BIZOMAT MAKEOS · Power Transmission
Belt Conveyor Drive Sizing
What belt pull and motor power does this belt conveyor need, and will the drive pulley grip without slipping?
Simplified sizing of a belt conveyor drive: load per metre from the throughput and speed, effective belt tension from idler and belt resistance (an overall friction factor) plus lift, power at the drive pulley and at the motor, minimum slack-side tension for the drive pulley’s wrap and friction (Euler), tight-side tension, pulley torque and speed.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Throughput | t/h | Material conveyed per hour. |
| Belt speed | m/s | Belt speed. |
| Conveyor length (centres) | m | Horizontal length between pulley centres. |
| Lift (positive up) | m | Height the material is lifted (negative for a decline). |
| Belt and idler moving mass per metre (both runs) | kg/m | Mass per metre of belt (both runs) plus the rotating parts of the idlers. |
| Overall friction factor | Overall resistance factor for idlers, belt flexing and material (about 0.02–0.03 for well-aligned conveyors). | |
| Drive pulley friction coefficient | Friction between belt and drive pulley (about 0.35 lagged, 0.25 bare and dry). | |
| Wrap on the drive pulley | ° | Angle of the drive pulley covered by the belt. |
| Drive pulley diameter | mm | Diameter of the drive pulley. |
| Drive efficiency | % | Efficiency of the gearbox and couplings. |
| Motor margin | % | Margin above the calculated power for the motor. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Throughput
- What it is
- Mass of material the conveyor must carry per hour at its design rate.
- Units and format
- Enter a number in t/h: t/h. The form accepts 0.000001 t/h to 100000 t/h. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100 t/h as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More throughput raises the material load per metre, effective tension and power.
- Get it right
- Use the peak design rate, not an average over a shift with stoppages.
What this means: Belt speed
- What it is
- Linear speed of the belt surface. With the throughput it sets how much material sits on each metre of belt.
- Units and format
- Enter a number in m/s: metres per second. The form accepts 0.000001 m/s to 20 m/s. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.5 m/s as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Pulley power is effective tension × belt speed; faster belts carry less material per metre.
- Get it right
- This is belt speed in metres per second, not drive pulley rpm.
What this means: Conveyor length (centres)
- What it is
- Length of the conveyor between the centres of the head and tail pulleys, measured along the run.
- Units and format
- Enter a number in m: metres. The form accepts 0.000001 m to 10000 m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Friction resistance rises in proportion to length.
- Get it right
- Use pulley centre to pulley centre; the tool applies its friction factor to this length.
What this means: Lift (positive up)
- What it is
- Vertical height the material is raised from loading point to discharge. Negative for a declining conveyor that lowers material.
- Units and format
- Enter a number in m: metres. The form accepts -500 m to 1000 m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5 m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Each metre of lift adds the material weight per metre × lift to the effective tension.
- Get it right
- Use a negative value for a decline; the tool reports when the conveyor would run on its own and needs braking.
What this means: Belt and idler moving mass per metre (both runs)
- What it is
- Mass per metre of conveyor of everything that moves apart from the material: the belt on both runs plus the rotating parts of the idlers.
- Units and format
- Enter a number in kg/m: kilograms per metre of length. The form accepts 0.000001 kg/m to 10000 kg/m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 30 kg/m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Adds to the friction resistance along the length.
- Get it right
- Count both the carrying and return runs of the belt and both sets of idler rolls.
What this means: Overall friction factor
- What it is
- Single overall resistance factor covering idler friction, belt flexing over idlers and material movement, used in the simplified method.
- Units and format
- Enter a plain number with no unit. The form accepts 0.005 to 0.2. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.025 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Friction resistance rises in proportion.
- Get it right
- Take it from the conveyor standard or belt maker for your idler quality and alignment.
What this means: Drive pulley friction coefficient
- What it is
- Friction coefficient between the belt underside and the drive pulley surface, which limits how much tension the pulley can transmit without slipping.
- Units and format
- Enter a plain number with no unit. The form accepts 0.05 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.35 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Higher friction lowers the minimum slack-side tension needed.
- Get it right
- Lagged pulleys grip better than bare steel; wet or dirty conditions lower it.
What this means: Wrap on the drive pulley
- What it is
- Angle of the drive pulley circumference in contact with the belt. Snub pulleys increase it.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 90° to 360°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More wrap lowers the minimum slack-side tension needed.
- Get it right
- Measure the contact arc on the drive pulley only, in degrees.
What this means: Drive pulley diameter
- What it is
- Diameter of the drive (head) pulley, including any lagging. It turns belt tension into torque and belt speed into pulley rpm.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 5000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Pulley torque rises and pulley speed falls in proportion to diameter.
- Get it right
- Include lagging thickness on both sides in the diameter.
What this means: Drive efficiency
- What it is
- Combined efficiency of the gearbox, couplings and any belt drive between motor and drive pulley.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 30% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 90% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Lower efficiency raises the motor power needed.
- Get it right
- Multiply the efficiencies of each stage; type the percentage.
What this means: Motor margin
- What it is
- Extra motor power above the calculated requirement, to cover start-up, surges and uncertainty in the friction factor.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Motor power rises in proportion to 1 + margin.
- Get it right
- Type a percentage of the calculated power; your standards or the conveyor maker set it.
Method and formulas
- Material load q = Q ÷ (3.6 v) kg/m.
- Effective tension T_e = f g L (q + q_m) + q g H.
- Power = T_e v; motor = power ÷ η × (1 + margin).
- No slip: slack tension T₂ ≥ T_e ÷ (e^(μθ) − 1); tight tension T₁ = T₂ + T_e (Euler); pulley torque = T_e D ÷ 2.
- Example: 100 t/h at 1.5 m/s over 50 m with 5 m lift needs about 2.7551 kW at the motor.
Limitations
- Single overall friction factor; detailed design uses the full DIN 22101 or CEMA method.
- Starting tensions are higher; check belt strength at start-up.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Estimate motor size for a belt conveyor
- Set take-up tension to stop belt slip
- Check a conveyor after raising its throughput
Who it is for
- Materials-handling engineers
- Plant engineers
- Maintenance engineers
What you get
- Material load and effective tension
- Power at pulley and motor
- Belt tensions, pulley torque and speed
Interpreting the result
- On long horizontal conveyors friction dominates; on short steep ones lift dominates.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2487–2512. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
The motor at low and high speed
In Variable-Speed Drives by the Numbers
What it covers: How load torque changes with speed for conveyors, fans and pumps, why a self-cooled motor overheats at low speed under constant torque, and what field weakening gives above rated speed.
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