Wind turbine mast construction

['Captain' Kirk DeHaan]

I have an Air 303 wind turbine. Still working fine. My issue is it is
not high enough. It's only 15' off the ground although we are a few
hundred feet off the valley floor on the side of a mountain and have
decent wind flow. The actual "good" wind stream is about 15' higher. I
plan to build a single pole tower of nested/stacked sched 40 steel pipe
with a pivot arrangement at the bottom. The bottom will start at 3" and
end up at the required 1.5 inch pipe. 3 to 2.5 to 2 to 1.5. I am
looking for information on lateral forces I may encounter so I make sure
I have enough concrete at the bottom and a stiff enough pole that will
hold up to the gusts. My current thinking is a 15' section of sched 40
1.5 inch as the last step with the remaining steps in 5' sections.
Overlaps at the welds will be 1.5 feet. I'm looking at about 800 lbs of
concrete for the base set 5 feet deep. I have a C band satellite dish
that has not moved in 12 years with this amount of weight at the base
and a huge surface area even though it is mesh. Do you have any pointers
to tech/engineering data that might help and what do you think of the plan?

Any help appreciated

Kirk

 

[wmbjk]

I have an Air 303 wind turbine. Still working fine. My issue is it is
not high enough. It's only 15' off the ground although we are a few
hundred feet off the valley floor on the side of a mountain and have
decent wind flow. The actual "good" wind stream is about 15' higher. I
plan to build a single pole tower of nested/stacked sched 40 steel pipe
with a pivot arrangement at the bottom. The bottom will start at 3" and
end up at the required 1.5 inch pipe. 3 to 2.5 to 2 to 1.5. I am
looking for information on lateral forces I may encounter so I make sure
I have enough concrete at the bottom and a stiff enough pole that will
hold up to the gusts. My current thinking is a 15' section of sched 40
1.5 inch as the last step with the remaining steps in 5' sections.
Overlaps at the welds will be 1.5 feet. I'm looking at about 800 lbs of
concrete for the base set 5 feet deep. I have a C band satellite dish
that has not moved in 12 years with this amount of weight at the base
and a huge surface area even though it is mesh. Do you have any pointers
to tech/engineering data that might help and what do you think of the plan?

Any help appreciated

Kirk

A 303 is a pretty light load, I've seen quite a few on un-guyed towers
of 20 -30', most of lighter construction than you have in mind. Your
plan sounds fine to me, although I'd probably simplify it with fewer
steps in the pole. I posted some info previously that might give you
an additional data point - "Here's a photo of a similarly constructed
windsock tower.
http://citlink.net/~wmbjk/images/windsock.JPG Sock is 18"X96", pole is
close to 30' tall. It only bends a little in a stiff wind. The brace
at the bottom doesn't hold anything up, it's attached to a
counterweight so that I can raise and lower the pole by myself.
Concrete is about 18" in diameter, 36" deep. I dug most of the hole
using a powered chisel, which should give you some idea of the ground
hardness."

Wayne

 

['Captain' Kirk DeHaan]

wmbjk said the following on 2/20/2007 4:43 PM:

A 303 is a pretty light load, I've seen quite a few on un-guyed towers
of 20 -30', most of lighter construction than you have in mind. Your
plan sounds fine to me, although I'd probably simplify it with fewer
steps in the pole. I posted some info previously that might give you
an additional data point - "Here's a photo of a similarly constructed
windsock tower.
http://citlink.net/~wmbjk/images/windsock.JPG Sock is 18"X96", pole is
close to 30' tall. It only bends a little in a stiff wind. The brace
at the bottom doesn't hold anything up, it's attached to a
counterweight so that I can raise and lower the pole by myself.
Concrete is about 18" in diameter, 36" deep. I dug most of the hole
using a powered chisel, which should give you some idea of the ground
hardness."

Wayne

Hadn't thought of a counter weight. Using that my plan should work fine
with some changes in the steps. I'll stick with the overkill on the
concrete since we have some wet spring thaws. Thanks!

Kirk

 

[[email protected]]

I have an Air 303 wind turbine. Still working fine. My issue is it is
not high enough. It's only 15' off the ground although we are a few
hundred feet off the valley floor on the side of a mountain and have
decent wind flow. The actual "good" wind stream is about 15' higher. I
plan to build a single pole tower of nested/stacked sched 40 steel pipe
with a pivot arrangement at the bottom. The bottom will start at 3" and
end up at the required 1.5 inch pipe. 3 to 2.5 to 2 to 1.5. I am
looking for information on lateral forces I may encounter so I make sure
I have enough concrete at the bottom and a stiff enough pole that will
hold up to the gusts. My current thinking is a 15' section of sched 40
1.5 inch as the last step with the remaining steps in 5' sections.
Overlaps at the welds will be 1.5 feet. I'm looking at about 800 lbs of
concrete for the base set 5 feet deep. I have a C band satellite dish
that has not moved in 12 years with this amount of weight at the base
and a huge surface area even though it is mesh. Do you have any pointers
to tech/engineering data that might help and what do you think of the plan?

V mph makes 0.00256V^2 lb/ft^2, eg 6.4 psf at 60 mph. If a 4' prop with
12.6 ft^2 of swept area pushes 80 pounds max (less, given Betz) with
guy wires every 10' up to 10' below the top, it needs to resist about
10x80 = 800 ft-lb = M = fI/C = 25KPir^4/(4r) = 19635r^3, so r = 0.34",
for solid pipe... 3/4" schedule 40 galvanized pipe with 1.05" OD makes
I = Pi/4((1.05/2)^4-(3/4/2)^4) = 0.044 in^4, so M = 25Kx0.044/(1.05/2)
= 2101 ft-lb, over twice the requirement.

The lower guy wires might have spreaders, with no ground connection.

Nick

 

[wmbjk]

wmbjk said the following on 2/20/2007 4:43 PM:

Hadn't thought of a counter weight. Using that my plan should work fine
with some changes in the steps. I'll stick with the overkill on the
concrete since we have some wet spring thaws. Thanks!

My original plan was to use a chain as a link between the
counterweight end and the tower. That way the tower could lower
perhaps 30% of the way before picking up the counterweight, and more
of the effect of the counterweight would be available when the tower
was in the lowered position. But since the windsock is mounted on a
10% slope, folds uphill, and is lowered onto a crutch, the
counterweight worked well enough with a fixed link. It's a bear to get
the tower started down, but after that it's easy to handle. If you're
on level ground, you might use the chain, and perhaps even dig a pit
for the counterweight to maximize its effective range. What are you
planning to use for hoisting power?

Wayne

 

[wmbjk]

It is not the balance that is the problem.

Balance is a serious problem Gymmy Bob. Have you ever tried raising a
30' long tower without equipment? No matter how he does it, a gin pole
is recommended, and a counterweight is a natural fit on the end of the
gin pole.

It is the side force. A
windsock does not have even the same magnitude of side pressuref from
the wind that a wind turbine does.

That windsock is on 2" pipe, and the OP plans 3". Plus, I already
described successful Air installation on poles more spindly than he
has in mind.

I suspect you will end up with a
damaged bent mast when you are done with those lighter pipes.

I "suspect" that you don't have any experience building towers. And I
can pretty much guarantee that as usual, you'll fail to contribute a
single useful idea to the thread.

Wayne

 

['Captain' Kirk DeHaan]

wmbjk said the following on 2/21/2007 6:38 AM:

My original plan was to use a chain as a link between the
counterweight end and the tower. That way the tower could lower
perhaps 30% of the way before picking up the counterweight, and more
of the effect of the counterweight would be available when the tower
was in the lowered position. But since the windsock is mounted on a
10% slope, folds uphill, and is lowered onto a crutch, the
counterweight worked well enough with a fixed link. It's a bear to get
the tower started down, but after that it's easy to handle. If you're
on level ground, you might use the chain, and perhaps even dig a pit
for the counterweight to maximize its effective range. What are you
planning to use for hoisting power?

Wayne

My original plan was to use a gin pole with the winch from my ATV with
the ATV anchored to a car or truck for "ballast".

 

[wmbjk]

My original plan was to use a gin pole with the winch from my ATV with
the ATV anchored to a car or truck for "ballast".

Excellent. Your tapered pole already has a low-as-possible cg. If you
limit the lift so that the turbine starts off at say, 5' off the
ground (still a convenient enough work height), and use a
counterweight to help with the initial lift, then you should be able
to hoist the tower *without* a normal gin pole. The counterweight arm
can be shorter and lighter than a gin pole need be, and would
eliminate the need for a pulley. The ATV's front wheels might come off
the ground a little part-way through the lift, but that shouldn't
hurt. Just make sure to have the winch cable wind and unwind neatly so
that it doesn't jerk under load. I helped a friend hoist a well pump a
few weeks ago with a $35 ATV winch (1/8" cable). Heaviest lift was
perhaps 400lbs, and it worked pretty well except for some jerking. We
should have pulled all the cable off the winch and rewound it neatly
before starting. Back to your tower... you might make part of it
telescoping. If everything works out OK at 30', you could extend it
another 5 or 10 feet.

Wayne