At 12:38 PM 12/19/2006, Eric Scace K3NA wrote:
>Hard to draw a diagram on a text-oriented reflector. If you read
>this message with a fixed width font it should work reasonably well.
>First, the tram line in this diagram is like the gondola lift you
>sited, Jim. Tram wire sits overhead, and the sheave of a pulley rides on it.
>The antenna dangles below, and attached to, the frame of the pulley.
>Sketch at the point where the pulley rests on the tram:
><-- tower is towards the left.
> | '-._
>(ant) '-._ tram line continues off to right toward ground anchor.
>There are three force vectors meeting at the pulley:
> -- antenna weight, points straight down. 100 lb in this example.
> -- up toward the tower to the left. I used 45 degrees in my
> quickie statics example.
> -- to the right down to the ground. I used 30 degrees below horizontal.
>If you resolve the last two vectors into vertical and horizontal
>components, you can create two equations with two unknowns, and solve.
>Of course, I did the algebra without the benefit of a morning cup of
>coffee... and got wrong answers. The answers for a 100 lb antenna should be:
> 333 lb up toward the tower
> 273 lb down toward the ground anchor
That's more what I would think. 700 lbs just seemed a bit too high.
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