KEVOS® MAKEOS · Power Transmission
Timing Belt Drive Design (Length, Mesh and Belt Width)
What belt length and centre distance does this timing belt drive need, are enough teeth in mesh, and how wide must the belt be for the power?
Design of a synchronous (timing) belt drive: pulley pitch diameters from the pitch and tooth counts, exact pitch length for the centre distance, rounding to a whole number of belt teeth and the centre distance that belt gives, teeth in mesh on the small pulley (as the timing belt tool), belt speed, effective pull from the power with a service factor, and the belt width needed from your allowable working tension per millimetre of width.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Power | kW | Power transmitted. |
| Small pulley speed | rpm | Speed of the small pulley. |
| Service factor | Service factor for the driven machine and running hours (from the belt maker). | |
| Belt pitch | mm | Pitch of the belt teeth. |
| Small pulley teeth | Teeth on the small pulley. | |
| Large pulley teeth | Teeth on the large pulley. | |
| Approximate centre distance | mm | Centre distance you would like; the tool finds the nearest belt. |
| Allowable working tension per mm of width | N/mm | Allowable working tension per mm of belt width at this speed and pulley size (your value from the belt maker). |
| Belt width chosen | mm | Belt width being considered. |
| Least teeth in mesh | Least teeth in mesh on the small pulley (the belt maker’s rule, often 6). | |
| Largest belt speed | m/s | Largest belt speed for the belt and pulleys. |
Method and formulas
- Pitch diameter = z p ÷ π; pitch length L = 2√[C² − ((D − d) ÷ 2)²] + π(D + d) ÷ 2 + (D − d) sin⁻¹[(D − d) ÷ 2C]; belt teeth = round(L ÷ p); centre distance found for that belt (as the timing belt tool).
- Wrap on the small pulley = 180° − 2 sin⁻¹[(D − d) ÷ 2C]; teeth in mesh = z₁ × wrap ÷ 360.
- Belt speed v = π d n ÷ 60 000; effective pull F_e = P × SF ÷ v; width needed = F_e ÷ allowable tension per mm.
- Example: a 110-tooth belt sets the centres at 199.36 mm; 9.4912 teeth mesh and the belt needs 11.586 mm of width.
Limitations
- Width from a single allowable tension per mm; makers’ rating tables include speed and pulley-size effects.
- Shaft loads depend on installation tension: follow the maker’s tensioning method.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Lay out a timing belt drive for a machine axis or pump
- Choose a belt width for a power
- Check teeth in mesh for a small pulley
Who it is for
- Design engineers
- Maintenance engineers
- Power transmission engineers
What you get
- Pitch diameters, belt length and actual centre distance
- Teeth in mesh and belt speed
- Effective pull and belt width needed
Interpreting the result
- If too few teeth mesh, use a larger small pulley or a wider belt rating with a mesh correction.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2473–2535. Topic reference; no source tables or recommended settings are reproduced.
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Open the Timing Belt Drive Design (Length, Mesh and Belt Width) calculator
