Sorry if this is a dupe, I'm having a problem posting to Towertalk today.
****************
Not always true. We regularly work on a 900' broadcast tower that is not
on a pier pin. It's a Dresser-Ideco
built in the late 50's. I suspect that (from that era) it's not an outlier.
A tower can be engineered this way, but it's certainly not the most
efficient way to do it material-wise.
-Steve K8LX
On 1/21/2023 11:43 AM, Rob Atkinson 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
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