Hi Paul: I believe I can describe the ingeneous system used to raise and
lower crank up towers. Lets assume that the tower does not have power
pull down. This feature is nice if the wind is blowing but adds greatly
to the complexity of the system.
1. Assume the tower has 3 sections and they are numbered 1 for the top,
2 for the middle and 3 for the bottom section.
2. Section 1 has a cable attachment point at its bottom.
3. Section 2 has a pulley built into its top and a cable attachment
point and a pulley at its bottom.
4. Section 3( the bottom section) has 2 pulleys built into its top and a
winch attached at its bottom.
5. The winch cable goes from the winch drum up thru one of the pulleys
at the top of the base section(3) down around the pulley at the base of
section 2, up thru the other pulley at the top of the base section and
down to the cable attachment point at the base of section 2.
6. You can see that operating the winch pulls the middle section(2) out
of its nested position inside the base section. The multiple cable runs
are for mechanical advantage in lifting the upper 2 sections.
7.The upper section has a cable between the top of section 3 (base)
where it is attached, up thru the pulley at the top of section 2 and
down to the bottom of section 1 where it is attached.
8. When the winch is turned, the sections separate proportionately i.e.
if the cable moves the middle section halfway out, the top section will
also be halfway out due to the bootstrap nature of the mechanism.
9. Unfortunately there is one additional bit of complexity, The winch
cable goes up the outside of the tower and the pulley it goes over is
turned at an angle so that as the cable leaves it, it goes back down in
the gap between the outside of section 2 and the inside of section 3.
the rest of the cable runs are in the gaps between the tower sections.
I believe this description is correct but it is possible I missed
something. If you follow the description you will see that additional
sections can be added at the top using single lift cables as in section
1. The lower part of the tower remains the same.
73, Dan, N5AR
Paul Walsh wrote:
>
> Hello all,
> I am interesting in making a crank up homebrew tower to
> support a 2ele quad, does anybody know where there is some good plans
> showing how the winch works for each section of the tower,
>
> Thanks in advance
> Paul
> G3PJV.
>
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