Monday, March 29

 

Article 300 Wiring Methods

mikeholt.com: The intent of this editorial change to the NEC was to clarify that a warning ribbon is required for service conductors (exposed or in a raceway) buried more than 18 inches. Author’s Comment: Often service lateral conductors are installed in nonmetallic conduit (which must have 18 in. of cover [Table 300.5]) by the electrical contractor; therefore, a warning ribbon must be placed at least 12 in. above the underground raceway.





Sunday, March 28

 

Hygroscopicity: Moisture and Wood

woodinsite.com: "Strength and stiffness properties of wood products generally increase with drying below the fibre saturation point. Wood shrinks as the moisture content (MC) is reduced below the fibre saturation point, which is the specific moisture content where the wood cell walls are fully saturated but there is no free water in the cell cavities. Drying below this fibre saturation point then removes water from the cell walls and cell wall shrinkage results in changes in member width and thickness. The fibre saturation point varies with species and is typically assumed to be around 24%."

 

No more unsafe shoelaces...

Ian's Shoelace Site The Shoelace Knots section offers not only the renowned "Ian Knot," but also other knots and advice on how to stop shoelaces from coming undone, fully illustrated with clear diagrams. The Lacing Shoes section offers 43,000 ways to lace a shoe with six pairs of eyelets. Knot Links connects visitors to other shoelace and knot-related web sites.

Tuesday, March 23

 

Concrete casts new light in dull rooms

optics.org Light transmitting concrete is set to go on sale later this year. A new type of concrete called LitraCon (disturbing name alert) offers the strength of concrete with the see through power of glass. According to optics.org: "Thousands of optical glass fibers form a matrix and run parallel to each other between the two main surfaces of every block," explained its inventor Aron Losonczi. "Shadows on the lighter side will appear with sharp outlines on the darker one. Even the colours remain the same. This special effect creates the general impression that the thickness and weight of a concrete wall will disappear."

Thursday, March 11

 

Automate this...

CalEarth: "Superadobe (mile-long sandbags and barbed wire construction) and Ceramic Houses (fired in-place adobe structures) are seen as solutions to global deforestation by organizations such as the Turner Foundation and Rex Foundation (Grateful Dead) who have lent their sponsorship along with other organizations to work at Cal-Earth. The United Nations with whom Khalili has built housing prototypes usimg these technologies see these as the answer to affordable housing worldwide and emergency relief housing because of their efficient simplicity. Up to one mile long Tubular Bags. Cal-Earth label. Shipped in compact rolls."