Capability Differences and Limits of Low Speed versus High Speed Torques in Hydraulic Motors

Blog | January 27th, 2017

The laws of physics include a conservation of energy limitation. It’s this primary law of thermodynamics that binds itself to fluid mechanics to shape hydraulic motors. The popular hydraulic parts either exhibit low speeds and high torques, or the action works in a retrograde configuration as a high-speed, low force device. Keep that basic performance limitation front and center as we evaluate the capability differences and limits of this hydraulics family.

Fluid-Based Power Reduction 

Gearbox speed reducers and electric motors are regarded as compelling choices when rotational energy is built to generate torque. They’re a dominant solution, to be sure, but they can stall. Windings burn out, and the damage is done. Low-speed high-torque devices solve these shortcomings. First and foremost, they’re stall-resistant and load capable. Those two features are compelling, but let’s not stop yet, not when we need to look at the high-speed low-torque counterpart.

The High-Speed Power Difference 

Let’s flip the hypothetical mechanism on its head by switching to a high-speed fluid solution. Torque transmission drops precipitously, but this force attenuating effect is generally part of the design, for it pure rotational velocity that’s desired here. Fast response times and superior positional attributes are addressed by the radial velocity increase, so control systems benefit from this operational model. Used commonly in power transmission systems and fast-response hydraulic control circuitry, the HSLT (High-Speed Low Torque) hydraulic motor embodies a proven design methodology, one that’s deemed a prime example of our aforementioned fluid mechanics law.

Low-Speed VS. High-Speed Hydraulic Motors 

These are two complementary forms of the same principle. Thermodynamic governance determines which device works in which power transmitting situation, but it’s typically the high-speed model that dominates the hydraulic motor landscape, for torque is an industry-centric resource, a source of kinetic energy that transforms pure velocity into pure mechanical momentum. The limitations of the device are few, although our energy conservation ruling could be perceived as a drawback. Otherwise, the motor reverses direction effortlessly, derives large gains from small energy inputs, and can work at very low speeds without stalling.

A comparable gear reducer or electrical motor would likely lock up if such low energy variables and tiny rotational speed factors were applied to their rotors. A LSHT mechanism doesn’t subscribe to this failure model, nor does its high-speed (HSLT) counterpart. Instead, they use closed loop hydraulic circuits and electronic feedback links to move wire-free parts, including hydrostatically charged vane motors, components that display great volumetric efficiency.

Mobile Hydraulic Specialties Pty Ltd

Factory 89, 38-40 Popes Road
Keysborough, Victoria, 3173

Phone: (03) 9798-6511

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