[TowerTalk] TowerTalk] Source for 20' Mast

[Ian White G/GM3SEK]

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