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Gin Pole Issue | 23 comments (23 topical)

Re: Gin Pole Issue (3.00 / 0) (#11)
by SparWeb on Tue Jun 30, 2009 at 09:21:31 AM MST

I can go overboard with the "thus" and "therefore" stuff.

If the situation I've drawn is what is happening, then you will never lift the tower. Like I said before, the gin pole is in compression. If it is pushing down on the tower like this, then it is holding the tower down.

As you pull more, the offset gets bigger and the situation gets worse. It may even magnify the compression load - causing more buckling than you would otherwise see. You're very lucky that you were stopping to check things as you started to pull.

I can't really tell if this is actually what is happening - this is yet another case where figuring out this stuff has to be done by the guy standing right there.

Why isn't your gin pole attached to the free stub on the base plate?
Steven Fahey
[ Parent ]

Re: Gin Pole Issue (3.00 / 0) (#12)
by behoof on Tue Jun 30, 2009 at 10:05:57 AM MST

Steven,

Appreciate your taking the time to follow up on this.

In your drawing you show the gin as if it were only attached to one leg of the tower, if you look at the pics you'll see that there is ample metal between all the legs but you are correct in that the gin would be able to pivot on its pin given the opportunity.

What I'm going to do is build a plate to attach directly to the back 3 - 1 1/2" base plate studs that go down into the footing and mount the gin directly to the base plate behind the pin currently looking open. It's the pin for the third leg of the tower when it comes over and anchors.

As I mentioned this tower has been in use for a number of years and been up and down probably more than 20 times without incident. Perhaps it was a disaster in the making and I was just very fortunate that it all happened as it did????? I feel pretty happy that it happened in the cradle rather than on the way up, damn, I am lucky.

I was still hoping that some kind engineering/math knowledgeable person would help me out with some numbers on what kind of forces are REALLY at work here, I'd sure like to know?

Also, if you care to use it, my email is skipb@greatlakes.net perhaps that way I won't clutter the board with all my gibberish?

Thanks again,
Skip

[ Parent ]

Re: Gin Pole Issue (3.00 / 0) (#13)
by SparWeb on Tue Jun 30, 2009 at 01:12:21 PM MST

...help me out with some numbers...

Well that's what I'm here for. We're still trying to define the problem, so the numbers come later.

Seriously, it is really hard to work this stuff out through a web forum or e-mail, because details missed in a photo could have major consequences. Sometimes just changing your perspective, plucking a tight wire, sighting along the length of the pole makes all the difference.

Just in case you didn't see the posting, I've seen my own tower crashing to the ground. Not fun at all, and I have to live with wondering if I had just checked this or that more carefully, maybe I would have caught the mistake before the accident.
Steven Fahey
[ Parent ]

Re: Gin Pole Issue (3.00 / 0) (#14)
by SparWeb on Tue Jun 30, 2009 at 01:35:51 PM MST

...build a plate to attach directly to the back 3 - 1 1/2" base plate studs that go down into the footing and mount the gin directly to the base plate behind the pin currently looking open...

Okay, that will help. I picture the gin pole coming down on top of the third stud, but of course you've probably thought of that and it won't be in the way. That will get rid of the knee joint so that will help a lot. Attaching all wires to the tip of the gin pole is also important. If you do both of those things and still see your gin pole buckling please let us know because then something else is happening.

Thank you for sharing the other photos. That's a very tidy setup. I don't usually spend much time painting things.
Steven Fahey
[ Parent ]

Gin Pole Issue | 23 comments (23 topical)

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