Wednesday, June 11, 2008
Unter Den Linden , A 20 Minute Tempest and a Tower Crane Moves ...
Just like the famous boulevard in Berlin many of the streets in NYC are lined with Linden trees. Avenue A is no exception here and last night strong winds brought one of those Lindens down on a phone booth and an SUV parked beneath it .
We did not feel this was much of a story and did not intend to cover it but we noticed today that the NY Post had a picture of the event under one of those Linden trees so we offer here our version of the evening .
The Linden tree that fell was a damaged tree . At the break in the trunk of the tree previous damage as well as a good bit of mold and dry-rot could be seen . The tree was not truly sound ; no surpise that a strong wind brought it down .
Surprisingly the SUV did not appear to be damaged ; the force of the falling tree having been mostly taken by a nearby phone booth .
NYPD emergency services personnel brought the tree to ground cutting it down piece by piece with a chain saw.
The tempest began around 9:15 with very strong gusts of wind . In Tompkins Square Park the Elm trees could be seen twisting and stretching close to the bearable limit before breaking .
Shortly the rains began and at 9:20 or so we picked up a signal on NYPD zone 2 radio reporting that the tower crane at the Cooper Union construction site at 7th street and 3rd avenue was moving in the high winds . We headed in that direction to take a look .
By 9:39 the deluge abated sufficiently for us to continue our westward stormy trek to the location of the tower crane . At the construction site we found the crane deployed out over 7th street and an adjacent building . Not a normally allowed situation .
We assume that the crane operator was rotating the crane , attempting to align the boom with wind flow much as a weather vane does in a strong wind in order to minimize the aerodynamic drag force presented to the crane boom in order to reduce the stresses in the boom and tower . The winds were later reported to have been in the 40 to 50 MPH range . Such winds produce very considerable forces for the crane's structure to resist .
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