Free to start, with no payment details required. The free tier includes the double-wishbone template with the core result channels; paid plans unlock the full template catalog, every channel and exports. No uptime or data-retention commitment is made beyond what the Terms of Use set out.

bellcrank

Suspension design, modernized.

Full kinematics and static load analysis. Roll center, anti-squat, bump steer, scrub radius — in the browser, no install, no license key.

Start free View the API docs

Permanent free tier
No payment details to start
No install, no license server

* The app solves the full spatial mechanism, not a planar approximation.

Channel ids the solver post-processor emits — per corner, per step.

solver

It solves your mechanism. It doesn't approximate it.

A constraint-based multibody kinematics and statics solver — the same class of formulation commercial MBS packages use.

Kinematics

Resolved at every step

Nothing is flattened to a sketch. A step with no solution fails loudly instead of guessing.

Anti-geometry

From the solve, not the sweep

Anti-geometry and motion ratios come from the real mechanism, never estimated.

Pinned to references

Checked against known answers

Roll center, instant centers, anti-geometry and statics — pinned against published values and known formulas.

the incumbents

Most suspension software belongs in a museum.

The tools the industry still designs suspension with are desktop software from another era — installed per machine, licensed per seat, barely changed in decades. Your car deserves software from this decade.

Exhibit 001

Desktop suspension software

c. 1985–2012 · compiled for one OS · licensed per install

Once the state of the art. Installed from a CD, tied to a dongle, exported to spreadsheet. Typically found on a single laptop in the shop — the one nobody is allowed to update.

Donated by teams that moved to the browser.

assembly

Model what you actually build.

Seven suspension topologies, four assembly slots per axle, joined into a full vehicle.

Expand a category, then click any image to view it larger.

Suspension 7

Double wishbone, five-link, MacPherson, trailing arm, control blade, live axle.

Double wishbone suspension, rendered in bellcrank's 3D viewer at design pose — Double wishbone front or rear

Five-link suspension, rendered in bellcrank's 3D viewer at design pose — Five-link 4 links + tie rod

MacPherson strut suspension, rendered in bellcrank's 3D viewer at design pose — MacPherson strut front or rear

Trailing arm suspension, rendered in bellcrank's 3D viewer at design pose — Trailing arm rear

Control blade — 2 link suspension, rendered in bellcrank's 3D viewer at design pose — Control blade — 2 link rear

Control blade — 3 link suspension, rendered in bellcrank's 3D viewer at design pose — Control blade — 3 link rear

Live axle — 4-link suspension, rendered in bellcrank's 3D viewer at design pose — Live axle — 4-link rear, triangulated

Steering 2

Rack and pinion, driven at the column through one or two universal joints.

Rack & pinion — three-piece column, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — Rack & pinion — three-piece column 2 universal joints

Rack & pinion — two-piece column, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — Rack & pinion — two-piece column 1 universal joint

Actuation 5

Coilover, damper or spring, direct-acting or via a push/pull-rod bellcrank — including the decoupled heave/roll layout.

Coilover, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — Coilover direct-acting

Damper, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — Damper direct-acting

Spring, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — Spring direct-acting

Push/pull rod, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — Push/pull rod bellcrank

Push/pull rod — decoupled, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — Push/pull rod — decoupled heave + roll

Anti-roll 2

U-bar or T-bar torsion crossbar.

U-bar anti-roll bar, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — U-bar torsion crossbar

T-bar anti-roll bar, rendered in bellcrank's 3D viewer at design pose on a double-wishbone corner — T-bar torsion crossbar

Or start from a car that already exists

Six one-click vehicles

Pick a preset, press Create: bellcrank builds the front axle, rear axle and full vehicle for you. Five FSAE presets plus a Baja SAE preset, all solving on the 7-post rig.

Build one free

motion

Drive it the way you test it.

Five motion types across two rigs. Build the sweep once, reuse it all season.

Motion	Rig	What it drives
Parallel travel	2-post	Both wheels together. Steering pinned centered.
Opposite travel	2-post	A pure roll input. Steering pinned centered.
Steering sweep	2-post	Column angle, through the real column, universal joint(s) and rack ratio.
Custom	2-post	Your own per-step curves for the left post, the right post and steering.
7-post	7-post	Four wheel posts plus chassis heave, roll, pitch and steering — 8 curves on the same steps.

result

Every channel a suspension engineer asks for.

Per corner, per step, straight from the solver's post-processor.

Wheel & axle Camber, toe, wheel travel, contact patch, track.
Centers Roll center and instant centers, front- and side-view.
Steering axis Caster, kingpin inclination, scrub radius, trail and ratio.
Installation Motion ratio, coilover compression, anti-roll-bar torsion.
Raw geometry Every hardpoint and body pose, at every step.
Rig inputs Plot any channel against the real rig input.

load case

Loads, not just motion — and not an upsell.

Kinematics tells you where things go. Statics tells you whether they survive. bellcrank does both, and static force solving — which the desktop incumbents sell as a paid add-on module — is included on every plan.

How it settles

Apply forces and moments at each corner, set chassis heave, roll and pitch, and solve — the car settles the way it would on a real rig.

What comes back

Joint reactions, per-body loads and steering torque — the full load path, rendered in 3D with force and moment arrows you can click through.

compare · export · api

What happens after the run.

Compare

Two or three, side by side

Stacked in one 3D scene, charted together, with color-coded deltas against a baseline you pick — checksum-verified, so you're never comparing stale data.

Export

CSV, CAD — and video

CSV export writes every channel the solver computed. IGES 5.3 hardpoint export drops straight into CATIA or SolidWorks, named and oriented correctly. The 3D viewer captures screenshots and video for design reviews.

API & workspace

Drive it from a script

A full REST API — create a key, hit /v1, and sweep a design space from your own tooling; a single request can queue a whole batch of runs. Workspaces save your dashboard layouts between results.

revisions

Every save is a revision.

Axles, vehicles, motions and load cases carry a git-style, append-only history — checksummed, authored, automatic. No "final_v3_FINAL" files, no versioning ceremony.

History

Browse and restore

Every design change appends an immutable revision — number, checksum, author, timestamp. Load any revision back into the editor and save it to restore; the chain is never rewritten.

Conflicts

No silent overwrites

Every save from the app declares the revision it was built on. If someone else saved first, you get a conflict and a choice — not a quiet last-writer-wins.

Pinning

Pin what must not move

Pin a vehicle's axle slots to exact revisions — the 3D preview and every simulation compose precisely what you pinned, while unpinned slots follow the latest.

Provenance

Results remember their inputs

Every new run records the revision checksum of the assembly and the motion or load case that produced it — so you know which geometry made which curve.

teams

One garage for the whole team.

Create a team and switch into its shared space: every axle, vehicle, motion, load case, result and workspace in one place — with revision history naming the teammate behind every change.

Shared space

Everything, together

Flip between personal and team context from the sidebar's team switcher. In team mode every asset type is the team's shared copy — created, edited and simulated by any member.

Invites & seats

E-mail or link, your call

Invite by e-mail or share a copyable invite link. Invitations reserve a seat and are bound to the invited address; owners manage seats, revoke invites and transfer ownership.

Student teams

Built for FSAE squads

A dedicated student team type: three seats on a shared university e-mail domain, verified by us. Formula Student and Baja teams run the same solver the pros do.

pricing

Simple plans. The free tier is permanent.

Start free with no payment details. The free tier is permanent; paid plans unlock the full template catalog, every result channel and exports.

Free

€0 /mo

Permanent — not a countdown

5 solver credits per month
Double-wishbone template, both rigs
Core result channels
Kinematics and static loads

Start free

Pro

€129 /mo

VAT included

1,000 solver credits per month
Every topology and template, both rigs
All channels, CSV and IGES export
Comparisons and labels

Get Pro

Teams

€89 /seat/mo

3-seat minimum, VAT included

Shared team space for the whole roster
1,000 solver credits per seat, monthly
Invite by e-mail or link
Everything in Pro, shared

Start a team

Student Teams

€0 /mo

3 seats included, domain-verified

200 solver credits per seat, monthly
University e-mail domain, verified by us
Everything in Pro, shared
Subject to verification and approval

Start a student team

Start free

Solve something today.

Create an account, model a suspension from your own hardpoints, and run it on the rig. No download, no license, no payment details — and the free tier is permanent.

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No payment details
Nothing to install
Runs on any OS
Permanent free tier