KEVOS® MAKEOS · Gears
Worm Gear Drive Design (Efficiency, Forces and Heat)
What torque and forces does this worm drive deliver, how much heat does it make, will the housing stay cool enough, and is it self-locking?
Design check of a worm gear drive: ratio, lead angle and efficiency from module, starts, teeth, worm diameter and friction (as the worm gear tool), sliding velocity, input and output torque, tangential, axial and separating forces on worm and wheel, power lost as heat and the oil temperature from the housing surface and heat transfer coefficient, and a self-locking check when the load must be held.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Input power | kW | Power into the worm shaft. |
| Worm speed | rpm | Speed of the worm. |
| Axial module | mm | Axial module of the worm (equal to the wheel’s transverse module). |
| Worm starts | Number of starts (threads) on the worm. | |
| Wheel teeth | Number of teeth on the wheel. | |
| Worm pitch diameter | mm | Pitch diameter of the worm. |
| Normal pressure angle | ° | Normal pressure angle of the thread. |
| Friction coefficient at the sliding speed | Friction coefficient between worm and wheel at the sliding speed found (falls as sliding speed rises; your value from the gear maker). | |
| Housing surface area | m² | Outside surface area of the gearbox housing. |
| Heat transfer coefficient | W/m²·K | Heat transfer coefficient from housing to air (higher with a fan on the worm shaft). |
| Ambient temperature | °C | Surrounding air temperature. |
| Highest oil temperature | °C | Highest oil temperature allowed for the lubricant. |
| Must the drive hold the load by itself? | choice | Whether the drive must hold the load without a brake. |
Method and formulas
- Lead = π m z₁; tan γ = lead ÷ (π d₁); efficiency η = (cos αₙ − μ tan γ) ÷ (cos αₙ + μ cot γ) (as the worm gear tool).
- Sliding speed v_s = π d₁ n₁ ÷ (60 000 cos γ).
- T₁ = P₁ ÷ ω₁; T₂ = P₁ η ÷ ω₂; wheel tangential force (worm thrust) F_t2 = 2T₂ ÷ d₂; worm tangential force (wheel thrust) F_t1 = 2T₁ ÷ d₁; separating force ≈ F_t2 tan αₙ ÷ cos γ.
- Heat = P₁(1 − η); oil temperature = ambient + heat ÷ (k A).
- Example: 1.1 kW at 1450 rpm through 40:1 gives 188.13 N·m at 64.923% efficiency; the oil runs at about 51.795 °C.
Limitations
- Mesh friction only; bearing and churning losses add heat.
- Static self-locking is not reliable under vibration: use a brake for safety-critical holding.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a worm reducer for continuous duty
- Find bearing loads on worm and wheel shafts
- Decide whether a worm drive can hold a load without a brake
Who it is for
- Design engineers
- Maintenance engineers
- Power transmission engineers
What you get
- Ratio, lead angle, efficiency and sliding speed
- Torques and forces on worm and wheel
- Heat, oil temperature and self-locking checks
Interpreting the result
- More starts raise the lead angle and efficiency but lose self-locking.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2191–2194. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Worm Gear Drive Design (Efficiency, Forces and Heat) calculator
