[TowerTalk] HDBX Tower Forces

[T A RUSSELL]

Posts on TOWERTALK have made it well known that
the HDBX towers are "rated" for a 10 foot boom, maximum.

Unfortunately, this is a very misleading type of rating since
NOTHING has been stated about the ELEMENTS.  

There is a BIG difference in torque from a 2L20 or  a  2L
tribander on a 10 ft boom and a multi element  VHF antenna
on a ten foot boom.   I would expect that a 2M beam on a
30 ft boom would be no problem for this tower, assuming that
it could handle a 32 ft long 20M DIPOLE  with NO boom.

A better specification for the tower would be TORQUE, or 
an antenna parameter that contributes more directly to 
calculating torque, such as surface area and offset from
the mast.  In addition, boom length and mass are also
factors to consider when stopping and starting rotation.

To reduce the torque applied to the tower when stopping
rotation, it is best to let the antenna COAST to a stop, rather
than releasing the rotor brake while the antenna is still 
moving.

Placing the rotor further down in the tower, in a wider
section, will also lessen the torque load on the tower.
A rotor at ground level with a continuous mast rising
through the full tower height will eliminate torque as
a consideration in the tower load.

de   Tom   N4KG


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