Taking the Measure of Automotive Noise Standards, Part 1

Just how loud is that squeaky wheel?

Published: Tuesday, October 28, 2014 - 15:23

We all know what happens to a squeaky wheel, right? But just how loud does a wheel need to squeak before it’s squeak-worthy of replacement?

During my years of auto repair, one of the interesting tidbits I was hipped to was this: What human ears perceive as a squeak is actually a high-frequency vibration. In the case of vehicle front-end accessory drive (FEAD) applications (e.g., power steering, A/C, alternator), causes of vibration range from worn pulley bearings to inconsistent torque supply. However, the engineering side of this phenomenon is definitely more interesting than the repair side.

Pulleys and belts on the front of Ford’s mighty-might Ecoboost engine. Courtesy Ford Motor Co.

SAKOR Technologies Inc., a leader in implementing instrumentation products for dynamometer testing, designed and built a belt noise test stand for Ford Motor Co., which the company will use to meet new SAE specifications for belt noise in FEAD applications, as well as other noise testing requirements. The SAE International standard J2432:2012—“Performance testing of PK section v-ribbed belts,” covers accessory drive belt testing methods and includes test configurations, pulley diameters, power loads, and guidance for interpreting test data.

The new belt-noise test stand uses a high-speed AC dynamometer system to simulate the engine, allowing testing to be performed in a clean laboratory environment without the need for the fuel, cooling, and fire-suppression systems necessary for fired-engine testing. The dynamometer precisely simulates the torque pulses from engine firing, which are critical for this type of noise testing. The test stand also includes a thermal chamber as well as a water mist system to simulate a wide range of environmental conditions that are also known to have a major effect on belt noise performance.

SAKOR FEAD test stand. Courtesy SAKOR



SAKOR FEAD test stand in Ford facility. Courtesy Ford Motor Co.

According to Scott Willis, a FEAD technical specialist at Ford, the belt test system can be used for testing belts of any length or width, and was designed to have test capabilities over and above what is required in the SAE specification. And the test stand can be used for testing both axial and angular belt misalignment, as well as for performing belt aging and durability testing.

“This test stand allows us to test in accordance with the current SAE specification and is versatile enough to adapt to further noise test development, which will allow Ford to continue to provide the highest quality product to our customers,” says Willis, who also leads SAE’s Belt Drive (Automotive) Systems Committee. “The test unit has been used for cold temperature NVH testing and also for warranty return part-problem verification on belts and idler pulleys.”

Test stand setup at Ford facility. Courtesy Ford Motor Co.

Beyond the J2432 testing, the unit is also capable of simulating misalignment and tilt to the pulleys, which can also be major contributors to engine belt noise. “The revised specification is J1459 and is available through SAE,” says Willis.  “The updated specification includes revisions to the misalignment noise test to improve test consistency and more easily induce noise on newer noise abatement belt constructions.”

The custom test stand allows Ford to test new formulations of rubber, new fibrous materials, or new pulley and belt shapes designed to minimize belt chirp under a wide range of environmental conditions.

Randal Beattie, president of SAKOR Technologies Inc. Courtesy SAKOR

“We are gratified that the new test unit has been so well received by Ford,” says Randal Beattie, president of SAKOR. “Several other major belt manufacturers have visited our facility to see the stand and have expressed intent in acquiring similar equipment.”

Which all comes back to how SAKOR and Ford address the SAE requirements regarding squeaky wheels in the design and manufacturing stages.

“SAKOR and Ford worked closely together throughout the design, manufacturing, and commissioning stages of the test stand project,” explains Willis. “There are several critical functional requirements for the test stand, for example, temperature setting and control, alignment accuracy, and belt tension control. Ford and SAKOR reviewed hardware and design proposals to ensure the functional requirements would be met and then went through a very specific sign-off procedure to confirm the stand functioned as needed.”

About The Author

Ryan E. Day

Ryan E. Day is Quality Digest’s project manager and senior editor for solution-based reporting, which brings together those seeking business improvement solutions and solution providers. Day has spent the last decade researching and interviewing top business leaders and continuous improvement experts at companies like Sakor, Ford, Merchandize Liquidators, Olympus, 3D Systems, Hexagon, Intertek, InfinityQS, Johnson Controls, FARO, and Eckel Industries. Most of his reporting is done with the help of his 20 lb tabby cat at his side.