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Making Propellers out of SCH40 PVC
After some more lengthy research on the web, I figured my best approach would be to make my propellers out of PVC as some other people are. Since making them out of wood would be a little more time consuming for me, plus the maintenace on wooden props is another annoyance, since rain drops and bugs have a tendency of pitting the props, and whatever bird flies into it now and then, if not properly maintained, the props would deteriorate and eventually be too inneficient, I would prefer a low maintenance approach, PVC! If the gray pvc is used, it would be better since that is more UV resistant than the white PVC, solid core is better than foam core. But all I have on hand at the shop is some 4" sch40 white PVC, so I decided to use that. It was only 27" in length, that would give me a 54" swept area, which I believe should be sufficient enough to turn the generator head pulley along with the motor with a load at around 4 to 6 mph winds.

(June 18, 2009)
I started out with a 27" long, 4" diameter schedule 40 DWV PVC pipe with a solid core.
Since I did not take pics when I did this part, I used Sketchup to illustrate how I cut the pipe ;)
I divided the circumference of the pipe into 3 equal sections, since I wanted to use only 3 propellers on my generator, since I have read that they are easier to balance and they are the most common, more so than the 5 or 6 blade kind.
I marked the pipe along its length and hand cut it with a jigsaw, since it would be hard to cut it into 3 pieces with a band saw!
I then marked it 1 1/2" from the back of the cut piece, on one end, and marked the pipe at 4" on the upper left side of the pipe piece. I also cut off a chunk off the top left hand corner.
I fabricated the mounting bracket for the propellers on the CNC plasma cutter, and welded on a collar I had turned on the lathe to attach it to the pulley shaft of the generator.
I fabricated the collar with 2 set screws (1/4-20) to hold it on to the shaft and the propeller mounting plate has a key on it that fits right into the motor shaft keyway to prevent it from slipping. The propellers are mounted on with some zinc plated 1/4-20 hex bolts and nylock nuts.
(June 19, 2009)
Each propeller had all the edges rounded off to reduce noise, and each one was carefully worked to weigh 1 lb 2.6 ounces. This made it a lot easier to balance the propellers once they were mounted.
(June 20, 2009)
Finally, we had all the hardware done, so me and Zack decided to put it up on saturday morning to see if what we had put together would work.
The winds that day were in the range of 5 to 10 mph. Unfortuantely the small blades were not enough to spin the generator shaft in lower winds less than 10 mph. They spun the shaft of the motor without the belt and pulley drive, but with the belt, it makes it harder to turn. So I guess back to the drawing boards.
(June 20, 2009)
We were really disappointed about the results of our first wind test, so within a few minutes of disappointment, we went down the road to Ewing's Well Drilling to see about purchasing a small chunk of their 6" well casing. They were nice enough to just give us a piece of scrap pipe they had left over on a job.  The New PVC pipe is 6" diameter and only 47" long. We had marked and cut it the same way we did with the smaller diameter pipe. Zack spent a couple of hours just sanding the edges smooth (Good job Zack!), once we had them on the generator and had it up, as soon as it turned to face the wind the propellers started spinning!! The winds at the time were anywhere between 4 to 7 mph. So the bigger surface area of the new props makes it work better in the lower winds, excellent, just what we wanted. Although with the bigger props, we had to change the weight and size of the tail fin, so just for testing we had attached a piece of ABS plastic to the tail, just to get the right dimensions and weight.
This is a comparison pic of the old smaller props and the new larger ones.
With a 5ohm 25 watt wirewound sandbar resistor as a load, we let it spin in the wind and we took some readings, at around 5 to 7 mph winds, it was producing over 18 volts! That should be sufficient to charge a 12 volt battery. Since we would need atleast 14.5 volts for charging and once the blocking diode is in place, that would drop it down to about 15.5 volts. The battery will draw down the output of the generator anyway down to the battery terminal voltage.
(June 23, 2009)
New tail fin is in place and all metal parts have been painted to prevent them from rusting, seems to work quite well in low winds around 4 to 7 mph. Now if I only had a much taller pole to put it on, I could get more use out of it! Right now it is only on a 12 foot pole.



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