Toe and lifter for working puppet valves in steam engines
Toe and lifter for working puppet valves in steam engines. The curved toe on the rock-shaft operates on the lifter attached to the lifting-rod to raise the valve.
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
- The rock-shaft is the one driven joint, rocked 0.5 rad either way at 0.4 Hz. Its curved toe works, by real contact, under the flat of the lifter, which is fast on the upright lifting-rod of a puppet valve. The toe's face is an involute of a circle of radius 6 cm about the shaft, so while it bears the flat rises 6 cm for each radian of rocking, and the contact stays 6 cm to the left of the shaft. Gravity is on. On the back stroke the valve's weight lets it follow the toe down; the toe then falls clear of the flat while the valve sits on its seat (the rod's lower stop).
- Measured
- While the toe bears, the rod follows it at 6.00 cm per radian (r² 1.0000). The valve lifts 2.93 cm off its seat at the top of each stroke and stays seated (within 0.001 cm) while the toe is below. The deepest contact is 0.04 mm.
- Notes
- Brown gives no sizes. The involute face is a choice that gives a uniform lift; the plate shows only that the toe is curved. Steam pressure on the valve is not modelled.
Film (MP4) · Still (PNG) · Spec (YAML) · Model (MJCF)
