Expansion eccentric used in France to work the slide-valve of a…
Expansion eccentric used in France to work the slide-valve of a steam engine. The eccentric is fixed on the crank-shaft, and communicates motion to the forked vibrating arm to the bottom of which the valve-rod is attached.
Only the input is driven; every other part of this model moves by physics (MuJoCo), and its ratios are measured. Run it live, change its parameters, or switch the friction off to see the output stop.
- Modelled as
- A circular eccentric of 5.5 cm radius and 1.5 cm throw is turned on the shaft (the one driven joint, 12 turns a minute). A C-shaped arm swinging on a pivot 18 cm to the right has a roller above and a roller below the eccentric (10 mm slack below); its weight holds the upper roller on the eccentric by real contact, and the valve-rod hangs from the lower roller pin. gen137.py.
- Measured
- The arm follows the exact roller-on-circle geometry: swing -0.062..+0.106 rad, slope -0.0907 / +0.0766 rad per rad of shaft in four windows (expect -0.0904 / +0.0767; r2 0.999). Penetration 0.11 mm.
- Notes
- With 3 mm of slack the two rollers jam on the eccentric (it is not a conjugate profile), so the lower roller is given 10 mm and only the upper one works.
Film (MP4) · GIF · Still (PNG) · Spec (YAML) · Model (MJCF)
