Planet gearbox with cylindrical roller bearing with high density roller packing

A gas turbine engine comprising:

• a fan including a plurality of blades extending radially from a hub and rotatable about a first axis of rotation defined centrally through the hub;
• a compressor disposed downstream from the fan;
• a turbine disposed downstream of the compressor;
• a rotatable input shaft mechanically coupling the compressor to rotate in unison with the turbine;
• an epicyclic gearing arrangement that has only a single input and that includes a carrier, a sun gear rotatable about a second axis of rotation that is parallel to the first axis of rotation, a ring gear disposed circumferentially around the sun gear, at least one planet gearbox that is carried by the carrier and houses a planet gear rotatable with respect to the carrier about a third axis of rotation that is parallel to the second axis of rotation, wherein the at least one planet gear meshes with both the sun gear and the ring gear;
• and
• an engine envelope surrounding the fan, the compressor, the turbine and the epicyclic gearing arrangement, wherein one of the ring gear and the carrier is non-rotatably coupled to the engine envelope;
• and
• the planet gearbox further including:
• a support pin fixed to the carrier and defining a cylindrical outer surface that is equidistant from a central axis that extends in an axial direction,
• an inner race defining an inner cylindrical surface that is non-rotatably connected to the cylindrical outer surface of the support pin, the inner race defining an outer surface that defines at least one track, each track being configured to receive and rotatably guide therein a respective plurality of cylindrical rollers,
• an outer race defining an outer cylindrical surface that defines a gearing surface of the planet gear and that is configured to mesh with both the sun gear and the ring gear, the outer race defining an inner cylindrical surface that is opposed to the outer cylindrical surface of the outer race,
• a plurality of rollers disposed in each track of the inner race, each roller being free to rotate about a fourth axis of rotation that is parallel to the third axis of rotation, each roller defining a cylindrical outer surface contacting both the inner race and the inner cylindrical surface of the outer race, each roller defining a length in the direction parallel to the fourth axis of rotation and wherein the ratio of each roller's length to each roller's diameter is within the range from 1.3 to 1.8, inclusive, and
• for each respective track, a respective roller cage disposed between the inner race and the outer race, wherein there is a small clearance between each roller cage and the inner race, each respective roller cage being configured to maintain in each respective track, a respective separation between each respective roller in each pair of adjacent rollers in that respective track, each roller cage defining a first plurality of generally cylindrical openings, each generally cylindrical opening defining a major axis in the axial direction and a minor axis in the circumferential direction, each of the openings being spaced equidistantly apart circumferentially around the respective roller cage by a plurality of equidistantly spaced apart webs, wherein:
• each web has a trapezoidal cross-sectional perimeter outline with non-parallel side sides,
• each web extends in the axial direction,
• each web defines a cross-web thickness in the circumferential direction,
• each web is bisected radially by a pitch circle of a planet bearing,
• the cross-web thickness increases above the pitch circle of the planet bearing, and
• wherein the diameter of one of the rollers establishes a cross-web thickness along the pitch circle of the planet bearing for each web of each roller cage so that each cross-web thickness is 15% to 25% of the diameter of one of the rollers.