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Posted by RicodJour on February 25, 2007, 12:18 pm
richard wrote:
> Whilst pounding the pavement on 18 wheels I came up with a little gadget
> purely as a fantasy thing.
> Picture something like a high steel construction crane but on a smaller
> scale.
> My gadget will be centered around a simple pillar in the middle of a huge
> parking lot.
> So that the single arm swivels 360 degrees about the pillar. The arm would
> reach out say like a 1,000 feet at the maximum point and be retractable.Or
> perhaps have a "chair" movable about it. The only thing it would hold would
> be something like a movie director's chair as seen on some pivoting cameras.
> Got the idea?
> Ok so the question is, what size steel beam would I need to extend to 1,000
> feet? Keeping in mind that weight on the beam would probably be less than
> 1,000 pounds at all times.
> Would pipe work better and have the "chair" inside a channel thing?
> Purely fictional of course.
> The main support pillar could also be placed beside a building. It would not
> have to be in the center of the lot.
Forget about the weight of a beam, and concentrate on the load
itself. You're essentially building a big balance beam. The load at
the end of that 1000' arm would be about four or five hundred pounds
(guy in chair with camera) > 500# x 1000' = 500,000 ft-lbs. If you
had a counterbalance on the other end of that beam, say 10' from the
fulcrum, you'd need a 25 ton weight to balance. When you factor in
the beam weight, the load would possibly be an order of magnitude
greater.
You're just looking to design a crane and there are no new inventions
in lifting loads. It's all been done. So base your design on an
existing crane design and just lighten up the structure and load.
Like this: http://photos.si.edu/crane/gifs/crane.gif
http://en.wikipedia.org/wiki/Crane_(machine)
Use a large factor of safety.
R
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