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SF Engine Man: Noise, Vibration, and Harshness

Within the engineering community, there is a discipline called NVH. It stands for noise, vibration, and harshness. Like a farmer who can survey a field to determine a good stand, an experienced engineer can listen to or feel an engine or machine and glean either the absence or propensity for NVH. 

A real-world example of two different levels of NVH is when you hear a cheap electric drill run in comparison to a high-quality unit that has efficient bearings instead of bushings. They both turn the drill bit, but the difference in NVH is apparent. The poor-quality drill is rough sounding, noisy, and seems labored; the low NVH example is smooth, quiet, and appears more powerful. 

When comparing machines, tools, or engines for purchase, a low level of NVH usually comes with a price tag. It is costly, in relative terms, to quell the three devils of NVH. It is important to note that in most instances, NVH can determine life expectancy. 

For example, let’s say you are looking at a fan system on a dryer as an investment. Listen to and feel the motor, if possible. Does it shake excessively or feel coarse? Is it noisier than you think it should be? Does the fan turn smoothly and in a circular arc, or does it seem to be out of balance and loud? These factors can be a valid predictor of the reliability of that dryer.

When purchasing equipment, your hands and ears need to check for NVH, and then you can make an intelligent comparison between brands or models. 

The effect that NVH has on a machine, especially an engine, is logarithmic. In other words, the frequency of the order of vibration that is causing the noise and harshness exponentially impacts wear. Just as a soil’s pH is not linear in its acidity or alkalinity and its impact on nutrient tie-up and plant uptake, so is the detriment of NVH. 

Your hands and ears are important diagnostic tools when working on machines and can foretell a future problem. It is a mind-set you need to cultivate. (Listen to the Successful Farming Podcast about the thought process needed in the shop.)

With rare exception, a machine, a component, and an engine announce their poor health through NVH. Touch and listen to engines and the like when they are operating to determine their condition. 

For example, feel around the engine when running. Place your hand on the alternator, any pump, and the engine itself. Do this from day one with a new purchase. This way you have a mental and tactile history of what the engine or component sounds like when all is well. It is very difficult to identify a minute degradation if you have no record. This same logic can be applied to a pump on a sprayer, a vacuum unit on a planter, the drive mechanism of a combine, or a motor on a center pivot. They all are willing to divulge their health if you listen and feel.

A very good investment is a mechanic’s stethoscope. It will allow you audible access to components that cannot be heard otherwise. A quick listen, especially if you have another of the same component for comparison, will reveal an abundance of information. If you have electric drive meters on your planter, run them in the shop and listen for any anomalies. The same holds true for listening to circuits such as hydraulic and those going to a sprayer tip. They all talk, albeit in their own language.

It costs nothing to listen and feel your engines. Pay attention for a change in components for vibration and the general smoothness by touch. When is comes to engines and machines, the most beautiful sound is that of smooth silence!

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Machinery Talk