Praxis Hinged Transmission Simulation

A New Drivetrain Architecture

Praxis recently unveiled a 4-speed chained gearbox under the name "Hinged Transmission" — a reference to the mechanism by which the larger sprockets are inserted into the chain's load path. Each gear change physically alters which sprocket in the gear set carries the chain tension, as opposed to a derailleur system where the chain moves laterally between fixed sprockets.

The architecture raises engineering questions that differ from those of conventional derailleur or hub-based systems: how do loads distribute across the chain contact zone during a shift, what are the power losses in each gear ratio, and how does the transmission ratio sequence affect the cadence distribution across a realistic power profile?

Simulation Approach

The same in-house simulation tools used to analyse the Classified PowerShift hub were applied here, testing their versatility on a novel drivetrain topology. The model computes drivetrain loads and mechanical power losses as the transmission cycles through its four gear ratios under representative cycling loads.

The simulation resolves the gear mesh forces in each stage, chain tension distribution, bearing loads, and the efficiency contribution of each component. Power losses are computed at each gear ratio as functions of load and speed.

Results

The animation shows the Hinged Transmission shifting through all four gears while instantaneous loads and cumulative power losses are tracked. The simulation demonstrates the adaptability of the modelling framework to new drivetrain topologies with minimal reconfiguration — a relevant capability when new drivetrain architectures are being introduced to the market at increasing frequency.

Further details on gear ratio steps, peak efficiency values and validation status are subject to ongoing product development timelines.