[Towertalk] 25GSSB New? Baseplate

[n4kg@juno.com]

On Thu, 01 Aug 2002 Chris BONDE <ve7hcb@rac.ca> writes:
> 
	SNIP

> I thought that the concrete was mainly to lower the centre of 
> gravity for the complete antenna structure  (VE7HCB)

N4KG:  WRONG !   Center of gravity has NOTHING to do with
	resisting overturning forces in a GUYED tower (and 
	only contritubes partially in a self supporting tower).

	My (guyed) towers are set in the ground with NO concrete.
	The center of gravity is pretty high but they have
	been up for decades and withstood 90 MPH winds.

	As stated previously, the purpose of a BASE is to
	provide sufficient AREA to support the weight of 
	the tower plus the vertical forces from the guys.

	Bottom Line:  

	The EARTH supports the tower.
	The BASE spreads the load over
	sufficient AREA to prevent it from sinking.

	In areas where FREEZING occurs in winter,
	the BOTTOM of the BASE must be BELOW
	the FREEZE  LINE to prevent the base from
	pushing UP on the tower which adds to the 
	tension in the guys.
	
	For self supporting towers, the BASE 'couples'
	to the earth to prevent sinking AND overturning.

	SNIP

> This is the bases of the three legged cow milking  stool.  (VE7HCB)

N4KG:  I believe you mean BASIS and not "bases".




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