Differential Thermal Muscle Motor (DTMM)

A thermodynamic engine is described that converts a sustained temperature differential — from as little as 5°C — into continuous mechanical rotation using a closed-loop belt of twisted polymer actuator fibres mounted over two cylindrical drums of different diameters. Continuous unidirectional rotation is achieved by two connecting rods linking the drum shafts at 90° phase offset, eliminating dead-centre stall by the same principle used in steam locomotive drives. The fundamental novelty of the invention lies in a previously unrecognised kinematic property: in contrast to all conventional belt drives, the velocity incompatibility arising from different drum diameters is not resolved by slip but by the thermally-induced differential elongation and contraction of the belt itself. The hot span continuously contracts at a rate equal to the peripheral velocity difference; the cold span continuously elongates at the same rate. The belt accommodates the kinematic constraint through its own thermodynamic cycle, requiring no gearbox, no slip mechanism, and no external tensioning device. The engine is self-regulating: its equilibrium speed is set by the thermal exchange rate of the working medium, not by any external control. The working medium — twisted nylon monofilament fishing line — is a commodity material available in any market in the world. The engine is constructible from wood, steel pins, and fishing line at any scale of manufacturing sophistication from artisanal to industrial. Applications span embedded cooling recovery (1–10 W), domestic heating cogeneration (100–500 W), industrial waste heat recovery (1–100 kW), off-grid community electrification (1–50 kW), and large-scale datacenter thermal recovery (megawatt class). This work is dedicated to the public domain under CC0 1.0.