Arizona republican. [volume] (Phoenix, Ariz.) 1890-1930, 1921-02-27

two camshafts are needed, since the |
valves are on opposite sides of the |
cylinder. The valve in-head engine |
demands the use of rods and rocker |
arms for actuating the valves, or as is |
done in some cases, the fitting of an
overhead camshaft In the sliding
sleeve or Knight type engine. there are
two sleeves instead of the conventional
poppet valves. The sleeves have ports
or opening cut in them and the taking
| in of the fuel charges and the driving
out of the burned gases are performed
| by the registering of the ports with in
| let and exhaust passages in the cylin
| ders.
| There are, of course variations of
these types, as for instance the design
used in the REQ engine, where one of
| the valves is in the familiar L-head
| pocket, while the other is located in the
head. This is simply combination of
two conventional types. There are
more variations in the valve in head
construction. For instance the valves
may be placed horizontally, or they
may be placed perpendicularly, so that
they open downward directly into the
combustion chamber. Also the valves
may be mounted at an angle between
/ horizontal and upright 1t is largely a
matter Of the Individual choice of the
designer as it bears on the design that
/ he is working out.
In the main it is considered good
practice to have the cylinder. combu-
stion chamber and all as nearly spheri-
4 cal as possible. OF course, the L-head
and T-head types of construction so
directly against this ideal. The perfect
sphere in these cases is spoiled by the
| pockets on the sides wherein the valves
| are contained. The assumption is that
| in all these designs with side pockets
a location is provided where the cur
rent of the gases is interrupted and a
certain amount of dead gas is permit
| ted to remain.
! In making comparisons of this kind
il must be remembered that all findings
along these lines are largely academic
at best. Presumably a valve in head
engine of exactly the same capacity as
! an l. head typei will perform somewhat
better from the engineers standpoint.
But in ordinary service the l. head en-
CINE, properly designed and construct
ed, will do all that the owner asks it to
do and that is surely all that is neces-
sary. In making comparisons between
the performances of the two engines 1t
must not be forgotten that to obtain
accurate results motors of precisely the
same. capacity and presumptive power
must be pitted against each other. This
can scarcely ever be done except in
the laboratory.
q From the engineers point of view
there is opportunity in the valve-in-
head design to realize most of what are
conceded to be the ideals of internal
combustion design. Large valves may
be secured, spherical combustion
chamber, efficient wave cooling, direct
gas flow to and from the cylinder-but
obviously all this will only be obtained
of the design is correct and construc-
ton satisfactory.
!. The governing factor in cylinder
construction for the ordinary automo-
bile is of course cost. 1t is because of
this that the l. head design is the most
, popular, for with this simplest design
: greater economies can be effected. For
Z this reason of cost also gray iron is the
! commonly used metal in cylinder con-
, struction. If the matter of cost did not
: enter in it would be possible to have
cylinders of steel, cut from solid
block, the completed cylinder being
: perhaps only lis or 1872 thick. CYL
inders of this kind are used in airplanes
, today, but of course the excessive cost
, makes it impossible for commercial
, automobile construction. Some few
racing cars have been given this type
. of cylinder, but only unusual service
, justifies the expense. Gray iron cylin-
i ders are cast and then go through
! various operations of drilling and cut
, ting and facing until the desired diam
eter and finish is obtained. The iron
! is not costly and the operations may be
seduced to very simple proportions
!, A reasonable amount of working makes
this comparatively cheap material per-
g fectly satisfactory for the purpose.
: A material that was achieving con-
!, siderable vogue before the war sent its
: price soaring and prevented further ex-
: Fermentation for the present, is alumni
4 mum. Alloys of aluminium make really
/ admirable castings though practicl
up TO now has made it essential to IN
\ sarf Slaaua Of stool in the "a sting 81
that the piston runs up and dowr
l against the steel instead of the softer
| aluminium. In Europe aluminium cast
ings have been used successfully with
out the steel sleeves.
The grouping of cylinders takes
i many different forms. In early con.
4 structior1s each cylinder was construct
ed separately and bolted to the crank
case. but this no longer done. Cylinders
may be cast in pairs; that is, one cost
ing contains two cylinders; they arr
also cast in threes. tours skies, eight
/ and twelves. Block casting is the pop
uar method today and ii has man,
virtues to recommend it. Rightly il
achieved and this is a very desirable
characteristic in actual operation.
Regardless of the method of group
Il ing. the cylinders may be cast with o
4 without the head. In the latter cas-
the head is bolted on to the top of TIL
l cylinder and a gaslxet is used to insur
1 tightness. The great advantage of tn
l detachable head is the ready access
4 affords to the interior of the engine
4 and this is a great advantage from tn
/ owners point of view, since it make
1 carbon removing, valve grinding. etc
l comparatively easy.
The cylinders may also be cast wit
1 the upper half of the cranlScase integra
l with them. This construction is almos
l entirely used in the medium and loN
l priced cars, as it is by far the cheapes
l method of construction. 1t has the ad
l vantage of giving great rightly, thong
4 it adds something to the weight. /
l one eight cylinder engine that I know
i each block of four cylinders has part c
tl,x. 1,,.a !, lcca CO cast viii il that tn