Product Details Supplier Info More products

Marzocchi applies micro-hydraulics to all of its gear pumps and motors, which undergo in-depth research and development to satisfy demands for efficiency, reliability and reduced noise levels.

The two main areas of gear pumps and motors are the ALP and ALM range – utilising aluminium flanges and covers – and the GHP and GHM range of gear pumps and motors – utilising cast-iron flanges and covers.

The R and D department at Marzocchi has applied the latest FEM simulation techniques that, together with the new tools for the experimental mechanics, has produced specific product optimisation aimed at satisfying current market demands.

The department, equipped with the latest testing equipment, analysed mechanical, hydraulic, acoustic and vibration criteria for performance and durability in the toughest working conditions.

This has resulted in the optimisation of the compensation geometry (used to balance the dynamic thrust caused by pressure in gear vanes), gear profiles and the undercut drain on the bushings in order to increase product reliability and reduce noise levels.

These were transferred to the production department by a wide-scale renewal of the run-in and test benches.

The current Marzocchi production range varies between 0.19 and 200.3cm3/rev (0.0104-12.223in3/rev) and is divided into eight groups according to gear size (0.25, 0.5, 1P, 1, 2, 3, 3.5, 4).

Within each group, the different displacements are obtained by changing the width of the gears.

A wide range of flange, shaft and coupling configurations is available; these components can also be manufactured according to customer specifications.

The cast-iron versions exist in groups 1, 2 and 3.

Maximum operating pressure depends on pump displacement and type: it varies on an average between 230 bar (3,300psi) on aluminium models and 280 bar (4,100psi) for cast-iron versions.

All products can also be supplied with Viton seals and special versions are available for temperatures between -40C and +120C (-40F/+248F).

Mono-directional and bi-directional motors are divided into three families covering a range of displacements between 2.8 and 87cm3/rev (0.17/53.1in3/rev).

The maximum working pressures for the motors are similar to those established for the pumps and they can deliver torque up to 250Nm and power up to 60kW.

The run-in is the last stage of the manufacturing process and it is one of the most important operations because it permits the optimisation and check of the product efficiencies.

During run-in in tests, increasingly higher pressure levels are created; the gears, inflected by the hydraulic load, act as tools machining the pump body, thus creating the best tolerances among the parts.

This process is performed under computer control.

The definition of the gradual increase of the pressure is particularly important because it establishes the machining speed of the material by the gears and thus the particles dimension; these particles must be small enough not to interfere with the running of the product under testing and its future performance.

Each motor of each group has a personalised pressure ramp so that no contaminating material remains in the circuit and the pump is able to attain maximum performance levels immediately.

Reversible motors and pumps are subject to run-in procedure on both rotations.

After this process product efficiencies are measured at fixed parameters.

Test data is automatically recorded to provide updated statistics on product performances, supplied on customer request.

After the run-in for gear motors another specific test follows on a dedicated test bench, where the relative operating conditions must be reproduced: under braking, when the energy of the fluid is transferred to the shaft to overcome the resisting torque; under counter pressure, when the fluid passes through the motor with the shaft free to turn without load; and under counter-pressure, inlet and outlet are under the same conditions: at maximum pressure the stress on the rotating parts is zero, while the flanges, body and external seals are subjected to the maximum stress.

Under braking the stress distribution is similar to that which exists on the pumps: if maximum pressure exists at the inlet and discharge pressure exists at the outlet, compensation seals and rotating parts are subjected to the maximum stress according to resisting torque.

A typical motor’s working conditions are between these two situations: part of the energy is transferred to the shaft and part is used, for example, by another motor connected in series.

Therefore, on the Marzocchi motors test bench, the final control is divided in three phases.

In the braking phase, at an established rotation speed a resisting torque is applied to the motor shaft.

The application of this torque creates a variation in the fluid’s inlet speed and pressure; the test-bench control system stabilises the motor in fixed conditions in which running parameters are acquired, such as volumetric and mechanical performances and draining flow rate.

In the counter-pressure phase, a fixed amount of oil goes through the motor without any resisting torque applied to the shaft; the outlet line is kept closed and therefore a bilateral pressure is established.

The drain flow rate is measured at these conditions.

In the start-up phase, without any resisting torque applied to the shaft, the start-up torque is determined by measuring the minimum inlet pressure at which the motor starts running.

In the case of bi-directional motors, the three phases are performed for both rotations.

After this test, the motor is delivered to the customer perfectly run-in and controlled: its reliability makes it suitable for use even under extreme conditions.

The following application example was developed in collaboration with the Elasis research centre in Lecce and concerns the fan drive hydraulic system used to cool the engine compartment of the new Wheel Loader range by Fiat Kobelco.

To make motor maintenance easier (model W270LB Evolution is mounted with a Cummins 6 cylinder, 10.8-litre direct-injection diesel, 202kW turbo air after cooler), the rear section of the vehicle can be opened.

This incorporates the fan directly connected to the Marzocchi gear motor and the air conveyor, permitting bilateral access to the radiant mass.

The rotation direction of the fan is reversible, providing self-cleaning action of the radiators.

This operation can be activated using an appropriate switch located in the cabin on the control dashboard.

The fan is driven by aluminium reversible motor (type ALM2BK1-R-20-T4-T-H, 14.1cm3/rev displacement), equipped with support bearing and specific seals for wide temperature range.

The aluminium fan (weighing 7kg) takes in hot hair from the engine compartment and the hydraulic motor working temperature is approximately 70-80C (158-176F).

The hydraulic motor is also subjected to vibration due to the wide swings of the rear side of the machine, when the bucket is rapidly moving.

Under extreme conditions acceleration up to 7G is possible.

Normally the motor performs with an inlet pressure of 200 bar and 50 bar in outlet pressure.

To ensure the best temperature control, the fan rotation speed is independent of the motor running speed.

For the project validation the hydraulic motor was subjected to an internal Marzocchi approval procedure (to which all new/special products are subject) and to a test performed directly by the customer.

Internal approval includes various endurance tests in which the components are checked on the test benches in the R and D department; they are subject to on-off pressure cycles at the maximum allowed pressure.

Periodically, an inspection is made in order to check the components conditions.

Where necessary, tests have been performed with similar operating conditions of the final application: same pressure cycles, temperature, oil type and so on.

Once the endurance test has been completed, a comparison is made between the initial and final product performances and a deep analysis of each component is performed to identify any possible failure.

No failure and no performance degradation higher than the internal specifications must occur to validate the project.

The test performed by Elasis is composed of a first cycle under continuous pressure at 210 bar (3,050psi) at a temperature of 110C (230F), followed by a second cycle at pulsating pressure (0-210 bar) at the same temperature conditions.

JBJ Techniques

JBJ Techniques is a specialist supplier of high-quality products for the mechanical power transmission and fluid power sectors. The company offers a high level of in-house expertise plus a huge selection of products to meet a very broad range of customer applications.

JBJ Techniques is a specialist supplier of high-quality products for the mechanical power transmission and fluid power sectors. The company offers a high level of in-house expertise plus a huge selection of products to meet a very broad range of customer applications.

From specification, through technical advice and manufacture to after-sales support, JBJ Techniques provides a comprehensive and valued service to the power transmission and hydraulics industries. The company fields a UK-wide team of technical sales engineers to ensure that the business is close to its customers, and it enjoys excellent associations with European manufacturers, acting as sole UK distributor in many case.

JBJ’s team is recognised for its expertise in the selection and configuration of hydraulic and mechanical transmission systems. Able to draw on an extensive product range that provides the building blocks for bespoke systems both large and small, the in-house design team offers a complete service, ranging from an assessment of customer requirements to full technical backup, including engineering calculations, CAD-based system design, system build and certification. Moreover, customers can take advantage of JBJ’s own machine-shop facilities and skilled craftsmen to guarantee quality and control cost.

JBJ Techniques provides probably the widest range of couplings available within the UK with 14 different designs and 22 different styles of gear couplings alone. The product portfolio includes miniature couplings, all-steel gear couplings, flexible spider couplings, shaft couplings, torque limiting couplings, disc and grid type couplings, ATEX compliant and shaft locking devices.

However, as extensive as the selection is, couplings make up a fraction of JBJ’s portfolio. In addition, the company can provide gearboxes, clutches, pumps, hydraulic motors, flow meters, fluid power accessories — including cooling systems, reservoirs, seals and indicators — as well as a variety of bellhousings and flanges, to name just a few of the product categories.

View full profile