# No. 426 (Brown 1868): "Another form of rotary engine, in which there are two stationary abutments, D, D, within the cylinder, and the two
# pistons, A, A, in order to enable them to pass the abutments, are made to slide radially in grooves in the hub, C, of the main shaft, B. The
# steam acts on both pistons at once, to produce the rotation of the hub and shaft. The induction and eduction are indicated by arrows."
# Model (cm, Brown's section, gravity on; only the back half of the cut cylinder is drawn). The hub C (5.2 cm) is fast on the shaft B at the
# cylinder's centre; the bore is 8 cm except at the two abutments D, D (left a little high, right a little low), which come in to the hub
# (5.28 cm), with easy ramps either side. The two pistons A, A slide radially in one groove through the hub, each pressed out by a spring in the
# groove (6 N/m), so each rides the bore: out across the working spaces and pressed back into the hub by an abutment's ramp to pass it. The
# only contact is the pistons' edges on the bore. The steam (the one input) acts on both pistons at once: in at one side of each abutment,
# out at the other, as Brown's arrows, so each piston has steam behind it from just past one abutment to just before the next; it is a
# push on each piston's face (up to 5 N, at the middle of the face exposed between hub and bore), let in and shut off by the hub's own
# turn, the shaft free against a load (0.0405 N m s). A steel fly-wheel on the shaft behind the cylinder (hidden by its back; not in Brown's
# figure) carries the pistons past the abutments, where the steam has no face to push on.
# Generator: opencode-runs/steam/gen426.py.
number: 426
slug: rotary-engine-sliding-pistons
name: Rotary engine with sliding pistons
brown: "Another form of rotary engine, in which there are two stationary abutments, D, D, within the cylinder, and the two pistons, A, A, in order to enable them to pass the abutments, are made to slide radially in grooves in the hub, C, of the main shaft, B. The steam acts on both pistons at once, to produce the rotation of the hub and shaft. The induction and eduction are indicated by arrows."
units: cm
sim:
  timestep: 0.0002
  integrator: implicitfast
  iterations: 100
  solver: PGS
  duration_s: 10
  floor: false
bodies:
  - id: hub
    shape: part
    pos: [0, 0, 10]
    density: 7800
    color: "#8f8a80"
    pieces:
      - {kind: disc, center: [0, 10], radius: 5.2, y: [0.4, 2.0]}   # the hub C
      - {kind: disc, center: [0, 10], radius: 1.0, y: [-0.3, 6], color: "#6f6a60"}   # the shaft B
      - {kind: disc, center: [0, 10], radius: 8, y: [3.0, 6], collide: 0, color: "#6f6a60"}   # the fly-wheel, behind the cylinder (carries the pistons past the abutments)
  - id: piston_a
    shape: part
    pos: [0, 0, 17.72]
    mount: hub
    density: 7800
    friction: 0.05
    color: "#a39d90"
    pieces:
      - {kind: poly, points: [[-0.3, 13.57], [0.3, 13.57], [0.3, 17.72], [-0.3, 17.72]], y: [0.1, 2.3]}   # a piston A, cut through
      - {kind: rod, from: [0, 0.2, 17.72], to: [0, 2.2, 17.72], radius: 0.25, capsule: true, collide: 2}   # its edge, on the bore
  - id: piston_b
    shape: part
    pos: [0, 0, 2.28]
    mount: hub
    density: 7800
    friction: 0.05
    color: "#a39d90"
    pieces:
      - {kind: poly, points: [[-0.3, 2.28], [0.3, 2.28], [0.3, 6.43], [-0.3, 6.43]], y: [0.1, 2.3]}   # a piston A, cut through
      - {kind: rod, from: [0, 0.2, 2.28], to: [0, 2.2, 2.28], radius: 0.25, capsule: true, collide: 2}   # its edge, on the bore
  - id: frame
    shape: part
    pos: [0, 0, 0]
    fixed: true
    color: "#cfc6b4"
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      - {kind: poly, points: [[5.2511, 9.4481], [8.8512, 9.0697], [8.8783, 9.3792], [5.2687, 9.6316]], y: [0, 2.4], collide: 1}
      - {kind: poly, points: [[5.2687, 9.6316], [8.8783, 9.3792], [8.8946, 9.6894], [5.291, 9.8152]], y: [0, 2.4], collide: 1}
      - {kind: poly, points: [[5.291, 9.8152], [8.8946, 9.6894], [8.9, 10], [5.3195, 10]], y: [0, 2.4], collide: 1}
      - {kind: disc, center: [0, 10], radius: 10.4, y: [2.4, 2.9], color: "#bdb4a2"}   # the cylinder's back
      - {kind: poly, points: [[-11.6, 10.6], [-7.8, 10.6], [-7.8, 12.4], [-11.6, 12.4]], y: [2.4, 2.9], color: "#bdb4a2"}   # the steam-ways at D, D
      - {kind: poly, points: [[7.8, 7.6], [11.6, 7.6], [11.6, 9.4], [7.8, 9.4]], y: [2.4, 2.9], color: "#bdb4a2"}
      - {kind: poly, points: [[-9.5, -0.8], [9.5, -0.8], [9.5, 0.2], [-9.5, 0.2]], y: [-1.5, 3.5], color: "#bdb4a2"}   # the bed
      - {kind: poly, points: [[-6, 0.2], [6, 0.2], [3.5, 1.5], [-3.5, 1.5]], y: [0, 2.9], color: "#bdb4a2"}
joints:
  - {id: j_B, type: hinge, body: hub, axis: [0, -1, 0], damping: 0.0405}   # the shaft and hub; + : anticlockwise as drawn (Brown's arrows)
  - {id: j_a, type: slide, body: piston_a, axis: [0, 0, 1], range: [-3.12, 0.4], stiffness: 6, springref: 12, damping: 0.02}   # the upper piston, in and out of its groove
  - {id: j_b, type: slide, body: piston_b, axis: [0, 0, -1], range: [-3.12, 0.4], stiffness: 6, springref: 12, damping: 0.02}
contact: {solref: [0.002, 1.0], solimp: [0.95, 0.99, 0.0005], margin: 0}
driver:
  joint: j_B
  kind: feet
  max_torque: 1.0
  feet:
    force: 5
    timed: {joint: j_B, gain: 2, offset: -1.5708}   # x = 2 x the upper piston's angle (deg from the right, anticlockwise)
    ports:   # the steam on the upper and the lower piston, square to it, anticlockwise (the hub's way)
      - {body: piston_a, at: [0, 1.2, 16.6], dir: [-1, 0, 0], frame: body, open: [350, 690], profile: [0.496, -0.4736, 0.1724]}
      - {body: piston_b, at: [0, 1.2, 3.4], dir: [1, 0, 0], frame: body, open: [350, 690], profile: [0.496, -0.4736, 0.1724]}
checks:
  - {type: monotonic, joint: j_B, direction: 1, max_back: 0.05, settle_s: 0.0, window_s: 9.5}
  - {type: turning, joint: j_B, direction: 1, min_mean: 3.5, min_fraction: 0.9, settle_s: 3.0, window_s: 6.5}
  - {type: amplitude, joint: j_a, min: 0.0129, max: 0.014, sustain: 0.95, settle_s: 3.0, window_s: 6.5}   # each piston is pressed into the hub to pass an abutment and goes out again to the bore (1.360 cm either way)
  - {type: amplitude, joint: j_b, min: 0.0129, max: 0.014, sustain: 0.95, settle_s: 3.0, window_s: 6.5}
  - {type: penetration, max: 0.002}
camera: {target: [0, 0, 9.6], position: [0, -95, 9.6], fov: 22}
display:
  output: j_B
  labels: {j_B: "Shaft B and hub C", j_a: "Upper piston A", j_b: "Lower piston A"}
  proof: {label: "Pistons out of contact", sub: "the hub turns but the pistons lie out on their stops, through the abutments"}