[TowerTalk] Mast diameter

[Bill Cotter]

Howard,

Over thirty years ago I bought a 21ft high carbon steel fence 
post/rail for chain link fence from our local fence wholesaler. It 
was 1.9" OD, 1/4" wall thickness and very heavy (75-100lbs). I used 
it to support a 3ele10M yagi, 3ele12M yagi and 3ele15M yagi with 
13ft out of the tower and 8ft in the tower, up at 85ft.

Perhaps ten years later we had a tornado nearby and winds in the 
100mph range bent the mast about 5deg off center. The mast no 
longer slid down the thrust bearing, and I had to remove the mast 
with two of the yagis still attached. It was a bear to remove. The 
lesson learned was to insert a 10ft smaller diameter high carbon 
steel tube inside the 1.9" mast 2ft below and 8ft above the thrust 
bearing to help mitigate the bending moment.

My point here is that you may not have a schedule 80 water pipe, 
but perhaps a similar mast to what I had. The weight may be the 
clue. Before about the year 2000 the galvanized 2" 146,000psi 
chrome-moly masts of the 22-24ft type were not commonly available. 
All you could easily find were the 90,000psi high carbon steel 1.9" 
masts (chain link fence posts) and undesirable schedule-80 water pipe.

73 es Merry Christmas - Bill N4LG




At 02:18 PM 12/23/2015, you wrote:
>TTalkians,
>
>I have a 20' long steel mast (looks like chrome moly) with 0.25" 
>walls, which until today I assumed was 2" in diameter.  I had 
>taken it down from the tower where it was in service, so at the 
>time I assumed (!!!!) it was made to be a mast.  Today I tried a 
>2" DX Engineering mast clamp on it and it was loose.  I did what I 
>should have done a long time ago and measured the mast with dial 
>calipers, and found the actual diameter is 1.903"...!!
>
>As a result I have queries for all you experts:
>1) What do I have?
>2) What is the best clamping gear available for that mast size?
>
>Thanks all for sharing your expertise and have a great holiday 
>weekend!
>
>Howie - WA4PSC
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