I have christened my wind turbine the "Spirit of Zubbly". I don't want his contributions to the art of home-built wind turbines to be forgotten. By dedicating this project to his inspiring work, I hope to remind everyone about the value of being creative and inventive, and sharing knowledge with others. It's the spirit of both science and art, and it's what makes projects like this so satisfying for me.
I'm finally done (almost), and it's up in the air. What a cold day for finishing this off (-12C / 10F!). This years' project was pretty complicated. Many things are changed, although many basic parts of the turbine remained the same. It still has the 8-foot diameter rotor blades, and the generator is the same motor-conversion I did a couple of years ago.
Wood blades and a motor-conversion: at its heart it is still a Zubbly-inspired
Improvements to the tower and the balance of the system meant that the entire system was taken apart all summer. It was also an opportunity to re-finish the blades and do some experiments with improving the generator. Some will remember that I had difficulty removing the old bearings from the generator's shaft, but that mess was minor compared to the piles of parts littered about as I went.
In all, this is what I changed:
The tower is taller by 10 feet, getting above my trees (which don't stop growing, dammit), now 50 feet tall,
The tower also has an additional group of guy wires to support the extra height,
Yaw-mount and chassis were re-designed to allow vibration isolators under the generator,
Tail re-designed to have a complete 90 degree swing when furled, and a harder running position,
Re-organized all batteries/inverter/charge controllers in a new building,
New underground cables buried from the new building to the tower and solar panels.
Since the new building wasn't built until September, and lowering the tower to work on it would be in the way of the construction, I had to wait, with most of the welding work on the tower parts and yaw mounting done early, but unable to install them. In the meantime, I also prepared a tachometer/ temperature sensor board that I fitted inside the generator, and an extension to the tower's gin-pole, but I don't really need either one, so they will wait for next year.
Adding height to the tower put higher loads on the gin pole and winch cables, so I was going to make the gin pole longer. Halfway through working on that, I realized that rather than extend the gin pole, it was far easier to add a pulley to the end of the gin pole instead. The pulley reduces the winch cable tension in half, which was the critical part of the equation. An unrelated project from last year had left me with a 10,000 pound load cell and a nifty program to monitor tension loads, so I used that to check that I wasn't going to over-stress the cables. Several test-lifts of the tower with the load cell attached proved that the pulley was effectively reducing the cable loads to a very safe margin. You can see two pulleys in the picture below. The one attached to the gin pole splits the load between the anchor underneath it and the one that's farther away (I'm using the anchor that was supposed to be end of the longer gin pole). The second pulley is for the right-angle turn from the winch (off to the left).
Last winter, an annoying noise took hold of the turbine. At certain speeds it would hum in a way that would be perfectly amplified by the resonant frequency of the wooden blades. With my series/parallel switch (similar to a Wye/Delta switch) I was able to narrow down the possibilities from the ground but all last winter I needed a working turbine, noisy or not. I resolved to eliminate as many sources of noise by building a chassis for the generator that would include vibration isolators under the generator mounting feet.
I came up with a way to assemble a set of pads, inspired by old-fashioned aircraft engine mounts, that would be easy to assemble, and avoid buying anything expensive. All I needed were flat sheets of neoprene to cut to fit as needed.
The frame of the chassis supports the feet of the generator with four over-sized bolt holes. By over-sizing the bolt-holes, there is room to slide in tubes of rubber, fitting snugly and allowing each bolt to pass through. On either side of that are rubber disks about 1/4" thick. Large washers put bearing pressure on the pads as the bolt is tightened up. The generator sits on top of the assembly, resulting in no metal parts in contact with the generator being in contact with the chassis, too.
The arrangement is, I admit, better at absorbing high-frequency noise rather than the low-frequencies that are giving me trouble, but I don't think it will hurt any, either. Sometime during my christmas holidays I will have to lower the tower again to see if the rubber pads are doing well. If not, I'll have to put metal sleeves into the oversize holes and go back to metal-on-metal mounting.
I also managed to build in the right sized hole for a kellum grip to hang neatly at the top, supporting the drop cable inside the tower. I hope to avoid the terrible amount of twist that had developed by the time I took the tower apart (about 15 complete turns CCW).
During the summer, my wife and I moved a number of our "movable" buildings to make room for a new one, and to make it easier for trucks to turn around in our barnyard. We chose a shed that wouldn't be needed any more to become the new home for the batteries, and electrical room for all the RE projects, so I call it the "Batt-cave".
I haven't insulated the compartment around the batteries yet, though they are enclosed for protection, now. Everything is accessible, wiring is sized out of the NEC, and I have more places with protection and shut-off means than I did before. Got all enclosures bonded to ground, too. I won't be sure I have all the details sorted out right until I draw a new schematic. It works, that's all I can say.
So, blame all this work, for me being a bit absent from the forum recently.
No I still haven't seen the WT running in the wind. You know how that goes...