cycloidgen v7.2.0

Numbers

• Every sweep in the app was running over a window that is not a period, and
  the numbers taken over it have moved. A lobe pitch, 360/N, is the period
  of the disc's shape. It is not the period of anything a sweep samples: a
  sweep samples the pins, and there are N+1 of those against N lobes, which
  is the entire mechanism. Pin k meets the profile at t_k = phi/N - 2*pi*k/(N+1), so the crank has to turn 360*N/(N+1) before each contact
  lands where its neighbour was — 330 degrees on the default drive, not 32.7.

  What gave it away is that the curve did not close. Peak pin force reads
  49.859 N at phi = 0 and 49.271 N one lobe pitch later, so the Ring pin
  load plot was a tenth of a cycle cut at an arbitrary phase, ending somewhere
  other than it began. Tiled, it steps at the seam. That is what it looked
  like, and it is what it was.

  The ring stage now sweeps 360*N/(N+1) and the output stage sweeps its own
  360*N/(n*(N-1)), which is a different number and always was — the two have a
  common multiple that runs to thirty input revolutions on some tooth counts,
  which is exactly why neither can be swept on the other's window. Each stage
  gets its own loop. This is not an approximation: a maximum per stage is a
  maximum per stage, and the mean of a sum is the sum of the means.

  Measured against 7.1.1, over the presets and several tooth counts:

  Quantity	Worst change
  Ring peaks — pin force, contact pressure, torque capacity	under 0.01%
  Efficiency, running temperature	0.6%
  Mean sliding speed	0.7%
  Output pin force, output PV, disc web shear	5.5%
  Torsional stiffness	12.6%
  Load concentration	8.6%
  Transmission error	7.4%

  The ring-side peaks barely move, and that is the expected result rather than a
  reassuring one: a maximum over the pins does not care which phase of the cycle
  you start at, only whether you covered it. What moves is everything averaged
  or ripple-measured, and the output stage, which was being swept over about
  half its period.

• A check that should have been firing was silent. On the 29:1 preset the
  output pin contact pressure exceeds the allowable, and HERTZ_STRESS_OUTPUT
  now says so. It did not before, because the peak output pin force was sampled
  over a lobe pitch — half the output stage's period — and came out 5.3% low,
  which was the wrong side of the limit. Anyone who took that preset as passing
  should re-run it.

• ring_period_deg in the transmission-error result was the lobe pitch, on
  a result type whose other field, output_period_deg, has been correct since
  it was written. It now reports the ring period: 330 degrees rather than 32.7
  on the default drive.

• Sweeps are 144 steps rather than 72. Sampling an exact period uniformly is
  unbiased at almost any count, so this is not what fixed the window — it is
  only about resolving the peak. Against a 20000-step reference, 72 steps miss
  peak pin force by 0.11% at 30 lobes and 144 by 0.004%.

• The transmission error's ring sweep needed four times the steps, and this
  one is about resolution. Twelve samples were enough across a lobe pitch and
  are less than one per pitch across the ring period, which read 11% low on the
  ring share; forty-eight is where it stops moving. What is left is bounded by
  the shared sweep rather than by that number, and is stated in the source: the
  ring share sits about 2% under a sweep four times finer, 0.7% on the total.
  Closing it means quadrupling the sweep every other study reads, and a
  transmission error 2% conservative on one of its two halves is not what limits
  this model.

Fixed

• No part in the 3D view was watertight, so the section could not cap them.
  A cut came out with some parts reading as solid material and others as empty
  shells — half the assembly sectioned, half of it hollow.

  The faces are emitted one at a time and each brings its own copy of every
  corner, so no face shared an edge with its neighbour: geometrically solid,
  topologically a heap of loose facets, every edge in it a boundary edge.
  vtkClipClosedSurface caps a closed surface and could not cap any of the
  fourteen.

  The comment on the filter that was supposed to prevent this said it merged
  the duplicate points. vtkPolyDataNormals does not merge points — with
  SplittingOn it creates them, which is what gives a cylinder's end cap a
  hard edge against its wall and is the right thing for shading. So the points
  are merged first and split afterwards, and the two surfaces have different
  jobs: the section and the edges take the closed one, the shading takes the
  split one. Twelve of the fourteen parts are now watertight.

  The same duplication had been doubling the edge overlay, which found every
  edge twice — once from each of the two faces that should have been sharing
  it. 12,614 line segments where 6,253 do.

  Two parts are still not clean, for reasons of their own, and are not fixed
  here: output_flange has 28 non-manifold edges where the plate and the boss
  both keep the face they meet on, and disc_1 has a four-edge hole in its top
  face where vtkContourTriangulator gives up on one arrangement of output
  holes and the code checks only that it produced some triangles. disc_2,
  the same part on a different hole phase, is clean.

• The screenshot tool drove the operator's real preferences. It forced the
  light theme, cleared the section plane and unhid the 3D groups, then put them
  back at the end — and anything that raised in between skipped the putting
  back, which is how a window starts opening in the wrong theme with no sign of
  why. It runs against a throwaway settings file now, which is what
  settings.ENV_VAR exists for and is a better answer besides: these images are
  meant to show a fresh install, and now they are taken on one.

• The output stage was swept over a lobe pitch in four more places —
  analyse_contacts, analyse_efficiency, the thermal solve, and the disc-web
  and output-pin fatigue checks. output_stage_period had been in the codebase
  since the transmission-error work, with a docstring warning that sweeping a
  lobe pitch "reports about half the ripple that is really there", and nothing
  outside that one function called it. Both period functions live in
  core.kinematics now, next to the sweeps that need them.

• Nothing in the suite asserted that a period was a period, which is why
  this survived four releases and 788 tests. There are now tests that advance
  each stage by its own period and require the load pattern to return — one pin
  along for the ring stage, one the other way for the output stage, because the
  pattern steps onto its neighbour rather than staying put. And a test that
  holds the mistake down directly: a lobe pitch must not close either stage,
  compared as multisets so that renumbering the pins cannot rescue it.

Changed

• The drawing says what speed it is showing, and the playback control says
  what "1x" means. These were one confusion. The animation runs at 3 degrees
  of input per 33 ms frame, which is one input revolution every four seconds —
  15.2 rpm — while the tooltip claimed "input revolutions per second of wall
  clock", four times faster than the thing it described. The control is
  labelled PLAYBACK now and carries a live readout of the rate it actually
  turns at, so the multiplier is answerable without a tooltip; the rate is
  derived from the two timing constants rather than written down beside them.
  The drawing carries the design's speed, which is the other half of the
  question: a picture turning visibly at fifteen rpm, describing a drive rated
  at a thousand, needs to say which of the two it is.

• The drawing and the datasheet name the arrangement. Ring fixed, output
  taken from the disc's pin holes through the carrier — the planetary
  configuration, as against grounding the carrier and driving the ring, which
  is the star configuration and gives Np rather than N. The reduction line
  and the output-speed line both now say the output turns against the input,
  which the geometry has always done and nothing ever mentioned:
  output_rpm has no sign to carry it. The README says which member is
  grounded, why that fixes the ratio and the direction, and that the disc rolls
  on the inside of the pin circle.

• The explanation panel answers two questions and sat beside one of them.
  It explains the selected check and the parameter you clicked, and it lived
  in the bottom-right corner — so clicking a parameter in the left-hand panel
  put the reply as far from the question as the layout allowed. It is under the
  parameters now, and the checks list has the full width it had been competing
  for. That also retires the machinery that used to hide the panel on a narrow
  window and hold a floor under the detail column: nothing competes for that
  width any more.

• The 3D tab's controls are grouped by what they do. Explode was alone at
  the top beside the view buttons while section was squeezed onto the end of the
  visibility checkboxes at 150 px, on a row that had already run out of width
  and wrapped. They are the same kind of control — drag to open the assembly up
  — and they share the top row now, at the same size. The second row is
  visibility and nothing else. No extra height.

• The wrapping toolbar lined its widgets up by their boxes, not their
  contents. Everything was placed at the top of its row, so the bearings menu
  — a few pixels taller than the checkboxes beside it — painted its own glyph
  low and read as dropped punctuation. Rows are measured before they are filled
  now, and each widget is centred in its own.

• The at-a-glance strip read as one run of words. Eight captions, each wider
  than the number beneath it, right-aligned in pairs: every value hung off the
  end of its own caption with a gap to its left, which put it nearer the column
  next door. Each pair is centred now and the columns are separated by a
  hairline.

• The status bar and the LOG tab look like one feature. They are not
  duplicates — the bar is the last line and forgets it after five seconds, the
  tab is the record — but nothing said so, and two places showing similar text
  read as one of them being redundant. The bar carries a permanent link to the
  log, badge and all.

• The drawing's title was cut in half by the top of its own panel.
  tight_layout solves for the size it runs at and writes the answer down as
  fractions, and the figure is then resized under it by the window. The drawing
  panel is a letterbox — 973x271 on a 1560-wide window — where the fraction
  solved at build time leaves the title 16 px and it needs 22. It is re-solved
  when the canvas resizes now, rather than on every draw: a layout engine would
  put a tight_layout pass back into each animation frame, which is most of
  what ProfileView exists to have removed, and resizes are rare.

• The About box leads with what the output is not. The disclaimer was the
  last paragraph of the informative text, in the dim ink, under three links —
  the least-read position in the dialog for the one paragraph with a
  consequence in it. It is boxed, in the primary text, above the links. It also
  only ever disclaimed the numbers; the geometry needed saying too, because a
  STEP file that opens looking finished is the easiest thing here to mistake
  for a drawing somebody checked.

---

Windows - cycloidgen_..._Setup.exe. It is unsigned, so
SmartScreen will warn on first run: More info -> Run anyway. A
signed build is planned.

Linux - cycloidgen-...-x86_64.AppImage. chmod +x and run it;
it needs glibc 2.35 or newer. If it will not start, the machine has no
FUSE 2: install libfuse2, or run the file with
--appimage-extract-and-run, which unpacks it instead of mounting it.

macOS - cycloidgen-...-arm64.dmg, Apple silicon. Drag it to
Applications, then run this before opening it:

xattr -dr com.apple.quarantine /Applications/cycloidgen.app

It is signed ad-hoc but not notarized, so Gatekeeper blocks the first
launch. On macOS 15 and later the dialog it raises defaults to
Move to Trash, which deletes the install - there is no Open
Anyway in that dialog, it appears in System Settings only after a
launch has been blocked, and right-click -> Open no longer bypasses
it. Clearing the flag first avoids the dialog entirely. On an Intel
Mac, use pip.

Anywhere with Python 3.10-3.12: pip install cycloidgen, then
cycloidgen.

The numbers this produces are preliminary sizing estimates, not a
certification. Validate against a physical prototype before anything
load-bearing depends on them.