1-13. CRANKSHAFT AND CONNECTING RODS. The crankshaft has an overhung crank-
throw which permits the use of solid end-type connecting rods (Figure 1-3). The crankshaft
is counterweighted to give proper running balance. The drive end is keyed to receive the
fan-type flywheel. The other end of the crankshaft is fitted with a crankpin cap on which is
mounted the centrifugal starting unloader. Each of the connecting rods is cast in one piece,
and both are readily replaceable. A single crankpin bushing serves as a bearing for the
crankshaft end of both connecting rods. A pressed-in solid bronze bushing is located in the
piston end of both connecting rods. Oil dippers are cast as integral parts of both connecting
rods and provide splash lubrication to all running parts. The one-piece construction of the
connecting rods assures proper alignment.
1-14. BREATHER TUBE. A breather tube (Figure 1-3) connects the interior of the crank-
case to the inboard side of the air inlet filter silencer. This connection permits pulsations
created by the reciprocating action of the pistons to be vented to atmosphere, thus preventing
any pressure build-up within the crankcase.
1-15. FAN-TYPE FLYWHEEL. The fan-type flywheel (Figure 1-3) is keyed to the com-
pressor crankshaft and is enclosed by the belt guard assembly. It moves ambient air through
the belt guard, drawing it over the aftercoole r and intercooler tubing and discharging it around
the cylinders, providing the required cooling for the compressor.
1-16. CYLINDERS AND PISTON ASSEMBLIES. The compressor has two cast iron cylinders
fins and is bolted to the crankcase with a gasket between the two. Each cylinder bore is
honed to provide a proper wearing and sealing surface for the piston rings. Each piston is
equipped with two single piece, taper-faced style compression rings; one four-piece, venti-
lated, chrome plated steel rail style oil control wiper ring; and one single-piece, non-
ventilated beveled-scraper style oil control wiper ring. Piston pins are hardened steel with a
ground finish. They are full floating, with snap rings to prevent them from striking the cyl-
inder walls. Both pistons are the trunk type, and made of aluminum.
1-17. AIR HEADS AND VALVES. Air enters and leaves each cylinder through an air head
and valve (Figure 1-3) at the top of the cylinder. The valves are stainless steel finger
type (Figure 5-4), consisting of valve spacer plates and inlet and discharge valves secured to
the plates with fillister head screws and nuts. The valve and spacer assemblies are secured
to the cylinders by bolts through the air heads, with appropriate gaskets. They are readily
accessible and may be removed without disturbing piping.
1-18. AIR INLET FILTER SILENCER. An air inlet filter silencer (Figure 1-2) located at
the first stage cylinder inlet filters all air entering the compressor and reduces the noise
level of the intake pulsations to a level which is not objectionable. The filter uses cleanable
pads to remove harmful grit and dirt from the intake air. If the air in the vicinity of the com-
pressor is unduly dirty or contains corrosive fumes, pipe the filter silencer to a source of
cleaner air.
1-19. STARTING UNLOADER. The compressor is equipped with a starting unloader (Figure
1-5
