Understanding V-Flat Drives
Discover how V-flat drives blend the best of V-belts and flat pulleys, unlocking smarter, more adaptable solutions for demanding industrial applications.
V-flat drives: All the advantages of V-Belts with the flexibility of flat pulleys
V-Flat drives combine the advantages of V-Belts with the flexibility of flat pulleys, making them ideal for certain industrial applications. Whether you’re working with classical, wedge, or hex belts, understanding the right design parameters is critical to performance, longevity, and safety. In this guide, we’ll cover the essentials — from pitch diameter corrections to arc of contact adjustments and pulley width recommendations — so you can design or troubleshoot your V-Flat drives with confidence.
What is a V-Flat Drive?
A V-Flat drive uses a flat pulley on one or more shafts, paired with a V-Belt on the other pulley. This setup can improve tracking and reduce wear in specific configurations. Suitable belts include:
- Single Classical V-Belts
- Banded Classical V-Belts
- Banded Wedge V-Belts
- Hex Belts
Three Key Design Factors
1. Pitch Diameter Correction
When the flat pulley is part of your drive, its “pitch diameter” must be adjusted to account for the belt section. Use the add-on values below when determining speed ratio and belt length.
2. Belt Tension & Arc of Contact
When (D−d)/C=1.0(D – d)/C = 1.0(D−d)/C=1.0, the flat pulley (driven) has ~240° arc of contact, and the V-sheave (driver) ~120°, matching a standard V-V drive’s tension. If the arc decreases, increase tension using the correction factors below.
3. Flat Pulley Width & Crown
Minimum flat pulley face widths ensure proper belt tracking and prevent lateral movement. Crowns should be avoided when possible; if required, limit to 1/8″ per foot of pulley width.
- Always correct pitch diameter for flat pulleys using add-on values.
- Adjust belt tension when arc of contact decreases.
- Follow minimum pulley face width guidelines to avoid tracking issues.
- Limit crown to 1/8″ per foot of pulley width.
