Quick return crank motion, applicable to shaping machines

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 disk (20 rpm) turns a pin 3 cm from its centre; the pin works in the slot of a swinging lever pivoted 9 cm above the disk centre (the slot is a real two-wall guide, 0.02 cm clear each side). A 16 cm link joins the lever foot, 21 cm below its pivot, to the ram in its guides. Because the pivot is off the circle of the pin, the forward (cutting) stroke takes 60.8 percent of a turn and the return the rest. A weak spring on the ram stands for the cut and keeps one slot wall loaded.

Measured

Ram speed against the disk at 0, 90, 180 and 270 deg: +0.1047, -0.0190, -0.0525, -0.0205 m/rad against the ideal +0.10457, -0.01941, -0.05247, -0.02030; stroke 14.0 cm; max penetration 0.05 mm.

Notes

The lever and link are hinged parts (pins); the ram slide has a range stop 0.4 cm outside the stroke and a 5 N/m spring.

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