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Breakthrough: The bonded and riveted aluminium tub

7 months ago

Writer:

David Twohig | Engineer

Date:

31 July 2025

I’m conscious that there is a whiff of the old library about these Breakthrough pieces. Now, I love old libraries. I love the tall shelves and that slight eau de mildew that they share with second-hand bookshops. But I acknowledge also that they’re a bit of an anachronism in an age where we all have access to the sum of human knowledge in our pockets.

So here for once is a breakthrough that took place not in the 19th century, nor in the 18th, nor even in the Golden Age of automotive startups (1900-1910, of course) but in my own adult lifetime – if it were a human being, it would be a millennial.

I’m talking about the adhesively bonded and riveted aluminium ‘tub’ or floorpan of the Series 1, 1995 Lotus Elise. Now, the Elise does not need any plaudits from me. It will never appear in a Ti Almost Great article, because no one would dare append that faint-praise qualifier to it. Julian Thomson himself has written about its design roots, and I could add not one word to that. But let me dwell a little on its underpinnings, because they reach far beyond the Elise. The genius idea of building the car not on stamped steel floorpan, nor a spaceframe like its pale rival the Renault Spider, nor yet a tubular ‘spine’ like so many Loti before it, led to a remarkable and elegantly simple technology that keeps most subsequent Lotus, many Aston Martins, and the Alpine A110 from scraping their asses on the tarmac.

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