The Washington times., 1922-10-07
SKIRTS
Of PISTON AID
LUbR|CAT|ON
New Style Gives Greater Serv-
ice Without Increasing
Weight.

Engineers are, with few excep'
tions. willing to admit that there are
great many problems concerning
the internal fabrication Of cylinder
barrel which have 50 far been solver
by compromise. Long before the
Importance. Of making the pistons
light was realized the practice was
to fully consider the guiding func'
ton OF the piston and to make the
skirt Of considerable length. Speeds
began to get higher. and when 1t be'
came apparent that the inertia forces
were beginning to go beyond
reasonable figure II was realized
that in order to save weight II would
be necessary to decrease piston
length. This tendency was carried
by some to such an extreme that
piston slap and noticeable cooking OF
the piston in the bore began to re-
suit. with the consequent increase
In cylinder wear, writes ]. Edward
Schipper in "Automotive Industries" u"
Wear Was Augmented.
Furthermore. II was quite un.
fortunate that as pistons began 10
be shortened. connecting rods were
shortened also. thereby increasing
their angularity and the relative side
thrust on the wall OF the cylinder.
This further augmented the rapid
wear Of the cylinder bore. particular
ly since. during all this time, engine
speeds were increasing.
The attempt to cure this condition
by the introduction Of a piston ring
at the bottom Of the piston skirt has
not been a success in all cases. II
Aa ri Ia tsNn IN, hA hnR
the upper part OF the piston Is
starved and rapid ring wear Is likely
to occur. II the ring at the bottom
is not efficient itmight just as well
be eliminated as far as a guiding
unit Is concerned. The natural re-
suit is a scraper ring Of some sort
which will permit sufficient oil to
work It's way up to the piston ring
without permitting an over-supply
to get by, thereby causing engine
smoking.
All Of these problems have lecr
on the mind of the automobile en-
g.neer for some time, and IL Is very
interesting to note the turn which
matters are taking this year. On"
OF the largest production comranic"
in the business has eliminated tho
ring from the bottom OF the piston.
and is making the pistol skirt LONGER
Two or three others Of Importance In
the industry. although perhaps not
as large from a manufacturing stand
point. have also done the same.
Engine Speed Increases.
The reasoning behind this IS 'I'l =.
obvious. In the first place. found.
methods have improved to such an
extent that it is possible to make IN,
longer pistons far lighter than wodid
have been believed possible six or
seven years ago. Engine speeds have
increased again to such an extent
that IL is necessary to have the add
tional guiding surface on the cNlin'
der wall. but to- offset any dhNculS
which may occur from this tenden"HE
the increa sed use Of pressure lu5ri'
cation has cut down wear to re-
markable degree.
A great deal Of the credit for inc
development OF satisfactory. light
weight. cast iron pistons must be
given to the aluminium piston. The
problems OF expansion in the alunpn-
um piston are so acute that. once
these have been solved, 1t is quite
simple to solve the expansion PROB
lens which occur with cast iron Thc