Crank-rocker Grashof screening calculator

Link length screening for a Grashof crank-rocker; fixed link choice remains explicit.

linkages-crank-rocker.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	marginmm
	10
	14

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.

length screening10.00 mm✓ passes

BASELINE INPUTS

crank20 mmcoupler60 mmrocker50 mmground40 mm

CALCULATED

margin10 mm

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Crank-rocker feasibility
# Scope: Link length screening for a Grashof crank-rocker; fixed link choice remains explicit.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

crank = 20 mm
coupler = 60 mm
rocker = 50 mm
ground = 40 mm

margin := ground+rocker-crank-coupler [mm]

check length screening: margin >= 0 mm

scenario alternative: crank = 16 mm

Calculated from your source · not saved

Baseline · Baseline

length screening10.00 mm ✓ passes

alternative · alternative

length screening14.00 mm ✓ 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.

margin: margin = ground+rocker-crank-coupler [mm]

Original worked example

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

Given

crank: 20 mm
coupler: 60 mm
rocker: 50 mm
ground: 40 mm

Calculated

margin: 10 mm

Assumptions and limits

Link length screening for a Grashof crank-rocker; fixed link choice remains explicit.

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: Crank-rocker feasibility. Inputs: link lengths; ground link; input rotation. Outputs: Grashof classification; rocker sweep. Model scope: Planar rigid-link geometry with explicit joints and branches. 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: link lengths, ground link, input rotation
Outputs: Grashof classification, rocker sweep
Modes: calculate, compare, sweep
Drawing: Interactive linkage

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