Yes, Soggy is correct. I have a buddy who works for the company that welded the helix once a week for 6 or 7 years. That's true. Since, it was built on rock AND the side of a ravine, the centrifugal force was pushing it into the ravine (not really, but by inches). Once a week, at night, they would re-weld the structure to the rock. I guess, now, they bedded and concreted re-rod into the ravine and the structure does not need as much mantainance as it did in the 80's. I hope this helps?!?!
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There's nothing like a woodie...