Runout
Runout turns up in 2 fields: gears, geosynthetics. Here is what it means to the people in each one.
Runout in gears
How much the teeth wobble radially relative to the gear's axis, measured with a probe in each tooth space.
The total variation in radial position of a probe, ball or pin placed in each tooth space in turn as the gear rotates on its datum axis. It mostly reflects eccentricity between the teeth and the bore or journals, plus some pitch and profile effects. Runout makes backlash vary around the gear and produces sidebands spaced at shaft speed around mesh frequency, and it is often the first thing checked on a noisy gear.
"Runout's eight tenths on the ball check, so the teeth weren't cut concentric to the bore, check the hobbing arbor."
Runout in geosynthetics
Flat length of geosynthetic between the crest of a slope and the anchor trench.
The runout spreads the anchoring force through friction under the cover soil before the sheet turns down into the trench. Too short a runout concentrates stress at the trench edge, while too long wastes material and space at the crest. Runout length and trench depth are sized together to hold the panel under placement and cover loads.
"Runout is three feet on the plans and they've got eighteen inches before the trench, so stop and recut it."