First-ever use of RoaDyn for microcar road testing in Japan

Winterthur, July 2021 – Thanks to a new approval from the Japanese government, Kistler can now meet the requirements for testing on public roads with the RoaDyn S635, its six-component wheel force transducer (WFT). The RoaDyn passed comprehensive tests to prove compliance with the local JWL (Japan Light Wheel Alloy) standard. For the first time ever, the WFT can now be used for tests in local road traffic on microcars from a Japanese manufacturer.

RoaDyn wheel force transducers from Kistler are used for test drives on public roads and test tracks, off-road testing, and also on vehicle test benches. They detect the load applied to the wheel by connecting each of the load cells to the wheel rim and hub, with the help of a vehicle-specific adapter. The signals are amplified directly in the load cells, and then they are filtered, digitized and coded by the hub electronics.

Next, the data is transmitted by telemetry (inboard transmission), via a rotor/stator pair mounted on the inner side of the wheel (rotor) and wheel suspension (stator); this is followed by processing with the onboard electronics, and output to a data acquisition device. In this way, the RoaDyn S635 delivers precise measurement results that provide a valuable basis for vehicle development work. 

Inboard transmission eliminates the need for external components

In the RoaDyn S635, the telemetry is located on the inner side of the wheel to minimize projection over the wheel contour. This allows the WFT to be used on public roads. All structural parts and wheel rims are designed and manufactured by Kistler. An FEM strength simulation analysis ensures that the six-component WFT can handle the loads stated on the data sheet.

Thanks to its modular structure based on individual load cells, this WFT has the flexibility needed to meet varying requirements for hub and rim geometries, load, and measurement range. All the signals are digital, ensuring that high data integrity is maintained during transmission.

RoaDyn S635 passes extensive series of JWL tests

The JWL (Japan Light Wheel Alloy) norm was introduced by the Japanese Ministry of Land, Infrastructure, Transport and Tourism as a standard to improve the safety of light alloy wheels. Use on public roads is permitted only if the requirements set by this standard are met. To comply with the JWL standard, the RoaDyn S635 from Kistler had to undergo three extensive tests. After successfully meeting the criteria, the six-component WFT from Kistler was granted JWL certification.

The first stage of the approval process was a rotary bending test, focusing on the rotational loads and moments that act on the wheel during driving. A clamping device on the rim flange was used to clamp the wheel force transducer – comprising load cells, structural elements, and the aluminum rim – onto the test equipment. The transducer was then exposed to a rotary bending moment over the mounting surface of the wheel hub. 120,000 cycles were completed. Next came a radial load endurance test, using a machine equipped with a drum: in this case, over 600,000 cycles were performed. The final hurdle was the impact test, when the wheel was placed on a mounting plate, fixed, and inclined by 13 degrees. A free-falling weight was dropped onto the edge of the rim flange, and the wheel was then examined for cracks, deformations, and air leaks.

After each of the three tests, a dye penetrant inspection was carried out to check for cracks. The RoaDyn S635 six-component wheel force transducer from Kistler successfully met the high requirements in all the test phases. And as additional proof of excellence, an electromagnetic compatibility examination of the telemetry yielded equally successful results.