ISO 8370-1:1993

Overview

ISO 8370-1:1993 specifies a dynamic test method to determine the pitch (primitive) zone location for single V-belts and joined V-belts running in pulley grooves. The standard defines how to express the pitch zone position as an effective line differential (be) or a datum/reference line differential (bd). A hexagonal belt may be treated as a single V-belt for test purposes. This test is used to establish the belt pitch diameter required for accurate transmission ratio calculations in belt drive design and verification.

Key topics and requirements

• Scope: Applies to a single V-belt in a single pulley groove or a joined V-belt in multiple pulley assemblies; hexagonal belts are included as single V-belts.
• Test principle: A dynamic running test on a two‑pulley test rig measures belt and pulley motion to compute the pitch (primitive) diameter and the offset of the pitch zone relative to pulley geometry.
• Test rig and equipment:
  • Two pulleys of the same diameter with prescribed measuring dimensions.
  • Adjustable center distance to accommodate belt length and a device to lock the center distance.
  • A means to apply and control the specified measuring tension.
  • Drive to rotate one pulley at a controlled speed (a speed around 1 000 rpm is suggested).
  • Instruments to measure pulley rotational speed and either belt linear speed or center distance plus the belt rotation cycle time.
• Procedure highlights:
  • Fit the belt, apply the prescribed measuring tension, and run the assembly for about 5 minutes to allow the belt to seat.
  • Lock the center distance, measure the required speeds or timing, and record values for calculation.
• Calculations: The standard provides formulae to calculate the belt pitch diameter from measured speeds/timings, and to compute the effective line differential (be) and datum/reference line differential (bd). Positive or negative values indicate whether the pitch zone lies at a smaller or larger diameter than the pulley effective/reference diameter.

Applications

• Belt and pulley manufacturers validating belt geometry and dynamic operating line.
• Design engineers calculating accurate transmission ratios for V‑belt drives.
• Test laboratories performing product verification and quality control.
• OEMs and maintenance engineers assessing replacement belts and troubleshooting belt‑drive performance.

Related standards

• ISO 1081:1980 - Terminology for trapezoidal belt drives and pulley grooves (referenced for definitions).
• ISO 8370-2 - Companion part covering ribbed/striged belts (part of the same series).

Keywords: ISO 8370-1:1993, V-belts, pitch zone, pitch diameter, effective line differential, datum line differential, dynamic test, belt drives, V-belt testing, pulley grooves.