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Time Line - 1984: Otter Tail Power Purchases Captive
Columns... |
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| Only 52 Pounds Each (40k) |
Simple Fittings (36k) |
Supporting A Truck (34k) |
Getting Ready For Delivery (57k) |
Otter Tail Power Company purchased twelve Captive Columns to be
used as Emergency Restoration Towers for downed 115-kv and 230-kv power lines. Power lines
are usually knocked down as a result of bad weather, which can also make it next to
impossible to get heavy equipment to the disaster site. This makes it imperative that an
emergency restoration system be capable of being transported and erected by hand if
necessary.
Designed by Lawrence R. Bosch, this Captive Column restoration system was optimized for
ease of deployment, requiring only hand tools and man power to put them into use at a
moments notice. Each beam was 12 feet long and weighed only 52 pounds (less than 5 pounds
per foot). The core was made of balsa wood, the columns were made of high-strength steel
rods with threaded ends for fittings, and the skin was made of stainless steel wire. The
fittings consisted of simple steel blocks that were treaded onto the column ends. These
fittings weighed only 1/3 pound each and were designed to allow the column loads to be
carried efficiently from section to section (see Simple Assembly photo above).
The 12 foot sections could be connected together to create towers of different lengths.
The most common tower height was expected to be 36 feet, consisting of three sections. Of
course taller structures could be constructed by simply bolting more beams together. One
of the photos at the top of this page shows a 60-foot tower (5 sections) with a truck
hanging from it (this is the same truck that Mr. Bosch used for his many moves around the
country).
A similar Captive Column was tested at EPRI (Electric Power Research Institute) to
verify the performance of the Emergency Restoration beam design. Transmission &
Distribution magazine, a utility trade journal, did an article on the Captive Column
Emergency Restoration Tower System and had this to say about the EPRI test:
"On Aug. 1, 1983, a 20-ft Captive Column section, one-ft sq, of similar design was
tested at the EPRI Transmission Line Mechanical Research Facility at Haslet, TX (News
and Trends this issue). The section consisted of four 1/2-inch dia steel rods
supported by a balsa wood internal core. This assembly was wound with a 0.02-inch dia
steel wire to provide the 'captive' column. It successfully withstood an axial compression
load that was substantially above the design requirements." -- Transmission &
Distribution, January 1984
While the magazine did include some photos provided by the inventor, for some reason
they refused to publish the one with the truck hanging from it.
After the article appeared, the Mr. Bosch was contacted by several American utilities
but none would place an order. Mr. Bosch was also contacted by some South American
utilities that had an urgent need for the Captive Column system and were willing to place
orders immediately. Unfortunately, Mr. Bosch did not have the resources to start an
international trading company.
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