Library version 2.0.5 · Blender 5.2 LTS and 4.5 LTS

This is the whole guide, for both packages, in one place. Everything in it is inComplete. The few things that are not in Core are markedComplete; if you own Core and a heading says that, you can skip it.

Two other files are in the download and this guide does not repeat them:ASSET_CATALOG.md lists every input of every group with its default and range,and MECHANICAL_CONVENTIONS.md has every equation and sign convention.

1. Install

There is nothing to install. This is a .blend file, not an add-on.

Either open the file that matches your Blender and work in it,

or — better — register the folder once so everything follows you into everyproject:

1. Edit → Preferences → File Paths → Asset Libraries
2. +, point it at the folder holding the .blend and blender_assets.cats.txt, name it Oh My Gear 2
3. Open an Asset Browser and choose that library. You will see:

Oh My Gear 2├── Basic          plain gears, pairs and trains├── Extended       worm, chain, bevel                     (Complete)├── Assemblies     the stacked controller                 (Complete)├── Curve Paths    the four curve systems                 (Complete)└── Materials      nineteen procedural finishes

Materials are in the same browser. Drag one onto any object.

2. Your first gears in one minute

1. Add any mesh object. A default cube is fine — its geometry is discarded.
2. Add a Geometry Nodes modifier.
3. Click the browse icon and pick OMG2_Mesh_Pairing.
4. Set Teeth A and Teeth B.
5. Click the Drive field, type #frame/96 and press Enter.

Press play. The second gear is placed at the solved centre distance, phased soits teeth fall into the gaps of the first, and counter-rotated at the correctratio. You changed two numbers.

3. The conventions you need

Everything in the library follows these. Learn them once.

Lengths follow scene units. At the default Unit Scale, 1 unit = 1 m.

4. Which group do I use

Groups prefixed OMG2__ (double underscore) are internal helpers. Theirinterfaces are not part of the public contract — do not build on them.

Helical and herringbone are not separate groups. Helix Angle andHerringbone are inputs. In a pair or a train, setting Helix Angle gives eachneighbour the opposite hand automatically, so every mesh stays valid.

5. What each value controls

Every group arranges its inputs into the same named panels, so the panel a valuesits in tells you what it can change. If a value is in Body or Appearance, itcannot change the motion, the ratio or the centre distance.

The values that do the real work

6. Animating

Everything turns from Drive alone, in turns.

• Driver (recommended): click the Drive field, type #frame/48, press Enter. One full turn every 48 frames. #frame/-48 runs backwards.
• Keyframes: hover the field and press I on two frames.

To chain groups, feed one group's Out Drive output into the next group'sDrive.

7. Gear trains on a flat curve

Put OMG2_Gear_Train on a curve object. Each curve point becomes a gearcentre. The modifier has to be on the curve itself.

Set Module yourself only when the train has to mesh with parts you havealready fixed at a module. Then the curve has to be long enough — see the rulein §13.

Input Index picks which gear receives Drive directly.

Draw the curve as a Poly spline

Every curve group (Gear_Train, Curve_Layout and the four paths) puts a gearon every evaluated point of the curve, not on every control point. A Poly spline evaluates to its own points, so a Polyspline with five points gives five gears. A Bezier or NURBS splineevaluates to many points along the smooth curve between its control points: threeBezier control points at the default resolution gave 25 gears with a tinymodule in testing.

Do one of these:

• Convert to Poly. In Edit Mode, select the points, press F3, search Set Spline Type and choose Poly. Best option.
• Or keep a Bezier and set Resolution Preview U to 1 (Curve data properties → Shape). Then it evaluates to its control points, joined by straight segments. Leave the render resolution at 0 so the render matches the viewport.

NURBS does not reliably give one gear per control point, even at resolution 1.Use Poly.

The ready models in the Asset Browser are already Poly curves.

8. Curve paths — drawing a mechanism Complete

Put OMG2_Gear_Path on a curve object and draw the mechanism with thecurve's points. Every point is a shaft. Each segment between two points isread against the axis the path is currently on, and becomes one of three things:

The first gears are always in the XY plane, axis +Z. So: draw the firstfew points in Top view, keep them at the same height, and leave the plane onlywhere you want a turn.

How the angle of a segment decides what it becomes

"Lean" is how far a segment leaves the plane the path is currently on. TurnTolerance (default 6°) is how forgiving the solver is.

The slope sets the ratio. The ratio of the bevel pair at a turn is1 ÷ tan(lean). 45° is exactly 1:1; steeper makes the gear after the turnslower, shallower makes it faster. Measured on a real path:

Tooth counts are whole numbers, so the solver rounds: the real ratio is close tothe table, not exactly on it.

Turn Tolerance — the one that surprises people

It works both ways: with a tolerance of 20°, a 10° lean became flat in testing.

What the values in the Turns panel do

The four systems

They share one solver and one set of rules. What you learn on one works on all.

Chains. A flat segment longer than Chain Distance becomes a chain drivebetween two sprockets instead of a gear mesh. 0 never uses a chain. Sprocketsare Sprocket A Teeth (driving) and Sprocket B Teeth (driven); their ratio isthe chain's ratio. Chain Pitch 0 means "π × Module", so the sprockets are thesize of gears. The chain runs under the gears and consecutive chains alternatesides — if one hits something, turn on Flip Chains.

Worms. The ratio of a worm turn is Worm Starts ÷ wheel teeth. WormDiameter is the worm's pitch diameter in modules (5 … 20): bigger is afatter worm and a smaller wheel. Left Handed turns every worm stage the otherway.

Ends (Mixed Path). Start = 1 adds a worm motor under the first shaft,driving it through a wheel of Start Wheel Teeth.End = 1 adds a rack, End = 2 a ring gear with the last pinion inside it.End Teeth is the pinion on the last shaft; Rack Teeth and Ring Teeth sizethe part it drives. Ring Teeth must exceed End Teeth.

Outputs worth reading

Gear Count, Turn Count and Chain Count tell you what the solver decided.If you expected a turn and Turn Count is 0, the segment was inside thetolerance and got treated as flat. Total Ratio is the overall ratio; Moduleis the solved module, which you must feed to anything else meant to mesh withthe path.

Drawing tips

• Start in Top view. Draw the first three or four points flat.
• Turn once, then carry on. One point up and sideways makes the turn; draw the following points in the new plane.
• Leave room. Every turn needs a flat run before it long enough for the hub, the gap and the bevel. A very short run before a turn is where overlaps start.
• Move a point and the whole path re-solves. Tooth counts are integers, so as you drag, the counts step; the mesh is exact at every position you stop at.
• Leave Module at 0 until you need to fix it.

9. The other mechanisms Complete

OMG2_Ring_Internal — pinion inside a ring

The ring sits at the origin with the pinion inside it; both turn the sameway. Ring Teeth must be greater than Pinion Teeth, otherwise the groupis invalid and returns nothing. Rim Width is the wall of the ring outside theroot circle.

OMG2_Mesh_Pairing does the same with Internal switched on. There, Teeth Bis the ring, and it must also exceed Teeth A.

OMG2_Rack_and_Pinion

One pinion turn moves the rack one pitch circumference; Travel and RackPosition tell you where it has got to.

OMG2_Worm — worm and wheel

The worm lies along +X and drives a wheel on +Z. Ratio = Starts ÷ WheelTeeth (the sign follows the hand). Diameter Factor (q) is the worm's pitchdiameter divided by the module; Worm Length is in axial pitches; LeftHanded reverses the thread. The group reports Lead Angle: a single-start wormat the default q of 10 is about 5.7°; six starts at q 10 is about 31°.

OMG2_Chain_Sprocket — chain drive

Two sprockets and a closed roller chain. Center Distance is a request: thechain has a whole number of links (always even), so the solved distance isslightly different and is reported as Solved Center Distance (a request of 3solved to about 3.09 in testing). A request smaller than the two sprocketsneed is rejected, not silently enlarged.

OMG2_Bevel_Pair

Two bevel gears on intersecting axes. Shaft Angle is the angle between the axes(10° … 170°); the cone angles are solved from it and the tooth counts.

Apex At Origin puts the shared cone apex at the origin. At small shaftangles the apex is far from the gears: at 10° the pair ended up about 11.6units from the origin with it on, against about 4.3 with it off. Leave it offunless you need the apex for alignment.

OMG2_Assembly_Controller

A worm, a spur pair and a rack stacked on shared shafts: the worm wheel and spurA are one shaft, spur B and the rack pinion the next, so each stage genuinelydrives the one below. One Drive runs all three and Total Ratio is the productof the stages.

10. Body styles

Body Style changes only the look of the web. The toothed rim, the pitch radiusand the ratio are untouched.

Shaping inputs: Spokes (count — 0 always gives a solid web), Spoke Width(how much of each sector is material), Spoke Curve (bend; the sign mirrors thesweep), Window Shape (low is square-cornered, 1.0 is round).

Bore Diameter above zero fixes the hole size in scene units — use it whenseveral gears run on one shaft. At zero, Bore Ratio scales the hole with thegear. Hub Ratio, Hub Thickness and Web Ratio size the hub and the web.

11. Materials

Nineteen procedural materials, no textures to unpack and nothing to lose. Findthem in the Asset Browser under Oh My Gear 2 → Materials, each with a renderedthumbnail and a one-line description. Drag one onto any object.

All are named OMG2_MAT_*. They are also in the material dropdown of everyobject in the file, because each carries a fake user and survives a save whetheror not anything is using it.

Putting one on a gear. The gear's material is an input of the modifier,not a slot on the object. Put it in Material (the toothed rim). Turn on TwoMaterials and Body Material takes the hub, the web and the spokes.Dark_Anodised is the one to reach for on the body: it stays dark under stronglights instead of washing out to grey.

What is in them. Every material bevels the shading normal, so tooth tips andwindow edges catch a thin machined highlight instead of ending in amathematically sharp line. The metals carry two scales of roughness variation:a broad one at about the size of the part, and a fine grain on top. The printmaterials band along the part's own height at a real layer pitch — PLA_Whiteis a 0.05 unit layer — with a slow wobble, because a printer does not lay aperfect stack.

Retuning them. Every finish is an ordinary node tree in the file. Open it inthe Shading workspace and change whatever you like; a material you edit is yours.

12. Quality and speed

Points Per Tooth is the only quality control you normally touch.

It is the main cost of every gear: halve it before anything else when theviewport is slow. Body Resolution (24 draft, 32 default, 64 close-up) sets howround the rim edge, hub, bore, holes and windows are.

Smooth Angle (default 50°) decides which edges stay sharp: edges bent furtherthan this stay sharp, flatter ones shade smooth. 30–60° suits gears; 180°smooths everything, which makes tooth flanks look soft.

A twenty-five gear train re-evaluates in well under a millisecond at the defaultquality.

13. What can break, and how to fix it

Find your symptom on the left. Where a group can tell you the cause itself, readits Valid and Warning Code outputs (§14).

Nothing appears

The layout is wrong

Parts collide or do not touch

It does the wrong thing

It looks wrong

Files and the Asset Browser

14. Diagnostics: Valid and Warning Code

Every public group has two diagnostic outputs. Wire them to a Viewer node, orread them in the spreadsheet.

• Valid — off means the configuration cannot be built. It returns empty geometry on purpose: the library would rather show you nothing than a mechanism that looks plausible and whose teeth pass through each other.
• Warning Code — the reason, but see the note below.

What you can expect, measured:

Each group documents its own codes on the socket tooltip, because 1 and 2 meandifferent things in different mechanisms. ASSET_CATALOG.md lists them.

15. What this library does and does not claim

Exact: nominal radii, centre distances, ratios, directions and mesh phase.The involute flank for spur, helical, internal and rack teeth, within 1e-6 rad ofthe analytic curve from 13 to 120 teeth. Verified by a test suite that builds acollision tree per part and asserts no triangle of one gear crosses a triangle ofits partner, across a full revolution — for spur, helical, internal, rack, beveland worm meshing, and for every combination the curve systems can produce.

Preview geometry (Warning Code 3): the worm thread flank, the chain linkshape and the bevel tooth flank. Their kinematics and nominal dimensions arecorrect; their profiles are not manufacturing profiles.

Not claimed: a production tooth profile. There is no profile shift(addendum modification). A gear train and a curve path are non-branching: onechain of shafts, not a tree. The rim, web and hub overlap as separate solidsrather than being booleaned into one watertight shell — correct for render andpreview, but union them yourself if you need a manifold mesh.

This is built for visualisation, motion design, previz and concept models.Manufacturing needs an independent check of tolerances, backlash, undercut,strength and process.