On 12/15/2011 3:42 PM, Jim Hoge wrote:
>
>
>
> ________________________________
> Mike,
>
> The perceived weight at the winch (with a single pulley) will be far greater
> than the weight of the tower because of the shallow angle of the layover
> cable when the tower is near horizontal. Block and tackle can reduce the load
> but you double the length of cable to spool out or take up for every pair of
> pulleys added. I don't know how to calculate the changing load but it was
> quite obvious based on my exertion levels when cranking the winch to lay over
> or raise the 70' Triex tower I had.
Don't forget to multiply the weight by the amount/percent of tower
past/above the attach point for the raising cable, so the actual load on
the cable and winch is even more than that calculated by the angle.
I need to know how high the pulley is on the tower supporting the
winch. Then I need to know the height of the tower and the location of
the attach point on it. Finally I need to know the weight of the tower.
The tower with the winch, the top pulley, the attach point on the tower
raised and lowered, and the tower itself form a right triangle when the
tower is down.
Straight trig can be used at that point to calculate the load on the
cable and side load on the support tower as they are the same at that
point. Typically the support tower requires back guying if you are
going to lift much load.
73
Roger (K8RI)
>
> be safe,
> Jim W5QM
>
>
>
> *
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|