What Geoff Roberts doesn’t know about making bicycles isn’t worth knowing, which is something of a privilege for the students of the frame building course at Enigma Bicycle Works.
From the hard graft of mitring to the delicate art of brazing, Geoff’s calm instructions and demonstrations are an invaluable source for the novice, who after five days at Enigma’s facility in East Sussex will have a frame they can truly call their own.
The course is an attempt by Enigma owner Jim Walker to restore, in some small part, Britain’s frame building heritage and ensure that the traditional skills of the builder do not die out entirely. By recruiting Geoff as tutor, Walker has built his admirable project on solid foundations.
Roberts was one of the most respected marques in British cycling, supplier to former world pursuit champion Tony Doyle, among many other top class riders, and Geoff is the son of Charlie Roberts, one of its most respected frame builders.
A schoolboy cyclist who rose to become a professional, Geoff, fresh from school, spent his fourteenth year engaged in nothing more than mitring tubes by day and racing and training each evening. Only after twelve months mastering this skill did his father teach him more of the frame builder’s art.
Such pedigree means that students on Enigma’s frame building course receive expert tuition in cutting tubes with a hacksaw and shaping the ends with a hand file. Both tasks are mechanically assisted on the other side of Enigma’s factory floor, where the professionals work on the flagship Excel Ti, but the simple tools used by the would-be artisans under Geoff’s tutelage are time-served.
The process begins with a bike fit using Shimano’s sophisticated bike fitting system, which generates a host of measurements. This is one of several ‘cross overs’ from Walker’s main business. For the craftsmen working on Enigma’s bikes, every detail from the raft of data generated by Shimano’s system is likely to be of value. For Geoff’s students, the most important dimensions are the head and seat angles, and lengths of the top and seat tubes.
The mitring of tubes follows, and then the most demanding stage: brazing. The skill of welding lies in drawing the brass through the lug to ensure full penetration. The most common mistake, Geoff says, is to position the flame too close to the metal. The tendency of the novice is to move closer and closer, with hands, face, and torch.
With goggles, there’s no physical consequence, but the quality of the weld can suffer if the flame is too close. It’s a matter of coordination, with torch in one hand, and brazing rod in the other. The bottom bracket area holds the greatest challenge for the beginner.
Multiple attempts can weaken the metal. Continued heating and cooling changes its molecular structure, and the frame can go out of true. This is an unavoidable consequence of working with metal, but often a welcome one. Its natural spring underlies the ride quality.
In the centre of Enigma’s factory floor is an engineer’s alignment table – a perfectly flat metal surface with locating bars on which the frame is checked. Geoff performs a similar inspection using a measuring bar, holding one end against the head tube and the other against the inside of the dropout. He uses a separate tool to check the distance between the dropouts.
Minute discrepancies can be tolerated, and even overcome with a little brute force (but never ignorance), such is the natural pliability of steel. Brazing, however, demands total precision, and it is for this reason that Geoff insists his students check their welds, and then check again. Some builders weld a frame on the jig, he says, but this is not a practice he follows. Accuracy and craftsmanship are everything.
Each weld is cleaned with emery cloth throughout the build, and has a notable effect on the appearance of the finished article. Shot blasting ensures that any of the residual elements, such as flux, are removed. It's a chemical process, in which fine grains of sand, glass, metal filings, or other abrasive material are fired at the frame. The treatment is robust and can leave the frame appearing ready to ride. It seems a shame to paint it, but if the material used is anything other than stainless steel, the consequences will soon be known.
Painting takes place in-house, but this task is handled by expert painter Jaco Ehlers, who brings the student’s design to life in a spray booth in the corner of Enigma’s small factory.
The results can be seen in the frame pictured, made by David Whild, a cyclist who grew up dreaming of owning a Roberts and who has wanted to build his own frame for almost as long.
“For me, it’s a ‘bucket list’ experience: something that anyone with an interest in bicycles should do. A lot of people are throwing money at carbon frames, but this is a much more rewarding experience.”
To find out more, visit Enigma Bicycle Works.