Symbrium introduced a series of four-square test machines in response to customer demand for more affordable, easier to operate and maintain gear fatigue testers.
This equipment is fast becoming the new standard for automotive, off-highway vehicle and aerospace powertrain laboratories in North America replacing established though antiquated gear test rigs with much improved designs and modern control technology.
Symbrium also provides small center distance gear testers for the plastic gear industry as well as very large center distance gear testers upwards of 1,000 mm for industrial and marine gear testing programs.
GT Series 80 to 110 mm Center Distance Testers
The GT series of four-square machines are vastly improved variants of older industry standard German designed 91.5 mm center distance test machines that have been reverse engineered so that the critical characteristics that dictate dynamic load factor are identical allowing correlation with a worldwide gear material data base that has been collected over the past sixty years.
Symbrium machines are capable of running at higher speeds with far better control of temperature, speed, load (for automatic systems) and automatic shutdown prior to gear failure.
All of these gear test machines can be field re-fitted with test and reaction gearboxes having other center distances with minimal effort by simply changing out the side plates of the test and reaction (slave) gear boxes and replacing the gears.
Test Gearboxes:
Symbrium four-square test gear boxes have several design features that greatly enhance ease of use, especially for the installation and removal of test gears and for the observation of test gears during planned inspection intervals.
Control Options
Symbrium has developed extensive software platforms for powertrain component testing that conform to testing protocols in use by nearly every North American automotive and aerospace powertrain test laboratory. Two different control options are available.
Stand-Alone machines are controlled using a PLC with dedicated touch screen Human Machine Interface (HMI) mounted to the machine. All controls devices are integrated into the machine base. Thus the only connections are power and cooling water. Data can be collected via network connection or USB flash drive.
Multi-Machine control where several four-squares can be connected to an external controller which houses the PLC, drives and other devices. The controller can be located up to 100 m from the test machines. Flexible cables with plug and play connectors are run between the controller and the test machines. This architecture, along with other mechanical design features, allows for an extremely compact test machine footprint.
All machines in a multi-machine installation are controlled by a single HMI that runs on a PC connected to the controller via Ethernet. Intuitive user-friendly software provides for multiple machine control, data acquisition and archival, and test monitoring. The controller is configured to operate from 1 to 6 machines at the time of production. Test machines can be added by simply plugging cables into the control unit up to the number for which the controller was designed to accommodate. The controller can also operate optional external pressurized lubrication systems, optional hydraulic torque actuators and an external hydraulic power supply, all of which can be implemented at a future date as testing demands increase or funding becomes available.
Remote Monitoring is standard on all Symbrium test machine controllers allowing machine status and test status to be securely viewed on a web browser from a computer or smart device. The systems can also alert users of test completion or fault condition via text or email.
GTA Series 91.5 mm Center Distance Testers 
The GTA series of 91.5 mm four squares was conceived by two very senior powertrain gear researchers, both having more than three decades of experience managing some of the largest gear research and testing activities in the United States. These new machines incorporate lessons learned from from dozens of engineers and technicians who have used outdated German designed testers and other machines.
The GTA series of machines were designed to be both very affordable and very compact thus allowing laboratories to install several machines in a relatively small area to accelerate the collection of fatigue data to high cycle suspension.
The extremely compact footprint requires less than one third the floor space of other 91.5 mm gear test rigs while having identical dynamic response. Many ergonomic features have been incorporated to make gear inspection, installation and removal very easy. Multiple machines are controlled by a single controller and computer interface resulting in operational efficiency and substantial cost savings for multiple machine installations.
Typical installations have several machines located in a sound proof room with the controller located external to the test chamber. Controllers can be configured to operate one to six systems simultaneously allowing the lab to be expanded by adding machines as testing demand increases or funding becomes available.
The compact design is due to two main features. The reaction gears shafts are hollow allowing the torsion shafts to be coaxial with the reaction gears. This allows loading to be on the end of the reaction gearbox. Secondly, the four-square loop is belt driven with the motor placed underneath the test bed. All signal conditioning for thermocouples, vibration sensors, and control devices is integrated into the machine base for improved signal to noise ratio. The only connections are two control cables which run from the machine to the main controller and cooling water lines, all of which have plug and play connectors.
GTA 500
The GT-500 is a compact 500 Nm machine with 30 mm test gear shafts and an 11 kW drive. The system can be loaded manually using a torque arm or can be fitted with an optional servo-hydraulic actuator that allows variable loading during test. The test gearbox comes standard with integral water cooling so that gears can be run partially submerged (so-called dip lubrication) at a constant temperature. The test gearbox can be fitted with an optional recirculating lubrication system that can supply heated or cooled oil to the test gear mesh under pressure at variable temperature and flow rate.
Footprint: Machine size is 0.55m wide by 0.81 m long by 1.22m high. The working height of the shaft centerline from the floor is approximately 1m. Control cabinet size depends on the number of machines (1 to 6 drives) for which it is configured and ranges from 0.9 m to 2 m wide by 0.4 deep by 2 m high. The control cabinet can be placed up to 100 m from the test machines. A PC is connected to the system controller via Ethernet and serves as the HMI.
Facility Connections: 13 kW of electricity per machine and 10 lpm of cooling water supplied at 25 °C or less. Multiple voltages are available.
GTA 750
GTA-750 is a 750 Nm variant of the GTA-500 with higher torque capacity and a 15 kW drive. Test shafts are 40 mm in diameter. The footprint is exactly the same as the GTA-500 as are all other features except for facility requirements which are 17 kW electricity per machine and 15 lpm of cooling water supplied at 25 °C or less. Multiple voltages are available.
GTA Options
Several Options are available for the GTA series machines.
Reaction Gears for both standard and non-standard ratios can be provided.
Precision Test Gears of both standard and customer supplied designs can be supplied. Material certifications, heat treatment process data, dimensional inspection charts and metallurgical analysis reports are provided with each test gear.
Optional Pressurized Temperature Controlled Lubrication System for Spray Lubrication of Test Gears. System plugs directly into the System Controller. External to the test machine. These systems can be used interchangeably with different GTA series machines. The system controller recognizes when a lube system is present. Only one machine can be serviced by a single lube system.
Optional Hydraulic Torque Actuator for Dynamic Loading. These systems can be provide with a new machine or can be fit onto existing machines with minimal effort. The Actuator must be powered by either a customer provided hydraulic power unit or an optional Symbrium HPU that interfaces directly with the system controller. Each GTA series machine is pre-wired to accept a hydraulic torque actuator with built in torque meter.
Load Arm with Calibrated Weight Set capable of dead weight loading to 750 Nm with 25 Nm increments. One load arm and weight set can be used with multiple machines.
Instrumentation Shafts with shaft-end mounted slip rings that facilitate strain gauging of test gears or dynamic TE measurements to be conducted using gear mounted angular accelerometers are available for all machine variants.
Spare Parts including perishable bearings and torsion shafts can be provided in lots at very affordable prices.
Similarly, any spare part including custom machined details or purchased items can be supplied upon requested.
GTM 500 and GTM 750 are variants of the GTA series machines with the drives and controller integrated into the machine base. These machines are larger than the GTA series, and are self-contained with integral controls and drives and a touch screen human machine interface mounted directly to the machine.
The rotating elements of the GTM series machines including gear shafts, bearings, torsion shafts and torque loading device are identical to the German 91.5 mm designs. The main differences are in gearbox construction, controls and packaging. These machines are much easier to work on and require less than one half the floor space of equivalent four-square machines supplied by different manufacturers. The machines can be set on a simple concrete floor with the only facility connections being power and cooling water.
The GTM 500 has 30 mm test shafts and a 11 kW drive motor while the GTM 750 has 40 mm gear shafts and a 15 kW drive and motor.
The machine is controlled from the machine mounted HMI. Standard loading is manual using dead weights and a torque arm. Automatic hydraulic loading is available as an option. Machine status can be monitored remotely from a web browser and data can be retrieved via thumb drive or network connection.
GTR 750 is a 750 Nm three-shaft machine that can be used for reverse bending testing by placing an idler gear in mesh with two larger gears. This machine has a 20 kW drive and is manually loaded using a torque arm. The footprint is exactly the same as the GTM series machines. An automatically loaded machine can be developed if required.
Custom Four Square Designs
The above machines are five of the most popular models sold by Symbrium. However, many smaller and larger machines are designed and built to satisfy unique customer demands. These range in size, complexity, speed/power and level of automation. Please contact us with your unique needs and we will be happy to work with you.
The Symbrium Advantage
Symbrium understands gear testing at a very deep level. We design high performance geared systems, we design and build gear testing systems and we operate a world-class gear material testing laboratory using our own equipment that collects data for some of the most recognized names in the automotive, aerospace, agricultural and polymer resin industries.
Please contact us for more information.