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imsmooth

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Joined: 07/02/2008
Location: United States
Posts: 214

Posted: 03:36pm 11 Dec 2009

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My original tower design had the stator assembly rotate 360 degrees on the top of the tower pole using a Yaesu thrust bearing. It turned smoothly; maybe too smoothly. It used four 5/16" (or maybe 3/8") bolts to secure the bearing to the tower. Four more bolts secured the top to my assembly plate. See images:
image1
image2

There have been some really strong winds these last few days, and I noticed the blades were leaning a little too far to one side. I took the tower down and found that two of bolts were sheared off. Two bolts were holding the bearing to the tower; the others were wedged in between. The bearing was tilted to one side. Although it was still held firmly, it is scary to think of 100lbs of metal falling 42' to the ground.

I have since corrected the problem by welding a 16" piece of 2.5" (OD) tubing to the bottom of my assembly. This tube articulates over the 2" (OD) tubing at the top of my tower.

JimBo911

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Joined: 26/03/2009
Location: United States
Posts: 262

Posted: 05:43pm 11 Dec 2009

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im
So you think that the support mast was to small and it was flexing and that's what snapped the bolts?

Jim

imsmooth

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Joined: 07/02/2008
Location: United States
Posts: 214

Posted: 05:59pm 11 Dec 2009

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Yes. There was about 3/16" gap between the outer diameter of the mast and the inner diameter of the thrust bearing. The bending forces must have exceeded the shear strength of the bolts.

JimBo911

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Joined: 26/03/2009
Location: United States
Posts: 262

Posted: 09:16pm 11 Dec 2009

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im
I'am thinking that the bolts and locking nuts that you used to keep the bearing and mill atop the tower did not have enough contact service to the mast or they did not dig into the mast deep enough therefore becoming loose. If you remove the 3/16 clearence via pipe or busching this may do the job. It's hard to over build this area of the mast going bigger/stronger is good.

Jim

imsmooth

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Joined: 07/02/2008
Location: United States
Posts: 214

Posted: 04:19am 12 Dec 2009

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They dug in plenty. I had pre-drilled holes so the bolts penetrated about 1/2 way through the thickness of tubing.

Anyway, it does not matter as my current solution is working well.

JimBo911

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Joined: 26/03/2009
Location: United States
Posts: 262

Posted: 05:06am 12 Dec 2009

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Good to hear that all is well. Let's hope for lots windy days.

Jim

KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 07:42am 12 Dec 2009

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I commented to Randy that I thought the yeasu thrust bearing was not much chop.

It appears my concerns were correct...

now to fix it on mine......

did you weld the tubing to the yeasu thrust bearing or directly to the weldment?

Luck favours the well prepared

imsmooth

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Joined: 07/02/2008
Location: United States
Posts: 214

Posted: 11:30pm 12 Dec 2009

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Karl,

I got rid of the thrust bearing altogether. The top of my tower has a 2' run of 1.875" OD tubing. I took a 16" piece of 2.5" OD (2" ID) tubing and directly welded it to the weldment. I made sure it was perpendicular to the rotational plane and used a combination of 6011 and 6013 welding sticks. It is pretty solid and has already survived a major storm with 50 mph gusts the last few days.

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