The Twmpa Cycles GR 1.0 is a gravel bike with a wooden frame. Made by a new company based in the Welsh Borders, the GR 1.0’s entire frame is constructed from ash and the finished product is remarkably standard looking compared to some wooden bikes we’ve seen.
The GR 1.0’s frame weighs a claimed 1.8kg, with complete bikes from just over 9kg. Twmpa charges £2,350 for the frame alone, with complete builds starting at around £5,000.
Twmpa Cycles is the brainchild of furniture maker and keen cyclist (he’s Everested not once, but twice) Andy Dix, who, having come up with the idea initially with a friend, spent the best part of two years in research and development, sketching out designs and thinking through problems – problems that other bike builders don’t have to think about, such as wood rot and disease.
Working together with Fablab, an organisation within Cardiff Metropolitan University, allowed him to use CAD and 3D software to refine the design of this first model, the GR 1.0 gravel bike.
Twmpa Cycles GR 1.0 – wood for the gravel
“The cell walls are what’s called a lignin matrix, and the substance they’re made from has viscoelastic properties – it’s both viscous and elastic. So wood’s cellular structure means every inch of the frame acts to absorb and dissipate the vibration – the whole thing is basically one micro-suspension system”.
Hang about, does this mean the frame flexes? “No! A flexible frame would make for a horrible ride. The damping is done within the material itself – it’s why wood, especially ash, is used for tool handles. Ash has an amazing strength to weight ratio, it grows straight, it’s nice to work with and very resistant to shock, so it sustains impacts with far less damage to the structure. Its carbon impact is very low, and all the wood we use is sustainably grown in the UK.”
The frame is built as a monocoque. The two mirror image sides have wall thicknesses of between 5mm and 6.5mm, and are bonded together.
The frame is then sanded and finished, and treated with three coats of epoxy clear-coat plus two more of UV-proof polyurethane yacht varnish.
Carbon inserts are used for the seat and head tubes, a steel bottom bracket is fitted and there are bespoke aluminium rear dropouts. Ash forks weren’t seriously considered because they’d have had to be too ungainly to cope with the forces, so those are carbon.
“It’s basically bombproof”, says Dix. And he has a certificate to prove it – the GR has been awarded an ISO rating for impact and fatigue, which simulates 10 years of hard use.