March 3, 2026Open Access

Torque Loss and Leakage in Piston/cylinder and Slipper/swashplate Interface at Low Speed―an Experimental Study with a Novel Tribology Test Chamber

Key Points

Frictional torque loss increases significantly at low speeds under high pressure, affecting pump efficiency.
Measured torque losses and leakage rates across speed ranges reveal the optimal operating speed for performance enhancement.
Assessment using a novel tribology test chamber enables precise measurement of mechanical interactions at targeted conditions.
Findings highlight the critical need for design adaptations in pumps to mitigate performance issues in low-speed scenarios.

Abstract

In this paper, the performance of swashplate-type axial piston pumps and motors' tribological interfaces, specifically the piston/cylinder, and slipper/swashplate, are investigated under low-speed and high-pressure conditions and two different temperatures. The study aims to identify frictional torque loss and external leakage from these interfaces under high pressure at extremely low speeds (ranging from 0 rpm to 250 rpm). The study uses a specially designed test chamber and a customized piston pump rotary group to measure frictional torque loss and external leakage. The design of the test chamber, rotary group, test procedure, and sensor specifications are also discussed. The result identifies the operating speed where hydrostatic pumps and motors need to be considered to win the start-up torque which highly affects the performances of the units in the low speeds operating condition.

Torque Loss and Leakage in Piston/cylinder and Slipper/swashplate Interface at Low Speed―an Experimental Study with a Novel Tribology Test Chamber

Key Points

Abstract

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