TILT-UP towers are the most user friendly tower since they are very easy to install, and allow for easy maintenance of your wind power generator. Standard tilt-up towers are guyed pipe/tube towers and are available either complete or in kit form. Tilt-up-towers are also available in the guyed lattice type. Tilt-up-towers require four sets of guy wires and fairly level ground. Typical guy radii range from 50 to 70% of tower height.
More on Tilt-up Tower Design and Construction
From our year of experience at EcoBuilders, we can say we are very fond of tilt-up towers. Climbing a 60 foot tower is neither fun nor conducive to a long and healthy life.
All work with tools and heavy wind generators can be done while safely standing on solid ground.
Tilt-up towers can be made from wooden utility poles, steel lattice radio towers, or 20-foot sections of steel pipe coupled together.
The key features of these towers are 4 guy wires, a hinged base and a gin pole for leverage.
To raise a tower, the 2 side guy wires are attached and tightened while the tower is lying on the ground to prevent lateral movement during the process and the guy wire opposite the winch side is cut to the correct length and attached to the earth anchor to prevent the tower from falling over if it passes plumb.
A winch or vehicle is attached to the remaining free side over a gin pole for leverage, and the tower is slowly pulled up. When it is plumbed with the turnbuckles, all guy wires are tightened. To lower it, simply reverse the process.
This whole procedure is rather exciting, but not as exciting as climbing 60 feet in the air!
A wind generator foundation must be very strong, especially at the hinge. If your tilt-up tower, foundation, or hinge is not strong enough, you will probably find out during the erection process. That is the only time when there is a great deal of sideways stress on the base--during raising and lowering.
Pouring a concrete foundation that extends down below frost line is highly recommended. 1/2 inch steel plate steel hinge brackets embedded directly in the concrete are suggested.
Earth anchors for the guy wires must be very strong--they have to resist the lateral thrust that is put on the windmill. There are a number of different earth anchors that can be used; A rugged mountain installation in the rocks might require a couple of different kinds.
Generally, anchors are designed to utilize the weight and shear strength of the surrounding soil to help hold them in place. The radius of your guy wires should be between 50 and 75 percent of the tower height. It is very important to lay out your 4 anchor foundations perfectly perpendicular to each other around the tower foundation--otherwise, the 2 side guys will not stay tight while raising and lowering the tower. Leveling is an issue too. If the guy wire pads are at different elevations, you will run into the same problems with loose and tight guy wires.
Use the highest quality turnbuckles that you can find. Try to find turnbuckles that have removable bolts at each end to hold the guy wire in. Use the thimbles that come with your cable clamps to avoid fraying the cable.
This is the all-around strongest solution. The hole for the concrete should be bell-shaped, so it is wider at the bottom than at the top--this allows the soil over the anchor to help hold it in place. A metal loop for the guy wire can be embedded directly in the concrete, preferably at close to a 90° angle from the attachment point near the tower top. Your footing should extend down below frost line. If you set an auger with a plate into concrete, it should be parallel to the guy wire.
If your soil has good shear strength you can purchase earth augers to anchor your guy wires. These metal rods have an angled plate at the end that allows you to screw it into the ground. Again, they should be angled into the ground so that they are parallel with the guy wire.
Metal T posts can make fast and easy earth anchors for 20 to 30 foot towers if they can pounded deep enough. If not, dig out around the post and poured in concrete for a very strong anchor on a 30 foot metal pipe tower. With fence posts, they should be angled into the ground at 90 degrees to the guy wire.
Windmill towers are subject to all sorts of vibration. Changing wind direction and the effects of the wind directly on the tower can cause all sorts of harmonic vibration, some audible and some not. Be sure to Loc-tite® all bolts on the tower. If harmonics are causing problems (such as a swaying metal pipe tower), the problem can sometimes be fixed by changing where the guy wires attach to the tower, or by adding additional guy wires farther down the tower.