary to use thimbles to ensure the guy rope is not bent on such a sharp angle as this would cause unnecessary wear. Also the reason I am using flexi cable to AS0607196 specification. Non flexi cable would break and this is recommended for guy ropes with high strain. It also has a breaking strain of 7T so it is spot on. I never knew they were called Crosby Clips so we learn something new every day huh. The bottom will be double looped with the use of Crosby Clips and again a thimble as the drawing below depicts. The tensioners I am using have rings in each end and a 40T load rating.
The blade diameter is 4m. The tower is engineered for the turbine to have a lateral force of 15.4KN at a 50m/s or 180km/hr wind speed...plenty strong enough.
Thank Bryan...those pictures were purely for reference only and hell yes they all have their faults. Either one of the three would be scarey to be around in a good wind.
The first one...I don't get the whole overhang and undersized footing and there doesn't seem to be a hell of a lot of welding there either.
The second one relies wholly on that one single bolt, great idea with the two plates but the "swing mount" bit could go an upgrade.
The third pic...I am pretty sure there should be more than those 4 bolts to secure it to the footing. "Bolting" the base to the footings will be done with long "J" shaped hooks threaded on the end to form the "bolt". The bottom of the J will be almost at the bottom of the footing slab.
So yeah, purely indicative of ideas...
My friend is a very well educated and experienced engineer who is helping with all of the maths etc to get this thing spot on. He will also supply paperwork for me so she is all legit. It will be conforming to Steel Structures Code, Wind Loading Code and the Design of Steel Towers & Masts.
Thanks for your input Tinker...
This is VERY important, I too was putting up a small 300W mill on a 60mm pole a few years back and was winching her up and then she just decided to do a big sideways shift using the base as a pivot....not a nice experience that is for sure. I have drawn from that experience but will be doing a few raises without the turbine mounted that will be for sure, also just to get a feel for it.
Yeah it is a bit misleading, I just whipped up a quick drawing on paint.net to give a visual explanation rather than trying to explain it and confuse everybody.
C and D are already almost level as the ground is close and the footings will leave them spot on. I am going to dig a trench into the ground leading up to the footing on A as it is a lot higher than the base and I plan to build a small wooden or concrete "box" to keep this trench clean and keep the earth/dirt at bay.
Foolproof systems do not take into account the ingenuity of fools.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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