C. Parsons’s patent device for converting reciprocating motion…

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

Side elevation of an oscillating-cylinder engine. The piston rod (the one driven joint) slides in a cylinder hung on trunnions to the right and carries the endless rack: 40 teeth inside a stadium. The 12-tooth pinion on the fly-wheel shaft gears with the top side on one stroke and the bottom side on the other and rolls round the round ends at the turns, the cylinder swinging to let the rack shift; a flange on the pinion runs on the core of the rack's groove and keeps the pair in gear. The steam is a double-acting push (two press-only actuators on the rod) let in by the cylinder's own swing, as an oscillating engine's ports are: it reverses as the cylinder tilts through the line of the pinion's centre (feet.timed on the trunnion joint), so it changes over at each round end, the dead centres. Teeth and flange are real contact.

Measured

The fly-wheel turns one way at 6.45 rad/s (62 rpm), 100% of the time faster than a fifth of the mean, never running back (0.000 rad); the cylinder swings 4.4 degrees on its trunnions; penetration 0.12 mm. Timed steam carries the pinion past both round ends (net 61 rad in 9.5 s); the same push on a fixed clock (0.15, 0.25, 0.4 Hz) falls out of step and runs the pinion back 3.7-10 rad.

Notes

Gravity is off (the engine lies on its side): the rack's weight about the trunnions stalled it at the lower side. The fly-wheel sits behind the pinion. The steam's timing is the engine's own (the cylinder's tilt), a feature added for this movement (src: feet timed by a joint's position).

Film (MP4) · Still (PNG) · Spec (YAML) · Model (MJCF)