Electric Automotive Test System Provides an Alternative to Hydraulics

Motion control company, Moog, has developed a compact electric multi-axis system that allows auto makers to test components such as seatbelt anchors in a lab setting. Most automotive component makers currently rely on hydraulic systems for testing assemblies. Yet growing concerns about reliability, maintenance, and safety with older hydraulic test systems have led some carmakers to look for alternative test rigs.

Automotive electric test systems, automotive hydraulic test systems, Moog, servo motors

Moog’s engineers designed the electric test system’s actuators to remain stable during use and arranged the harnesses in a way that eliminates interference with the actuators in any position. (Source: Moog)

Moog representatives pointed to some of the specific problems carmakers cite with their hydraulic test systems:

  • Many are large and respond slowly
  • They leak oil and create environmental issues
  • Many of the systems require a complex infrastructure, including a cooling tower

Moog developed an electric system built on recent technology. Prior to advances in servo motors, the hydraulic system was the only choice. “People traditionally did hydraulics because it’s a known technology,” Craig Lukomski, manager for solutions commercialization, simulation, and test, at Moog, told Design News. “Electric test systems have become more prevalent in the last five years. Things have changed in electric. Servo motors offer competitive cost, and the technology has matured in recent years.”

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Electrification of Mobile Hydraulics Keeps on Truckin’

With advances in variable-speed electric drives, more and more industrial hydraulic power units now use variable-speed pump drives as an energy-efficient alternative to conventional fixed-speed drives with variable-displacement pumps. Several companies now offer similar drives for off-road equipment, but Allied Motion Technologies, Amherst, N.Y., recently introduced a variable-speed hydraulic pump drive intended for power steering systems in trucks, buses, and similar vehicles.

Allied Motion’s EHS series brushless hydraulic pump motors contain integrated drive electronics to directly drive electrohydraulic pumps on large trucks, buses, and other commercial vehicles. The motors come in two frame sizes and seven models rated for 24- or 48-Vdc power to meet the requirements of a wide range of vehicle sizes. Allied normally supplies the motor itself but can supply complete assemblies incorporating an integrated hydraulic pump.

Allied Motion Technologies now offers 24- and 48-Vdc electric motor drive for powering hydraulic pumps in work truck, commercial, and off-highway vehicles.

EHS series motors provide vehicle OEMs or their second-tier suppliers with a fully integrated electric power steering system that substantially improves vehicle fuel efficiency over all-hydraulic systems. They also offer greater design flexibility because the pump can be installed just about anywhere in the vehicle rather than having to be powered by a vehicle’s gas or diesel engine or power takeoff. Additional benefits include reduced lifetime maintenance and repair costs. Allied officials say EHS electric pump drive motors have exhibited durability and long life in even the harshest environmental conditions.

The EHS’s on-board electronics enable the motor to serve as an intelligent node in modern vehicle networks. Thus, the EHS provides an important component of an intelligent motion solution for electrohydraulic power steering and auxiliary power systems for heavy trucks and commercial buses.

Allied officials also point out that the pump drive motors are also well suited for use in lift trucks with hydraulic steering, larger warehouse trucks, construction vehicles, and agricultural equipment.

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Compact Track Drives Integrate Gearing with Hydraulics

Compact construction machinery isn’t just for small construction and equipment-rental companies. Large construction projects also use several smaller and compact machines to reach areas inaccessible or inconvenient for larger machines to reach and remain productive. Today’s compact machines are also more powerful than ever, so they can do more.

This means smaller and compact machines need drive components that can transmit more power within the same or smaller package as before. That’s the strategy behind 705XT track drives from Bonfiglioli. The 705XT track drive is designed for use in such machines as 5½ to 7½-ton compact track loaders, small dozers, and 12- to 15-ton pavers.

Bonfiglioli’s 705XT track drive integrates an axial-piston hydraulic motor, parking brake, and two-stage planetary gearbox into a single component that is compact and easy to install.

The drive incorporates a double-reduction planetary gearbox with a fixed or variable-displacement axial-piston hydraulic motor and parking brake. The design produces not only a compact drive, but simplifies installation as well. This drive unit provides output torque of up to 17,000 N-m. The motor itself is rated for a continuous pressure to 450 bar, maximum flow of 160 l/min and can achieve zero displacement. It also exceeds the 2:1 displacement ratio limitation found in other axial-piston motors.

The 705XT drive comes with a two-position hydraulic displacement control for two-speed operation. It can also be equipped with an electrical proportional control and a built-in speed sensor for closed-loop, continuously variable displacement.

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This BIK Hydraulics crane is ready to tackle concrete forming

BIK Hydraulics has modified its BIK 67 crane to serve the concrete forming industry.

Elemer Ivan, president of BIK Hydraulics, demonstrated the crane’s capabilities at the inaugural Canadian Concrete Expo, held in Toronto on Feb. 7.

“The BIK 67 was an idea of ours to create a crane that is simple, cost effective, quick and efficient,” said Elemer Ivan, president of BIK Hydraulics.

The crane was first released for use in unloading drywall. Since its release, BIK has sold about 100 of the machines.

“The boom has technically been around for about five years in different application,” Ivan said. “It’s been field tested and proven, and we’re very confident. So, we brought it out as a foundation crane.”

The revamped crane features a horizontal capacity of 3,356 kg at 8.5 metres and 998 kg at 20.4 metres.

“You have great horizontal capacity. The reach is good and you can run it hard. In the forming business, they run cranes fast and hard, it takes a lot of abuse,” Ivan explained. “This size of crane can take that abuse just a little better.”

The 67-foot (20.4 metre) boom fits into the ideal size for formwork, Ivan explained. The BIK 67 also features a dual-power link system at the main and secondary booms for greater lifting power, and the overload and safety valves are hydraulic to increase uptime.

“In this style of articulating boom, 60 feet is a little bit short, and 74 feet we find is a little too big,” Ivan said. “The 67 is right in the middle where you can still run the crane quickly. You get good speed, good efficiency, the crane is still light and you can carry a good payload.”

Furthermore, the BIK 67 is equipped with 7.3 metre span, extra wide stabilizers that are double beam and fully hydraulics out and down.

“The front stabilizer legs are optional,” Ivan said. “You can go all the way up with a set of forms without using the front stabilizer.”

Read more: This BIK Hydraulics crane is ready to tackle concrete forming

 

Crop Sprayer is All About Hydraulics 

Experts at Motrac Hydraulics B.V., a distributor and system integrator headquartered in Baak, The Netherlands, recently developed the hydraulic system for a self-propelled agricultural sprayer. The machine requires precise coordination of operations to ensure efficient and consistent application of pesticides or other chemicals despite varying vehicle speed, ground conditions, and routes.

The sprayer has a tank capacity of 4,500 l (corresponding to a load of about 9½ tons) and boom widths from 21 to 40. It is powered by a 218-hp diesel engine and uses a twin-piston diaphragm pump to deliver up to 530 l/min of field chemicals. The engine also drives a hydraulic pump group, consisting of variable-displacement piston pumps and gear pumps.

The drive package uses pendulum tandem chassis with four-wheel drive and independent suspension on all wheels. The chassis, developed specifically for spraying machines, ensures that no motion from the vehicle is transferred to the spray boom. Hydraulics is used for adjustable track width of the wheels and machine height—versatility to accommodate different crops and conditions.

Motrac Hydraulics also designs and installs integrated hydraulic circuits (manifolds and cartridge valves) in-house for all pumps. Depending on the machine, the main pump is generally connected directly to the engine via a mounting flange, with subsequent pumps mounted behind. Motrac often performs this work in-house, furnishing the complete pump line and diesel engine assembly delivered as a unit to the equipment manufacturer’s production line.

This crop sprayer uses hydraulics for propulsion, steering, regenerative braking, and all operating functions.

Open or Closed?
The pumps deliver hydraulic fluid to separate circuits that share a common reservoir. on either open or closed circuits. A hydrostatic drive for propulsion uses a closed circuit, which is more efficient than an open circuit in this application and has fewer valves and greater design freedom. Regenerative braking captures kinetic energy from the moving vehicle and feeds it back to the engine via a one-to-one linkage, which would not be possible with an open system. The closed circuit is also more compact and lighter than an open circuit would’ve been.

A typical layout for the hydraulic system of a self-propelled field spray unit is shown in the graphic. The first pump downstream of the motor is the ground drive pump, a Linde model HPV model. This pump has a maximum operating pressure of 420 bar and variable displacement adjustable to a maximum of 165 or 210, depending on the machine. A manifold mounted on the pump splits the pump’s discharge flow and routes it to four wheel drives; return fluid is routed to a cooler

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Hydraulics and the Tangent Bender 

The Tangent Bender is a basic production machine designed to bend sheet metal and to form rounded corners in a single operation. This is accomplished by wrapping a ram-type rocker plate die around a radius forming die against which the stock to be formed is clamped. The power arm of the machine is a swinging wing assembly to which the rocker plate is attached by a rack and pinion. In the loading position the rocker plate is horizontal and acts as a female die directly or as a base platen for the die fixture.

A heavy spring on the outer half of the power arm is adjustable and fits against a bearing block supporting the pressure roll. The rear end of the power cylinder is anchored on a clevis mount against the rear base of the machine, the front end is similarly mounted on a projection of the bearing block housing at the approximate center of the power arm.

The Tangent Bender was first—and still is—widely used for forming shells of refrigerator cabinets. Other production uses include washing machines, electric stoves, space heaters, vending machines, tubular chair frames, camera and small-appliance bodies. When originally introduced, the machines were air-cylinder operated. These units did—and still do—credible work. However, they had some limitations that were troublesome on some classes of work.

Production Difficulties
The application of hydraulic power to the machine was the result of an effort to find a power source that would correct and compensate for the commonly encountered production difficulties. The first difficulty was the interruption in production due to uneven power flow. The second problem arose from the need for greater power to form heavier sheets. A third difficulty was due to the fact that variations in the thicknesses of commercial sheets required sorting and interruptions m production to adjust the machine.

On heavy-duty jobs, cylinders had a tendency to pause until the air pressure could build up sufficiently to overcome the resistance of the metal sheets. When pressure did build up, the cylinders jumped ahead, resulting in a wrinkling or “orange peel” effect on the finished work. These irregularities, when severe, caused rejection. The salvageable work required considerable hand finishing.

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Log Loader Stacked with Hydraulics 

Logging equipment has to be tough and reliable to deliver productivity under demanding conditions. Hydraulics are used extensively to meet these requirements in the new Komatsu PC290LL-11, the latest addition to the company’s line of log loaders. These machines sort logs that have been cut, stack them into piles, and load them onto trucks.

Powered by a 196-hp Komatsu SAA6D107E-3 diesel engine that meets stringent EPA Tier 4 standards, the machine is available in either a live-heel log loader configuration with a 40-ft. reach or a road builder configuration with a 34-ft. reach. Log loader and roadbuilder operating weights are 40,700 kg (89,730) lb and 37,300 kg (82,240) lb, respectively.

Tandem Pumps Power Multiple Functions
The heart of the machine’s hydraulic system contains two variable-displacement piston pumps. Pump displacement has been increased over previous models to provide greater flow output and ensure operation at the most efficient engine speed. Each pump has a maximum output of 65 gpm (245 lpm) for a total maximum flow of 490 lpm (130 gpm).

The pumps’ displacement is controlled by load-sensing pressure, in which the load-induced pressure is sensed, and pump flow is adjusted by appropriate valves to maintain a constant pressure drop—and, therefore, constant flow. In addition, electronic proportional control solenoids provide load-sensing and horsepower control.

Each of the log loader’s tracks is driven by a variable-displacement piston motor powered by each main pump. Each hydraulic motor has a maximum displacement of 182.4 cm3/rev (11.13 in3/rev) and drives a planetary gearbox, which reduces rotational speed and increase torque. The final drive generates 64,250 lb of drawbar pull. By pairing the variable-displacement motors and pumps, Komatsu’s machines can achieve three travel speeds (low, medium, and high) instead of the more common two. This is accomplished by changing motor displacement and controlling pump displacement electronically.

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Extension Answers: Hydraulics – Open vs. closed 

Hydraulic power is something that is easy to use but not always easy to understand. At its root, hydraulics is the science of how fluids are harnessed to perform mechanical tasks. That can be anything from folding a disc at the end of a field to running a generator at the bottom of a huge dam.

Hydraulics – Open vs. closed take me back to my days as an undergrad at Virginia Tech. Even though I was not an engineering student, many of my friends were and they would engage me in their discussion on the topics of “fluids”… namely “was air a fluid?”

A fluid can be defined as having no shape, yield easily to external forces and have the ability to flow. The sticker to the fluid question dealt with the subject of compressibility. Air is compressible; most fluids are not.

I think about this sometimes when I am using one of my floor jacks. The oil inside the jack is not compressible so as I increase the pressure on the oil by pumping the jack, the jack raises the cylinder and, in turn, the vehicle as well.

The hydraulic oil inside your tractor acts in much the same manner. As the hydraulic pump creates pressure within the system, the oil inside the tractor or the oil within the hoses connected to the tractor transfers that pressure to the point of mechanical action, which might be the cylinders on your round baler or the brakes that stop you from rolling where you really don’t want to go.

A properly working hydraulic system is a must in today’s world of high-horsepower, heavy equipment. Let the power steering go out of your pickup truck and you understand quickly how important good hydraulics are to the completion of our tasks.

In tractors, two main types of systems are used: open-center and closed-center hydraulics. “Center” is a bit of a misnomer. It would probably be more accurate to replace center with circuit, but it is the term that many of us have grown up with so there is no sense in debating the point here.

Closed-center hydraulics are just that, closed in a continuous loop. It has the advantage of using a single central pump. Open-center hydraulics have more than one pump in stages that supply power to different applications as the needs arise. For example, in an open system, the tractor’s steering and PTO would have separate pumps that supply the oil to make those important systems work. A closed system would use only one to supply power to both.

Open center refers to the open central path of the control valve, when the valve is in neutral position. The hydraulic pump is a continuous flow type. When the valve is neutral, then hydraulic fluid goes back to reservoir or the tractor housing. This design is a bit more simple and generally uses pumps that are less expensive.

Closed-center circuits supply full pressure to the control valves, whether any valves are actuated or not. The pumps vary their flow rate, pumping very little hydraulic fluid until the operator actuates a valve. The valve’s spool, therefore, doesn’t need an opencenter return path to tank. Given the pump’s need to react or sense what the need of the machine is or is not, these systems tend to be a bit more complex and expensive. They are powerful and are used in most heavy equipment and modern high-performance aircraft.

So in a nutshell, open-center systems always have oil flow. Closed-center systems are always under pressure but oil does not flow until you activate a lever asking the system to perform. Closed systems build and hold pressure, and, in the past, took some hits because the pressure held at high levels made initial power at start up more difficult.

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For Starters, Look to Hydraulics

Most of us are familiar with the starting systems in our cars. Electrical power is stored in a battery, and an alternator keeps the battery charged when the engine is running. Activating the car’s ignition switch creates a circuit that routes a surge of electrical power from the battery to a starter motor. There’s a little more to it, like solenoids, regulators, and such, but it’s a simple system that has remained relatively unchanged for decades.

The Coast Guard’s newest National Security Cutter, Munro, is 418 ft. long, and has a top speed in excess of 28 knots and a range of 12,000 nautical miles. Powered by a pair of 9,900-hp diesel engines and a 30,000-hp gas turbine engine, the Munro relies on non-electric starting systems to get it on the move.

Shortcomings of Electrics
But as simple as an electrical starting system is, several potential problems exist. Any of several contacts or connectors can corrode to prevent electrical power from reaching the starter motor. Extreme temperatures—hot or cold—can prevent the battery from providing enough power to start the engine. Plus, starter motors are designed only for intermittent duty. That’s because they’re expected to run for only a few seconds to start an engine. Once the engine is running, the starter motor may not be needed again for several minutes, hours, or days.

Malfunctions of the starting system in our personal vehicles are usually just an inconvenience. They may rob us of time or money, but they usually aren’t a major catastrophe. Starting problems in commercial vehicles can be more costly, but still can be dealt without any long-lasting effects. Not so with submarines, ships, marine equipment, and even mining and other land-based equipment.

The corrosive effects of marine environments make electrical starting systems less reliable. But perhaps more importantly, the electric motor and array of batteries needed to start an engine rated for thousands of hp would be impractical. No wonder, then, that the U.S. Navy, U.S. Coast Guard, and similar organizations use non-electric systems to prevent reliability problems.

Read more: For Starters, Look to Hydraulics