British custom carbon brand Filament has created a unique handbuilt bike that pays tribute to the golden era of bike design in the 1990s, in which Graeme Obree and Chris Boardman battled for supremacy using ever more outrageous bikes and positions before the UCI’s Lugano charter put a stop to it in 2000. However, the Filament FX is far from retro: it is fully equipped for riding in the 2020s with hydraulic disc brakes, electronic gearing and 32mm tyres and, says Filament’s Richard Craddock, it even has practical advantages over the standard diamond-framed race bike.
Harnessing a huge amount of experience in creating custom racing tandems, including for the recent Paris Paralympics, Craddock was able to create a carbon structure that he says supplies a much smoother ride than its traditional twin-triangle counterpart. Additionally, since the Filament frame has fewer elements – it consolidates the down tube and top tube and has a single rear fork rather than separate seatstays and chainstays – the thicker walls mean that the carbon is more damage-resistant.
Craddock admits he is a huge fan of the radical bikes of the 1990s, but since he was too young to have owned one at the time, he finally decided to make one for himself and update it for the 2020s. “We’re so used to seeing triangles, so there’s something about a non-traditional frame pattern that says something to you: this is different, this is special,” he says.
Was there a particular 1990s bike that inspired him? “It’s not accidental that the paint echoes Old Faithful,” he says. “It’s a bit of an homage to what Graeme Obree did – somebody not afraid to try something out, to be misunderstood and still achieve what he did.”
The Filament FX doesn’t have the skinny tubes of the original Old Faithful and is made from carbon rather than steel – but it’s not as curvy as the Lotus or Hotta. Is there a hint of the Corima Fox in its design? “Yes, exactly,” says Craddock. "But the idea wasn’t to make it a TT or aero bike because these days, you need to take it to the wind tunnel and present the data. I just wanted it for everyday riding.”
Did Craddock actually get hold of a 1990s monocoque bike at the start of the design process to examine it? “First of all, this is not a monocoque,” he explains. “My technique is to join carbon elements together in a custom fashion. Essentially, it’s tube to tube, taking precured carbon tubes, cutting them in a traditional frame-building way with a milling machine, putting them in the fixture, tacking them with epoxy adhesive and then laminating over the joints to make them sound. That’s almost the necessary way to make carbon tandems for all different sizes, and for road, track or time trials and with aero or round tubes. So I’ve got a technique to do it essentially mould-free or with simplified moulds to make the custom elements viable."
As Craddock explains, “a huge amount of what I do is custom racing tandems, and you learn as you go along to develop the techniques to make doing custom items viable. Whereas a normal mass-produced carbon road bike is made in a series of moulds with a fixed number of sizes available, and it’s a costly business.”
Furthermore, Craddock makes his own carbon tubes, with the Columbus fork the only part of the Filament FX not made in his workshop in Bromsgrove. “I buy rolls of pre-preg and make everything here. Inside my tubes is a structural core of very lightweight, high-compression-resistant foam. The foam is the foundation: it starts as a solid block that gets shaped and machined, and the pre-preg is added to it. It supports the carbon skin and adds durability and stiffness, while the carbon skin protects and spreads load over the core. It’s not something you see in carbon construction so much now except in some cranks or front wheels in particular, but we're starting to see lattices inside a 3-D printed part. When you’re bringing together the top tube and the down tube into one element, and the chainstays and seat stays into one pair, the walls are thicker to handle those forces – but these are not super thick walls; the core makes an enormous difference. You can’t have the same efficiency to weight as a diamond frame, so you’re having to work hard to manage those forces,” he says. “There’s a lot to be said for the designer of the object getting into the workshop, and handling the materials and seeing how it goes together rather than outsourcing everything.”
The by-product of those slightly thicker walls is better durability compared with traditional diamond-shaped race bike frames. Craddock says: “The traditional bike frame is a marvel. The triangle design is wonderful at holding up the rider’s weight so you can make a really light carbon frame, but you get such thin tubular elements that what you often see in bike racing is a crash when the rider is OK to continue but the bike is broken. Maybe that’s alright if you’re professional – you’ve got a team car with another bike on it, and someone else is paying. But it’s not really how you want to see your own bike after a bump or the little knocks that you get over the life of a bike. Especially with the higher modulus carbon-fibre types with super thin tubes – it gives great performance for the riding but maybe not for the life of the bike.”
Craddock concedes that this first version is not as light as a diamond-framed carbon race bike, but he made it for himself – a track sprinter who competed at the World Masters last year. “What I was after with this, for me in particular, was a smooth ride. We talk about vertical compliance, but a vertically aligned triangle is not very compliant in the vertical direction. But with a frame design based on a central spar, you can get a little bit more smoothness. It’s like a prototype for me really and there’ll be some tweaks and changes as it develops.”
The Filament FX is priced at £6,000 – go to Filament’s website for more information.
