Operator`s manual

OVERHAUL
MANUAL
TEXTRON
LYCOMING DIRECT DRIVE
AIRCRAFT ENGINES
Section 7
Crankcase,
Crankshaft,
and Reciprocating Parts
the threads are undamaged. The threads can be cleaned
by running
a tap through
them. Use a standard
.3125-24NF3
(P.D. .2854/.2878)
tap for 5/16 inch threads.
Use a standard
.500-20NF3 (P.D. .4675/.4701)
tap for 1/2
inch threads.
Check the depth of the
thread by threading
a gear retaining
bolt to the bottom of the
hole and com-
paring the exposed
length of the bolt with
the thickness
of the gear and lockplate.
CAUTION
Use extreme
care when cleaning
threads with
tap.
AFTER GRINDING
CHAMFER
45
°
x .03
MACHINE TO THIS
DIA. BEFORE
PLATING. PLATE
DIA. ONLY. GRIND
DIA.
TO 2.126/2.125
AFTER PLATING.
PLATING - NOT PERMIT-
TED IN THESE HOLES
THIS SURFACE AND PILOT
DIA. MUST RUN TRUE
WITHIN .001 IN. TOTAL IN-
DICATOR READING. DO
NOT PLATE THIS SURFACE.
Figure 7-12A.
Details for Repairing
Pilot
Diameter of Crankshaft
2. Check
the condition
of the dowel
in the end
of the
crankshaft.
It should be perfectly smooth
with no indica-
tion of
nicks or deformation.
If
it is out-of-round,
it should
be removed and
replaced with a new one.
Replacement
instructions are in
step 4. If dowel condition
is acceptable,
insure that it is installed
as shown in Figure
7-12B. or
Figure 7-12C.
CAUTION
If the dowel must
be removed, it is very
impor-
tant to do
so without damaging
the hole in the
crankshaft.
A satisfactory
method consists
of
drilling
a 1/8 in. dia. hole
through the center
of
the
dowel; then
fill the
hole with
oil and insert
a piece of 1/8 in. dia.
drill rod in the hole.
Strike
the end of
the drill rod a sharp
blow with a ham-
mer. Hydraulic
pressure of the
oil will force the
dowel from the crankshaft.
3. Check the pilot diameter
of the counterbore
on the
end of the crankshaft
for size and evidence
of damage.
The diameter
should not exceed
2.1262 inches when
measured
at any location.
If found to be oversize,
the
crankshaft may be repaired as described in the following
steps. Do
not attempt to reuse
a crankshaft with an over-
size pilot diameter.
a.
After removing the
dowel, machine the
pilot
diameter in the end of the crankshaft to 2.129/2.130
inch as shown
in the illustration. See
Figure 7-12A.
Also, cut the .09 deep x .06R undercut as shown.
b. Chrome
or nickel plate the surface
of the pilot
diameter
with a firmly bonded
deposit that is
free of
pin holes, blisters
and any other imperfections
that
could
impair the function
of the parts.
c. After plating,
stress relieve the
shaft by baking at
390 to 410°F. for 3 to 5 hours.
d. Grind
the plated pilot
diameter surface
to
2.125/2.126 inch. Note that the diameter must run true
with rear main
journal within .001
inch total indicator
reading.
CAUTION
The crankshaft
counterbored gear
mounting face
should be checked
for damage. If
the surface face re-
quires repair other than specified in CAUTION follow-
ing paragraph 7-53,
the crankshaft
should first be
measured
as shown in Figure
7-12G. If the crankshaft
measures
more than the minimum
dimension shown
in Figure 7-12G, the surface may be reworked down
to
the dimensions shown.
(Do not plate the surface.)
The
surface must be true
within .001 in. total indicator
reading to rear main bearing and the surface finish
must be held to 45 to 90 microinches.
e. Chamfer
edge of pilot diameter
450 x .03 as shown
in Figure 7-12A.
STD-1065 DOWEL IS
DRIVEN
TO LOCATE
SHOULDER OF DOWEL
.010/.020 IN. BELOW
SURFACE.
Figure 7-12B.
Section Thru End
of Crankshaft
Showing
Driven
Height
of STD-1065
Dowel
Revised June, 1993
7-10A