PRIN. OF INTERNAL COMBUSTION ENGINES - OD1619 LESSON 1/TASK 1
FIGURE 14.
CONTROLLING PISTON EXPANSION.
(c) A variation of the split-skirt piston is the T-slot piston.
The T-slot
piston is similar to the split-skirt piston, with the addition of a horizontal slot
that retards heat transfer from the piston head to the piston skirt.
(d) Some
aluminum
pistons
have
steel
braces
cast
into
them
to
control
expansion.
(4) Cam Grinding (figure 15 on the following page).
By making the piston egg-
shaped, it will be able to fit the cylinder better throughout its operational
temperature range. A piston of this configuration is called a cam-ground piston.
Cam-ground pistons are machined so that their diameter is smaller parallel to the
piston pin axis than it is perpendicular to it. When the piston is cold, it will
be big enough across the larger diameter to prevent rocking. As it warms up, it
will expand across its smaller diameter at a much higher rate than at its larger
diameter.
This will tend to make the piston round at operating temperature.
Virtually all pistons in automotive applications are cam-ground.
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