BIZOMAT MAKEOS · Power Transmission
Conveyor Drive Train Check (Belt Pull, Motor Power, Reducer Ratio, Gearbox Torque)
For a belt conveyor driven through a gear reducer, is the motor big enough, does the reducer ratio give the right belt speed, and is the gearbox rated for the pulley torque?
Check of a belt conveyor drive train: the load per metre, effective belt pull from friction and lift, the power at the pulley and at the motor with efficiency and margin, the tight and slack side tensions, the pulley torque and speed (as the conveyor drive sizing tool), then the reducer ratio needed from the motor speed, the belt speed with the reducer you have, and the pulley torque with a service factor against the gearbox rating.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Throughput | t/h | Material carried per hour. |
| Design belt speed | m/s | Belt speed the conveyor is designed for. |
| Conveyor length (centres) | m | Length between the terminal pulley centres. |
| Lift (positive up) | m | Height the material is lifted (negative for downhill). |
| Belt and idler moving mass per metre (both runs) | kg/m | Mass per metre of the belt and rotating idler parts, both runs. |
| Overall friction factor | Overall friction factor for the idlers and belt (about 0.02–0.03). | |
| Drive pulley friction coefficient | Friction between the belt and the drive pulley (lagged pulleys are higher). | |
| Wrap on the drive pulley | ° | Angle of wrap of the belt on the drive pulley. |
| Drive pulley diameter | mm | Diameter of the drive pulley. |
| Drive efficiency | % | Efficiency of the reducer and couplings. |
| Power margin | % | Extra power for starting and uncertainty. |
| Motor and reducer | ||
| Motor speed | rpm | Full-load speed of the motor. |
| Reducer ratio fitted | Ratio of the reducer you have or propose. | |
| Belt speed tolerance | % | How far the belt speed may differ from the design speed. |
| Motor power fitted | kW | Rated power of the motor fitted. |
| Gearbox rated output torque | N·m | Rated output torque of the gearbox. |
| Gearbox service factor | Service factor on the gearbox for the conveyor duty and hours. | |
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
- The mass of material the conveyor carries per hour at its design rate. With the belt speed it gives the load on each metre of belt.
- 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
- The load per metre, belt pull and power rise with the throughput.
- Get it right
- Enter it in tonnes per hour of material, not a volume rate; convert with the bulk density if needed.
What this means: Design belt speed
- What it is
- The belt speed the conveyor is designed to run at. It sets the load per metre, the power at the pulley and the pulley speed.
- 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
- For the same throughput a faster belt carries less load per metre; the pulley speed rises with belt speed.
- Get it right
- Enter it in metres per second; a speed in m/min must be divided by 60.
What this means: Conveyor length (centres)
- What it is
- The length of the conveyor between the centres of the head and tail pulleys. Friction pull is worked over this length.
- 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
- The friction part of the belt pull rises in direct proportion to length.
- Get it right
- Use the length between pulley centres, not the belt length, which is about twice as long.
What this means: Lift (positive up)
- What it is
- The vertical height the material is raised from loading point to discharge. A negative value means the conveyor runs downhill.
- 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 pull equal to the weight of the load per metre.
- Get it right
- Use the vertical rise, not the length along the slope.
What this means: Belt and idler moving mass per metre (both runs)
- What it is
- The mass per metre of conveyor length of the belt and the rotating idler parts, counting both the carrying and return runs.
- 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
- A heavier belt and idler mass raises the friction pull and power.
- Get it right
- Include both runs of belt and the turning parts of the idlers, not the idler frames.
What this means: Overall friction factor
- What it is
- An overall friction factor covering idler rolling resistance, belt flexing and similar losses along the conveyor, from a conveyor design standard or the idler maker.
- 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
- The friction part of the belt pull rises in direct proportion to the factor.
- Get it right
- This is the overall conveyor factor, not the belt-to-pulley friction coefficient entered below.
What this means: Drive pulley friction coefficient
- What it is
- The friction coefficient between the belt and the drive pulley face, which sets how much pull the pulley can transmit without slipping. Lagged pulleys grip better.
- 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 slack and tight side tensions needed.
- Get it right
- Use the value for the pulley surface you have, bare or lagged, and for wet conditions if they occur.
What this means: Wrap on the drive pulley
- What it is
- The angle of contact of the belt round the drive pulley, larger when a snub pulley is used.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 90° to 480°. 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 slack and tight side tensions needed.
- Get it right
- Enter it in degrees, not radians.
What this means: Drive pulley diameter
- What it is
- The outside diameter of the drive pulley the belt wraps round. It sets the pulley torque and the pulley speed.
- 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
- A larger pulley raises the pulley torque and lowers its speed for the same belt speed.
- Get it right
- Include the lagging thickness if the pulley is lagged.
What this means: Drive efficiency
- What it is
- The share of motor power passed to the drive pulley through the reducer and couplings, from the gearbox maker’s data.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 10% 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 in inverse proportion.
- Get it right
- Type the percentage itself, not a fraction.
What this means: Power margin
- What it is
- Extra motor power added above the running requirement for starting, uncertainty and future changes.
- 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 200%. 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
- The motor power needed rises in proportion to one plus this share.
- Get it right
- Type the percentage itself. It changes the motor power needed only, not the gearbox torque.
Motor and reducer
What this means: Motor speed
- What it is
- The full-load speed of the drive motor. It sets the reducer ratio needed and the belt speed with the reducer fitted.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 0.000001 rpm to 100000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1450 rpm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A faster motor needs a higher reducer ratio for the same belt speed.
- Get it right
- Use the full-load speed from the nameplate, not the synchronous speed.
What this means: Reducer ratio fitted
- What it is
- The ratio of the reducer you have or propose: motor speed divided by output speed. The belt speed it gives is compared with the design speed.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 10000. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher reducer ratio lowers the actual belt speed in inverse proportion.
- Get it right
- Use the exact ratio from the gearbox data, not the nominal rounded ratio.
What this means: Belt speed tolerance
- What it is
- How far, above or below, the actual belt speed may differ from the design speed and still pass.
- 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 50%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Type the percentage itself; the band applies equally above and below.
What this means: Motor power fitted
- What it is
- The rated output power of the motor fitted or proposed, from its nameplate. It is compared with the motor power needed.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0.000001 kW to 100000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the rated output power in kW, not the input power.
What this means: Gearbox rated output torque
- What it is
- The rated output torque of the gearbox, from the gearbox maker’s catalogue. The pulley torque times the service factor is compared with it.
- Units and format
- Enter a number in N·m: newton-metres. The form accepts 0.000001 N·m to 100000000 N·m. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 500 N·m as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the catalogue rating at a service factor of 1, since the tool applies your factor separately.
What this means: Gearbox service factor
- What it is
- A multiplier on the pulley torque for the conveyor duty, shock and daily running hours, from the gearbox maker’s selection tables.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 5. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.5 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The gearbox duty torque rises in direct proportion to the factor.
- Get it right
- Take it from the gearbox maker for your driven machine class and hours per day.
Method and formulas
- Load per metre = Q ÷ 3.6v; effective pull = f g L (q_L + q_m) + q_L g H; power = T_e v; motor = power ÷ η × (1 + margin) (as the conveyor drive sizing tool).
- Pulley speed = v ÷ (π D) × 60; ratio needed = motor speed ÷ pulley speed; belt speed with the fitted reducer = π D × motor speed ÷ ratio ÷ 60.
- Pulley torque = T_e D ÷ 2; gearbox duty = torque × service factor.
- Example: 2.7551 kW needed; ratio 20.246 for 1.5 m/s; the fitted 20 : 1 gives 1.5184 m/s and 450.83 N·m gearbox duty.
Limitations
- Steady running with an overall friction factor; detailed resistances and starting need a full conveyor design.
- Power and torque at the design speed.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a conveyor drive before raising throughput
- Pick a reducer ratio for a conveyor
- Check a replacement gearbox
Who it is for
- Bulk handling engineers
- Maintenance engineers
- Plant engineers
What you get
- Belt pull, tensions and power
- Reducer ratio and belt speed
- Motor and gearbox against the duty
Interpreting the result
- The lift term dominates on inclined conveyors; on long flat conveyors friction does.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2487–2512, 2122–2160. Topic reference; no source tables or recommended settings are reproduced.
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