Eccentrically loaded bolt group calculator

Equal-radius circular group: direct and moment loads conservatively added.

fasteners-bolt-group.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	directN	momentForceN	maximumN
	250	166.667	416.667
	200	166.667	366.667

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.

bolt load budget416.67 N✓ passes

BASELINE INPUTS

load1000 Nmoment20 N*mcount4 radius30 mm

CALCULATED

direct250 N

momentForce166.67 N

maximum416.67 N

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Eccentrically loaded bolt group
# Scope: Equal-radius circular group: direct and moment loads conservatively added.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

load = 1000 N
moment = 20 N*m
count = 4
radius = 30 mm

direct := load/count [N]
momentForce := moment/(count*radius) [N]
maximum := direct+momentForce [N]

check bolt load budget: maximum <= 600 N

scenario alternative: load = 800 N

Calculated from your source · not saved

Baseline · Baseline

bolt load budget416.67 N ✓ passes

alternative · alternative

bolt load budget366.67 N ✓ 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.

direct: direct = load/count [N]
moment force: momentForce = moment/(count*radius) [N]
maximum: maximum = direct+momentForce [N]

Original worked example

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

Given

load: 1000 N
moment: 20 N*m
count: 4
radius: 30 mm

Calculated

direct: 250 N
moment force: 166.667 N
maximum: 416.667 N

Assumptions and limits

Equal-radius circular group: direct and moment loads conservatively added.

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: Eccentrically loaded bolt group. Inputs: bolt coordinates; force; applied moment. Outputs: individual bolt loads. Model scope: Explicit load paths, preload uncertainty and joint stiffness. 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: bolt coordinates, force, applied moment
Outputs: individual bolt loads
Modes: calculate, compare, sweep
Drawing: Joint load diagram

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