Brompton Roller Nut Machinery Brompton Roller Nut Machinery

Spotlight on: The Brompton Roller Nut Machine


A deep dive into one of our latest machines, designed and developed from the ground-up for the Superlight Advance rear frame.

Go inside with a Go-Pro camera and discover what the Roller Nut Machine does and why.

Since the early days, the design of the Brompton folding bike and its manufacture have been intrinsically linked.

Doing everything under one roof means our engineers invent and develop tools and machines to build and assemble the unique Brompton frame and components.

Frame Design

The all-new superlight titanium rear frame is an advancement on all that came before - the ride, the fold and portability.

The Brompton engineering team used Finite Element Analysis to study every millimetre of the existing frame. The 3D modelling techniques allowed them to add and remove material to impart greater strength, stiffness and robustness, yet reduce overall weight.

3D modelling of Brompton frame

Brompton bikes fold down into a small compact package that rolls on two small rear wheels. On the existing frame, the roller wheels screw into a welded threaded nut on the inside of the two curved tubes (Fig. i).

Focusing on weight-savings and increased durability, the manufacturing engineering teams partnered with experts at Henkel to create a new method and machine to fit the roller wheels to the new frame.

Fig.2: The Advanced Superlight Rear Frame the roller wheels are fixed to one single, larger diameter tube.

sketches of A Line C Line P Line and T Line Brompton frames

Inside the machine

1. The rear frame is secured at a set angle inside the sealed unit.

2. A small nozzle precision-sprays a measured quantity of adhesive to the inside of each tube end.

3. The threaded aluminium nuts (cross-hatched for the increased surface area) are fed into the machine.

Brompton staff working in the factory

4. They flow down a 3D printed track into the tube ends.

5. The nuts are pressed with the perfect level of force to deliver a tight fit.

6. The frame is removed and then heat-treated to strengthen the bonds further.

the brompton roller nut machine in action


When researching a new manufacturing process, the engineer teams carefully consider if the job best suits humans or machines. Efficiency and finance are factors but never the deciders. Quality and working environment are the priority.

In this case, the automated Roller Nut Machine delivers unmatched precision and isolates the adhesives from human contact.

The team on the Factory Floor focus on assessing the machine’s work through touch, look, feel and experience.

A man's tattooed hand unscrewing a hinge clamp on the T Line Brompton folding bike A person carrying a folded Brompton T Line bike in a studio
Our P Line and T Line Bromptons are made with titanium parts. Learn more about these lightweight folding bikes.

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