Raising a Yagi Using A Tram Without the Need for Tag Lines

Transcription

1 Raising a Yagi Using A Tram Without the Need for Tag Lines The photo slide show that follows was presented to the FRC Meeting of 12/14/10. The narrative and diagram in this PowerPoint presentation was not included. An attempt has been made to capture the essence of the live commentary from the meeting, along with some additional notes and information.

2 The following diagram shows the general idea of how a tram line is used to raise an antenna to the top of the tower. The essential ingredients are: Tram line Attached at top of tower Attached to a structure at the ground level that is sturdy (tree, truck, etc.) Can be adjusted in tension Pull rope Attached to the pulley that rides on the tram Pulley at top of tower turns pull line down Capstan hoist at ground provides slow steady pull

3 Rigging Diagram

4 A few words on safety Raising a yagi must be done with safety in mind. Inspect all ropes for evidence of damage. Don t ever use frayed ropes. Make sure that ropes, pulleys, and come alongs, and other equipment is rated for the loads to be imposed. If possible, climbers should wait until the antenna is near the top of the tram line and stable before ascending. Climbers should use full body harnesses, and be clipped in at all times, both ascending and descending. When using a tram line approach, the tram rope can be under significant tension. The load rating of the tram, the come along, and any other item subjected to the tram line tension, should be several times higher than the actual stresses anticipated. There is no substitute for high quality ropes, pulleys, slings, and come alongs.

5 What? No tag lines? The rigging diagram shows the antenna hanging down from the pulley that rides the tram. The antenna is attached at its center of gravity, so that it hangs down in a stable manner. Normally, two tag lines would be attached to the antenna with a ground crew person pulling on each to keep the antenna from turning in azimuth as it s raised. This is to keep it from getting tangled in guy wires, etc. The approach described here and shown in the photos eliminates the need for the tag lines. This not only eliminates the need for two ground crew, but assures that the antenna is raised in a totally controlled and stable manner.

6 The Tag Line Gadget In the photos, notice that the antenna is hung on piece of aluminum angle, with a pivoting extension that clips into the tram line. This gadget keeps the antenna from turning as it rides up the tram line.

7 Photo 1 The yagi is mounted at its center of gravity. The element tips are pivoted up to help the yagi clear trees and guy wires. The no-tram fixture is keeping the antenna lined up and stable. The come along needs to be tightened significantly to raise the antenna higher.

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9 Photo 2 Tram line has been tightened by the come along. Only tighten the tram to the extent needed to clear obstacles. This will minimize the tension in the tram line. The capstan hoist is pulling the antenna up the tram line. Note no tag lines!

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12 Photo 4 This photo shows a clear view of how the rigging and fixture works. The thin black line hanging down is attached to the tram pulley, and is used to pull everything back to ground after the antenna is removed.

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16 Photo 7 With the yagi clear of all obstacles, the tension in the tram can be decreased. The yagi is hanging in a safe and stable mode. It is time for the climber to ascend.

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18 Photo 8 The tram line stops at the top of the tower, but the antenna needs to be mounted on the mast. A come along will take the load of the antenna, after which the rigging and ropes can be detached.

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20 Photo 9 A sling over the 80m rotary dipole provides a convenient place to attach the come along. An eye-bolt on the fixture provides a convenient place to clip in the come along. Note that all the ropes have been detached, and the antenna has been hoisted with the come along to mounting height. A couple of short ropes are all that is needed to pull the beam s mounting plate into the mast for mounting with the U-bolts.

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22 Photo 10 Rigging and mounting done. Total crew required, not including observers: Capstan hoist operator Tram tensioning come along operator Climber This job could have been done with just two people, and SAFELY.

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