We have developed extremely compact and low-power modules, designed for mounting on rotating parts (including sun and planets in epicyclic gearboxes), with power supplied by internal batteries. Housings are custom machined to fit within the available space envelope. The modules perform ultra-fast, simultaneous sampling on all 8 strain gauge channels, allowing instantaneous face load distribution readings during each mesh cycle. This greatly improves the quality of face load intensity measurements, specifically in cases where the alignment changes dynamically (for example due to the large weight of the planet carrier used in high power gearboxes). Data is transmitted using wireless (2.5 GHz) communication. 300 X analogue gain and 12-bit, 14 kHz per channel sampling, with unrivalled noise immunity (1 mV peak to peak), provides extremely accurate, useable data.
The inset picture shows our JRD-2115 ultra-slim gear alignment module which is designed specifically for in-situ installation through the gearbox inspection cover.
This module includes an integral battery, complete electronics and wireless communication which, with modern power management techniques, allows operation for more than 10 months between battery changes. In most practical applications this duration is sufficient to install strain gauges and the module, close and re-commission the gearbox and complete in-service measurements to evaluate and correct gear misalignment. Larger housings with higher capacity batteries can provide power for many years, allowing the modules to function as ongoing condition monitoring systems inside production gearboxes.
With modern strain gauging and wire encapsulation techniques recently developed and well proven in-service, it is possible to install our gear alignment system in-situ, which in large marine propulsion and wind turbine gearboxes offers a significant saving when compared with traditional methods involving the removal of gear elements for strain gauging in a laboratory.
Our Gear Alignment Modules can be specified with up to 8 channels and 32 axial strain gauge positions. By using quarter, half or full bridge configuration we will optimise the resolution of measurement positions across the gear face width. Strain gauges are bonded in the root and respond to the load applied during the mesh cycle.
When the data from all strain gauges placed across the face-width is processed, the load intensity distribution can be plotted. From the measured load intensity distribution, the value of KHβ (face load factor for surface durability) and KFβ (face load factor for tooth bending strength), as defined in Method A of ISO6336, can be determined. For epicyclic systems, the load sharing between planets, Kγ, can also be determined.
Our bespoke software allows adjustment of gain, channel offset, absolute calibration, channel mapping, data acquisition and automated evaluation of misalignment.
Temperature gradient across the gear face width can also be measured to provide indication of the effects of lubrication and thermal expansion. Parameters such as shaft bending load or output from other transducers can also be acquired. Our experience of load measurements in gear systems enables us to deliver compact and reliable installations capable of long-term operation. Strain gauges bonded in the root of a sun gear. The gauges are connected to the Gear Alignment Module using low profile PTFE coated wires, and protected with a ceramic layer, enabling installation where tip-to-root clearance is as little as 1mm. We also use heat-cured epoxy phenolic adhesive where tip-root clearance is limited to only 0.3mm.