RDF Joint Simulators / Run Down Fixtures

Joint Simulators (also referred to as Rundown Fixtures or Adapters) are required for accurate torque measurement for power-driven torque controlled tools (electric, hydraulic or pneumatic). They are not necessary or useful when measuring torque on manually-operated torque tools (screw-drivers, wrenches, etc.). They simulate the conditions found when using the tool in real-world conditions, allowing the speed of the power tool motor to ramp-up to normal operating speeds resulting in a more accurate and repeatable measurement of the torque.

Joints are defined by the degrees of rotation or the increase in torque per degree of rotation. A soft joint ensures that a tool has more time to operate and typically produces more repeatable test results, contrarily the hard joint provides less time for the tool to operate and generally produces more variation.

Per ISO 5393;

HARD Joint, which is 30 degrees or less of rotation from "snug" to final.
MEDIUM Joint, which is generally 180 - 400 degrees of rotation from "snug" to final.
SOFT Joint, which is typically 720 degrees or more of rotation from "snug" to final.

They are typically fabricated from machined steel with the appropriate drive size as needed. Internally it is comprised of a series of Belleville washers, designed to compress as the bolt tightens. By varying the arrangement of these washers, various joint rates can be simulated soft, medium and hard. Unless otherwise, specified, Joint Simulators are configured to simulate a medium joint. The joint rates can be adjusted by the user by changing the orientation of the Belleville washers upside down.