Gravaa Engineer at work

From the ideation phase ...

Because the surface of roads and gravel paths changes throughout the ride it’s always a compromise (or gamble) which tyre pressure you need for the front and rear tyre when you go out for your ride. In the end you often settle for the middle ground regarding tyre pressure. After years of research and engineering we have developed high-end wheelsets which enable you to manage your tyre pressure during your ride.

After the idea was born (read more) it was time to explore the feasibility. This began with the definition of clear high-level requirements, which were considered to be key for a successful product. The major requirements as defined from the beginning:

  • Adapt pressure while riding The system must allow for pressure control (both up and down) while riding.
  • Endless The possibility to inflate and deflate must be infinite.
  • Human power The system must be driven by human power: no electric motor on-board!
  • Lightweight The add-on weight compared to standard high-end wheels must be very small: less than 250 grams per wheel!
  • Invisible The appearance of the wheel must remain similar to standard high-end wheels: the complete system shall be covered safely within our hubs – the center of the wheels – with a diameter less than 70 mm.
  • Plug and play The system has to be 1:1 exchangeable with standard wheels. No or very limited changes to a user’s bike configuration are allowed and it needs to be easy to install, configure and use the system.
  • Energetic benefits Clearly, the system shall give energetic benefits, meaning: the efficiency must be high!

Based on extensive market research, it appeared that tyre pressure management systems alike did not exist. They do exist in various forms and shapes, but none of them was able to fulfill all of the requirements above.

... to the drawing board ...

With the high-level product requirements defined, a technical feasibility study was executed in Eindhoven, The Netherlands. Together with a team of highly skilled and experienced engineers, various conceptual ideas were generated and evaluated. The final outcome is a patented, advanced pneumatic device covered inside the hub of each wheel. The tyre pressure is controlled via a wireless control unit, mounted on the handlebars, which communicates with the advanced hubs. By means of smart choices, the fundamental design was made to work. Some key choices which make the unique GRAVAA technology possible:

  • A miniature, reciprocal membrane pump Energy efficient and of a very small size. The pump cylinders are moved by a camshaft, which is driven by the rotation of the wheels: powered by you! The pump is the heart of our system.
  • A pneumatic clutch The pump consumes only a little energy when switched on. To limit this amount of energy required to inflate your tyres even further, the pump is (automatically) switched on/off for you via a pneumatic clutch unit. This clutch is actuated via a pneumatic membrane and the pressure inside your tyre is also used to (de)activate the clutch.
  • Booster valves Since our technology contains many miniature parts, the air flow shall pass through narrow sections, which limit the air flow. To accommodate a fast response of our system upon your commands, we make use of pneumatically actuated booster valves, which create a larger opening for air to pass through.
  • Ultra low-power electronics The complete system is driven by human power, but our ultra low-power electronics allow for communication with and control of our system. Hardware and software design choices are all driven by function and low-power usage. Each hub has a rechargeable battery inside, which can be charged via USB chargers.
  • Wireless control Our system makes use of Bluetooth low energy and ANT+ protocols to enable communication between both wheels, your smartphone, bike computer and button unit.
  • Button unit To regulate the air flow, we have put lots of effort in the design of a human machine interface. The outcome is a dedicated button unit, which can be placed ergonomically on your handlebars. By pressing up/down, the system reacts on your commands directly.
GRAVAA collection

... we proudly present: KAPS.

We call our technology KAPS: the Kinetic Air Pressure System:

  • Kinetic – Meaning: Resulting from motion. The pump inside is driven by the rotation of the wheels. It is you, who’s driving the pump
  • Air – Naturally, what’s inside your tyres
  • Pressure – The parameter which can now be controlled
  • System – The complete mechatronic device covered inside the hub of your wheel

With our system, you can:

  • Adapt your tyre pressure levels while riding, both inflate and deflate,
  • Keep your tyre pressure at a set level,
  • Display the actual tyre pressure,
  • Lower the chance of punctures,
  • Protect against excessive wear, and
  • Compensate for leakages in case of punctures.

Below, some of the design features are explained further.