Roger Parsons wrote:
>When I moved to Canada from England I was surprised to
>find that neither aluminium alloy nor steel scaffold
>poles appear to be available here. (It seems to be
>that tower scaffolds are universally used.) These
>tubes have an outside diameter of slightly over 2"
Slightly under - 1-29/32in. The steel ones were originally based on
"1-1/2 in" water pipe schedules, though they have their own
specifications now.
The aluminium version is a special tube with the same standard OD as the
steel, but a thicker wall thickness to increase the strength. Although
they are lighter than the equivalent steel, they are also more expensive
and have the usual problems of aluminium alloys compared with steel -
particularly that they're more readily weakened by fatigue and salt
corrosion, and are more liable to fail by snapping.
>and
>are immensely strong, although I admit that I have no
>figures for them.
When searching a few years ago, the only spec I could find for the
allowable bending moment was based on the length and rating of a pulley
arm for hauling up barrels of bricks (cue for song).
>They are also relatively inexpensive
>as they are produced in great quantity. If I had
>realised I would have included half a dozen in the
>container!
Yep, they come in 20ft lengths, so they're wonderful for 40-60ft
rotatable Field Day masts.
However, they are now being phased out of the construction industry, so
now is the time to rescue them. (GMs: a scrappy in Dumfries still has
some :-)
--
73 from Ian G/GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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