Raising / Lowering a 40' aluminum antenna tower

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Discussion Overview

The discussion revolves around the mechanics and considerations involved in raising and lowering a 40-foot aluminum antenna tower. Participants explore the setup, including the winch, pulley system, and weight distribution, as well as safety concerns and operational techniques.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Chris describes the setup of a 40' aluminum tower, detailing the weight distribution and the mounting of the winch and pulley.
  • Some participants inquire about the winch's placement, cable length, and power specifications, suggesting these factors are crucial for the lifting operation.
  • There is a request for a diagram to visualize the tower's sections and weight distribution, emphasizing the need for clarity on the center of gravity.
  • One participant explains the concept of calculating the center of gravity and its importance in determining the tension in the lifting cable.
  • Another participant raises concerns about the need for additional support to prevent the tower from slamming into the ground as it approaches vertical.
  • Several participants discuss the potential tension in the cable during lifting and the importance of safety factors in the setup.
  • There are anecdotes shared about personal experiences with similar setups, highlighting the practical challenges faced during such operations.

Areas of Agreement / Disagreement

Participants express various viewpoints on the mechanics of the lifting operation, the calculations involved, and safety considerations. There is no consensus on the best approach or the specifics of the setup, indicating ongoing debate and exploration of ideas.

Contextual Notes

Participants mention the need for flexibility in cable attachment points and the implications of weight distribution on the lifting process. The discussion includes unresolved mathematical steps and assumptions regarding the center of gravity and tension calculations.

Who May Find This Useful

Individuals interested in antenna installation, mechanical lifting systems, or those seeking practical insights into the challenges of erecting tall structures may find this discussion beneficial.

  • #31
DaveC426913 said:
a Mac comes with a mast-raising pole as standard equipment.
I'm wondering where the OP's pulley is attached. Sky hooks would be ideal for sailing but you can find them on the sides of buildings - it's another world on land.

The original Westerly centaur had a massively over-specked mast and it was not intended for bridges or for towing (two massive iron keels) so the mast raising pole was not standard equipment, afaik).

berkeman said:
I don't really understand that,
A worm drive is often very inefficient and will only work from worm to pinion. A great example where Velocity ratio is much higher than 1/mechanical advantage - People still insist on using the wrong one, even here on PF.
 
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  • #32
berkeman said:
The hardest part is when the tower is on the ground, because the angle θ is the sharpest.
Lifting it off the ground manually and resting it on a prop (or another person) can take care of the worst case of theta is zero). They can also hold a rope to control rotation when near vertical.
Basically there's no substitute for a few spare muscular blokes for these events.
 
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  • #33
sophiecentaur said:
I'm wondering where the OP's pulley is attached.
1698338311119.png
 
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  • #34
Sorry I missed that image. Another thing to reduce the extreme of tension the lifting from the ground would be to use a pole or A frame, starting at say 45 degrees elevation - like the boat mast lifting gear. It would make things much less dramatic and stressful on the pulley fixing.
DaveC426913 said:
 

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