Introduction

The system implements a gearbox for crown-chain-pinion systems by translating the sprocket set instead of the chain tensioner. It allows the movement to be implemented without obstructions in the radial direction, to be also applicable directly to the wheel hub. The electronic management through servomotors with feedback control allows high speed and accuracy of shifting.

Technical features

The sprocket box is housed on a sleeve which in turn slides on a splined shaft. The chain tensioner no longer acts laterally as a rear derailleur, but only recovers the excess links while remaining aligned with the main chainring. The implementation takes place by means of one or more servomotors mounted on a support and managed through a branch board and a micro-controller (Arduino, Raspberry Pi or similar). When the cyclist presses an actuation on the handlebar (e.g. lever or button), the micro-controller verifies that the gearbox has not already reached the extreme in the required direction and, if not, sends a signal to the branch board, which drives the servomotors. These then act on the control rods, determining the translation of the sleeve and the sprocket box to the position memorized in the preliminary calibration phase.

Possible Applications

• Traditional bicycles, racing, mountain bikes or other specialties;
• Electrically assisted bicycles;
• Recumbent bicycles;
• Velomobiles.

Advantages

• Increased transmission efficiency thanks to the constant alignment of chainring-chain-sprocket and chain tensioner;
• Increase in accuracy and shifting speed;
• Less aerodynamic drag from the sprocket cassette at higher speeds as it would be mostly hidden inside the wheel hub.