Anotherpower.com Forum
Project Journals => User Journals => WooferHound => Topic started by: WooferHound on February 05, 2012, 09:01:41 pm
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Many years ago, one of our users was trying to make some PVC blades and was having trouble on a few details. I decided to help out and came up with some plans for a 2 blade prop cut from a single piece of PVC pipe. The original idea came from Zubbly a user who is now deceased and highly missed around here. I helped perfect the props and drew up the plans to show how easy it is to make them. So Zubbly invented them and I (Wooferhound) made the plans, naturally these props became known as ZubWoofer blades.
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For any kind of serious wind power I would use 8 or 10 inch (maybe larger) PVC pipe. Using smaller pipe will cause the blades to be very slender and thin. Using 6 inch pipe is OK for some fun projects, using 3 or 4 inch pipe is only going to create Yard Art and won't make any Real power.
Start by cutting the PVC pipe to the length of your planned prop diameter. Then mark a line down the length of the pipe to be the Centerline. To mark a good straight line down the pipe I like to push the pipe into the hinged area of an open door, or use a piece of Angle Iron against the pipe to mark the line. Then mark a point halfway down the centerline to be the bolt hole used to mount the prop.
You can control the twist of the blade, just decide what the angle will be at the hub, and what the angle will be at the tip. If you are experimenting for the first time with these blades, then use the suggested angles of 25 degrees at the hub and 7 degrees at the tips. Put the centerpoint of a protractor against the inside centerline mark on the pipe and find where the 7 degree point is on the inside of the pipe, make your mark there. Next find where the 25 degree point is on the same side of the pipe, and mark that point on the inside of the pipe. accurately mark the outside of the pipe at these points too. Repeat this step on the other end of the pipe.
The center of the prop is a circle (or oval) with the bolt hole in the middle of it. The outsides of this circle will be the same distance from the centerline as the 25 degree marks that you marked on the ends of the pipe. I would cut out a thin cardboard circle and wrap it around the pipe centered on the bolt hole mark and trace around it with a marker.
Turn a metal tape measure around backwards and lay it numbers-down onto the pipe with one end lined up to the circle and the other end lined up to the Tip Angle mark at one end of the pipe. draw this line onto the pipe, and repeat for the other end of the pipe.
All the markings are done now. Since there are no cuts into the circle or through the blades you might want to erase or markout the areas in the center that don't get cut. These areas are the dotted lines in the drawing above.
Time to start cutting. I think a Reciprocating Saw (jig saw) works great. You can just cut straight into the pipe and get Good results. As shown in the above drawing, if you can angle the cuts you will get better results from this type of prop. However cutting angled cuts into round PVC pipe is not easy to do, and you will need to offset the cut line to get some cuts to line up correctly. You will see when you try to cut it.
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If you look at the drawing about "Finding your Angle Points", you will see that a hub angle of 45 degrees will result in the full diameter of the pipe being used. A hub angle that is more than 45 degrees is not possible since the pipe would be curving around itself and defeating the wind. A 45 degree hub angle is not much use anyway except for yard art, the steep angle makes startup easy even in slower winds but will quickly stall as it gathers speed. The suggested hub angle of 25 degrees is about half the pipes diameter and has much better performance in faster winds.
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-- A few more points about PVC pipe props. --
Due to the Curved shape of pipe, the props will tend to have a Top Speed. As the props go faster the curved surface creates turbulence and decreases their efficiency, so they tend to Top Out in speed at some point.
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The PVC pipe that I have used have cracked and warped over years of flying as Test Props. It would be good to paint these props with something that will stick to PVC plastic and resistant to the weather. Put big washers around the Bolt Hole to prevent breakage there. Be aware that it can possibly break at anytime and keep clear of it when it spinning.
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It is possible to creatively cut 2 of the props and make a 4 blade prop
Hope this helps Ya'll to make some cheap wind power.
Thanks to Zubbly for the inspiration to make the props and the ideas for the drawings !!
Also Thanks to many on IRC Chat who have helped with the details !!
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Woof;
Thanks for pulling this out of the archive, dusting it off and reposting it here!
Lots of old threads it would be nice to see resurrected here. Problem is the original poster really has to do it to be legitimate as a repost from another site.
Thanks again, Woof!
Tom
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I took the picture of my Test Prop with the Blue Tail Fin today. When it spins real slow it makes a peculiar sound. I always tell myself that "It's Zubbly talking to me".
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I took the picture of my Test Prop with the Blue Tail Fin today. When it spins real slow it makes a peculiar sound. I always tell myself that "It's Zubbly talking to me".
It just may well be Woof....it just may well be....
Norm.
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If you ad this graphic to the tail it will be Zubbly talking to you!
(http://zubbly.com/Wayne_Abraham.jpg)
He will tell you all aboot his many projects.
Tom