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ReductionPulleySystem

Reduction Pulley System

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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 with also another pivoting mast at Node FSK. 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


Image-1: Pulley system

Pulley System

Image-2: One end of the pulley system attached to the wall.

Pulley System House Side

Image-3: How it looks when completed.

GHD Mast



Node-GES

Node GES 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 External linkbox halfway up (below the waveguide) is the computer that is NodeGES 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...


Critical stages

The whole lifting exercise could be called critical but I refer to two stages in particular;

  1. The start where gravity is doing all the wrong things for a masts design (there strength is NOT in the horizontal position)
  2. Towards the finish when the mast is vertical but not fully anchored, so the tendecy is to topple sideways if the rear guys detach.
  3. 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:

  1. Attach and tie off the pulley system.
  2. Release and move one set of guys to the jib, firmly attach - (double check)
  3. Release second set of guys - hang on and test the weight in case of brainfarts (see step 2)
  4. Move to rope - stand out of the way and feed rope evenly through pulley block.
  5. Once down, tie off rope.
  6. 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 External linknitric oxide of it toppling while the guys are tied back off.

With this system, raising and lowering the mast is External linkdesigners trivial.

Image-4: The pulley system and Halfway up

The pulley systemhalfway up

Image-5: Almost up and Vertical, before tying off

Almost up Vertical


Version 4 (current) modified Sat, 22 Jan 2011 20:52:39 +1100 by Derec
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