Mangle or star-wheel, for producing an alternating rotary 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

Brown's figure 54: the wheel's rim is a ring of 45 radial staves between two rings, open front and back, with a gap at A; the pinion B on an upright (radial) shaft under it works on the staves from the front or the back, its carriage sliding across; its shaft's follower runs in a groove between the wheel's cheeks, round the rib's ends at A

Measured

wheel/pinion −0.2001 (front), +0.2001 (back, after rolling round the end stave), −0.2000 (front again) against ∓rp/R = 0.2; max penetration 0.09 mm; also passes at 40 and 90 rpm (windows scaled)

Notes

Staves are capsules (r 0.2, clearing the root of the tooth space); the pinion is No. 36's tooth extruded along its axis, its face narrow (0.4) as the staves splay with the radius; the groove's turns are lofts whose faces follow the follower's path (a staircase of flat steps stopped it). A pulley on B gives the velocity drive inertia (a free light pinion ran away). batch7/gen054.py. Negative control: staves out of contact → the wheel stands (0.000).

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