Stepper speed, torque and positioning calculator

Static torque demand with supplied speed-derated available torque.

motors-stepper.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	demandN*m	margin
	0.4	2
	0.34	2.35294

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

torque margin target2.00 ✓ passes

BASELINE INPUTS

loadTorque0.3 N*minertia0.0002 kg*m^2acceleration500 rad/s^2available0.8 N*m

CALCULATED

demand0.4 N*m

margin2

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Stepper speed, torque and positioning
# Scope: Static torque demand with supplied speed-derated available torque.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

loadTorque = 0.3 N*m
inertia = 0.0002 kg*m^2
acceleration = 500 rad/s^2
available = 0.8 N*m

demand := loadTorque+inertia*acceleration [N*m]
margin := available/demand

check torque margin target: margin >= 1.5

scenario alternative: loadTorque = 0.24 N*m

Calculated from your source · not saved

Baseline · Baseline

torque margin target2.00 ✓ passes

alternative · alternative

torque margin target2.35 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

demand: demand = loadTorque+inertia*acceleration [N*m]
margin: margin = available/demand

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

load torque: 0.3 N*m
inertia: 0.0002 kg*m^2
acceleration: 500 rad/s^2
available: 0.8 N*m

Calculated

demand: 0.4 N*m
margin: 2

Assumptions and limits

Static torque demand with supplied speed-derated available torque.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Stepper speed, torque and positioning. Inputs: load; inertia; acceleration; torque-speed data. Outputs: required torque; increment; speed limits. Model scope: Motor and load parameters with explicit operating limits. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: load, inertia, acceleration, torque-speed data
Outputs: required torque, increment, speed limits
Modes: calculate, compare, sweep
Drawing: Torque-speed and duty plots

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS