Piston And Piston Rings; Connecting Rods - Westerbeke Universal M-50 Operator's Manual

PISTON AND PISTON RINGS
Piston circumference has a special elliptic shape in consideration of expansion due to explosion
heat. Piston head is flat-formed. Furthermore, ribs are provided between the piston head and top
ring to reduce distortion and to help heat radiation.
Piston is made of special aluminum alloy of low thermal expansion and high temperature
resistance.
Top ring is of key stone type which can stand against heavy load, and the sliding surface to the
cylinder wall is shaped into barrel face which is well fitted to the wall and plated with hard chrome.
Second ring is of under-cut type which is effective to prevent oil rising.
Oil ring is effective to scrape oil because it is closely fitted to the cylinder wall by coil expander
and the upper and lower ends of its sliding surface are cut diagonally to raise fare pressure to the
cylinder walls.
A part of scraped oil is forced into the inside of piston through oil escape holes of rings and
piston. The oil ring is plated with hard chrome to increase wear resistance quality.
Pistons and piston rings
(4)
1. Rib
2. Top ring
3. Barrel face
4. Hard chrome plating
5. Second ring
6. Coil expander ring
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(3) (2)
~
~/~.o§
i
0
(1)
(6)
CONNECTING RODS
Connecting rod is used to connect the piston with the crankshaft. The big end of the connecting
rod has crankpin bearings (split type) and the small end has a bushing (solid type).
( 3 ) - _ A
(1)-----111
1. Connecting rod
2. Crankpin bearing
3. Bushing
I
1
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