[AT] Silo roofs

[Dean Vinson]

Very common around here to see old concrete silos with no roofs, such as the
1950-vintage silo on my farm:
http://www.vinsonfarm.net/photos/farm_and_goat_20141025.jpg

I've been assuming the roof blew off in a storm at some point, but now I'm
wondering if there was ever one there to begin with.   I have an aerial
photo of this place from 1965, and just like today there's no roof on the
big silo.   But in the 1965 photo, a tractor and silo blower are parked at
the base of the silo, hooked to the fill pipe, and a herd of Holsteins is
ambling about in the pasture.    That's only 15 years after the silo was
built, and it sure looks to still be in active use, but there's no roof.  

At the top of this silo--and of several other very similar concrete silos I
see as I drive around the local area--there's a steel frame that forms a
three-sided pyramid.   A length of steel cable hangs straight down from the
peak of that pyramid, and some more of that same cable is wound around the
remains of an electric winch mounted down about head-height on one side of
the silo, so I assume it was the hoist for the silo unloader.   But did the
pyramid also support a roof, or did this type of silo never have a roof?

Dean Vinson
Saint Paris, Ohio