VALICALC · ENGINEERING WORKFLOW
Belt drive speed and geometry check
Check pulley speed ratio, open-belt length and wrap angle from pitch diameters and centre distance before selecting manufacturer belt hardware.
Start this workflowWhat do I need to know first?
- Driver RPM and both pulley pitch/effective diameters
- Measured or proposed centre distance
- Whether the belt is open, crossed, toothed or slipping
Goal and model boundaries
Reconcile speed and geometry for an open two-pulley belt drive.
- The linked length/wrap tools describe an open two-pulley arrangement.
- Use manufacturer pitch-length conventions; nominal belt outside length may differ. No belt catalog/reference is invented here.
Check driven RPM
Identify driver and driven pitch diameters before entering the driver speed.
Ideal driven RPM = driver RPM × driver diameter / driven diameter.
- Expected output
- A no-slip driven speed estimate.
- Next step
- Use the same two pitch diameters in the belt length check.
Estimate pitch belt length
Enter both diameters and proposed centre distance.
The open-belt approximation combines straight spans, semicircumferences and the unequal-diameter correction.
- Expected output
- An estimated belt pitch length.
- Next step
- Compare available manufacturer lengths and reverse-check centre distance if needed.
Review wrap and belt speed
Check the smaller pulley wrap and pitch-line speed at the operating RPM.
Wrap depends on diameter difference/centre distance; speed follows πDn/60.
- Expected output
- Wrap angle and belt speed for the stated geometry.
- Next step
- Check manufacturer power, tension, alignment and installation requirements.
Units and context
- Keep the two pulley diameters and centre distance in the same physical unit.
- Ideal speed ratio ignores slip; belt speed depends on the pitch circumference.
Common mistakes to avoid
- Mixing outside and pitch diameters
- Using an open-belt model for a crossed belt
- Assuming adequate wrap proves power capacity or correct tension
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