[TowerTalk] RE: Tower bolts

[darrel]

Old US Towers catalogs showed L shaped J-bolts for the foundations, new
catalogs show straight bolts with nut/washer on the bottom.  Same lengths and
diameters.

Like so much else these days, it probably came down to cost or availability,
but it could be they found a better or different grade of steel.  

The area presented by the washer is similar to the L bend, so I'd expect
similar pullout resistance.  The J bolt would be more resistant to rotation,
but that's not an issue with 3 or 4 bolts through one base.  From a crude
calculation, my guess is the bolts are stronger than the rated wind load with
pretty ordinary grade steel.  The most commonly reported failure seems to be
the tower folding over, not bolt failure anyway.

Darrel AK6I