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Turbine assembly showing the 3 phase industrial motor/generator, gearbox, bearing,
and slip rings.
The very first project I completed at
home was the rough cutting of the blades. They are formed from 12' lengths of 2
x 10's. A good hand planer is required for this phase. The book clearly
describes how to build the blades. Once they were roughed into shape, the ends
were painted to seal for cracking. They were stacked on the floor (on skids) and
heavy weights were installed on them to keep them straight as they continued to
dry. The boards used are longer than needed, but help by giving you the ability
to trim cracking of the ends after drying is complete.
Final blade finishing was done many months later, after much of the rest of the project was completed. The Prairie Turbine Book provides for a procedure to deal with any cracking, and I had one blade needing work. I sanded out a trough and installed several layers of fiberglass on each side of the blade to strengthen and close the crack. All final sanding was completed and the blades were ready for initial balancing (a final balancing is done after painting).
I pre-weighed the hub and the blades, using this information to match the heaviest blade to the lightest side of the hub. The blades were all fitted to the hub, and the hub was suspended from a hoist for the balancing. Each blade had a support beneath it about 6" below the static level point. Lead was set on the lightest (highest hanging) blades until I was close to the balance point. I drilled large holes in the blade and melted lead and poured it into the blades. Two blades were worked several times with the lead until I got to the balance point, leaving those blades just a tad light to compensate for the final fill at the lead inserts. A fiberglass patch was placed on each blade over the weights and body filler was added for the final finish.
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At this time it made sense to cut out the tail vane (3/4" plywood), as I wanted to paint all the "wood components" at the same time. I sanded it for paint (my plywood was in the form of an old unused sign that was in excellent shape). The blades were hung from a bar and the tail on a couple 5 gallon pails. They were painted outside with a HVLP spray gun. I was not happy with the painting results on the blades; some runs and not as smooth as desired. Painting the tail outside presented challenges too; bugs. Everything was moved into the garage, sanded again (180 grit) and repainted. The results the second time with a more controlled environment were excellent.
Once the actual generator mount was completed, I took the mount, generator, and all the small parts home for final assembly. The first project was to cut and form 1/4" Luan scraps I had to fit the various sides of the mount. I had a "two part" super glue that I used to attach the "mold" pieces to the mount. Once the unit was totally covered, I taped the entire surface with clear packaging tape as a release agent for the fiberglass after it cured. I laid up multiple layers (4) for the two side covers. When they were done, I laid up the top cover with 5 layers for a little more strength because this cover spans across the top of the generator unsupported.
Turbine assembly ready for cover.
A 3" x 8" hole was cut into the bottom of the mount, between the two motor supports, for a ventilation "intake". A mold was made out of Styrofoam for the outlet and this was attached once completed. Both ventilation openings were covered with mesh to avoid animal or larger insects getting into the enclosure. Another mold was made of Styrofoam for a "front bearing cover" to protect the bearing from the elements. Pictures are enclosed of some of the molds, but unfortunately I didn't get any pictures taken during the actual fiberglass process. The covers were primed and painted white, as fiberglass should be painted a light color to protect the composite material from excessive solar heat.
Molds for making the turbine housing.
When the covers were
completed, they were installed with
Clecos to fit, and then the frame was
drilled and tapped for 1/4" bolts to secure the covers. We discovered that some
additional light angle and strap needed to be welded along the main frame to
secure the covers. I also had to do a "release" to fill in an area at the rear
that would require sealing. This was done with a micro/flox filler mixed with epoxy. If I was
to build another unit, I would provide for a gap for the cover to extend below
the rear edge of the mount. We attached the tail mount right to the top of the
main mount, and this was not the best design for sealing.
While sandblasting the tower, I also sand blasted the "Gen Mount", related small steel parts and the steel tail assembly. The "Gen Mount" was primed and painted white, while the rest of the parts were painted black. The motor was dropped into the mount and all the parts were installed for the drive. Other than wiring, the unit is ready to be installed on the tower.
Turbine assembly with the blade support mounted.
October 20, 2008