Calculating the Specific strength for the rod

AI Thread Summary
To calculate the maximal length and minimal width of a rod made from materials like steel or carbon nanotubes, specific strength is a crucial factor. The discussion highlights the need to understand how the rod's length affects its structural integrity when held horizontally. Calculating the maximum possible length involves using specific strength values to determine the material's ability to withstand bending and breaking forces. The conversation also touches on the feasibility of holding extremely long rods, such as 5 km or 50 km, and suggests that advanced materials like carbon nanotubes could provide better performance. Ultimately, a formula or method for these calculations is sought to assess the structural limits of such rods.
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Imagine the skyscraper and the very long rod placed on its top that rotates from horizontal position to upwards.
http://img109.imageshack.us/img109/4817/fhfn.png
I would like to know how is it possible to calculate/ascertain the maximal length and minimal width of the rod made of some certain material, let’s say steel. For example, is it possible to hold the rod with the length of 5 km horizontally (not by hands of course :smile:)? The rod will be broken? What, if I need to hold much longer rod (let’s say 50 km)? Which material should I use? How can I calculate its maximal possible length? As far as I know I need to use the values of Specific strength, right? In Wikipedia I found the article: http://en.wikipedia.org/wiki/Specific_strength and the values for various materials, then what? Let’s assume I am using the carbon nanotubes and I created the rod (not the elastic ribbon like Space Elevator’s cable), how can I calculate its possible maximal length? Is there any formula for this purpose? :smile:
 
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Does not anybody know this? :smile:
 
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