Lignum Vitae, Latin for the ‘tree of life’, has a set of properties that cause a newfound awe in natural materials. Also known as Ironwood, it is the hardest and heaviest traded wood, being 3 to 4 times the hardness of English Oak. It was the alleged medicinal properties of Lignum Vitae which have earned it the title ‘tree of life’. Sometimes brewed into a tea or as a herbal medicine; historically - it was used to treat symptoms of gout, arthritis and syphilis. Its properties / uses are still being explored.
What is particularly impressive, are the undoubted properties that make Lignum Vitae so attractive in engineering. Its unique uses come from its strength, ranking highest of traded woods on the Janka scale of hardness with a hardness of 4,390 lbf, combined with natural oils causing self lubrication and wear-resistance. These oils also provide resistance to rot and to degradation from insects.
Lignum Vitae was used for the aft main shaft strut bearings of the USS Nautilus - the first nuclear powered submarine. Similarly it is also used as the main shaft bearings of the Pointe du Bois generating station. Its oily finish and relative density give it the perfect combination to act as a friction-free bearing when submerged in liquid. Historically, its uses were many and varied, colourfully being used for an English policeman’s truncheon, alongside many tools and bearings.
Unfortunately Lignum Vitae is a diminishing resource, found between Jamaica, Florida and the Bahamas. It is likely that, due to overconsumption of the wood, we will run out of it in the wild before younger trees grow to maturity. The wood can be taken only from two species of tree, and due to its attractive density, these are both extremely slow growing. Lignum Vitae is still allowed to be traded however, but the species is CITES II listed and also on the IUCN red list
Above left is a jpg of the flowers of Lignum Vitae.
Oliver @ www.geography.co.uk
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