Vintage Windmill and Wind Generator Forum

Can one assume that all the wear on the tailbone is on the “outward” end of the top hole and the inner end, side of the bottom hole? And should the pin be 90 degrees from the top frame member of the tailbone? Dang, sorry so long but don’t know how else to word it.

If i translated it right. Yes

180 degrees and I threaded a set screw to hold in position .

This part Mike,

OH , my bad , wrong part in my mind .
your right , it is "worn "

If I overlay this with 1/4” flat bar and locate the hole to where the back side of the hole matches the existing hole shouldn’t it be correct? This tailbone is over a grand at Aermotor

Mark before you do the over lay make sure the tailbone will still fit between the two ears on the gear box

Yes sir. I was goi g to do in on the top piece only. And then machine a new pin with a longer threaded end

Oh okay sounds like you have it figured out.

Generally the wear on the bone is elliptical as you describe but not always an ellipse directly inline with the bone. Variations come either from the amount of tail spring tension or being in a gusty wind area. Even tho the tail pin is fixed to the bone, there is some movement. If you look at the wear pattern on the top of the lower angle brace in your pic 2, the wear is not quite inline with the bone. When tail pin holes in the case are worn, they are off at an angle.

The bone must be for a 16 or 14 as it has the riveted extra brace for the bottom short bolt. The top flat bar and the bottom angle of the bone are NEITHER 90 degrees from the tail pin. The degree angle between top flat and tail pin is different for each size of Aermotor mill. You can attribute this to Aermotor cases not being uniformly scaled between sizes. The lack of exact scaling is evident with different issues in one size Aermotor and not in another.

I remember assembling a 12 many years ago that had a bone overlap repair and longer top threads on the tail pin as you describe. It was difficult to assemble because you had to enter the top flat bar before the larger OD of the tail pin got in to the upper lobe of case.

I have seen repairs on larger bones where an exact duplicate of the end 6" was butt welded when the old end was cut off. Evidently these repairs held. Back in the day when Aermotor had reps in the field, it seemed there was a lot of shared info on and commonalities on repairs.

Ron Stauffer
Montrose CO