The problem I have had with the method given below is that IFif a (and it
ususally IS) the upper pulley is some distance horiz. from the center line
vert. of the mast, then the further the mast gets pulled up, the greater
the horiz sidewise pressure on it, it seems. This sidewise pressure from
the rope and pulley arrangement binds the mast in the thrust bearing (even
tho the bearing is fully opened, i.e., not tightened) and keeps the mast
from coming fully up into position for rotor installation.
US Tower sells a mast raising fixture which runs a cable through a small
hole in the tower's top plate (the TB plate)that lets the cable come down
right beside the mast with very little horiz sidewise pulling.
If u do something like this, ok--
Otherwise, in four installs I have done, the mast binds before u get it
high enuf to install the rotor. K4VUD
On Fri, 22 May 1998, K7LXC wrote:
> In a message dated 98-05-22 15:08:59 EDT, BILL.MADDOCK@fluordaniel.com writes:
>
> << I will be trying to raise a 24 ft long mast 2" OD 1/4" wall to the top
> of my tower Rohn 45. The mast is already inside the tower it will just
> need to be raised up! I have a Rohn 25/45 ginpole, will this be strong
> enough for the job or should I look for another means? The mast weighs
> about 130 pounds. >>
>
> The easiest thing to do is to hang a pulley on a horizontal rung at the
> top of the tower and run the haul rope through it and then run it down the
> inside of the tower. Attach the haul rope to the mast about 1/3 down from the
> top of the mast with a sling choker. Wrap it around the mast 2 or 3 times and
> pull it through itself and it'll never slip.
>
> Attach a pulley at the bottom of the tower and run the haul rope through
> it. This is called a snatch block and changes the direction of the haul rope
> run from vertical to horizontal. Since you will need 260 pounds of pull to
> hoist the mast (130 pounds up the rope inside the tower and 130 pounds down
> the rope on the outside of the tower), you'll need a lawn tractor, winch or a
> bunch of friends to pull it up.
>
> When the mast reaches the thrust bearing, guide it in and through until
> you run out of haul rope. Tighten the TB bolts to capture the mast. Now you
> can move the choker down the mast (all you have to do is take tension off the
> choker and it'll slide). Have the ground crew put tension on the haul line,
> loosen the TB bolts and they can continue lifting the mast up. Keep going
> until you can slide the rotator in under the mast. Install the rotator, lower
> the mast into the rotator and then tighten the rotator mast clamp. You're
> done.
>
> If you want to install antennas on the mast before you hoist it up fully,
> feel free. Mount the antenna and feedline pigtail, hoist the mast up, mount
> the next antenna, etc.
>
> The other option is to install the naked mast and then climb the mast
> with angle iron or aluminum steps pushing the antenna(s) up as you go. (This
> is an advanced technique.)
>
> Cheers and GL, Steve K7LXC
>
> --
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>
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