Cast Iron NMRV Gearbox Selection Guide – How to Choose the Right Heavy Duty Model

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H1: Cast Iron NMRV Gearbox – 4-Step Selection Guide

Step 1 – Determine your ratio
Ratio = Motor RPM ÷ Desired Output RPM

Example: 1,400 RPM motor, need 20 RPM output → 1,400 ÷ 20 = 70:1-

Step 2 – Calculate required torque
Output Torque (Nm) = Motor Torque × Ratio × Efficiency

Always apply service factor for shock loads – heavy duty applications require higher SF

Step 3 – Match to frame size

Required Torque	Recommended Model
Up to 1,050 N·m	NMRV110
Up to 1,550 N·m	NMRV130
Up to 2,700 N·m	NMRV150

Step 4 – Confirm configuration

• Input: Hollow bore with B5 flange (standard) or shaft input (NRV)

• Output: Solid shaft, hollow shaft, or flange

• Mounting: Foot, flange, or torque arm

FAQ

Q: What happens if I choose the wrong frame size?
A: Undersizing leads to overheating, premature wear, and failure. Always select based on required torque + service factor, not motor power alone.

Q: How do I know if I need cast iron or aluminum?
A: Cast iron for NMRV110-150. If your torque requirement exceeds 1,000 N·m or your application has shock/vibration, cast iron is mandatory