One of my major concerns has to do with the height of the tower, and in a catastrophic event that it were to fall. I wanted to be sure that it fell onto my property.

Since I am making my own wind turbine, my intension was to have them help out with the tower and site selection, along with the back end electronics and wiring for connecting the turbine output to my house and the main grid.

Everyone that know much about wind power typically says that the higher up you put the turbine the better the outcome, primarily due to turbulence and ground drag, putting up higher puts it into a more laminar/smoother flow of air. Initially I was interested in putting up a 50' (even knowing that I would loose some output) or so tower but in the end went with the decision that an 80' tower would be best.

So I went back to the 20' and 17' websites to do comparisons. The framework for the 20' was beefed up considerably over the 17' turbine that they made and it weighs in at about 400lbs, while the 17' one weighs in at 160lbs.

In addition I saw some notes that mentioned that they had to do a couple of repair jobs on the 17' after it was put up.

In the mean time I have been researching towers and recently I was referred to a tower company that manufactures and installs towers AN Wireless. Typically the towers that they sell are for communications equipment and not for wind turbines. They are fairly close and just over the border in Somerset county PA.

After talking to Dan Simmonds for a while and filling him in on the details of my project he decided that to ensure that there would not be any problems that I would need to pay $550 for an engineering study. For this their engineers will decide if their current series of towers were suitable, if not then they would propose a design for my application.

At first I balked at the cost, then realized that it would be money well spent so I agreed and sent them out a check.

He stated recently that they did mount a Skystream 3.7 generator (12' blade diameter) on top of a 100' HD series tower that they make, however the 17' diameter might exceed the capacity. The price for a 70' freestanding HD series tower seemed quite reasonable at just over $3100. One side note is that none of their towers are tiltable, meaning that either a crane is used for raising/lowering the tower or a davit be constructed for raising/lowering the wind turbine.

Dan had also mentioned that there was a 3 month wait for towers, as this is their busy period. I figure that the timing would be just about right for me to build the turbine and make the tower base which puts the installation into September, so I had him put my name in the queue.

Here are a list of my requirements:

• 70' tall tower
• freestanding, no guy wires
• 10' stub extension on the top (I will be building the 10' stub as it should be simple enough to do)
• 17' diameter, 3 bladed rotor
• 350lbs total turbine weight

I have decided that I do not want to total solely rely on the ability to short out the stator to stop the turbine from spinning - period.

What I have decided to do is to put an additional plate (to act as brake rotor) on the back side of the hub and using a hydraulic brake caliper to engage the rotor. This brake system will incorporate a hydraulic master cylinder that will be engaged using a linear actuator or a rotary screw mechanism.

The hydraulic brake system will be mounted directly behind the turbine and on the yaw bearing. This way it is out of the way of incoming air flow (causing little turbulence) and it rotates along with the entire top of the turbine assembly. I will make a slip-ring assembly which will be used for any electrical connections to the brake actuator so that I do not have to deal with untwisting a cable.

Using this system I should be able to positively shut down the turbine, even if the stator burns out.

Here is a quick drawing showing a hydraulic brake system:

The free standing lattice towers are typically *not* lowerable, you pretty much have to use a crane to raise/lower them. So my thoughts have been about how to raise/lower the turbine unit leaving the tower up all the time.

There is actually three parts to providing a solution, the first part: Use a davit

The davit is simply a crane-like device that will be used at the top of the tower, it pivots so that when raising/lowering the turbine it will safely guide it away from the side of the tower. When not in use the davit can be 'folded' so that it is away from the top portion of the tower. The davit should incorporate a screw mechanism roughly at it's center point, the screw mechanism allows you to control the 'tilt' of the davit so that when connecting to the turbine it is roughly vertical and using the screw to make the davit incline beyond the towers edge when raising/lowering the turbine.

The pivoting screw mechanism can be operated either by hand with a crank or using a small motor, being up that high I would be more comfortable using the motor rather than manually operated, as any extension and effort to move stuff can easily be nerve wrenching.

Ok so how do you raise/lower the davit?

The second part of the solution is: Use the stub tower.

The stub tower needs to have a loop or connecting point so that a cable/rope can be used to raise the davit from it's normal folded position and bring it so that it is vertical. Ok, so now at this point I have the davit vertical and ready for use, one problem that quickly comes up is: With the turbine actually being 10' above the top of the lattice tower the problem is how do you snatch a cable from the davit to the top of the turbine? I am 6'1" and my reach extends only to about 7'6" which leaves a bit of distance to the top of the turbine still, and don't forget that my lattice tower is 70' to the top from ground level!!!

The third part of the solution is: Use a telescoping stub section on top of the tower.

With a telescoping top stub you can use the davit to snatch a cable onto the non-rotating section of the stub onto the davit. Using a simple hand cranked winch (similar to one on a boat trailer) the top stub can easily be raised and lowered, the stub section can easily be lowered by 6' or so. The winch should only be used as a temporary means to raise and lower the top stub, once in place retaining pins and/or collars should be used to hold the stub so that there is no pressure on the winch cable.

Once the stub is retracted you should easily be able to move the cable to the top of the turbine, raise it off the stub, tilt the davit so that the turbine is away from the side of the tower, and finally lower it down to ground level.

This sounds a bit complicated, but the only other option is to use a crane...

Below is a rough drawing showing the system that I am considering (it is not to scale):

One other option that could possibly work nicely is that the davit can have a linkage connected to the bottom of the stub. So that when the stub is lowered, the davit is automatically raised and conversely when the tower is raised, the davit is lowered.

The weight of the top stub along with the weight of the turbine should be more than sufficient to perform the task of raising the davit.

Two ideas come to mind one being a simple 'A' frame located on the top of the tower as envisioned below:

The second one being a telescoping/rotating boom type of device, I tend to like this solution the best as it is easy to raise/lower and it gives the most functionality without being obtrusive. A simple locking collar would be used to keep it extended, and still allow it to rotate. When in use you snatch a cable to the top of the turbine, lift the turbine off the stub, rotate the boom so that the turbine is away from the tower, and then lower it to the ground. A removable lever can be used to assist in rotating the boom/turbine to make life easier.

When not in use the rotating handle is removed the boom collapsed and rotated to be unobtrusive. When not in use the rotating head should be locked to the tower:

In addition they specified using their A style pad/pier foundation (which they show here), so it would appear that their towers are plenty strong enough and the weak link would be the foundation. In the drawing it is not really clear how the rebar structure should be built, however there are pictures of an actual foundation construction which clarifies this issue.

Their location is less than an hour from my house so I will be picking it up myself and saving a bunch of money instead of having the tower shipped to me by truck! During this week they preassembled each individual section so that I do not have to assemble them (nice). I will be using my car trailer to haul it back home.

The combined weight of the seven tower sections weigh about 1,600 lbs and my trailer has a capacity of 7,000 lbs so weight should not be a problem.

Here is the breakdown of the tower costs:

• $3152 - HD-70 tower
• $280 - step bolts for 7 tower sections ($40/section)
• $450 - 3/8" complete steel life-line system for 70' tower
• $240 - life-line steel safety sleeve with carabineer
• $80 - dual base grounding kit
• $48 - 6 mounting brackets with bolts/nuts/washers to connect (2) mounting plates for stub

Some of the sections are small enough that they could go inside other sections making it stack better. In the plastic tubs are an assortment of nuts/bolts/etc for assembling the tower sections, including the 3/8" diameter life-line, dual grounding kit and the mounting brackets for the top stub.

Out here there is very little 'flat' land, it is all mountain or hill side so the top side of the hole was almost a foot deeper than the bottom.

Here is a picture of my prize tractor, it's not real big but just about the right size. I don't know what I would do without it now days, I have a bunch of attachments for it, brush hog, post pounder, back hoe and front end 60" snow blower for the winters.

I did not have to weld up the rebar, but I feel that it makes installation a whole lot easier than trying to hold everything together with wire. The final assembly will be done using wire however as it would be too difficult to completely weld up all the rebar the assembly would be too heavy and awkward to move - easily that is.

I was able to get all the rebar into the pit and wired up, this took a while as I was working alone and the large 8' 6" sections of welded up rebar turned out to be quite a handful. I cut up about 12 lengths of 12" long rebar to separate out the two large rebar layers.

By the end of the day I got the 4 sections of the center pedestal rebar in place, along with the 5' long tower section all in, wired up and basically sitting on top of the large bottom layer of rebar. I forgot to take a picture of the rebar, but here is an image from the AN Wireless website that shows the large rebar pad on the bottom with the columnar pier rebar and the tower base in the center section of the pit. One thing that is missing is additional diagonal braces on the tower base that tends to get in the way of the rebar:

Again working alone I cut up the 3/4" plywood into 4 pieces of 42" x 70" long sections and put three lengths of 2x4's horizontally, one across the top, bottom and middle. Two of the sections had the 2x4's cut 3" longer so that they overlapped the other section and could tie them together.

I lowered all four of the sections into the pit and temporarily rested it on top of the bottom rebar platform, the wire ties held up fine (this was a concern.) Once in place I screwed all four sections of the plywood together with essentially about 2# of 2" long screws.

Along the top outside lengths of two of the sections I screwed 2 lengths of 2x6's which extended out from the form by about 5'. The ends of these lengths were used to lift the entire plywood form assembly up off the rebar by about 4" and leveled off on the ground using cinder blocks, wood blocks, whatever so that the entire top of the form was level in all directions. It was also centered around the central rebar so that each inside of the form was about 4-5" away from the rebar.

I needed to lift slightly the tower section so that it would be the proper height above the finished level of the form, so I used some rebar to make up a small A-Frame. Here is the A-Frame that I quickly made up out of some rebar:

I used this A-Frame along with a come-along to lift each leg of the tower section and then using a C-clamp I clamped it onto a 2x6 that rested on the top of the form. This not only lifted the 5' tower section but also the central rebar assembly, in all probably about 200# total.

Paul Schreiner (a former concrete guy) came by to help out with the concrete pour today and brought over his arsenal of concrete tools, most importantly a concrete vibrator! This vibrator is used to ensure that there are no air pockets trapped in the concrete and that it is a single solid mass.

Prior to the concrete truck arriving I double checked that the tower base inside the form was level and that each leg was at the proper width. I ended up making some minor tweaks as once the concrete is poured this can not be adjusted. An 1/8" error at the base for level can turn out to be a foot at the top of an 80' tower so it is best to get it as close as you can before you pour the concrete!

We ended up using almost 12 cubic yards of concrete! Initially I had ordered up 10 yards but we ended up a little short, they had to make a second trip with the final 2 yards to finish off the job.

One important side note is that with my climbing around on the top of the suspended form yesterday, it 'tweaked' the horizontal supports and one corner ended up being about 1" too high. During the short break between the first concrete delivery and the second we tacked on some boards along two sides and marked out a level top plumb line in which to finish off the concrete.

The concrete truck made *huge* divots into the pasture that I had to fill with dirt after the job was done.

Lastly, prior to the concrete setting I put down about 1 gallon of sealer onto the top of the wet concrete. We used this method on my driveway and I liked the results.

I have been trying to find a hydraulic brake caliper that retract the brake pads and have not had a lot of luck, so I opted out for a mechanical disc brake caliper. It is important to retract the brake pads so that they do not put any resistance on the rotor, otherwise the wind turbine could have problems in starting.