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2.22
FRONT FRAME DESCRIPTION
a.
The front frame (Figure 2.5) forms the aerodynamic flow path to
the rotor inlet and serves as the mounting and support structure for all
other fan components.
The frame is constructed of 17-7 PH sheet and forgings.
b.
The basic sub-assemblies of the front frame are the hub,, two major
struts, two minor struts, and four bellmouth sectors.
The front frame sub-
assemblies are permanently joined with fusion welds.
The major and minor
struts are first joined to the hub; then the belimouth sectors are joined
to the hub and strut assembly.
The entire unit is heat treated prior to
final machining.
2.23
Hub
a. The hub, which forms the inner flow path to the rotor, houses both
the ball bearing and roller bearing which support the overhung rotor.
It
also mounts the closure doors and closure door actuating accessories.
The
ball bearing housing and roller bearing support flange are machined from
forgings.
The housing and flange are connected with a cylinder formed from
0.032" sheet.
The outer skin of the hub (or bulletnose base) is formed in
two 1800 sections from 0.032" sheet.
Sixteen gussets of 0.032" sheet
attach the bulletnose outer skin to the bearing housing flanges and center
cylinder.
The top plate is machined from a forging to 0.090" thickness
and is concentrically located on the roller bearing support flange.
Four
pads and supporting brackets are keyed into the top plate and serve as an
attachment location to accommodate an aircraft inlet closure system.
Additional stiffeners
at
the
3 o'clock support strut position are made
from 0.180" sheet; those
at
the
9 o'clock support strut are made of
0.062" and 0.125" stock.
The stiffener around the bottom side of the bullet-
nose is formed from 0.032" sheet.
The entire assembly is a fusion weldment
except for:
spot weld attachment of the gussets and bulletnoze stiffeners,
and for the rivet attachment of the bulletnose skin to the sixteen gussets.
1-2.9
R-1
-V
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