[TowerTalk] Tower Collapse in South Dakota

[Gary Johnson]

Spot on, Rob. Also, the pier pin guarantees zero bending moment at the base. Many of you may have seen the K7NV analysis of guyed towers that proved the superiority of pier pins vs. fixed in concrete.

Speaking of our dearly departed K7NV: Since his website is defunct, has someone acquired that content and posted it somewhere else yet?

73, Gary NA6O

> On Jan 21, 2023, at 9:00 AM, towertalk-request at contesting.com wrote:
> 
> Professionally constructed guyed lattice towers are always on pier
> pins even if a base insulator isn't needed.  No commercial guyed tower
> is ever put in the ham way of sinking the legs in concrete because the
> tower has to be able to turn without twisting, because twisting will
> cause a failure.  Hams seem to think that if their 100 foot R25 tower
> loses its guys, it will stay vertical because the base is sunk in
> concrete.  You can't treat a uniform cross section guyed tower as if
> it is free standing.  The only reason hams get away with that business
> of sinking the legs in concrete is that the majority of guyed ham
> towers aren't very tall relative to face width and aren't heavily
> loaded.  Any guyed tower hundreds of feet tall will _never_ be sunk in
> concrete; they have to be on a pin or they won't survive.  The pin
> likely helped the tower stay up at least at first, because the added
> wind loading caused by ice added to the turning force.  If it had been
> twisting with ice it would have collapsed a lot sooner.
> 
> 73
> Rob
> K5UJ