Flit’s folding e-bike replaces welds with aerospace-style adhesive

Flit’s latest folding electric bicycle takes an unusual approach to frame construction: instead of welding its aluminum tubes together, the company bonds them with aerospace-grade epoxy. According to New Atlas, the Cambridge-based manufacturer developed the M2i as a lightweight alternative to Brompton’s titanium T Line electric bike. The Flit weighs 13.3 kilograms (29.3 pounds), about half a kilogram less than the comparable Brompton model, while its listed UK price is £2,999. The Brompton T Line electric is listed at £5,799. The M2i uses anodized 6061 aluminum tubing joined with precisely machined sleeve connections. Flit’s design relies on two-part structural adhesives, which harden into a cross-linked polymer that grips the microscopic texture of the metal. The company’s approach avoids the heat distortion associated with welding and is intended to preserve accurate alignment in the folding mechanism. The use of aluminum also allows wider tubes to accommodate the bike’s 230-watt-hour battery while maintaining rigidity, the report says. Flit combines the frame with hydraulic disc brakes supplied by Hope, Goodyear Eagle F1 R tires, integrated LED lighting and a carbon-reinforced fizik Vento Antares R3 saddle. Optional mudguards add 450 grams. Adhesive joints can be vulnerable to peeling forces, but the report says they are particularly effective at handling shear stress, in which loads move along the length of the joined tubes. To test the design, Flit subjected bonded frames to repeated laboratory loading, with the joints required to endure as many as 500,000 stress cycles without developing micro-fractures. The company also tested overloaded prototypes on rough roads, including impacts from curbs and potholes. One test caused a rear swingarm to bend slightly, but the bonded joint reportedly remained intact. Flit then redesigned the swingarm to increase its strength. New Atlas describes the M2i as a single-speed folding e-bike aimed at urban commuters. International buyers are directed to contact Flit for export pricing, with shipping charges and import duties applying outside the UK.