To see these posts in the same order as the build (from start to current), click the ‘wind turbine’ link on the right.

With the frame of the wind turbine done, it’s time to make the tail boom.

This is the beginning of the tail bearing which will hang on the pivot that is already welded to the back of the yaw bearing. It is made from 1-1/4″ sched 40; is the same length as the pivot (9″); and will be notched halfway-up to fit over the pivot bracket and to allow for a ‘positive stop’ to prevent the tail from swinging into the blades when the machine furls.

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I had decided in the beginning of this project to save the metalwork for close to last because I knew it would be no big deal to bang-out in a couple of days. Now that I’ve made all the other pieces, it’s time to fabricate the frame of the machine so I can assemble it.

The stator bracket is cut from a piece of 1/4″ plate. The outer diameter is 15″ and the inner circle is 4″. The spokes are 1-1/2″ wide at the top, 2″ wide at the base, and 120 degrees apart. One 1/2″ hole for mounting the stator is on each spoke 13-3/4″ from the center. In the center of the bracket is a 1-1/4″ hole for the wheel spindle.

While I could’ve had something custom machined, I chose to go with standard parts for easy parts replacement & maintenance (bearings, etc). Therefore the spindle is a standard 1000 lb trailer axle piece that I got from Northern Tool. The assembled machine won’t weigh half that and larger ones are available for the next (upsized) machine should this one work well here.

When you get it where you like it, weld it.

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I decided to finsh some details on the stator while I was kicking around the shop today.

The biggest concern when drilling the bolt holes through the stator was to not hit any of the copper coils or internal leads with the drill bit. You can see with the solid green that it could get difficult, but I was successful drilling the three 1/2″ holes 120 degrees apart for the mounting bracket hardward.

The generator terminals will eventually need to get connected to the line so I installed stainless terminal end lugs. The stainless will hold up to weather with no problem, but the main reason for using it is that it’s non-magnetic and I didn’t want them interfering with generation since these will be be in an area between the rotors.

You can see how each phase of the generator output is attached in the photo above and, on the flip side (below) how the line will connect to the opposite side of each lug. It should be an easy matter to hook it up when the time comes.

With the rotor metalwork completed and the layout of the magnets done, it’s time to cast the rotors in fiberglass.

I have no doubt that these magnets would hold fast to the backing plates by their own strength & with the bead of CA adhesive around each one… and then embeding them in epoxy fiberglass, but I’m giving the outer edge a few wraps with fiberglass reinforcing tape. It will hold a magnet in should one start to slip from the rotational forces but will also help prevent any minor long-term stress cracking.

 

Nothing jumps together by itself and there’s two rotors that need to be cast. We could make one mold and re-use it to pour each rotor, but while I was at it, it is just as easy to make two at the same time and then pour both rotors at the same time. 

 

The base of each mold is a 14″ x 14″ piece of 1/2″ plywood because I had 1/2″ on hand ;) , but since the rotor backing plate is 1/4″ thick and the magnets are an additional 1/2″ it was necessary to use 3/4″ plywood for the center piece with the 12.5″ hole in it.   Continue Reading »

Indexing the Backing Plate

Once the magnets get mounted, it’ll be imperative that these rotors be assembled properly oriented to each other. We drill a small divet (not all the way through) on the back side of each rotor where the 1st magnets will be mounted as an index mark to ensure the correct alignment of the rotors to each other now, and in case the machine ever needs to be disassembled in the future. 
 

Magnet Layout
A blank rotor is on the left and the one on the right has the magnet template laid over it. The magnets are in between with the spacers used for shipping them. They are not toys and are so much stronger than a regular magnet that I was unable to pull them apart - even with the plastic spacers between them.

A safe way to separate them is to place the entire “bar” on the workbench with just one magnet overhanging the edge. You can then forcibly slide the overhanging magnet down and away from the rest, but even then it’s a blood-blister inducing ‘pinch’ waiting to happen. ;)
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