CALCULATORS / VEHICLES AND GROUND TRANSPORT

Suspension ride and travel calculator

Single corner linear spring static sag and natural frequency; damping omitted.

vehicles-suspension.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

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

Scenario	sagmm	frequencyHz
	16.35	3.89848
	13.08	4.35864

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.

sag budget16.35 mm✓ passes

BASELINE INPUTS

mass25 kgrate15 N/mmgravity9.81 m/s^2

CALCULATED

sag16.35 mm

frequency3.8985 Hz

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Suspension ride and travel
# Scope: Single corner linear spring static sag and natural frequency; damping omitted.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

mass = 25 kg
rate = 15 N/mm
gravity = 9.81 m/s^2

sag := mass*gravity/rate [mm]
frequency := sqrt(rate/mass)/(2*pi) [Hz]

check sag budget: sag <= 25 mm

scenario alternative: mass = 20 kg

Calculated from your source · not saved

Baseline · Baseline

sag budget16.35 mm ✓ passes

alternative · alternative

sag budget13.08 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.

sag: sag = mass*gravity/rate [mm]
frequency: frequency = sqrt(rate/mass)/(2*pi) [Hz]

Original worked example

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

Given

mass: 25 kg
rate: 15 N/mm
gravity: 9.81 m/s^2

Calculated

sag: 16.35 mm
frequency: 3.89848 Hz

Assumptions and limits

Single corner linear spring static sag and natural frequency; damping omitted.

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: Suspension ride and travel. Inputs: sprung mass; spring and damping; motion ratio. Outputs: ride frequency; sag; travel demand. Model scope: Longitudinal vehicle models with declared road and drivetrain losses. 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: sprung mass, spring and damping, motion ratio
Outputs: ride frequency, sag, travel demand
Modes: calculate, compare, sweep
Drawing: Road-load and range plots

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