New-York tribune., 1919-10-05
18-V alive Design
=. OF Holmes Car
Has Three Aims
Clearing of Dead Gases from
Cylinders Makes for Pow
er, Flexibility and Silence
of the Cars Operation

A new development in automobil,
engines Of the overland valve type
is presented in the Holmes improved
air-cooled engine in the present serie.
Of production. The use of eighteer
valves comes as the result of work done
by Arthur Holmes, designer Of the
Holmes car. as consulting engineer or
alr-cooled engines used in combat air
planes.
There are three valves to each CYL
inder, all in the head. The dual ex-
haust valves are actuated by one rocker
arm which is operated from the cam
shaft by the usual type of valve litter
rod construction.
Three objects are aimed at by the
lS-valve design in the Holmes engine
The first is the development of greater
power through q better use of the fuel.
accomplished by more rapid clearing
OF the dead gases from the cylinders:
the second, a more flexible engine, due
to more complete ignition Of the fuel;
and third, quieter running engine
than has hitherto been associated with
overhead valve construction.
In general details of construction
the Holmes improved, air-cooled en-
glnes follow the lines developed by Mr.
Holmes in the sixteen years he has
been the leading engineer in the coun-
try on alr-coolcd engines for autorno-
biles The six cylinders are cast in
dividually. Cylinder dimensions are:
bore, "a inches; stroke. Il inches,
giving an N. a. C. c. rating of 29.4
horsepower. The crank case and oil
pan are aluminium. Zach cylinder has
outer cylinder walls. The radial fins
give total cooling area Of approx
mately 500 square inches. Over these
fins steady current of air is drawn
by the suction fan in the flywheel of
the motor
The direction of the air currents
over the cylinders is controlled by the
hood, a metal deck located just below
the cylinder heads and extending the
full length and width of the hood.
Metal side plates close the upper com
partment formed by the deck from the
lower compartment. The upper COM
partment is practically alright in its
relation to the lower compartment, be-
ing closed by metal plate at the front
end Of the motor and by the dash at
the rear end.
The cylinders are further enclosed
by q metal plate on either side. extend
ing the full length of the fins and
shaped in semicircles partially around
each cylinder These cylinder side
walls are held in place by the metal
deck forming the division between the
upper and lower compartments.
AS the tlywheel starts to revolve
with the turning over of the engine
the suction fan sets up partial vac
uum in the lower compartment. To
fill this vacuum air is drawn IN through
the grilled opening at the front of the
hood, into the upper compartment and
down around the radial fms. Thence
the air. which has cooled the cylinders,
passes out through the blades OF the
| hywheel.
The advantages claimed for this type
of cooling are: First, a controlled
amount of cooling medium at any
time; second, the application of the
cooling medium TO the hottest part Of
the cylinders, that is, the heads, when
tire medium is coolest-the reverse of
water cooling; third, greater margin
of cooling efficiency in the cooling me-
dunn IN relation to outside tempera-
ture; fourth, the maintaining of a
greater degree of heat efficient in the
cylinders than is possible with water
cooling; fifth. less jacket loss and
sixth, an entire independence of out
side temperature conditions as affect
ing the cooling medium.
With the usual valve -in-the- head
engine it is necessary to time the
valves when the motor as hot to get the
best operation This is because OF the
expansion Of the valve-operating
mechanism under the heat OF the
motor. In the Holmes the action OF
heat on the valve mechanism is com
pensatcd for in standard which sup
ports the Incorporating mechanism,
Designs and construction are such that
the expansion Of this support is uni
form with the expansion Of the cylin-
der head and the valve cages. Adjust
ments made while the motor is cole
are not changed whsp the motor is