Lark prototype

The Lark is a full carbon downhill bicycle prototype with a high-pivot design and uniquely modular drivetrain. Completely developed in Sweden by Huldr bikes. This is the designer Artur Adson's story about development.


I was involved in the development of several prototypes for Huldr, responsible for the overall construction and applied composite design for manufacturing. The Lark was designed together with industrial designer Daniel Manfredsson and professional downhill rider Tim Hedman. My focus was on the overall product requirements and specific design features such as the modular seat mount with shock window, drivetrain mount and the compact linkage design.


The Lark concept features a dual chain high-pivot design, meaning that the swingarm point of rotation is above the rear axle. The rear wheel moves slightly rearward during shock compression, as if it’s being pulled by the obstacle. This allows the rear wheel to clear obstacles smoother and faster.

Linkage design

Another key feature is the compact suspension linkage. On most downhill and mountain bikes the shock is placed inside the triangular open space of the frame. On the Lark we wanted to free up this space for a large battery pack. The compact design achieves this without compromising the responsive and progressive shock characteristics expected from a high-end downhill bike.

Modular drivetrain

The frame can be configured with 3 different drivetrains thanks to a uniquely modular adapter system, ranging from an enduro bicycle with a manual gearbox to a high-power ultra-light motorcycle.

Pinion drive
A 12-speed manual gearbox that allows you to shift gears without pedaling. Since the gears are all internal, the chainpath remains the same throughout the gears. As a result there is much less wear on the drivetrain system.
TQ Systems
1000 W motor with 120 Nm. Carefully selected and outperforms all other well-known e-bike motors from Bosch, Shimano and Bafang. With 1000 W power it is considered a moped or S-Pedelec with a speed limited to 45 km/h (+60km/h unlimited).
This is the most powerful option with up to 5000 W peak power. It can reach a top speed of over 70km/h with the Sonceboz and is considered an ultra-light motorcycle.
Mold pattern manufacturing. A full scale model of the first concept was machined in hard foam, then processed by hand. I later used the model as a pattern to make carbon fiber molds.
Carbon frame manufacturing. I personally manufactured several frame prototypes using prepreg carbon fiber. Each frame consisted of hundreds of individual pieces that had to be applied by hand. The types of fibers and their orientations were slightly varied between the prototypes to evaluate frame stiffness, durability and strength.
Carbon swingarm. All carbon parts were cured in an autoclave in high temperature and pressure many times greater than the atmospheric, the same method used in aerospace and Formula 1. The heat cures the epoxy resin binding the fibers, while the pressure helps compact the layers together, especially in sharp corners and hard-to-reach areas.
Lark tooling design. I designed the tooling required for the revised Lark frame design incl. swingarm. The main frame was designed to be manufactured completely as a one-piece monocoque, which had to be reflected in the tooling design. The carbon layup on the latter prototypes was outsourced to a Swedish sub-contractor that had produced high-end carbon components for Koenigsegg One:1.