Winch Drum Fleet Angle
The sideways angle a wire rope makes running from a fixed lead sheave onto a winch drum: fleet_angle = atan(lateral_offset / lead_distance), where the offset is the sideways distance from the sheave's groove plane to where the rope lands (largest at the drum ends) and the lead is the perpendicular drum-to-sheave distance. A 6 in offset over a 240 in lead is atan(0.025) = 1.43 deg -- inside the guideline. The Wire Rope Users Manual / ANSI E1.6 guideline keeps it at or below 1.5 deg (grooved) / 2 deg (smooth); too large and the rope crushes earlier wraps or climbs the flange, too small (under ~0.5 deg) and it piles up. Lengthening the lead or centering the sheave lowers the angle. A design guideline; the equipment manufacturer governs.
Formula and source
fleet_angle = atan(lateral_offset / lead_distance), in degrees.
Winch drum fleet angle (the Wire Rope Users Manual; ANSI E1.6 entertainment rigging), by name; the drum, rope, and equipment manufacturer govern.
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