Windpower
Jigs
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When I build anything in any kind of quantity, which I plan to do with these windmills, I like to build a jig or two to help me in the process. I'm not much of a finesse kind o' guy, so the jigs help me a lot when it comes to uniformity and repeatability. Both these aspects, I think, are important with these windmills to make them as efficient as possible and to make sure they last at least a little while before shaking themselves apart :) Currently, I have 4 different jigs that help me in certain aspects of the windmills' construction, and I'll list them individually, or you can use the links to jump to the pictures and info about a specific one. Don't mind the date on the pictures - too lazy to change the camera's calendar :)
Keeping the weight and size the same are relatively simple propositions. The main concern I had was having each blade mounted at as close to the same pitch as possible and having the bolt holes in the same position to try to reduce vibration and imbalances. To accomplish this, I made the jig at the right. I made it out of pieces of 1½" angle iron, and a few small pieces of 1" angle iron and 1" x 1/8" steel box tube. Basically the way it works, is you
lay the two pieces of electrical conduit in the V of the 1½"
angle iron, and clamp them in place. The angle iron that
the shorter section of pipe used for the blade root lays in, is set
at ~25 degrees below horizontal. This will be the blade angle
for the first windmill - I'll see how it works based on rough estimates
of other blade designs. Once the pipe is laid in the V, I
welded about half the cirumference of the short pipe, to the side of
the long pipe at a 90 degree angle, as pictured above. After welding the top half of the
pipe's circumference, I left the blade in the jig, and drilled the holes
that will be used to mount the blades to the windmill hub. At
the end of the blade jig, I welded a small piece of 1" angle iron
to use as a stop for the end of the pipe. I used some small
pieces of angle iron and box tube to make a small tunnel that the pipe
slides into and the hole drilled through both sides of the box tube
works as a great drill guide to make sure that the blade ends are all
drilled in the same place and at the same angle. At the present
time, I'm using ¼" bolts to fasten the blades to the hub. If
I find the bolts need to be bigger, I'll enlarge the jig holes as required. Once
the mounting holes are drill, I rotate the blade root up and finish
welding the bottom half of the circumference. While the current blades are about 36" long and 8" wide, if I find I need to make them longer, wider, or both, I can clamp any length of pipe into the V of the angle iron. If I need to flatten the pitch a bit (which I think I might need to do) I can do this by simply wedging something under the end of the short piece of angle iron. I'm thinking I might drill a hole at the end of the root piece of angle iron, weld a nut on the bottom of it, and use a bolt (possibly with washers) to more accurately adjust the pitch of the blades. I'll update the pictures when I do this. Update: After reading numerous posts on the forums at otherpower.com, I decided I'd make a new set of blades, just in case, with a flatter pitch. To ease the process, I welded 2 nuts to the bottom of the blade root's pipe holder. I originally added the one at the end, but then realized that I should have measured as it was too far out and would only work if the blade root was 9" +, which is likely way too wide at the root. I added a second nut a few inches further in, and it works just fine.
On the left side of the picture, you can see the two bolts with red plastic wing nuts pressed onto them. I wanted to be able to adjust the pitch without having to use tools. I welded up the blade root to the main blade pipe, and then I put the blade back in, adjusted the pitch to the desired angle, clamped the blade, and then drilled the holes to mount it to the blade hub. I can go anywhere from the original 25 degrees up to about 3 degrees of pitch.
On the left side, is an end view of the pitch adjusted to about 10 degrees. For all three of the new blades, I welded them all together first, then adjusted the pitch once, and clamped and drilled them all. I left the drill hole for the adjustment screw with a few burrs on it so the screw would be tight and not change adjustment on me. In the right picture, I welded on a small piece of 1" angle iron that is parallel to the table top. I use the top of the blade's root pipe and the angle iron to lay my protractor on to make sure I adjust it to the angle I want before clamping and drilling.
I made it out of a few more pieces of 1" angle iron and 1" steel box tube. The pieces of box tube were all drilled together, to make sure their holes are all located in the same place, and then the whole metal assembly was clamped in place on my axis lines, and welded together using MIG and TIG. At present, the jig is set up for a 14" diameter blade hub, but it can quickly and simply be modified to work on anything from 12" to 16" diameter hubs or bigger, if I decide to change the design. I can drill the mounting holes in both the top and bottom pieces of my blade hub at the same time to make sure the holes are in identical locations and perpendicular to the hub's face. I didn't want there to be a problem with blades that weren't all very close to identical in pitch. I don't know how critical this is, but I figured it was, so I didn't want to take a chance. At a later date, if I decide to go to 6 blades, for whatever reason, I can use the same jig and just rotate it another 60 degrees on the blade hub, to locate the extra 3 blades.
The winder is made to hold pretty much any standard size wire reel at one end, with the coil holder and handle at the other. I made it sort of heavy so it wouldn't move around much while I was winding, and I just hold the wire spool with my free hand to provide a little tension while winding the coils. The wooden spool is big enough to accomodate 30 or so windings of about #12 wire, and makes nice, neat little coils about ¼" high and about 3/8"to ½" thick on each side. I made it so the handle and the wooden spool can be replaced in case I need to changes sizes, wires, or it breaks and needs repairs. We found the trick to actually winding the coils was very simple. The first few coils I tried to be very careful and wind them neatly and tightly. This made the coils rather difficult to get off of the wooden spool, and they didn't appear to all that neat. In the end, I just used light tension, let the wire wrap where it wanted to, and the coils were far easier to get off and actually looked neater, and would lay flatter than the tightly wound coils. My friend put a few drops of crazy glue on his coils to make them keep their shape better before he took them off the winding spool - it worked pretty well.
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To
my way of thinking, the most important aspects of the blade construction
are uniformity of weight, size and angle/pitch.
To
make it easier to weld the short pipe to the round side of the long
piece, I made another small jig out of 1" angle iron and 1"
box tube to use as a means to cut a half-round profile in the end of
the short piece of pipe. Due to equipment issues, the biggest
bit I can use at the moment is a ½" bit. The
jig holds up to 1" OD pipe in place while the drill bit cuts a
half round profile in the end of the pipe. The electrical
pipe is 15/16" OD, but the ½" bit does a pretty good
job of rounding out the end of the pipe enough to make it much easier
to fillet weld to the side of the long piece. When I get
a different bit or bigger chuck, or both, I'll be able to enlarge the
jig's hole to a size closer matching the pipe's diameter.
My
friend, "Fast Ed", used a MIG to weld his pipe, but I prefer
TIG. Either one would work fine and the galvanized coating
was quite easy to almost entirely remove with a wire wheel.
My
next concern was getting the blades at 120 degrees, every time, without
it turning into an IQ test. After laying out 3 blade axis
at 120 degrees apart, I decided to make another jig to make sure that
the bolt hole, and blade locations were as close to exact as possible
when mounting time came.
Based
on a rough guess at the details of the coil winder made by the boys
at otherpower.com, I made a similar one out of 1" steel box tube,
a little ¼" steel rod and a couple small pieces of ¼"
plywood.