If there is one thing that truck drivers routinely comment as something they would love to either lessen or eliminate, it’s noise, vibration and harshness in the cab. Still, manufacturers consistently say that engineering it out of their products is notoriously hard to do.
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Today, truck manufacturers are putting their sights on cab noise and engine mounts. Yet where improvements are made, suddenly truck drivers can hear every other squeak and rattle from other places in the cab.
Another consideration is that not all noise and harsh vibration comes from multiple sources. From tires to suspension and the drive train, there is still more to consider than just the cab and engine mounts. Fortunately, the industry is pressing ahead with manufacturing modifications that help reduce noise, vibration and harshness.
All About Tires
Take tires, for instance. Tire manufacturers have been experimenting with more aggressive tread patterns. Lug and open-shoulder treads, for instance, are often noisier than rib-tread tires. Rib-tread tires Rib-tread patterns prevent noise from making its way into the cab by eliminating any potential physical contact with it.
Where truck drivers generally feel the most vibration is through the steering column. By ensuring tires are balanced when a complaint comes in, fleets can prevent exacerbated wear and thus unnecessary vibrations.
Another area where vibration becomes a problem is around downspeed drivelines. While engine downspeeding is a great way to improve a reliable method for improving efficiency and fuel economy, it creates a challenge where unwanted noise and vibrations are concerned.
When the engine downshifts, torsional vibrations produced by the shift are transmitted through the transmission, drive shaft and axles. All this movement can easily be felt by the truck driver as low frequency vibration.
Still, the industry is hard at work tackling these problems. Dana, a driveshaft manufacturer, is producing a driveshaft specifically designed for downspeeding. They claim it has characteristics allowing it to be balanced to one-half the industry standard, thus greatly reducing its vibrational footprint.
Suspension in Mind
Suspension also plays a huge role in reducing unwanted noise and vibration. Not only does the suspension help to minimize road inputs, but it also helps limit vibration inputs coming from the drive train.
In general, when handling noise and vibration coming from the drive train, air suspensions perform much better than leaf spring suspensions. Four air spring cushions are ideal, though this configuration is admittedly less spec’d.
Outside of spec’ing the right equipment to begin with, always make sure the equipment you are currently running with is in proper working order. If you see an obvious defect, such as a non-functioning shock absorber or a broken spring, make sure it is fixed immediately. This is a matter not only of noise and vibration, but a potential safety issue.
Transmissions, Clutch and Axles
Transmissions and clutch axles also contribute to in-cab noise. To combat this, clutch designers have come out with new schematics that provide a softer dampening rate. They also have longer travel to handle the high torque generated by a modern engine.
To cut down on transmission noise, manufacturers are focusing on the high-frequency whining sound that comes from the metal-to-metal contact when the gear interfaces with other components in the transmission.
Vehicle specifications surrounding axles also impact noise and vibration. Consider options like overdrive and single versus tandem axles. Even recent innovations in gear manufacturing are resulting in a quieter operation across the board.
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With all the recent innovations in truck design, does this mean we can expect a radical change in road noise, vibration and harshness? As the marriage of trucking and technologies continues unabated, only time will tell.