On Wed, 23 Aug 2006 08:29:37 GMT, Owen Duffy wrote:

Thankfully, it didn't come here. I just Googled for "aluminium house
wiring fires" and got 1,080,000 hits, whereas for "copper house wiring
fires" I got 736,000 hits. I guess there may have been an issue.

Hi Owen,

To say the least. The problem with aluminium/um house wiring was
identified as "cold flow" where over time the mechanical joint would
fail, increase resistance and electrical failure followed. Given the
correspondence here on connecting aluminium/um, it appears that
problem has been solved by professionals, but it would also seem to
offer dim prospects in the housing industry.

Using that approximation, shouldn't you have taken the weight of a
half span? Then, isn't that weight evenly distributed over the half
span, so you should halve it again?)

No, upon further investigation, my numbers appear to be ball-park
without an order of two correction (other corrections may be
necessary).

A parabolic approximation is better than the triangular approximate,

More properly a "catenary" for sags which is a curve of constant
tension; and for our antenna use, this is a classic application. The
difference is slight in this regard as both involve hyperbolic
transcendentals, but the point of constant tension is more to be
noted. When we add the kicker of center feed weight, the curve is
obviously pulled out (which suggests linear analysis).

From my 1912 copy of "Standard Handbook for Electrical Engineers"
comes coverage of stringing power lines and calculating sag for a
given tension. Tables and calculations are not remarkably different
from my first approximation. This volume states "the working stress
should not be over one fourth this [ultimate breaking strength]."

Try using a rope runner.

Do you mean a rope as a carrier for the conductor... runs into some
other issues like differential stretch, and huge wind resistance.

True.

The
structure may stay in the sky, but the wire might be fractured anyway.

How do you come by the conclusion that the wire is destroyed, but the
rope remains?

73's
Richard Clark, KB7QHC