Operating instructions

JANUARY 1985 6-5
NOTE... If "Alodine" does not adhere to
metal a more severe cleaning method must be
used. A solution of 12 to 16 ounces of Oakite
No. 61, or equal per one gallon of water is
preferred. Apply and remove the solution
with caution because an alkaline cleaner of
this type will remove any "Alodine" film
previously applied. Remove cleaning
solution thoroughly with plenty of hot water
and vigorous brushing.
6-14. ENAMEL COATINGS. Ferrous parts when
painted with gold enamel will be baked with infrared
equipment for 15 minutes at 275-285° F. following
application of each coat. Magnesium parts will be
pickled and primed before painting; then baked with
infrared equipment for 15 minutes at 275-285° F.
following application of each coat of enamel.
NOTE ...If a part which was originally
"Alodized" is to be refinished with enamel it
will not be necessary to apply zinc chromate
primer accept to the surface areas completely
stripped of "Alodine".
CAUTION ...Before application of primer
and enamel to a part, carefully mask all
connection joints and mating surfaces. No
primer or enamel is permissible on interior
surfaces of any parts contacted by engine
lubricating oil after assembly.
6-15. SPECIFIC INSPECTIONS.
6-16. CRANKCASE. If any cylinder base nut was
loose at disassembly or if any of the cylinder attaching
studs are bent, even slightly, or if there is definite
evidence that a cylinder was loose at any time, then it
is possible that reversal of stress has fatigued the studs
and through bolts installed on that cylinder pad, in
which case all of them should be replaced. Test for
bent studs with a toolmaker's square. When
inspecting for casting cracks pay particular attention
to areas on and adjacent to the cylinder mount pads,
tappet guides, bottom flange and bearing bosses.
Look for nicks on machined surfaces and scoring in
shaft bearings and the shaftgear bushing. The castings
must be clamped together at all attaching points before
dimensional inspection of camshaft bearings.
NOTE...If camshaft bearings are excessively
worn, the crankcase may be line bored for a
0.020 inch oversize camshaft.
6-17. CRANKSHAFT. In addition to magnetic
particle, visual and dimensional inspection, the shaft
should be mounted on matched vee blocks on a sur-
face plate (supporting the front and rear main journals)
and rotated under a dial indicator placed to bear on the
center main journal in order to detect excessive
bending. This is of particular importance if the
aircraft has been involved in an accident resulting in a
broken or bent propeller. (Refer to the Table of
Limits for limits of "runout" at the center journal).
6-18. CRANKSHAFI' AND COUNTERWEIGHT
PINS AND BUSHINGS.
a. Excessive localized brinelling of the crankshaft
dampener pin bushings can affect propeller blade tip
stresses. It is therefore recommended that at each
major overhaul the pin bushings be inspected and
replaced as required. This applies to both the
dampener bushings and the crankshaft blade bushings.
Worn or out of round counterweight bushing holes
will require counterweight replacements.
b. Inspect in the following manner: Measure the
inside diameter of bushing across points A, B and C.
Take the average of A and B and deduct this from C.
If the difference exceeds .001" then the bushing
should be replaced.
1. The C measurement should be the point of
maximum diameter which is generally a point
perpendicular to the lengthwise centerline of the
crankshaft.
2. Measurements A and B should be taken at points
approximately 60° either side of Point C.
3. After removing the bushings from the dampeners
or the crankshaft blades, measure the inside diameter
of the holes. Select a replacement
bushing which will give an interference fit of 001"-
003" into each the dampener or the dampener or the
crankshaft blade holes.