You are here: Home » Blog » Conveyor Gearbox Selection Guide: Ratio, Torque, Mounting and Load Conditions
Conveyor Gearbox Selection Guide: Ratio, Torque, Mounting and Load Conditions
Views: 0 Author: Site Editor Publish Time: 2026-08-04 Origin: Site
A conveyor gearbox converts motor speed into the lower output speed and higher torque required to move belts, rollers, chains, buckets, or screws. Selecting the wrong ratio, torque capacity, mounting arrangement, or service factor can cause belt slippage, overheating, shaft damage, and unplanned downtime.
A reliable conveyor gear motor must match the required conveyor speed, starting torque, continuous torque, duty cycle, output shaft arrangement, installation space, and environment—not only the motor power.
This guide explains how to determine ratio, estimate torque, evaluate load conditions, select a mounting method, and compare common industrial conveyor gearbox designs. It also describes how Victory supports conveyor manufacturers, OEMs, distributors, and industrial users with complete gearbox and motor solutions.
Why Motor Power Alone Is Not Enough
A 5.5 kW motor can be connected to gearboxes with very different ratios, output speeds, torque ratings, housing sizes, and thermal capacities. With a 10:1 gearbox, it may drive a relatively fast conveyor. With a 50:1 gearbox, the same motor may provide much lower speed and much higher torque.
Selecting a conveyor gearbox only by motor power can cause incorrect belt speed, insufficient starting torque, excessive temperature, poor service life, or installation problems.
A complete conveyor gearbox selection should evaluate the motor, gearbox, pulley or sprocket, coupling, conveyor load, operating schedule, and surrounding environment as one drive system.
Information Required for Selection
Collect the following information before selecting an industrial conveyor gearbox:
Conveyor type and maximum load
Motor power and rated speed
Required belt, chain, or screw speed
Pulley or sprocket diameter
Required gearbox output speed
Horizontal, inclined, or vertical operation
Empty or loaded starting
Operating hours and starts per hour
Reversing or braking requirements
Mounting and output shaft arrangement
Ambient temperature, dust, water, or corrosion
For a replacement conveyor gear motor, also provide motor and gearbox nameplate photographs, overall photos, and installation dimensions.
How to Determine Conveyor Gearbox Ratio
What Is Gear Ratio?
Gear ratio is the relationship between input speed and output speed. It may appear as i = 25, ratio 25:1, or reduction ratio 25.
Gear ratio = Motor rated speed ÷ Required output speed
If a motor runs at 1450 rpm and the required gearbox output speed is 58 rpm:
1450 ÷ 58 = 25
The required ratio is approximately 25:1.
Use Rated Motor Speed
Use the rated speed on the motor nameplate instead of synchronous speed. A four-pole motor at 50 Hz has a synchronous speed of 1500 rpm, but its rated speed is normally around 1430–1470 rpm. At 60 Hz, it is commonly 1720–1770 rpm rather than exactly 1800 rpm.
The difference may affect dosing conveyors, packaging lines, food processing equipment, and synchronized production machinery.
Calculating Output Speed
Output speed = Motor rated speed ÷ Gear ratio
For a 1750 rpm motor with a ratio of 20:
1750 ÷ 20 = 87.5 rpm
Output Speed and Belt Speed
Gearbox output speed is not the same as conveyor belt speed. Belt speed also depends on drive pulley diameter.
Belt speed = π × Pulley diameter × Pulley speed
For a 0.3 m pulley rotating at 60 rpm:
3.1416 × 0.3 × 60 = 56.5 m/min
The required conveyor speed can be adjusted through gearbox ratio, pulley diameter, motor speed, or VFD frequency.
Selecting a Standard Ratio
The exact calculated ratio may not be available. If the calculated value is 24.7 and the available ratios are 23.8, 25.1, and 26.4, compare their actual output speeds and choose the nearest acceptable option.
A VFD can provide additional adjustment, but the conveyor gear motor must remain within the permitted motor and gearbox speed ranges.
How to Calculate Conveyor Gearbox Torque
Output Torque from Motor Power
Approximate output torque can be calculated as:
Output torque (Nm) = 9550 × Motor power (kW) × Gearbox efficiency ÷ Output speed (rpm)
For a 7.5 kW motor, 60 rpm output speed, and 95% efficiency:
9550 × 7.5 × 0.95 ÷ 60 ≈ 1134 Nm
The selected conveyor gearbox should have a rated torque above the calculated operating torque after applying the required service factor.
Operating Torque and Starting Torque
A loaded conveyor normally requires more torque during startup than during steady operation. Starting torque may increase because of static friction, belt tension, material already on the conveyor, packed material in a screw conveyor, large inertia, or an inclined load.
Loaded Starting
A conveyor that starts empty has a different requirement from one that frequently starts under full load. For loaded starts, the motor, gearbox, coupling, shaft, key, and pulley must all withstand peak torque.
A gearbox may operate normally after startup but still fail if repeated starting torque exceeds its allowable peak value.
Acceleration Time
Fast acceleration increases torque demand. A soft starter or VFD can reduce shock by extending acceleration time. The drive must still provide enough low-speed torque, and prolonged low-frequency operation may require an independently cooled motor.
Service Factor
Service factor provides a margin between actual load and gearbox capacity. It depends on conveyor type, operating hours, starting frequency, shock loading, reversing, ambient temperature, and reliability requirements.
A light conveyor operating eight hours per day may need a lower service factor than a mining conveyor or bucket elevator operating continuously.
Because manufacturers may calculate service factor differently, also compare rated torque, peak torque, and thermal capacity.
How Load Conditions Affect Selection
Uniform Load
Packaging conveyors, assembly lines, carton conveyors, and light roller conveyors usually have stable resistance and relatively low shock. Starting torque and operating hours still need to be checked.
Moderate Shock Load
Warehouse conveyors, food processing lines, inclined belt conveyors, and chain conveyors may experience changing material flow. The conveyor gear motor should include sufficient capacity for temporary load increases.
Heavy Shock Load
Mining, quarry, scrap, timber, and crusher discharge conveyors may experience repeated torque peaks, vibration, contamination, and long operating hours.
A larger helical gearbox or bevel helical gearbox may be required even if a smaller unit appears adequate from motor power alone.
Inclined and Vertical Conveyors
Inclined conveyors must overcome both friction and gravity. Vertical conveyors and bucket elevators may move backward when power is removed.
These applications may require a brake motor, backstop, higher service factor, controlled starting and stopping, or an emergency holding system. The backstop direction must be confirmed before installation.
Reversing Conveyors
Repeated reversal adds stress to gears, shafts, keys, couplings, and the conveyor frame. Confirm reversal frequency, load during reversal, acceleration and deceleration times, brake requirements, and peak torque.
Jammed Conveyor Conditions
Bulk material conveyors may become blocked by wet, frozen, oversized, or compacted material. A jam can create torque far above the normal operating level.
Protection may include motor overload protection, a torque limiter, fluid coupling, VFD current limit, shear pin, speed monitoring, or an emergency shutdown.
Selecting the Correct Conveyor Gearbox Type
Inline Helical Gearbox
Inline helical gearboxes are widely used for belt, roller, packaging, and food processing conveyors.
Their advantages include high efficiency, low noise, compact construction, multiple ratios, and good continuous-duty performance. They are suitable when the motor can be installed behind the conveyor drive shaft.
Parallel Shaft Helical Gearbox
A parallel shaft helical gearbox allows the motor to sit parallel to the conveyor shaft. It is suitable for long belt conveyors, overhead conveyors, space-restricted installations, and shaft-mounted drives.
Common configurations include foot mounting, flange mounting, hollow shaft, shrink disc, and torque arm.
Bevel Helical Gearbox
A bevel helical gearbox changes the transmission direction by approximately 90 degrees. It is often selected when the motor must be installed beside the conveyor.
It is suitable for heavy belt conveyors, mining conveyors, bucket conveyors, chain conveyors, and compact material handling systems. Solid-shaft, hollow-shaft, shrink-disc, flange, foot, and torque-arm versions are available.
Helical Worm Gearbox
A helical worm gearbox combines a helical input stage with a worm stage. It can be used for moderate-torque conveyors, packaging machinery, and compact right-angle drives.
Its efficiency is generally higher than that of a basic single-stage worm gearbox at a similar total ratio, although performance still depends on ratio and operating conditions.
NMRV Worm Gearbox
NMRV worm gearboxes are common in small belt conveyors, packaging lines, light roller conveyors, and food processing machines.
They offer compact right-angle construction, simple installation, wide ratio availability, and competitive cost. However, heat generation and efficiency must be checked, especially at high ratios or during continuous operation.
Cycloidal Gearbox
A cycloidal gearbox provides a large reduction ratio in a compact structure. It may be used for slow conveyors, screw conveyors, feeders, and bulk handling equipment.
Cycloidal reducers offer robust load sharing and good overload resistance, but rated torque, service factor, output speed, and mounting position must still be verified.
Selecting the Mounting Arrangement
Foot-Mounted Gearbox
A foot-mounted gearbox is bolted to a rigid conveyor base. It is common when the gearbox connects through a coupling or when the drive pulley shaft has external bearings.
The base must be flat and rigid. Poor alignment can cause vibration, bearing damage, coupling wear, and shaft failure.
Flange-Mounted Gearbox
A flange-mounted gearbox connects directly to the conveyor frame or driven equipment.
Confirm the flange diameter, pilot diameter, bolt circle, hole quantity and size, and output shaft dimensions. The structure must support the complete motor and gearbox weight.
Shaft-Mounted Gearbox
A shaft-mounted gearbox installs directly onto the conveyor drive shaft through a keyed hollow shaft, shrink disc, bushing, or locking assembly. A torque arm prevents the housing from rotating.
Data Required for Shaft Mounting
Confirm:
Conveyor shaft and hollow-shaft diameters
Keyway dimensions
Shaft insertion length
Torque-arm position
Motor direction and installation side
Available clearance
The conveyor shaft and key must also withstand continuous and peak torque.
Vertical and Special Mounting Positions
Mounting position affects oil quantity, oil level, breather position, drain plug location, bearing lubrication, and seals.
A gearbox supplied for horizontal mounting should not be installed vertically without confirmation. Vertical output shafts may need additional lubrication arrangements.
Thermal Capacity and Environment
Continuous Operation
A conveyor gearbox operating 24 hours per day must dissipate heat continuously. Thermal performance depends on efficiency, power, ratio, speed, ambient temperature, airflow, lubricant, and mounting position.
A gearbox may have sufficient mechanical torque capacity but insufficient thermal capacity.
Dust, Water, and Hazardous Areas
Mining, cement, grain, timber, and aggregate conveyors may require IP55 or higher motor protection, reliable seals, and protected breathers.
Outdoor or washdown conveyors may require IP65 or IP66 protection, corrosion-resistant paint, special seals, suitable cable glands, or food-grade lubricant.
Conveyors handling combustible dust, gas, chemicals, grain, coal, or powder may require an explosion-proof conveyor gear motor. Confirm the hazardous zone, gas or dust group, temperature class, and required certification.
Common Selection Mistakes
Common mistakes include selecting only by motor power, ignoring loaded starting torque, changing pulley diameter without recalculating speed and torque, using the wrong mounting position, and replacing a gearbox by model number alone.
A gearbox that works for short periods may also overheat during continuous service. Worm gearboxes should not automatically be treated as self-locking; use a brake or backstop where reverse movement creates a safety risk.
Step-by-Step Conveyor Gearbox Selection
Step 1: Identify the Conveyor
Determine whether it is a belt, roller, chain, screw, bucket, inclined, or reversing conveyor.
Step 2: Determine Output Speed
Use the required conveyor speed and pulley or sprocket dimensions to calculate gearbox output speed.
Step 3: Calculate Ratio and Torque
Divide motor rated speed by required output speed, then calculate operating torque and select the nearest standard ratio.
Step 4: Check Starting and Service Conditions
Confirm whether the conveyor starts empty or loaded. Consider shock, jams, reversing, operating hours, and starting frequency.
Step 5: Select Gearbox Type and Mounting
Compare inline helical, parallel shaft, bevel helical, worm, and cycloidal gearboxes. Confirm foot, flange, solid-shaft, hollow-shaft, or torque-arm installation.
Step 6: Confirm Environment and Drawings
Check temperature, dust, water, corrosion, food-grade, or hazardous-area requirements. For replacement projects, approve the gearbox drawing before production.
How Victory Supports Conveyor Gearbox Projects
Victory Machinery Technology Co., Ltd. supplies industrial conveyor gearboxes, conveyor gear motors, and IEC electric motors for conveyor manufacturers, OEM equipment builders, distributors, maintenance companies, and industrial plants.
Options include customized voltage, frequency, shaft, flange, mounting position, terminal box, paint, nameplate, PTC or PT100 protection, and anti-condensation heaters.
Replacement and OEM Support
When the original conveyor gearbox is discontinued, unavailable, or too expensive, Victory can evaluate an equivalent based on ratio, output speed, torque, service factor, mounting, dimensions, and application duty.
Victory can recommend a standard model where possible or evaluate customized shafts and flanges when direct replacement is required.
With 22 years of manufacturing experience, Victory also supports OEM nameplates, custom paint, technical datasheets, outline drawings, samples, batch production, quality inspection, CE and ISO9001 documentation, and an 18-month warranty.
Information to Provide
For an initial recommendation, provide:
Conveyor type
Motor power and rated speed
Required output speed or ratio
Pulley or sprocket diameter
Maximum load and inclination
Operating hours and starts per hour
Mounting and shaft dimensions
Environmental conditions
For replacement projects, also provide nameplate photos, overall photos, and installation dimensions.
FAQ About Conveyor Gearbox Selection
What Gear Ratio Is Best for a Conveyor?
The correct ratio depends on motor rated speed, required output speed, and pulley or sprocket diameter. There is no universal ratio.
How Do I Calculate Conveyor Gearbox Torque?
Use:
Torque = 9550 × Power × Efficiency ÷ Output Speed
Also consider starting torque and service factor.
Which Gearbox Is Best for a Belt Conveyor?
Inline helical, parallel shaft, and bevel helical gearboxes are common choices. The best type depends on torque, layout, mounting, and available space.
Can I Use a Worm Gearbox?
Yes, especially for compact and light-duty conveyors. Check efficiency, heat generation, starting torque, and continuous operating time.
What Is a Shaft-Mounted Conveyor Gearbox?
It connects directly to the conveyor drive shaft through a hollow shaft, shrink disc, bushing, or keyed connection. A torque arm prevents the housing from rotating.
Does an Inclined Conveyor Need a Brake?
Many inclined conveyors require a brake, backstop, or both to prevent unintended reverse movement.
Why Does a Conveyor Gearbox Overheat?
Common causes include overloading, excessive input speed, incorrect oil level, unsuitable lubricant, poor ventilation, wrong mounting position, or insufficient thermal capacity.
Can Another Brand Replace the Original Gearbox?
Yes, provided the ratio, torque, service factor, mounting, dimensions, and operating conditions are correctly matched.
Conclusion
Correct conveyor gearbox selection requires a complete review of ratio, output speed, torque, mounting, service factor, load, and environment.
Motor power alone is not enough. Loaded starting, continuous operation, inclination, reversing, shock, and possible jamming must also be considered.
Inline helical gearboxes suit many general conveyors, while parallel shaft and bevel helical gearboxes are often preferred for compact or heavy-duty systems. Worm and cycloidal gearboxes can also be effective when selected according to efficiency, torque, ratio, and duty.
By providing the conveyor type, motor power, output speed, load condition, mounting position, and installation dimensions, customers can obtain a more accurate gearbox selection.
Victory can help conveyor manufacturers, distributors, and industrial users select or replace a complete conveyor gearbox and motor solution, including standard gear motors, customized shafts and flanges, VFD motors, brake motors, and explosion-proof conveyor gear motors.
