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Heart cam with roller follower (uniform motion)

Why is a heart cam heart-shaped? · Hardware · basis: Xem Studio drawing; classic mechanism (Brown No. 96)

Also called: heart cam, heart shaped cam, uniform motion cam, leva de corazón, came em forma de coração, Herzkurve Nocken, came cardioïde

Exact dimensions. True size, with no printing tolerance added.

sizes
3 in table

Notes

  • Radius = r₀ + h·θ/180° on the way out and back on the way in: equal angle steps give equal lift steps, so the follower moves at a constant speed (20 mm each way per turn here).
  • The cusp at the top and the dip at the bottom are where direction reverses (infinite acceleration in theory): fine for slow traverse, e.g. thread winding.
  • A roller follower's pitch curve is the profile offset by the roller radius; this file is the pitch-correct profile for a knife-edge follower — offset by 5 mm for the Ø10 roller.
  • Parts (each has its own page): heart-cam-r15-h20, roller-follower-10, crosshead-guide-8mm. Brown's movement No. 96 shows it (1868).

Heart cam with roller follower size chart

parametervalue
base radius r₀15 mm
lift h20 mm
motionuniform velocity

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

Henry T. Brown (1868, public domain)Five Hundred and Seven Mechanical Movements — scan on archive.orgwebPublisher's page; dimensions are facts

Free files

★ Free files 1 parts. Generated by Xem Studio from the standard; threads are plain cylinders at major diameter. CC BY 4.0. index.json

heart-cam-mechanism-assemblyAssembled mechanism, all parts placed (STEP keeps each part separate)STEP · STL
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Plain text: sheet.txt · JSON: /api/geometry?object=heart-cam-mechanism

Heart cam with roller follower (uniform motion), isometric render of a generated part
Render of heart-cam-mechanism-assembly from the free STEP; not to scale.

Fits with

Heart cam, base radius 15, lift 20 mm, isometric render of a generated part
Heart cam, base radius 15, lift 20 mm3 sizes★ 1 file
Roller follower Ø10 on a Ø3 pin, isometric render of a generated part
Roller follower Ø10 on a Ø3 pin2 sizes★ 1 file
Crosshead guide, Ø8 bore × 30, isometric render of a generated part
Crosshead guide, Ø8 bore × 305 sizes★ 1 file

Questions

Why is a heart cam heart-shaped?

Radius = r₀ + h·θ/180° on the way out and back on the way in: equal angle steps give equal lift steps, so the follower moves at a constant speed (20 mm each way per turn here).