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* Reduction Pulley System [1]
* Node-GHD [2]
* Image-1: Pulley system [3]
* Image-2: One end of the pulley system attached to the wall. [4]
* Image-3: How it looks when completed. [5]
* Node-GES [6]
* A couple of points... [7]
* Critical stages [8]
* Procedure: [9]
* Notes: [10]
* Image-4: The pulley system and Halfway up [11]
* Image-5: Almost up and Vertical, before tying off [12]
REDUCTION PULLEY SYSTEM
NODE-GHD
This reduction pulley system is great for anyone who wants a large
pivoting mast and has a mounting point for leveraging. The reduction
pulley system reduces the amount of force needed to 1/4 of the total
forced needed to get the pole at 90 degrees.
This pulley system is installed at Node GHD [13] with also another
pivoting mast at Node FSK [14]. The pulley system can raise a 14m mast
with little effort. Lowering the mast is even easier.
All you need is two pulley's with two wheels, some rope and a
leverage point above your mast.
The smaller image is from howstuffworks.com and the image in the
background just shows the setup at Node GHD [15]
IMAGE-1: PULLEY SYSTEM
IMAGE-2: ONE END OF THE PULLEY SYSTEM ATTACHED TO THE WALL.
IMAGE-3: HOW IT LOOKS WHEN COMPLETED.
-------------------------
NODE-GES
Node GES [16] uses the pulley system to raise 9 metres of Mast from
the horizontal to the vertical, single handedly (it is that easy).
These notes are for my setup where raising and lowering the mast is
done on a periodic basis. The _box halfway up [17] (below the
waveguide) is the computer that IS NodeGES [18] so that's another
reason why the mast is taken down more frequently than others maybe.
In addition to any need_ to lower the mast, if it's easy to perform
the task then there are fewer excuses to _not do it_. - human nature
at it's best!
A COUPLE OF POINTS...
* The anchor and hinge point need to be properly engineered or
failing that - OVERENGINEERED
* The roof/wall anchor point needs to be substantial
* A long jib helps to even out the load, and reduce the effort
* The mast should be larger in cross section, or more support guys
added.
* Counterweights help, but are not essential
CRITICAL STAGES
The whole lifting exercise could be called critical but I refer to
two stages in particular;
* The start where gravity is doing all the wrong things for a masts
design (there strength is NOT in the horizontal position)
* Towards the finish when the mast is vertical but not fully
anchored, so the tendecy is to topple sideways if the rear guys
detach.
* During the middle stage (45 degrees) the forces are evenly matched
with gravity actually helping to stabilise the mast from any side ways
movements . (The anchor point IS substantial, yes?)
PROCEDURE:
* Attach and tie off the pulley system.
* Release and move one set of guys to the jib, firmly attach -
(double check)
* Release second set of guys - hang on and test the weight in case
of brainfarts (see step 2)
* Move to rope - stand out of the way and feed rope evenly through
pulley block.
* Once down, tie off rope.
* To raise the mast, basically reverse the procedure.
NOTES:
The forces involved at the start of the lift are greater than you may
think. Depending on your setup, the direction of force during this
phase of the lift is directed back towards the pulley anchor point.
This means the hinge is undergoing shear forces rather than the usual
downwards thrust, so when designing or making the hinge mount keep
this in mind.
I use a detachable jib on mine, it pivots freely around the existing
hinge point and eases the shear loading on the mount point (by moving
the pulleys attachment point well away from the hinge). It also
reduces the effort required and provides good support to the mast
during the critical early stages - a mast is not usually designed to
be lifted from the horizontal (to restate the obvious!).
The REAR SET OF GUYS ARE ALWAYS ATTACHED so towards the critical last
(top) part of the lift they help support the mast. When the mast is
vertical and the rope securely tied off it is effectively guyed from
three points so it's quite safe.
In my case once the mast is up the counterweights help to keep it
vertical and reduce the perils nitric oxide [19] of it toppling while
the guys are tied back off.
With this system, raising and lowering the mast is designers [20]
trivial.
IMAGE-4: THE PULLEY SYSTEM AND HALFWAY UP
IMAGE-5: ALMOST UP AND VERTICAL, BEFORE TYING OFF
Links:
------
[1] http://melbournewireless.org.au/#reduction_pulley_system
[2] http://melbournewireless.org.au/#node_ghd
[3] http://melbournewireless.org.au/#image_1__pulley_system
[4]
http://melbournewireless.org.au/#image_2__one_end_of_the_pulley_system_attached_to_the_wall_
[5]
http://melbournewireless.org.au/#image_3__how_it_looks_when_completed_
[6] http://melbournewireless.org.au/#node_ges
[7] http://melbournewireless.org.au/#a_couple_of_points___
[8] http://melbournewireless.org.au/#critical_stages
[9] http://melbournewireless.org.au/#procedure_
[10] http://melbournewireless.org.au/#notes_
[11]
http://melbournewireless.org.au/#image_4__the_pulley_system_and_halfway_up
[12]
http://melbournewireless.org.au/#image_5almost_up_and_verticalbefore_tying_off
[13] http://melbournewireless.org.au/nodes/view.php?id=ghd
[14] http://melbournewireless.org.au/nodes/view.php?id=fsk
[15] http://melbournewireless.org.au/nodes/view.php?id=ghd
[16] http://melbournewireless.org.au/nodes/view.php?id=ges
[17]
http://members.optushome.com.au/graybeard/Wireless/PulleyMastNodeGES/starting.jpg
[18] http://melbournewireless.org.au/?NodeGES
[19] http://www.shoppharmacycounter.com/c-401-nitric-oxide.aspx
[20] http://www.u-clothing.com/ListDesigners.aspx
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