cypriotcamelUrban and Civil

Nov 29, 2013 (4 years and 7 months ago)



Piston Design Considerations

Pistons must:

Contain cylinder pressure

Transmit the pressure created by combustion to
force on the connecting rod

Provide a place for oil control and compression
rings to be located

Piston Design Considerations

Pistons must:

Be rigid enough to not deform under the
tremendous pressures and forces encountered

Be ductile enough to absorb pressure peaks and
not shatter

Retain the proper shape under the extreme
temperatures encountered

Piston Construction


Cast iron (used in very old engines)

Cast aluminum (most common)

Forged aluminum

Hypereutectic alloys (high silicon content

Carbon Graphite (being tested)

Piston Construction

Piston Construction

Piston head


Approx. .040 undersized

Ring grooves

Ring lands

Drain holes and slots

Wrist pin boss

Piston Construction

Reinforcing struts

cast pistons contain
steel struts to control expansion and aid in
wrist pin support

Lock ring grooves

for full
floating piston

Piston skirt

Full skirt

Partial skirt

Piston Construction

Cam ground pistons.

Most pistons are cam ground, this means they
are not perfectly round.

The diameter is larger on the non
thrust sides,
because they tend to expand more as the
temperature of the piston increases.

Piston taper

pistons may be tapered from
top to bottom

Piston Construction

Piston Pin Offset

The piston pin is offset towards the major thrust
side of the piston to reduce piston wear, and
piston noise

The major thrust side is the side that is loaded
during the power event

The minor thrust side is the side loaded during
the compression event

Major/Minor Thrust

Piston Direction

Pistons should be positioned so arrow, dot or other marking
faces the front of the engine (except reverse rotation

Piston Head Design

Pistons may have a dished, flat or domed

Piston Inspection

Abnormal skirt wear


Melted aluminum or pits in the head

indicates detonation


check ring lands, pin boss, and
skirt closely

Pin bore

check for scoring and wear