RoaDyn S635® wheel force transducer authorized for operation in Japan

Test vehicles fitted with measuring equipment are not allowed on roads in Japan. This is because of frequent road traffic incidents in the past due to the extensive external structures built onto such vehicles. To increase safety, Japan's Ministry of Land, Infrastructure, Transport and Tourism introduced the JWL Japan Light Alloy Wheel (JWL) standard. Authorization for operation in road traffic can only be obtained by meeting the standard's demanding requirements. After extensive testing, Kistler's RoaDyn® S635 wheel force transducer became the only wheel force transducer to obtain JWL certification.

Kistler's RoaDyn® S635 is a 6-component wheel force transducer used in test drives on public roads and test tracks or for off-road testing; it can also be used directly on a vehicle test bench. During tests, the loads acting on the wheels are captured by five individual load cells connected to the rim and the hub via structural elements as appropriate to the vehicle. The signals are then amplified in the load cell and fed directly to the wheel electronics, where they are filtered, digitized and coded. Finally, the data stream is transmitted by telemetry (inboard transmission) via a rotor/stator pair (with the rotor mounted on the inner side of the wheel and the stator on the wheel suspension); the data stream is then transformed in the onboard electronic unit for output to a data acquisition device. Precise measurement results from the RoaDyn® S635 wheel force transducer provide a crucial basis for vehicle development.

Inboard transmission eliminates external components

A special feature of this transducer is the positioning of the telemetry equipment on the inner side of the wheel. This eliminates the need for fixtures and mounting components that would project over the wheel contour and increase the vehicle's width beyond the permitted dimension. It is this feature that allows operation of the RoaDyn® S635 on public roads. All the structural parts and rims were designed and manufactured by Kistler. FEM analyses were carried out to simulate strength and for this reason, Kistler can guarantee that the wheel force transducers are suitable for the loads stated on the data sheets. Thanks to its modular structure based on individual load cells, this wheel force transducer can be flexibly adapted to specific hub and rim geometries and varying requirements for the load and/or measurement range. The high level of measurement accuracy is also maintained during transmission, thanks to end-to-end digital signal conditioning.

Kistler's wheel force transducer passes the tests with flying colors

To comply with the JWL standard, Kistler's RoaDyn® S635 wheel force transducer had to undergo three extensive tests. Our wheel force transducer met the demanding requirements for durability, mass and moment of inertia. The electronics and telemetry also underwent EMC tests, which they passed. A 'rotating bending' test was also carried out; this involves simulation of the rotary forces and moments to which the wheel is subjected during driving. For this purpose, a clamping device on the inner rim flange was used to clamp the entire wheel force transducer (comprising the load cells, structural elements and aluminum rim) rigidly onto the test machine; the transducer was then exposed to a rotary bending moment over the wheel mounting surface. After 100,000 cycles, a rolling test was carried out for 500,000 cycles on a rolling test rig.

In the final '13-degree impact test', the wheel disk is placed on the mounting plate, fixed and inclined by 13 degrees. A free-falling weight is then allowed to fall onto the edge of the rim flange, and the wheel is examined for cracks, deformations and air leaks. After each of the three tests, a dye penetrant inspection (DPI) is carried out to check for cracks. Here too, Kistler's RoaDyn® S635 wheel force transducer provided no cause for complaint.


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