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Unformatted text preview: engines, all descendants of the H ispano-Suiza a nd Curtiss. I n all these engines t he valves
w ere seated in inserts embedded in the a luminum head, a nd t hus h ad
b etter valve cooling than t he o riginal Hispano-Suiza design. I n every case
t he basic structure consisted of cast aluminum crankcase with e n bloc
w ater jackets a nd c ylinder heads, also of cast aluminum. Cylinder barrels
w ere uniformly of steel. Design details varied, especially in the m ethod of
t aking t he c ylinder-head-to-crankcase l oad. This was successfully done as
follows (fig. 34 i llustrates t he evolution of liquid-cooled cylinder construction) :
37 T hrough the cylinder b arrels—Liberty (fig. 3 4b), H ispano-Suiza (fig.
3 4c), P ackard (fig. 34e), and Daimler-Benz (fig. 34h)
T hrough the aluminum water-jacket s tructure—Curtiss (fig. 34d and f)
a nd Junkers V-12 gasoline engine
By long bolts from cylinder heads to c rankcase—Curtis OX-5 (fig. 34a),
R olls-Royce (fig. 34g) and Allison
T h e i m p r o v e m e n t in performance of liquid-cooled engines since 1 918
h as been astonishing. T h e following figures for two engines of nearly the
s ame piston displacement a n d representing design ideas 30 years a p a r t illustrate this d e v e l o p m e n t :
Liberty E ngine 12
2 .04 N umber of cylinders
Bore and stroke, in
M aximum hp
B rake mean effective pressure, psi . . . . . .
M ean piston speed, ft-min
H p per sq in. piston area
W eight, lb, per hp, dry (without water, oil,
r adiators) 1948
0. 78 Figure 34.—Liquid-cooled cylinder development: a
1 935 Name
C urtiss O X-5
C urtiss K -12 '
P ackard V - 1 2 -'
C urtiss C -12 3
R olls-Royce Merlin
D aimler-Benz 4 Barrel
C ast iron
S teel Jacket
M onel s heet
S teel, w elded
C ast a l u m i n u m
// it S teel, w elded
C ast a l u m i n u m //
// 1 //
;/ Load by
B arrel //
B arrel Water jacket is cast integral with crankcase.
A luminum casting containing valve ports and camshaft was continuous over 6 separate steel
Improvement on K-12 by bolting separate water-jacket casting to crankcase for easier assembly
Unique fastening of cylinder barrels to crankcase by means of a ring nut.
2 39 T hese improvements are attributable not only to i mproved detail design,
b ut also to important developments in fuel, supercharging, and cooling
fluid, which will be discussed later. s gs» F igure 3 5.—British a ir-cooled cylinder d e v e l o p m e n t : Left, A BC steel cylinder with f i n n e d a l u m i n u m cap, 1 9 1 7 ; this cylinder had poor head and valve cooling ( f r o m Journal of the American
Society of Naval Engineers, v ol. 3 8, n o. 4, p. 8 7 2 , 1 926). Right, C ylinder developed by Dr. A. H .
G ibson at Royal Aircraft Establishment, 1918, anticipated the essential features of m o d e r n aircooled aircraft-engine c ylinders—that i...
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