AutoLISP Routines

SPURGEAR draws a spur gear to standard proportions from the numbers an engineer actually has: the tooth count, the module or diametral pitch, and the pressure angle. The tooth flanks are true involutes computed from the geometry, not arcs fitted by eye, so the drawing can be trusted for manufacture, for checking a mating pair, or for cutting on a machine. What SpurGear … [Read more...] about SPURGEAR LISP: Involute Spur Gear Generator for AutoCAD

SPIRALSTAIR builds a spiral stair as real 3D surfaces — treads winding round a centre column, climbing to a given height over a given sweep, with a railing. What SpiralStair does Two railing treatments. Panels makes the treads one surface and the inner and outer railings separate panels of a stated thickness — use this when the railing is a solid … [Read more...] about SPIRALSTAIR LISP: Build a 3D Spiral Stair in AutoCAD

HELIX3D draws a helix that climbs as it turns, as an ordinary 3D polyline. What SpiralPath does Why, when AutoCAD has had a HELIX command since 2007 that asks for much the same numbers? Because HELIX makes a HELIX object — a spline underneath — and there are things you cannot usefully do with one. You cannot offset it, you cannot get at its vertices, … [Read more...] about HELIX3D LISP: Draw a Rising Helix as a 3D Polyline

Draw a run in plan and get the elevation drawn at the same time, directly below it and in line with it. What SideView does Each leg of the plan carries a bottom and a top level. As you pick your way along, the plan line goes down as usual and the side view gets the matching panel — bounded by those two levels and by the X positions of the leg’s two … [Read more...] about SIDEVIEW LISP: Draw a Plan and Its Elevation Together

SERIALTAG places a running sequence of labels — 1, 2, 3 or A, B, C or GL-1, GL-2 — one at each point you pick, optionally enclosed in a circle or a hexagon. What SerialTag does Grid references, door numbers, item marks, revision letters, detail keys: anything that counts up as you go round the drawing. Three counter styles. Number steps by any … [Read more...] about SERIALTAG LISP: Place Incrementing Number and Letter Tags

SECTPROPS reports the full set of section properties an engineer needs for a built-up or cut-out cross section: area and centroid; Ix, Iy and Ixy about the origin and about the centroid; principal moments I1 and I2 with the angle of the principal axes; radii of gyration; and section moduli to the extreme fibres. What SectionProps does Holes are handled. Select the … [Read more...] about SECTPROPS LISP: Cross-Section Properties With Holes