A couple of years ago we had a particularly violent storm (for our area) go through here. Winds here rarely get past 60-80kmh, this storm packed far stronger gusts. We watched branches the size of my arm fly past horizontally - after comming off a tree 100 metres away!
Anyhow, one branch went through my cheap chinese turbine, resulting in one of the blades being deflected into the tower and coming to an instant dead stop from a howling, screaming speed. I was waiting for a small lull in the wind to shut the turbine down, hand on the kill switch. 1KW rated turbine was churning out 1.3KW estimated. Then there was a bang and output stopped instantly. Followed by another thump. I was sure the turbine had come down.
A short time later the wind had calmed a little, I scooted outside to survey the damage and found this:
One blade found near the base of the tower, shredded.
The next day we found the other two blades, close to 600m downwind. They had torn free of the hub. No damage to the blades, except at the root where the 4 bolts and clamp plate were. (The blue scuffing is where they pulled out past the clamp)
Damage to the yaw shaft was immediately evident, and the broken outer cover showed how violently the head swung around to hit the tail.
The missing fibreglass from the blades is still attached to the bolts
The tower shows the impact - and the top rung of my steps has been squished
The shaft suffered a slight bend... 0.065" total deviation (so .0325" bend)
Finally got started on fixing the thing. Once I got the yaw shaft out, the damage was more evident.
I got a lump of suitable steel (70mm dia) and started to turn down a new shaft.
Playing with ideas on how much to replace, and how...
Getting a perfect fit and a glass-like finish on the shaft where the bearings are pressed on took a little patience and some fine paper. I know it didn't need this finish, but I did it anyway.
Next was to further cut up the old shaft and try to get the slipring assembly off.
And turn the new shaft to take it
I machined down the old base plate to make a snug-fitting socket for the new shaft.
It was almost a press-fit, but I still drilled and tapped a locking grubscrew for it.
The sliprings went on next, and they were a tight fit. (Shown here only part-way on)
Cut a 1.8mm grove for a circlip
Cleaned the sliprings and checked the circlip will fit properly before re-assembling.
Hard to really see here, but the hole up the middle for cables to come out still left a LOT more steel than the original thin shaft offered.
(to be continued)