Wire span design tool
Richard Clark wrote in
:
On Mon, 12 Mar 2007 07:29:09 GMT, Owen Duffy wrote:
Owen Duffy wrote in
:
....
Classic work includes wind load, ice load, and temperature, with
comined loads usually expressed in pounds per foot lengths. It is a
tedious translation to check your page though. Try researching Pender
and Thomson.
....
Ok, so it is not for you apparently.
Calculating wind loading of cylindrical wire is problem enough, ice
loading might be cylindrical in laboratory tests, but is isn't reliably
so in real life. The surface isn't necessarily smooth either (so the
assumptions about laminar flow vs turbulent flow are affected). There has
been much written on the effects of ice on HV power lines, where they can
develop shapes that give them lift, with serious consequences when
adjacent lines fly into each other. (Differently to antenna wire spans
where wind load dominates the tension, large HV power conductors are so
strong and heavy for their diameter, that high winds only marginaly
increase tension, ice loaded spans are more affected.)
However, if you want to model ice loading, just increase the weight per
unit length of your wire for your chosen ice scenario, and increase the
windage diameter, change the GBS if necessary for the lower temperature
and run the numbers. I wouldn't propose an example, as I think the
results are unreliable.
The calculator probably has its greatest value as a learning tool in
individuals exploring scenarios for themselves, they might come to the
view that 160m dipole spans made from #16 magnet winding wire are not
practical in high winds.
Its not that we design to fail, its that we often fail to design.
Owen
PS: the calculator is metric units only to avoid the complication of
comprehensively dealing with imperial units, eg dimensions in decimal
inches, fractions, wire diameter in several gauge systems, lbs/mile etc,
force in pounds, slugs etc.
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