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.

The notch should allow somewhere between 120 - 160 degrees of tail swing; any less than that and the tail may not fold enough to allow the blades to get out of direct wind. Any more than that and the tail could potentially pitch itself into the rotating blades in the highest winds.

It’s much easier to work on the bench and transfer my marks than it is to try to measure and mark-up the end of a pipe, so I drew a circle the same diameter as the pipe and disected it to find 135 degrees.

Then I stood the pipe on the circle and transferred my marks.

Since I’m going to reuse the scrap that comes out of this notch, I didn’t want to use the torch to cut it. A bandsaw would work nicely here, but I don’t have one and I don’t mind a little workout. ;-)

This is what the notched piece should look like from the bottom.

I need to flatten the scrap piece enough so that its inside diameter will fit over the outside diameter of the tail bearing (the piece with the notch).

Slip the bearing over the pivot and insert a 1-1/4″ x 1/4″ plug in the top – to be welded to the bearing.

The bearing also needs to be turned complete counter clockwise to stop against the notch. This will be the normal (unfurled) position. Tack weld the scrap that we flattened as a reinforcement should the tail come slamming down out of the furled position back to normal.

The tail boom is fabricated from a 5′ x1″ sched40 pipe w/ one end fish-mouthed to fit the tail bearing.

Since the pivot is already at an angle to the yaw bearing / tower, if I make the angle between the tail boom and the tail pivot 90, the boom will actually point downward, kind of limp, and nobody wants that flying high in their back yard… so I’m making it a 110 degree angle and it should point up a little.

It’s a quick but effective fishmouth from the chopsaw and will be a nice fit with a little help from the hand grinder.

Looking down from the top, you can see that I also didn’t point the tail straight back. Remembering that the generator will be offset to one side of the tower by 5″: The force of the wind pusing against the offset generator/blade assembly is going to try to continually swing the whole machine around the tower. To counteract that force, I’m offsetting the tail a few degrees out of parallel with the wind direction.

Side View

Here, in the furled position, you can see I’ve added a lower gusset to support the tail and a ‘stop’ that will hit the yaw bearing to prevent the tail from contacting the blades.

It furls up nicely and gravity should have no problem bringing it back to ‘normal’ when the wind subsides.

Back to ‘normal’.

I’ve added a verticle 1″ x 1/4″ x 34″ piece of flat 9″ from the back to attach the tail ‘feathers’ to the boom

Tags: Wind Turbine

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