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arrow1.gif (893 bytes) Time Line - 1984: Otter Tail Power Purchases Captive Columns...
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Holding Beam Simple Fittings Supporting A Truck Ready For Delivery
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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Copyright 1998-2004 by Lawrence R. Bosch.