Dynamometers With Oil Shear Load Brakes ‘Ideal’ For Testing Winches

A new type of dynamometer, which can measure torque accurately at very low speeds, is being touted as uniquely suited to marine uses. The dynamometers are made by a company called Force Control and feature oil shear load brakes absorbing extreme torque at very low speed, down to zero rpm. Force Control says this makes them ideal for testing capstans, winches, windlasses and other marine and maritime deck equipment.

This ability allows the dynamometers to accurately capture data at these critical junctures, the company says, where dynamometers equipped with traditional load brakes cannot. Oil shear technology can provide instant load spikes and static lock-up of up to three times the continuous load rating. High cycle counts (up to 300 torque changes per minute) allow for tests with a hammering effect on the tested subject. Quick, controllable response allows virtually unlimited test capabilities, the company claims, while their extremely quiet operation allows gearbox, transmission or final drive noise testing.

High-torque, low-speed testing is commonly used for testing life cycles, shock loading, overall machine life/performance and more for snowmobiles, forklifts, tractors or tracked vehicles, commercial truck axles, helicopter transmissions, gun turrets, winches, hoists, hydraulic motors and more. Oil shear technology eliminates wear for service-free endurance testing and requires no adjustment or friction material dust cleanup.

Force Control Industries says it can furnish a complete test stand including frame fabrication, controls, data acquisition and support. This can be a benefit to many companies that often build testing facilities in-house but either lack the ability or time to design and support the complete system. Force Control also works with many test engineers who are makers of their own design that prefer to handle certain aspects or components of a system in-house. A variety of sizes and arrangements are offered for through-shaft mounting, flange mounting and shaft coupled foot mounting as well as vertical, horizontal or incline mounting orientations.  Load brakes can be supplied with a torque arm and load cell, cooling/filtration/actuation systems and data acquisition software as well as control valves, structures and other ancillary components.

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How Oil Shear Technology Works

Oil shear technology is a system that provides a film of transmission fluid between alternating friction discs and drive plates of a mechanical, multi-disc friction brake. As the discs and plates are brought together, squeezing the fluid film, it initiates hydro-viscous shear. This phenomenon transmits torque through the fluid through laminar flow. This phenomenon is based on the laminar flow of the fluid film between the friction discs and drive plates. The fluid tends to flow in layers, with each layer moving at consistently different speeds between the rotating friction disc and the static drive plate. As the pressure squeezing the disc and plate together increases, the hydro-viscous force of the molecules sliding past each other increases, providing torque. In other words, torque output is directly proportional to the pressure applied to the friction stack.

Actuation pressure can be provided by a proportional regulator for pneumatically or hydraulically actuated units, or by a servo valve in hydraulically actuated units requiring more accurate response. With the fluid layer between the friction disc and drive plate, there is no tendency to stick, slip or chatter at very low differential speed, providing a smooth transfer of torque down to zero rpm.

The second part of the equation is heat energy that must be dissipated from the system. Using oil shear technology, the fluid is circulated through the friction stack and is cycled out of the brake to a forced lube cooling and filtration system. The cooled fluid lubricates the brake components, including the friction material, eliminating the typical degradation found in dry friction brakes. This also allows for a more compact load brake that can, in many cases, be directly mounted to the output of a test device (i.e. axel, auger head, etc.).

Force Control load brakes utilizing oil shear technology, which it brands as Positorq, are available in a variety of sizes ranging from 50 lb. ft. (68 Nm) to 300,000 lb. ft. (406,700 Nm) and can absorb up to 3,000 thermal horsepower (2,237 Kw). Mountings vary and include flange mounts, foot mounts and shaft mounts. Custom designs and load carrying capacity are commonly developed for specific applications.

Headquartered in Fairfield, Ohio, Force Control Industries Inc. is the world leader in oil shear technology, offering a full line of clutches, brakes and clutch-brakes combinations for OEMs in diverse applications. Their manufacturing campus includes three manufacturing facilities with more than 100,000 square feet of manufacturing space along with engineering, design, customer support and administrative offices.