Posted by Franz on Saturday, August 30, 2003 at 9:54PM :
In Reply to: Re: Gin Pole Picture and disctiption posted by Jumper on Saturday, August 30, 2003 at 1:33PM :
While that is an excellent site depicting a Gin Pole used for erecting straight leg towers, it is NOT the definition of a gin pole.
A gin pole is any single leg support system held in vertical orientation verticle by 2 or 3 guys. Back before hydraulics became so common, gin poles were commonly used for erecting poles over 50 feet in height. The gin pole was usually a 30 foot pole sitting in a 3 foot deep hole a few feet from the hole the tall pole was to be set in, and held erect by a deck winch from one line truck while the winch of a second line truck lifted the tall pole via a pair of snatch blocks secured to the short pole, one at the top and one at ground level.
A frames employ 2 legs of equal length, secured at the base and lift via a cable running thru a snatch block at the apex of the triangel formed by the base and 2 legs.
In the old Bell System manuals, both A frames and Gin Poles are shown, and their use is fully described.
The misuse of the term Gin Pole seems to have evolved from Braden's design for small trucks such as the power wagon, as is pictured farther down this page. Braden sought to manufacture an erection system that had the height of a gin pole without the guy structure, and accomplished this by building a long lifting pole that was stiff leg braced at the midpoint. While that system did sort of work, it was a major pain in the a$$ to erect and work with. The Braden gin pole was however loved and desired by engineers and purchasing agents, who, of course never had to set one up. I've had the experience of both setting one up, and using it, and the thing flat SUCKED. On a 1 ton Power Wagon, that contraption had the capacity to break the front springs easily when the truck was moved with the pole erected.
Any truck being used for lifting with a front mounted device, be it an A frame or gin pole needs front spring lockouts, and even then has very limited lifting capacity because the front axel simply isn't designed for the extra weight, even without the load multiplication factor of leverage to the point of the frame.
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