How Lotus cars, munitions and dolphins came to form the world's first carbon monocoque mountain bike

We get a peek into mountain bike history as Chris Hornzee-Jones shows us the world’s first carbon monocoque mountain bike that was first designed in 1992.

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Keep your eyes skinned on the South Downs because they might pop out if you come across Chris Hornzee-Jones. He’ll be riding a piece of mountain biking heritage — the world’s first carbon monocoque mountain bike frame. Even without a blue plaque saying “Designed 1992. One of 400. Built 1993-1994”, you’ll be able to spot it easily from its unique silhouette — best described as a leaping dolphin.

Carbon monocoque lotus rgb

Chris shows off his little bit of history – the Lotus Sport mtb

In the early Nineties Chris moved from the UK to California to work in aerospace composites — in his baggage there was a love of cycling, including a fascination with human powered vehicles. The lot came together in a sketch that morphed into a prototype that evolved into an extraordinary, original off-roader that was eventually sold back to the UK under the Lotus brand.

The Lotus Sport

Look at it. No top tube. No seatstays. It’s a softail hardtail, with compliance built into the chainstays to give it some vertical flex. And who could make titanium dropouts just 1mm thin?

“That was a military munitions company that was having a hard time so gave us these hot isostatically pressed components ridiculously cheaply,” says Chris. “They etched them with chemical dips to get them that thin.” And is that the original XTR groupset? “No — but I was lucky to replace it with a near-perfect set off eBay,” he says.

Dropouts carbon monocoque

Military might helped engineer the slender dropouts

The frame is a true monocoque — made in one piece. Attempts by others in the early days had all been of two pieces (or more) joined together. Its shape may or may not have been inspired by Chris’s interest in dolphins, which he’d studied in the Bahamas. Internal cable routing keeps the lines clean.

The chainstays came in for special carbon attention too, because of that softail element: the sides use high-grade aerospace material called Intermediate Modulus Carbon, and along the top and bottom glass-fibre is used with a Kevlar surface for impact protection.

1992 all over again

With hindsight, would Chris change anything if he had to do it all over again? “It was built like the proverbial brick shithouse and was very, very robust,” he says. “We’d already started to pull laminate thickness out of the main beam. And I’d include new disc brakes — we did try one on the prototype but the rotor was the size of a dinner plate.”

No joints carbon monocoque

Look, no joints! The frame owes a lot to its aerospace construction

Chris still finds time to ride his very own model regularly, when he’s finished working for the clients around the world who enlist the world-class expertise of his Brighton-based wind turbine design company, Aerotrope.

He also helps solve engineering problems for artists who design massive structures, including  Turner Prize-winner Anish Kapoor. The Lotus Sport mountain bike is, in its own way, a modern masterpiece.

Taken from the MBR Archive 2015.