An Engineer in Wonderland – Lignum vitae bearings

A programme about a chair from the Caribbean from Radio 4′s A History of the World in 100 Objects mentioned the wood lignum vitae, which reminded me of the clocks of John Harrison.

According to the book Longitude, Harrison used the wood in clock bearings for its long-lasting and self-lubricating properties.

So little wear is experienced that the Royal Observatory Greenwich, I am told, runs three of the four Harrison longitude clock full time without fear of deterioration.

The fourth – the actual longitude clock – does not use lignum vitae and cannot be run for fear damage.

Anyway, I was googling away trying to find out why the stuff wears so little,

and failed.

However, I did discover that not only has it been used for clock bearings, but it was the material of choice for great big applications including propeller shaft bearings in ships – even after the second world war – and plenty of people claim it was used for the same job in the world’s first nuclear submarine.

And it has also been used in the bearings of generators within hydroelectric power stations – where it has operated for 50 years – without maintenance claimed one site.

I read that for lack of porcelain insulators, replacements for the San Francisco cable car system were turned up from lignum vitae in 1906, a few of which were finally removed in 2009.

How much of this is true, I have no idea.

I hope it all is.

Does anyone actually know why the wear rate is virtually nil?

‘Alice’

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Tags: Alice, Engineer in Wonderland

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2 Comments

  1. Bob shortridge
    January 12, 2011 15:21

    Hello, In response to your question of “why” lignum vitae is so slippery. the raw wood has about 20-30% of its weight in guaic gum along with being the hardest wood in the world makes the wood a great choice for underwater bearings. All the information you mentioned is correct as I have plant operators telling me first hand experiences with very long life. In fact I have a recent testimonial from the Army Corp of Engineers stating 67 years of service in lock 15 on the Mississippi. For more information please visit http://www.lignum-vitae.com Thanks, Bob

  2. Bob Shortridge
    October 08, 2010 16:45

    The reason lignum vitae wears so little is three fold first this is the hardest densest wood in the world coupled with about 25%of Guaic gum embedded in the wood. the gum is slicker than teflon. Also the wood is woven into a an interwoven structure allowing the material to withstand a working load of about 12,000 lbs per sq. inch. When installed in hydro work it also has the ability to absorb grit and keep it away from the shaft, it has been called the most steel friendly material known evidenced by one of Henry Fords plants running 85 years continuosly on the same set.

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