Gear motor drive assembly

01

Choose the ratio and check torque

AutomationDirect's gearbox guide explains that a gearbox reduces speed by its ratio and increases torque by the same ratio while power stays the same less efficiency losses: a 10:1 gearbox gives roughly motor speed divided by 10 and motor torque multiplied by 10. [1]

As an editorial calculation example only: a drum that needs 500 N·m at 36 rpm absorbs about 500 × 36 × 2π ÷ 60 ≈ 1.9 kW at the output shaft. With a 1,450 rpm motor the ratio is about 40:1; the motor power then depends on gearbox efficiency, as shown below.

Ask the supplier for rated output torque, output speed at your supply frequency and the actual (not nominal) ratio.

02

Apply a service factor for duty and shock

AutomationDirect's service-factor table for electric-motor-driven gearboxes ranges from 1.00 for uniform loads run occasionally or under 3 hours a day, through 1.25 for moderate shock at 3–10 hours, to 2.00 for extreme shock over 10 hours; shock includes sudden stopping, restarting or reversing, heavy loads dropped onto a conveyor and impact loads such as punch presses. [2]

It instructs dividing the gearbox power, overhung load and maximum mechanical capacity ratings by the applicable service factor. [2]

Continuing the editorial example: at moderate shock for 3–10 hours a day (service factor 1.25), the gearbox should be rated for at least 500 × 1.25 = 625 N·m at the output.

Give the supplier the driven machine, its load type, hours per day, starts per hour, reversing and any shock, so the service factor is chosen with the right table for its product.

03

Check overhung load from pulleys, sprockets and pinions

AutomationDirect rates overhung load as a force perpendicular to the output shaft at its midpoint, from a gear, pulley or sprocket, and divides the rating by a K factor for the drive type: 1.00 for chain and sprocket, 1.25 for gear, 1.50 for V-belt, 2.50 for flat belt and 3.50 for variable-pitch belt, as well as by the service factor. [2] [1]

Give the supplier the pitch diameter of the pulley, sprocket or pinion and its distance from the gearbox face, or ask for a flexible coupling and separate bearings where the side load is too high, as on drum and girth-gear drives.

04

Compare worm and helical efficiency

In AutomationDirect's cast-iron worm gearbox tables, listed efficiency falls as ratio rises: for one frame size, 93% at 5:1, 88% at 10:1, 83% at 20:1, 62% at 40:1 and 52% at 60:1. Its helical-bevel gearboxes are listed at 91%. [1] [2]

Completing the editorial example: delivering 1.9 kW through a 40:1 worm at 62% needs about 3.1 kW from the motor, against about 2.1 kW through a helical-bevel unit at 91%. Over long running hours the difference becomes an energy and heat question as well as a sizing one.

AutomationDirect also lists separate mechanical and thermal ratings for worm gearboxes, the thermal rating being the limit for continuous use without overheating. Ask for both, at your ambient temperature and duty. [1]

05

Compare what suppliers offer

Suppliers linked to this page list AC helical and helical-bevel gear motors, worm and planetary gear motors, BLDC gear motors and planetary gearboxes. [3] [4] [5]

Shengjie lists inline, parallel-shaft, helical-bevel and helical-worm gear motors; DMK lists BLDC planetary, worm, hypoid and parallel-shaft gear motors; ZGC lists brushed planetary and spur gear motors for small drives. [4] [5] [6]

06

Trace the drive assembly components

This is a functional reference built from the sources cited; it is not one maker's parts list.

07

Fill the specification fields with values for your drive

A gear drive quotation needs drive-specific values. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

08

Send the load, duty and mounting data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Load: [output torque; output speed; driven machine; inertia]
Duty: [hours per day; starts per hour; reversing; shock type]
Drive: [motor speed; supply; ratio; efficiency target]
Output: [pulley, sprocket or pinion size and position; axial load]
Mounting: [foot, flange or shaft-mounted; orientation; base frame]
Environment: [ambient temperature; washdown; IP rating]
Documents: [rating table with service factor; thermal rating; drawing]

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