Torsional vibration measurement
When measuring torsional vibrations, strain gauges are often used on the shaft, with which both couple (load) and torsional vibrations can be recorded. This is done to verify calculations during testing, or as a tool while analysing problems. The actual rotational non-uniformity can also be measured by making use of our torsion lasers, which are able to determine the momentary velocity of a turning shaft by means of the Doppler shift without direct physical contact. This technique is especially suitable for locations unsuitable for strain gauges or for installations in which multiple locations need to be measured fairly quickly, after which a comparison can eventually be made by means of torsional vibration calculations.
One of the typical applications is the monitoring of the torsion damper of a diesel engine, in order to see whether this still has the desired damping characteristics. Based on registration of the non-uniformity of the crankshaft end in combination with the calculations, a verdict can be brought in so that a time-consuming or expensive inspection or replacement can be avoided. This is a technique that is accepted by a number of Class societies so that the required surveys of dampers that are still in good condition may be cancelled.
During the past few years we have been able to add noise, in particular on board of yachts, to our list, in which torsional vibration measurement proves its value in finding solutions. Although traditionally no relation is seen between torsional vibrations and lateral vibrations, it may be clear that a reaction force to the foundation arises through alternating torsion, and this appears to be significant. This can be amplified by the dynamic behaviour of flexible structures, through which a fairly harmless level of torsional vibrations can lead to noise problems after all. Meanwhile, this has also reluctantly been recognised by suppliers of such systems and often our combination of knowledge, skill and a range of contacts in this market result in better alternatives.
In the field of torsional vibrations in combustion engines the applications as well as the problems are numerous and therefore our advice is to contact us to discuss possibilities. Often, based on an evaluation of existing or new calculations, we can already gather considerable understanding of the case, so that conclusions can be drawn based also on this understanding, or an optimal measurement campaign can be suggested.