Learn/Shape Generator/Built-in profiles
Trigger Wheel
At a glance
- Hall Effect (square teeth) and VR / Variable Reluctance (angled converging flanks)
- Set total positions, outer diameter, tooth height, and duty cycle %
- Missing-tooth sync gap: configurable count — supports any pattern (e.g., 60-2, 36-1)
- Bore diameter option
The Trigger Wheel shape (Engine category) generates crank and cam position wheels for aftermarket EFI — the missing-tooth reluctor a Speeduino, MegaSquirt, or Haltech reads for spark timing. Pick it from the Shape Generator dialog, set your pattern, and cut it from steel plate.
Sensor type
Hall Effect teeth are square: radial flanks with a flat tip arc, the standard form for Hall and optical sensors. VR (variable reluctance) teeth taper from a full-width root to a point at the tip — the triangular cross-section that maximizes the rate of flux change a VR sensor needs for a clean zero-cross. Match this to your sensor, not your ECU.
Tooth pattern
Total Positions is the full count of evenly spaced tooth slots (default 60), and Missing Teeth removes consecutive teeth to create the sync gap (default 2 — the classic 60-2 crank wheel). Any combination works: 36-1, 24-1, 12-3, or a plain 0-missing cam wheel. The missing positions are skipped entirely, leaving one continuous root arc across the gap, so the sensor sees a single long low spot rather than fill geometry.
Dimensions
- Outer Dia — tip circle diameter (default 3.937 in = 100 mm)
- Tooth Height — radial depth from tip to root (default 0.157 in = 4 mm)
- Duty Cycle (%) — tooth width as a fraction of the slot pitch (default 50%, clamped 5–95%); at 50% the tooth and gap are equal width, the usual spec for Hall wheels
- Bore Dia — center bore (default 0.787 in = 20 mm; 0 omits it)
Tips
- VR sensors want ferrous material — cut from steel, not aluminum. Hall sensors with a back-biased magnet also need a ferrous wheel.
- Root and tip arcs are true arcs, so tooth spacing accuracy comes down to your machine, not the drawing. Add mounting holes in the workspace after insertion; the wheel imports as ordinary editable geometry (see editing workflow).