In body jig systems and automated equipment — whether you’re moving a welding gun along a slide or pushing heavy components into position — the combination of a servo motor (or stepper motor) + reducer + rack & pinion (or timing belt) is one of the most common drive configurations you’ll encounter on the shop floor.
“If I run a 1,800 RPM motor through a 1/20 reducer with a Ø50 mm gear, how far does it travel per second — and how much push force does it generate?”
This is exactly the kind of sanity check every equipment designer needs before committing to a spec. No manual number-crunching required — just enter the specs into the calculator below and get your answers instantly.
1. How Motor Rotation Becomes Linear Speed and Force
- Output RPM and Linear Speed: Divide the motor’s rated RPM by the reducer ratio to find the final gear RPM. Multiply that by the gear’s circumference (π × pitch circle diameter) to get the linear travel speed in mm/min.
- Output Torque and Linear Thrust: Adding a reducer trades speed for torque — the output torque is amplified by the reduction ratio. Dividing that amplified torque by the gear’s radius converts it into a linear thrust force acting on the load.
A 10× torque multiplier doesn’t mean 100% of that force makes it through. Friction losses at the gear mesh mean real-world mechanical efficiency typically falls between 80% and 95%. Always factor in efficiency when calculating actual output force.
2. Motor Drive Spec Calculator
Enter the rated specs from your motor catalog, reducer datasheet, and gear geometry below. (Default values are based on a typical 400W servo motor.)
A Final Note: What to Watch Out for in Real-World Design
The thrust values produced by this calculator are theoretical figures based on the motor’s rated specifications. When selecting components for actual equipment, there are two additional factors you should always account for:
- Peak torque during acceleration and deceleration: When a machine starts from a standstill or comes to a hard stop, it must overcome inertial load — and that demands significantly more torque than the rated value. Make sure your drive system has enough headroom to handle these transient peaks.
- External friction and resistance: Rolling friction from LM guides, drag from cable carriers, and the dead weight of the load itself are all resistances that aren’t accounted for in the basic calculation.
Rather than cutting it close and selecting a motor that barely meets the calculated thrust, the safest engineering practice is to apply a safety factor of 1.5× to 2× over the calculated thrust when finalizing your motor and reducer specs.