Geared Motors

NMRV series worm drive gearboxes, frame NMRV030 to NMRV130. Ratios 10:1 to 100:1. Aluminium (NMRV030–050) and cast iron (NMRV110–130) housing. B5 face flange input for direct IEC motor mounting. Motor and gearbox combination packs available. In stock Glen Waverley.

HankeMotor stocks NMRV series worm drive gearboxes from frame size NMRV030 to NMRV130, covering reduction ratios of 10:1 through to 100:1. All units feature B5 face flange input for direct IEC motor mounting, stocked at our Glen Waverley, Victoria warehouse. Motor and gearbox combination packs are available for the most common applications.

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NMRV Frame Size and Shaft Specification

Frame size determines physical dimensions, torque capacity, and shaft sizes. Select the frame based on required output torque, then confirm the input shaft matches your motor shaft diameter.

Frame Housing Input Shaft Ratios Available Typical Motor Best For
NMRV030 Aluminium 11 mm 10:1, 30:1 0.25–0.37 kW Light conveyor, shutter drives, small agitators
NMRV040 Aluminium 14 mm 10:1, 100:1 0.37–0.75 kW Gate automation, light conveyor belt take-up
NMRV050 Aluminium 14 mm 40:1, 100:1 0.75–2.2 kW Cement mixers, conveyor drives, irrigation pumps
NMRV110 Cast iron 38 mm 50:1 4–7.5 kW Heavy conveyor, large agitator, mixer paddle
NMRV130 Cast iron 24 mm 100:1 3–5.5 kW Very slow output applications, winch drives

B5 flange mount is standard on all HankeMotor NMRV units. If your motor has a B14 face (small square flange), an adaptor plate is required. 

How to Calculate the Reduction Ratio You Need

The ratio = motor speed ÷ required output shaft speed. Australian motors run at either 1400 RPM (4-pole) or 2800 RPM (2-pole) at 50 Hz. Example: a 1400 RPM motor with a cement mixer drum requiring 35 RPM needs a 1400 ÷ 35 = 40:1 ratio (NMRV050 40:1 is the standard choice for this application).

Ratio Output (1400 RPM input) Output (2800 RPM input) Typical Application
10:1 140 RPM 280 RPM Slower conveyor, light mixer
20:1 70 RPM 140 RPM General purpose conveyor
30:1 47 RPM 93 RPM Slow conveyor, light auger
40:1 35 RPM 70 RPM Cement mixer drum, gate opener
50:1 28 RPM 56 RPM Slow paddle mixer, winch
100:1 14 RPM 28 RPM Very slow output, roll-up door drive

Self-Locking at High Ratios — The Property Most Buyers Miss

NMRV worm gearboxes at ratios of 30:1 and above are self-locking (non-back-drivable): the load cannot rotate the output shaft backward when the motor is off. This is a safety advantage for hoists, gate drives, and vertical lifts — the load holds position without a separate brake. 

This same property is a trap for manual override applications: if you need to hand-crank a machine into position when the motor is off, a 30:1+ worm gearbox will prevent this completely. At 10:1, limited back-driving is possible. If manual override is required, specify a helical or bevel-helical gearbox instead — call us before ordering.

Efficiency Loss at High Ratios — Motor Sizing Implications

Worm gearboxes trade efficiency for compactness. Unlike helical gearboxes at 95%+ efficiency, worm gearboxes lose efficiency as ratio increases due to sliding worm-wheel contact. At high ratios the motor must be oversized to compensate:

Ratio Approx. Efficiency Motor Sizing Note
10:1 85–90% Standard sizing applies
20:1 80–85% Add 15–20% to calculated motor power
40:1 70–75% Add 25–30% — size motor up one step
50:1 65–70% Significant heat under continuous load — ventilation required
100:1 50–60% Not suited for continuous duty at full torque — use two-stage gearbox instead


Worm Gearbox FAQ

What is the difference between NMRV and NRV worm gearboxes?
NMRV has a hollow bore B5 flange input designed for direct IEC motor face mounting — the motor shaft slides into the hollow bore. NRV is the same gear unit but with a solid input shaft instead of a hollow bore, connecting to the motor via a coupling or belt. For most Australian applications pairing directly with an IEC motor, NMRV is the correct choice. NRV suits installations where the motor drives through a belt or coupling rather than direct-mount.
Do worm gearboxes need oil changes?
Yes. NMRV gearboxes are factory-filled with synthetic gear oil. In continuous duty applications, oil should be changed every 2,000 to 5,000 operating hours depending on ambient temperature and load. In intermittent workshop use (less than 4 hours per day), annual oil inspection is sufficient. Check oil level via the sight glass or level plug — low oil is the most common cause of premature worm wheel wear.
Can I use a VFD to control an NMRV gearbox and motor combination?
Yes — worm gearboxes are compatible with VFD-controlled motors. However, at low VFD output frequencies (below 25 Hz), motor fan cooling is reduced and the motor may overheat under continuous load. An inverter-duty motor or independently powered cooling fan is recommended for VFD operation below 25 Hz continuous. Note: VFD variable speed does not eliminate the need for a gearbox — the VFD adjusts speed within a range while the gearbox sets torque multiplication and operating speed band.
What oil type goes in an NMRV worm gearbox?
NMRV gearboxes use ISO VG 220 or ISO VG 460 synthetic or mineral gear oil, depending on the application temperature and duty cycle. Most units are factory-filled with ISO VG 220 synthetic for general workshop temperatures of 0–40°C. In higher ambient temperatures or continuous heavy-duty operation, ISO VG 460 provides a thicker film and better protection for the worm/wheel contact. Do not use engine oil or hydraulic oil.
Can an NMRV gearbox be mounted in any orientation?
No — oil fill and drain positions vary by mounting orientation. NMRV gearboxes have specific mounting codes (M1 through M6) that define which face is the base and which direction the output shaft faces. The oil fill hole is positioned based on the mounting orientation. If you mount a gearbox in an orientation other than its rated mounting code, the oil level sight glass and fill/drain plugs will be in the wrong position, risking insufficient lubrication. Specify the mounting orientation when ordering and confirm it matches your installation.