Brompton breaking new ground

Brompton has launched the G Line as the biggest innovation in its history. Daniel Blackham speaks to chief design and engineering officer Will Carleysmith about the product’s origin and development.

When a brand as storied as Brompton markets a product as its “biggest innovation in 50 years” it certainly peaks interest. Step forward the G Line. From a distance, you could be forgiven for wondering what the fuss is all about. When folded, the bike looks the same as its predecessor with the folding mechanism identical and creating a similarly compact form factor. On two wheels there are many commonalities with the frame’s silhouette almost identical. But a closer look reveals an entirely new frame, bulkier 20 inch wheels wrapped in Schwalbe custom-made rubber, a Shimano 8-speed hub gear, and the first Brompton to feature disc brakes from production.

“It started as a bit of an engineering and design experiment eight years ago,” explains Will Carleysmith, chief design and engineering officer at Brompton on the origins of the G Line. For the last 10 to 20 years, people have taken the Brompton and done more and more, pushed it further and harder, so we thought: ‘How capable could you make the bike? How far could you take it?’ That took us to the wheel size that we have.

“The first test was ‘does it have a purpose?’, because if it had felt the same as a 16-inch bike, there’d be no point in it.”

When considering the design, the fundamental DNA of a Brompton had to remain, keeping the tri-fold which has become so synonymous with the British brand. However it still had to be distinct. “It had to have its own personality,” adds Carleysmith. “And it did. It felt different. It felt capable.”

In short, the concept of the G Line is “one bike to do it all”, but Brompton has not moved far away from what has made it a success so far.

“It’s the most capable Brompton yet, with the ability to deliver on all sorts of surfaces, with the feel of a full-size bike,” explains Carleysmith. Yet it transforms into a compact package that stores and travels easily. The company has not changed its focus, but it has broadened its view,” says Carleysmith.

“We started as urban and [were] seen as a commuting tool for London. We’re now about 84% export so most of our products are going overseas and I think 40% of them are in Asia. People aren’t just commuting in those markets, they’re using them as leisure bikes.

The hidden work

The first hurdle for any new Brompton is ‘does it fold?’ which the designers resolved with 2D jigs, bits of cardboard and simple CAD sketches. After that, it was geometry.

“We started with a blank sheet of paper,” says Carleysmith. “We didn’t look at the existing bike, particularly, but we did look at full size bikes. We built some quite specialised prototype rigs which were fully rideable and completely adjustable and went through every aspect of the geometry, adjusting it, going too far, bringing it back, ending up with something that we wanted.

“So [for example] we made a bike that was so stable and boring that it stopped being fun. It didn’t feel like a Brompton. So we tuned it back to something we thought was fun. As it’s one frame size, it then had to work with different parts to still feel good whether you’re 5’2” or 6’5”.”

Gearing up for mass production also took lots of effort with the brand planning to have a manufacturing capacity of between 15,000 and 20,000 a year.

“It’s always harder than you think it’s going to be,” says Carleysmith. “The mainframe has a bigger bend to wrap around the bigger wheels. On the surface it looks the same as the current bike, but actually we had to bring in new production methods. Production is a series of processes, you change one thing here, then all the downstream processes have to change.”

As an example, Brompton had to purchase a number of new auto brazing machines, each taking a year to build and costing several hundred thousand pounds each.

“The product is the tip of the iceberg,” says Carleysmith. “Under the water is a huge amount of hardware, equipment, testing and validation.”

The Electric G Line

Alongside the launch of the G Line, Brompton has also debuted the Electric G Line. It sees an all-new electric system, and features new advanced software and hardware for optimal performance, self-diagnostics and latest features available through future software updates.

There is also a completely fresh 250-watt rear-hub motor with three levels of assistant which was put through its paces on a 24/7 durability rig, with 20+ motors going through a combined mileage of more than one million kilometres.

“The first generation [system] launched for us seven years ago so this was a big, big programme,” explains Carleysmith. “If you can buy Bosch, and you can fit Bosch, that’s great, but you can’t for a Brompton and Bosch have got very little interest in making a tiny little system. Neither have Shimano, Mahle, Brose etc.

“If we wanted an e-bike, we had to make our own one and that was quite a job.”

But with new software, new electronic hardware, Carleysmith believes this offers lots of potential for the future.

“There’s a lot of flexibility,” he adds. “As a business, electric is a big priority for us in terms of where we put our R&D money and investment.”

The results

While Carleysmith and his colleagues have been riding an iteration of the G Line for three or four years as part of its development, it has only just come to market and the early feedback has been overwhelmingly positive.

“It’s been like cooking an enormous dinner,” he says. “By the time you have made Christmas dinner, you’re starting to get sick of the site of sprouts. But what’s really cool is when other people experience it and you get the reaction. What’s been awesome over the last few weeks is that we’ve exceeded people’s expectations.”

Last month the brand hosted a dealer event for the G Line over two days, one with sunshine and the other in pouring rain on a 20 kilometre off-road route.

“It really sold the bike and you saw the dealers responding to that,” says Carleysmith. “We really wanted this launch to be in partnership with dealers so we’ve been working hard to support them with promotional materials and demo bikes as well.

“We’ve done the titanium bike and the electric bike, but it’s still speaking to the same consumer, maybe a consumer that’s willing to spend more. But I think this is the first time in a long time, if not ever, that we’ve said ‘we think we can bring a different consumer to Brompton and to your store.”