Standard engine test of Curtiss D-12 high and low compression engines (Power Plant Section report)

              File D 52.41 / Curtiss / 42
AIR SERVICE INFORMATION CIRCULAR
Vol. VI
<AVIATION)
PUBLISHED BY THE CHIEF OF AIR SERVICE, WASHINGTON, D. C.
January 25, 1926
STANDARD ENGINE TEST
OF CURTISS D-12 HIGH AND LOW
COMPRESSION ENGINES
(POWER PLANT SECTION REPORT )
Prepared by J. W. Carl and W.W. Bishop, Jr.
No. 550
Engineering Division, Air Service Ralph Brown Draughon
McCook Field, Dayton, Ohio LIBRARY
April 13, 1925
WASHINGTON
GOVERNMENT PRINTING OFFICE
1926
MAY 2 9 2013
Non·Depoitory
Auburn University
/
CERTIFICATE: By direction of the Secretary of War the matter contained herein
is published as administrative information and is required for the proper transac­tion
of the public business.
II
INDEX
Object of test ______ - - _ - -- ___ _________ _______ __ ___ _______ ____ ___ ____ ____ _______ ___ __________ _
Summary of tests results _ ____ ______ __ _____ __ __ ____ ________ _______ ___ _____ _____ ___ ________ __ _ Conclusions--- - - - ----- - - -- - -- -- -- ----- -- - - -- - - ------- - --- - ----- - --- - - - - - - - ------------------
Description of engine ___ ___ _______ __________ _______ ______________ ____ ____ ______________ _____ _ Table of dimensions-- --- - -- -- --- -- -- - -- -- - - - ---- -- -- - ----- - -- - - - - - ---- - ------- --- - -- - ------ --
Summary of clearances _________ ____________ ___ ____ __________ _______ _________ ___ ___ __________ _
Weight of engine parts ___ ______ ______ __ _____________ __ ___ ___________ _____ ___ _____ ________ ___ _
Reciprocating and centrifugal weights ______ ___ ___ ____ ____ ______ _____ ____ _________ __ ___ __ _____ _
Record of engine t est :
Introduction ___ __ ______ ____ ____ __ ___ __ ______ __ __ __ _______ ___ ____ _______ ______ ________ .. __
l\1'ethod of test------ --- --- --- - - --- -- -- --------- - -- -- - - -- --- -- -- -- ---- - -------- -- - -- - - -- -
Observations during test __ ___________ _________________________ ___ ____ ___ __ ___ ______ ____ __ Results of test ___ ____ ________ ___ _____ ____ ___ ______________ ____ ______ _________ ___ ________ _
Analysis of performance _____ _____________________________ __ _____ _____ __ ___ ___ _____ ______ _
Conclusions-
Dedgn ___ ____ _________ ____ ___ ________ _____________ _____ __ __ ___ ~- - - - - - - - - - - - - - - - - - - -
Production _____ __ _____ _____ ______ ______ ____________ ______ ___________ _____ ____ ______ _
Performance _____ __________ ____ ___________ ___ _______ ________ __________ __ _____ __ __ __ _
Suitability for airplane installation ______ ___ _______ ___ ___ ____________________ ____ ______ _
Maintenance ______ _________ __ ___ _____ ____________ ______ ___ ________ __ ____ ______ __ ___ _
Performance tables _____________ ___ __ _________ ____ ________________ ___ _______ ___ ___ ___ __ __ ___ Performance curves _____ ___ __ __ __ ______ __________ __ ___ __ ____ __ ___ ____ ___ ______ __ ____ __ ___ ___ Valve lift diagram _____ _ -- --- --- ____ ____ _____ __ _______ __ ___ _________ ___ ____ ____ ________ _____ _
Illustra tions: ·
Three-quarter front view ____ __ _____ __________ ___ _____ ___ ___ _____ __________ ______ __ ___ __ Three-quarter rear view ___ ___ ______ _______________ ____ ____ ___ ___ ___ ____ ______ ____ _____ __ _
Top view ______ __ ______ _____ ___ ________ ________ _________________ ___ ____ __ ______ ____ ____ _
Side view------- - ------- ---- ----------- - --- - -- -- --------- - ------ - - - - - - - --- - ----- -- - - -- - ­Gear
end view----------- -- --------------------- - ------------ -- -- - - -~ - -- --- - -------------
Longitudinal section view _____ ____ ____ __________ __ __ ______ ____ ___ ____ _______ ____ _______ __ _
Cross-section view ___________ _____ _______________ __ ________ ___________ __ ___ __ __________ _ Crank case (outside) _____________ _______ ____ ____ __ ______ ____ ___ ____ ____ _______ ___ ______ _ Crank case (inside) __ ___ ___ ______ _______ ___ ____ _______ ____ ____ __ _______ _____ __ __ ______ __ _
Crank shaft - ---- - --- - -- ---- - --- -- -- -- -- --- --- --- - - - ------ - ---- - --- - -- ~- --- - ---- - ---- - ---
Comparison of Curtiss and Liberty crank shafts _____ ______ ____ ___ _____ ___ ___ __ ________ - - ___ _
Connecting rods and pistons ________________________________ _______ __ ___ ____ ________ - - - - - -
Sectional views of pistons _______ __ ___ __ __ ___ __ __ ___ __ __ ___ __ __ __ ________ ____ ___ _________ _ Cylinder block assembly ____ __ _______ ___ __ ___ __ ___ __ ________ ____ _______ __ ____ ___ __ ----- - --
Gear housing a ssembly _______ ________ ______ ____ _______ _______ _____ _________ ___________ __ Exhaust valves showing seat condition after 50 hours _ __ __ __________ ______. ____ ___ ___ ____ ___ Intake valves showing seat condition after 50 hours ____ __ ___ ___ _____________ ________ ___ - _ - _ - _
Exhaust valves showing stem condition after 50 hours _________ __ ____ ____ _________ __ ____ _____ Camshafts---- --- -- ---- - - ---- ----------- --- -- - -------- - ---- - --- -- - - -- ------ - - ----------
Curtiss water pump ___ ___ ___ __ __ __ _________ _______ ___ __ __ __ ____ __ _____ _______ ___ -- _ - -- - - -
Assembled view of carburetors a nd ma nifolds ______ ___ ______ ___ _____ ________ __ _ --- - - _____ ___ Intake manifold assembly ________ ______ ______ __ _____ ___ ____________ __ ___ _______ _____ - ___ - -
Side view of Stromberg N A-Y5 carburetor _______ ____ ____ ____________ _________ ___ - - -- - - - - - - -
Three-quarter view of Stromberg N A-Y5 carburetor _____ ________ __ ------- -- - - __ __ -- - --- - - -- -
Sectional view of Stromberg NA-Y5 carburetor ___ ___ _______ __ ___ ____ _____ ____ _____ ___ _ -- - -- -
Magneto co4plings----------------------------- - - - ----- - ----- - --- - - - ------------ -- -------
Oil line installation diagram _____ ________ _________ _____ ____ __ ___ __ ___ _______ ___ ______ - -- - - -
Oil passage through engine (longitudinal section) __ ________ ________ ____ ___ ___ ______ ____ ____ _ Oil passage through engine (cross section) _____ ________ ______ ___ ______ ___ _____ __ ____ ___ __ ___ Fuel line installation diagram __ _______ ____ ___ ______ _________ ___ _________ ___ ___ ____ _______ -
Splitdorf switch and wiring diagram _____ ______ ____ _____ _______________ ______________ ___ - _ - _
Marking for timing ______ ____ _________ __ ___ ______________ ______ __________ __ ______ _____ __ Timing data ________ ____ ____ ____ ______ ____ ____ __ __________ ___ ___ __________________ ____ _ Seating operation for valves ___ ______ ____ ____ ____ ___ ____ _____________ ________ __ __________ _ (III)
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STANDARD
OBJECT OF TEST
The object of this test was to obtain information
on the design and performance of the high (6.0 : 1)
and low (5.3 : 1) compression Curtiss D-12 aviation
engines.
SUMMARY OF TEST RESULTS
[Averages for fi ve high and five low compression engines]
Compression ratio
Normal brake horsepower (full throttle at 2,200
revolutions per minute) .-- --- -- - ----- - -- -- -- -- - ­Fuel
horsceopnoswuemr ppteior nh oautr _n _o_r_m_ _a_l __p_o_w_ _e_r_, __p_o_u__n_d_ _p__e_r _
Oil consumption at normal power, pound per
horsepower per hour_ ___ ___ ______ _______ ____ ___ _
Normal ~rak e mean cfl'ecti\·e pressure, pound per
Tostqaula wree imghctl,L d _r.y -,- -p-o-u-n--d- _-_--_-_-__- -_-_-_-__-_-_-_-_-_-_--_-_-__-_-_--_-_
Weight, dry, per normal brake horsepou' er, pound.
6.0: l 5.3: l
443. 000
. 510
• 010
13i. 500
694. 000
f 566
431. 000
• 540
. 010
133. 800
693. 000
I. 607
CONCLUSIONS I
In the light of contemporary development the
Curtiss D- 12 engine shows excellent characteristics
both in performance and in general design. Its mean
effective p ressures are well above those of concurrent
service engines and its weight-horsepower ratio cor­respondingly
lower. The fuel consumption, however,
is rather high, a result of uneven mixture distribution
and an oversize standard carburetor setting. In
general outward appearance it is clean and compact,
and the fact that the engine has satisfactorily com­pleted
several 50-hour endurance tests at considerably
above th ~ design normal speed indicates excellence in
detail design.
From the point of view of rapid production and over­haul
maintenance in event of national emergency the
engine has several undesirable features, chiefly the
general use of intricate aluminum castings and rather
diffi cult cylinder-block assembly operations, some­what
beyond the capabilities of the usual war-time
overhaul stat ions.
DESCRIPTION OF ENGINE .
General.
Name: Curtiss.
Model: D- 12.
Year of manufacture: 1924.
Manufacturer: Curtiss Aeroplane and Motor Cor­poration,
Buffalo, N. Y.
Manufacturer's serial numbers of engines tested:
High compression, 14, 15, 125, 126, 128; low
compression, 93, 180, 112, 22, 53.
-12 HIGH AND
ENGINES
General-Continued.
Air -Service numbers of engines tested: High com­pression,
68869, 23- 218, 23- 154, 23-155, 23-157;
low compression, 23-144, 23- 173, 23-123,
23-112, 23-115.
Number and arrangement of cylinders : Two
banks of six.
Cooling: Water.
Drive: Direct.
Unusual f eatitres.
Two valves are operated by a cam follower which
is actuated by a single cam. (See fig. 23.)
The cylinder construction is also unusual. Six
steel cylinder liners, with integral combustion
chambers, are screwed into a Lynite head cast­ing.
A water jacket is cast in one piece into
which the six cylinders are pressed. This
jacket is bolted to the head. (See fig. 23.)
Crank case. (See figs. 17 and 18.)
Material: Cast Lynite No. 112.
Tensile strength: 17,000 pounds per square inch.
Crank case sections parted on center line of crank
shaft. Upper half supports cylinder blocks and
capped type main bearings. Lower half is oil
drain pan with _oil pumps at antipropeller end.
Number of crank-shaft main bearings: Eight.
Type of main bearings: Plain.
Material of main bearings: Babbitt on bronze.
Bearing support: Bearing caps.
Method of securing bearings: Four machine screws
in each half.
Provision for bearing adjustment : Xone.
Location and nature of oil passages: From oil
manifold through main bearing caps. (See figs.
37 and 38.)
Location, number, and construction of breat hers:
Two breathers cast on inside of each cylinder
block.
Crank shaft. (See figs. 19 and 20.)
Type: Integral.
Material: Forged low chrome nickel steel.
Carbon, 0.35- 0.45 per cent.
Manganese, 0.50- 0.80 per cent.
Phosphorus, 0.04 maximum.
Sulphur, 0.04 maximum.
Chromium, 0.60-0.90 per cent.
Nickel, 1.25-1.8 per cent.
Ultimate strength, 130,000 pounds per square
inch.
'Elastic limit, 110,000 pounds per square inch.
Elongation, 16 per cent.
Reduction of area, 54 per cent.
Counterweighting: None.
(1)
Crank shaft-Continued.
Method of securing gears and thrust bearing:
The drive gear is splined to the shaft. The
thrust bearing is pressed on and locked by a nut.
Type of thrust bearing: Single row ball bearing.
Thrust bearing adjustment: None.
Oil passages in shaft: Main bearing journals
bored and ends plugged. Tubes carry · oil from
holes drilled in cheeks to outer edge of hollow
crank journals.
Oil seal about shaft at crank case: Felt retainer
ring. Helical groove in bushing shrunk on
shaft.
Propeller hub. (See fig. 19.)
Material: Hub and inner flange of chrome nickel
steel, the same as used for the crank shaft. The
outer (loose) flange is of duralumin No. 32.
(Curtiss Co. spec.)
Method of securing to shaft: Key and taper,
using qne differential lock nut having 12 U. S. F.
threads on inside and 16 U.S. F. on the outside.
The nut is locked by a spring wire clip.
Provision for adjustment: Outer flange movable.
Connecting rods. (See fig. 21.)
Type: Articulated.
Material: Forged chrome nickel steel, same as
used for crank shaft.
Yield, 145,000 pounds.
Elongation in 2 inches, 10 per cent.
Reduction in area, 45 per cent.
Brinell test, 332-387.
Column section: I section.
Main rod big-end arrangement: A split lug is
forged on one side with a hollow steel pin
holding the articulating rod in place. A bolt
holds the lug together and keeps the pin from
turning. Bearing is held in rod and cap by
dowels. Cap is held on by four bolts.
Secondary rod big-end arrangement: Forked.
Each side of fork fitted with bronze bushing.
Piston pin bearings : Bronze, pressed in small ends
of rods.
Oil passages in connecting rods: Large bearings a re
lubricated through holes in crank pin. Hole
through rod bearing to articulating rod link pin.
Small ends are lubricated by splash through
hole in end of rod.
Pistons. . (See figs. 21 and 22.)
Type: Straight cylindrical.
Material: Y alloy.
Internal ribbing on head: Four equally spaced
radial and one circular.
Number and location of piston rings: Three above
pin.
Type of piston rings: One-piece diagonal cut.
Piston ring material: Cast iron.
Provision for oil scraping and drainage: Piston
beveled into lower edge of ·bottom ring groove,
with oil holes in the bevel.
Piston pin. (See fig. 21.)
Material: Forged high nickel chrome steel.
Carbon, 0.30--0.40 per cent.
Manganese, 0.30--0.60 per cent.
Sulphur, 0.04 maximum.
Phosphorus, 0.04 maximum.
Nickel, 3.00--3.50 per cent.
C!iromium, 1.0Q-l.50 per cen~,
2
Piston pin-Continued.
Bore: Tapered to center.
Retention: Wire clips.
Oil holes : None.
Cylinders. (See fig. 23.)
Grouping: Blocks of six, with 60° included angle
between blocks.
General construction: Closed-end forged steel
barrels screwed into cast aluminum head and
pressed into cast aluminum water jacket; head
and jacket bolted together.
Method of attaching: Crank-case studs and nuts.
Material : Barrels.
Carbon, 0.30--0.40 per cent.
Manganese, 0.50-0.80 per cent.
Sulphur, 0.05 per cent maximum.
Phosphorus, 0.045 per cent maximum.
Scleroscope, 29-33.
Head and jacket of Lynite No. 112.
Valve seat material and construction: Machined
in steel barrel head.
Material and retention of valve guides: Cast iron,
pressed in.
Total carbon, 3.00--3.50 per cent.
Combined carbon, 0.4-0.7 per cent.
Manganese, 0.4-0.7 per cent.
Phosphorus, 0.6--1.0 per cent.
Sulphur, 0.1 maximum.
Silicon, 1. 75- 2.25 per cent.
Spark plug location: One set of plugs pointing into
the Vee and one diametrically opposite per­pendicular
to cylinder center lines.
Spark plug boss construction: Screwed in dura­lumin
bushings with pipe thread. Locked by
dowel.
Water jacket construction: Lynite No. 112 in­tegral
casting; connection at bottom of cylinders
sealed by rubber ring. Jackets bolted to head,
with rubber packing between.
Water jacket ribbing: Cylinders ribbed; jacket
casting smooth.
Auxiliary drives. (See figs. 24 and 41.)
Shafts:
Purpose Material Location
---
Vertical drive __ Steel. ___ Pump drive ____ ___ do _____ }Alhl oudsirnivge s aint
Cam sbart ___ do __ ___ antipropell e r
drives. end or engine.
Bearings:
Location Type Material Retention
Top of cam Ball___ Steel_ __ Press fit__ __ _
shaft drives.
Bottom or ___ do •.. ___ do _________ do ______ _
cam sbart
drives.
Top of verti- ___ do ___ ... do _________ do ______ _
cal drive.
Bottom of Plain _ Bronze. Dowel pin _
vertical
drive.
Pumps drive ___ do ___ .•• do __ ____ ___ do ______ _
shaft.
Gun syn- 2-ba!L Steel_ __ Set screw __ _
cbronizer.
Magneto ___ do ______ do ____ Press fit in
drivesba[ts. auxiliary
housing.
Lubrication
Drain from
sbart and
cam shaft
housing
Lubrication
All bearings
lubricated
by drain
from cam
s b a ft
housing.
Valves. (See figs. 25, 26, 27, 42, and 43.)
General type: Poppet, tulip.
Material: Silchrome steel.
Valve interchangeability: Valves are interchange­able.
Retention of spring collars: Tapered nuts locked
by a pin.
Valve spring type: Helical wire.
Valve spring material: Chrome vanadium steel.
Carbon, 0.45-0.55 per cent.
Manganese, 0.50-0.80 per cent.
Sulphur, 0.04 per cent maximum.
Phosphorus, O.~ per cent maximum.
Chromium, 0.80-1.10 per cent.
Valve spring interchangeability: Springs are inter­changeable.
Valve gear. (See figs. 9 and 28.)
Cam shaft.
Type: Integral.
Material: Low carbon steel, casehardened.
Carbon, 0-. 10-0. 20 per cent.
Manganese, 0.30-0.60 per cent.
Sulphur, 0.05 per cent maximum.
Phosphorus, 0.045 per cent maximum.
Scleroscope, 75 or over on working faces
and bearings; other parts soft.
Oil passages: Through shafts to bearings.
Interchangeability: Not interchangeable.
Cam forms: Ta ngentia l.
Cam lift diagram: Figure 9.
Cam shaft housings.
Material and construction: Separate alumi­num
castings.
Number, type, and material of cam shaft
bearings: Six, plain, aluminum No. 4
(Curtiss Co. specifications).
Method of securing bearings: Bolted to
pedestals which are bolted to cylinder head.
T ype and material of cam follower bearing:
Phosphor bronze bushing.
Oil passages in bearings: None. Circum­ferential
oil retaining groove.
Cam follo wers. .
Material: Low carbon steel, casehardened.
Carbon, 0.10-0.20 per cent.
Manganese, 0.30-0.60 per cent.
Sulphur, 0.05 per cent maximum.
Phosphorus, 0.045 per cent maximum.
Scleroscope, 75 or over on ground surfaces.
Construction: Machined forgings.
Type of cam contact surface: Cylindrical.
Type of tappet: Capped bolt.
Tappet adjustment: Screw and lock.
Oil passages: Oil hole in center of follower.
Interchangeability: Tappets interchangeable.
Valve timing adjustment: See photographs (figs.
41 and 42) for complete date on timing adjust­ments.
L ubrication system. (See figs. 36 to 38, inclusive.)
Pressure oil pump: One pressure gear pump.
Housing of aluminum and gears of steel.
Scavenging oil pumps: Same as pressure pump
but with wider gears. Two scavenging pumps
and one pressure pump grouped together.
3
Lubrication system-Continued.
Oil strainer: One strainer of No. 40 mesh brass
screen. Mounted behind oil pump on bottom
of oil pan.
Relief valve: One poppet type on outlet of pres-sure
pump. .
Main oil circuit: From tank through strainer to
pressure pump; through relief valve at bottom
to middle of right flange of upper crankcase;
down middle of web to main bearing distributor
pipe; through No. 1 main bearing to cam shaft,
spilling out cam shaft bearings and returning
to gear housing through cam shaft drive hous­ings;
thence to sumps and scavenge pumps.
Tube drains propeller end of sump.
Cooling system.
Water pump : One centrifugal pump.
Material: Casing, Lynite No. 112. Impeller,
Lynite No. 145; shaft steel.
Carbon, 0.30-0.40 per cent.
Manganese, 0.30-0.60 per cent.
Sulphur, 0.04 per cent maximum.
Phosphorus, 0.04 per cent maximum.
Nickel, 3.00-3.50 per cent.
Chromium, 1.00-1.50 per cent.
Location: Base of auxiliary drive housing.
Main water circuit: Radiator to pump; through
two outlets to cylinders; out tops of cylinders
to radiators. Part of water by-passed from
cylinder outlet pipes around intake manifolds.
Induction system. (See figs. 30 and 31.)
Arrangement: Two duplex manifolds. Each
manifold feeds three adjacent cylinders on each
side.
Material and construction of manifolds : Each
manifold consists of three aluminum castings.
Water jacket · cast in at center of each.
Interchangeability: Manifolds are interchangeable.
Carburetors. (See figs. 32 to 34, inclusive.)
Number: Two.
Name: Stromberg.
Manufacturer : Stromberg Motor Devices Co. ,
58-68 East Twenty-fifth Street, Chicago, Ill.
Model number : NA- Y5 and NA-Y5A.
Type: Single venturi, double barrel.
Material : Body, aluminum; discharge nozzle, alu-minum;
jets, brass.
Throttle type: Butterfly.
Venturi type: Removable.
Float type: Duplex.
Strainer: Straight barrel at inlet; removable.
Mixture adjustments : 1 The fuel enters the car-buretor
through a fuel inlet and strainer cham­ber
provided at one end of the carburetor. This
fuel inlet is normally located toward the gear end
of the engine, which is to the rear when the
engine is used as a tractor. From the strainer
chamber the fuel passes through a drilled pas­sage
to the float needle valve, located at the
side of the carburetor. This valve, operated by
the two floats, controls the flow of fuel to the
float chambers and maintains the proper fuel
1 See Eng. Div. Report, Serial No. 2426.
•
=
4
Carburetors-Continued. Couplings-Continued.
level. Fuel passages are provided from the
float chamber at the strainer end of the car­buretor
to the main discharge nozzles. The
main metering jets are placed in these passages.
The main discharge nozzle assembly, which is
fastened to the carburetor and extends up into
the venturi, consists of a main discliarge nozzle,
a main discharge nozzle stud, and a main dis­charge
nozzle screw. The main discharge
nozzle is a brass casting with an arm which ex­tends
up behind the venturi and in which the air
bleed plug is located. This air bleed is con­nected
by drilled passages to an annular space
formed between the discharge nozzle and the
discharge nozzle stud, which space acts as an
auxiliary well, providing the necessary fuel for
smooth acceleration. Drilled passages and an
annular groove in the main discharge nozzle
screw provide fuel for the idling system. The
idling system consists of an idle metering
nozzle, an idle tube with a venturi-shaped end
which fits over the idle nozzle, a fixed idle air
bleed, and an idle discharge nozzle located at
the edge of the butterfly valve. The mixture
control is of the back suction type, using a
variable air bleed. A flat plate mixture con­trol
valve is used, which, when in the full rich
position, allows air to pass from the air intake
through the valve chamber to the left barrel of
the carburetor. When the valve is .moved
toward the lean position the air bleed from the
air intake is closed off, thus decreasing the pres­sure
in the valve chamber. This chamber is con­nected
directly with the float chambers, so that
changes in pressure in the mixture control valve
chamber cause corresponding changes in pres­sure
in the float chamber.
Carburetor interchange ability: Carburetors are
interchangeable.
Ignition. (See figs. 35 and 40.)
Type of system: Magneto.
Name of system: Splitdorf.
Manufacturer: Splitdorf Electrical Co., 98 War-ren
Street, NP.wark, N. J.
Model: SS-12.
Number of magnetos; Two.
Type of magneto: Inductor, high tension.
Type of distributor: Jump spark.
Provision for starting: Starting magneto connected
through switch.
Direction of rotation (facing drive shaft): Anti­clockwise.
Couplings. (See fig. 35.)
The magneto is driven t hrough an Oldham
coupling and flexible thennoid disk. The
driving part of the Oldham coupling .is keyed
to the magneto drive shaft, and the driven
part, which contains 34 holes on its circum­ference,
is fastened by two bolts to the ther­moid
disk. A steel ring flange, perforated at
the circumference by 32 holes, is bolted to the I
thermoid disk by two bolts which pass through
lobes on opposite sides of the inner circum­ference.
The steel ring flange is fastened by
two bolts to a saucer-shaped duralumin flange
which is keyed to the tapered magneto shaft.
The duralumin piece is held on the shaft by a
nut.
Timing adjustment: Moving the bolts one hole
changes the t iming 0.44 degree.
Spark advance mechanism: Rotating the breaker
mechanism.
Switch: Splitdorf model A-232, which provides
for starting magneto~ ground, right and left
magneto.
Spark plugs.
Name and type symbol: A. C., B. G. IX-A,
or B. G. lX-B.
Manufacturer:
Champion Ignition Co., Flint, Mich.
B. G. Corporation, 136 West Fifty­second
Street, New York City.
Number per cylinder: Two.
Material of insulator: A. C., porcelain;
B. G., mica.
Material of body: Steel.
Type of gap:
A. C., straight center
shell electrode.
eiectrode, bar
B. G., straight center electrode; straight
shell electrode.
Type of terminal connection: Ball.
Auxiliaries.
'
Fuel pump: One, located beside oil pumps; tri­plex
plunger type.
Tachometer drive: One, on antipropeller end of
one cam shaft cover. 31 C. S. speed.
Gun synchronizer drives: One, located on each
inclined cam shaft drive shaft housing. Driven
C. S. speed from cam shaft d1fre shaft.
Starter: None of the engines tested was equipped
with a starter. The Curtiss company, however,
supplies two types of hand starter which are
describ'ed in the Curtiss handbook. The
standard Engineering Division electric starter
is easily adapted to the engine.
Controls and connections.
Carburetor: One straight rod connects butterfly
valves between carburetors. The cockpit con­trol
is connected to the carburetor at the anti­propeller
end. The altitude control levers are
connected by a rod, the antipropeller end
carburetor being also connected to the cockpit
control.
Fuel system: The fuel line is connected to the
antipropeller encl carburetor, and through a
tee to the propeller encl carburetor. The
priming system is also connected at the anti­propeller
end.
Cooling system: The water enters the pump at the
bottom of the auxiliary drive housing and re­turns
to the radiator from a pipe -on each side of
the top of the cylinder blocks.
5
Controls and connections-Continued.
Lubrication system: All oil connections are made
at the oil pump except the pressure line to the
gauge, which is connected to the right side of
crank case just above the parting line.
Ignition system: One rod connects the magneto
breaker mechanism arms. The control from
the cockpit is attached to either magneto, as
might be necessary.
TABLE OF DIMENSIONS
General.
Bore: 4.5 inches.
Stroke: Main rod, 6.0 inches; auxiliary rods
6.150 inches.
Compression ratio: High compression, 6.11 :1; low
compression, 5.35:1.
Reduction gear ratio: Direct drive.
Direction of propeller rotation: Facing propeller,
counterclockwise.
Total piston displacement: 1159.0 cubic inches.
Approximate head resistance: 4 square feet.
Firing order of cylinders : 1 L., 6 R., 5 L. , 2 R.,
3 L., 4 R., 6 L., 1 R., 2 L., 5 R., 4 L., 3 R.
Cylinder numbering shown in Figure 12.
Crank case.
Distance between cylinder centers: In Nos. 3
and 4, 6.0; other cylinders, 5.75.
Angle between cylinder banks: 60°.
Number of engine hold-down bolts: 10.
Diameter of engine hold-down bolts : Ys inch.
Crank shaft.
Main journals:
Number I Outside Total Radius Bore
------·· diameter length of fillet diameter
Inches I11ches Inches Inches
2L _--_--_-_--_----_-_-_-_-- _ 3. ()() 1. 928 o. 125 2. 2.'iO 3 ________________ _ 3. ()() 1. 928 . 125 2. 250 4 ______ _______ ___ _ 3. ()() 1. 928 . 125 2. 2.'iO ,5 ____________ __ __ _ 3. ()() 2.178 .125 2. 250 3. ()() 1. 928 . 125 2. 250
67 _-_------ -_--_---_-_-_- -_ 3. ()() 1. 928 . 125 2. 250
8 ______ ____ ______ _ 3. 00 1. 928 . 125 2. 250 3. ()() 1. 928 • 125 2. 250
Crank pins:
Number Outside \ Total Radius Bore
----- diameter length of fillet diameter
!_ ________ _______ _
2 _________ _______ _
3 _______ ____ __ __ _ _
4 ________________ _
5 __________ ___ __ _ 6 ____ _____ _______ _
Crank cheeks:
I11ches
2. 500
2. 500
2. 500
2. 500
2. 500
2.500
Inches
2.129
2.129
2.129
2.129
2.129
2.129
Inches
0.125
.125
.125
.125
. 125
.125
Width (maximum): 3.750 inches.
Thickness: 0.837 inch.
Thrust bearing:
Inches
1.875
1. 875
1.875
1.875
1.875
1.875
Manufacturer and number: Hess-Bright, No.
6217.
Number of ball rows: One.
Number and diameter of balls: 10, 0.78125
inch diameter.
Outside diameter of race: 5.9055 inches.
Inner diameter of race: 3.3465 inches.
Width of race: 1.1024 inches.
S. A. E. bearing number: Light series No. 217.
75863-26t-2
Propeller hub.
Smallest diameter of hub body: 3.06 inches.
Distance between flanges: Maximum, 7.00 inches;
minimum 5.78 inches.
Diameter of bolt circle: 8.00 inches.
Number of bolts: Eight.
Smallest diameter of bolts: 0.500 inch.
Taper: 1-10.
Connecting rods.
Length of main rod, C. to C.: 10.000 inches.
Length of secondary rod, C. to C.: 7.688 inches.
Rod stroke ratio, based on main rod: 1.67.
One section: Height, 1.20; width, 0.750; height of
web, 1.00; web thickness, 0.125.
Piston pin bushing, length: 1.625 inches.
Piston pin bushing, inside diameter: 1.109 inches.
Crankpin bearing, overall length: 2.15625 inches.
Link pin bearing length: 1.25 inches.
Link pin diameter: 1.00 inch.
Link pin, inside diameter: 0.8125 inch.
Piston.
Length over all: 3H: inches.
Length of skirt: 3 inches.
Minimum head thickness: U inch.
Skirt thickness at top, below fillet: -/.; inch.
Skirt thickness at bottom: 0.0875 inch.
Number of piston rings: Three.
Width of piston rings : 0.0937 inch.
Length of piston pin: 3H inches.
Outside diameter of piston pin: 1.1235 lnches.
Inside diameter of piston pin: 0. 943 to 0. 75
inch taper at center.
Height of center of piston pin hole from bottom
of skirt: 2-;\ inches.
Cylinders.
Bore: 4.50 inches.
Stroke, main rod: 6.00 inches.
Stroke, secondary rod: 6.150 inches.
Stroke bore ratio, based on main rod stroke: 1.33.
Piston displacement, per cylinder, average: Main
rod, 95.4 cubic inches; secondary rod, 97.8
cubic inches.
Total engine piston displacement: 1159.0 cubic
inches.
Compression volume of cylinder, average: L. C.,
22.2 cubic inches; H. C., 19.1 cubic inches.
Total volume of cylinder, average: L. C., 118.8
cubic inches; H. C., 115.7 cubic inches.
Compression ratio, average: 5.35: 1, 6.11: 1.
Per cent co~pression: L. C., 18.69; H. C., 16.50.
Port openings at flanges, diameter: 1% inches.
Ports.
Number per cylinder: Intake, 2; exhaust, 2.
Approximate area per cylinder: Intake, 4.1
square inches; exhaust, 4.1 square inches.
Intake valve seat inside diameter: 172 inches.
Exhaust valve seat inside diameter: 172 inches.
Angle of valve seats with cylinder axis: 90°.
Outside diameter of valve guides: 0.533 inch.
Over-all length of valve guides: 1 H inches.
Length of bearing surface in valve guide bosses:
lYs inches.
6
Cylinders-Co tinued.
Cylinder barrel thickness, aboYe mounting flange
fillet: 0.079 inch.
Mounting flange thickness, outside fillet: rlf inch·
Cam shafts.
Smallest diameter, cam shaft body: 1.00 inch.
Diameter, cam shaft bore: ti inch.
Journals:
Number Diameter I Length
l_ _ _ _____ ··---- - - -- --------- -- -- ·- - --
32 _____- -__-_-_-_-_-_--_-_-__-_-_-_-_--_-__-_- -_-_-_-_-_-__-_-_-_-_-_-_- -_
4. - - ---- ---- ------- - - ----- - --- - - - ---
56 ___- _-_- _-_- -__-_-_-_--__-_--_-_-_-_-_-• -__--__--_-__- -_-_-_-__-_-_-_- _-
Cams :
I
Inches
1.0605
1.0605
1.0605
1.0605
1.0605
1.0605 I
Inches
JV.
IY,i
lY.i
lY.
lY.
lJ/o
Base,
diameter
Inches
Width I Lift Rofa ndoiuses
- ------
In ch Inch Inch
~I o.418 -n
~ .418 -n Intake_ _______ ___ I. 124
Exhaust. ________ I. 124
Valves.
Number per cylinder ______ ___ _____ ______ ___ _
Over-all length _________ ___ ___ __ ___ _ inches __
Outside diameter ____ ______ ---- -- - __ .. do .. __
Lift.-------------------- -- -------- ----do __ _
Angle of seat with stem ___________ _ degrees __
Stem diameter_---- --- -- __ __ __ _____ _ inch ___ _
Tappet clearance. - ----- ---------- ____ do ___ _
Valve springs:
Intake
2
4H
1. 718
. 403
45
. 340
. 015
Exhaust
2
4H
1. 718
.403
45
.340
. 015
In take and exhaust
Inner Outer
Total number of coils ______ : ___ __ _
Number of effective coils _________ _
Outside diameter. ____ ____ inches __
Free length ______ ____ _____ __ do ___ _
Diameter of wire ___ ______ .. do ___ _
~~~~l~~ ~:l~: ~Fo~~~:: :'.'_o_'d~~s::
Valve timing, designed.
Intake opens: 5° B. T. C.
Intake closes: 35° A. B. C.
Exhaust opens: 55° B. B. C.
Exhaust closes: 10° A. T. C.
Oil pumps.
11 L. H .
9
H
ltt
0.092
19
9Y. R.H.
7Y. ln
2-h
0. 12
39
18
Pressure Scaveng­mg
Number of pumps used __ _________ __ _______ _
Speed relative to crank shaft ____________ cs ..
Number of gears __ -- -- - --------- --- ----- ___ _
Pitch diameter of gears ____ ___________ inch . .
Number of teeth . __ ____ ___ ___ ---------- - -- --
Face width __ ___ _____ ____ ______ ______ _ inch __
1
1. 7
2
l. 25
10
0. 747
2
1. 7
2
1. 25
JO
1.122
Oil pumps-Continued.
Oil connections.
Inlet to engine: Inside diameter, to inch;
outside diameter, %'. inch.
Outlet from engine: Inside diameter, %'. -inch
pipe; outside diameter, %'. inch.
Water pump.
Number of pumps used: One centrifugal.
Speed relative to crank shaft: 1.7.
Diameter, rotor: 3.997 inches.
Inlets.
Number: One.
Inside diameter: 172 inches.
Outside diameter: ltf inches.
Outlets.
Number: Two.
Inside diameter: tt inch.
Outside diameter: 1-.\ inches.
Water connections.
Inlet to engine ____ ___ _____ __ __ __ _
Outlet from engine . . ______ -------
Carburetors.
2
2
Inch ts
lYs
IYs
I
17lches
l~
l~
Number of carburetors used : Two Stromberg
NA-Y5 or NA-Y5A.
Inside diameter at flange: 2-.\ inches.
Flange type: Two bolt.
Carburetor setting, low and high compression.
Venturi size: lfi inches.
Main metering jet size, drill size: 45.
Main discharge nozzle bleeder, size, drill size:
49.
Fixed idle bleed, drill size: 40.
Fuel inlet fitting size: U-inch pipe thread.
Ignition.
Distributor rotor speed relative to crank shaft: 72.
Breaker speed relative to crank shaft: 172.
Magneto rotor speed relative to crank shaft: 172.
Breaker gap: 0.020 inch.
Spark plug thread size: 18 mm.
Spark plug gap: 0.015 inch.
Fuel pump.
Speed relative to crank shaft: 1:7.12.
Bore: 1 inch.
Stroke : 72 inch.
Inlet connection: 72 inch.
Outlet connection: 72 inch.
Tachometer drive fitting.
Speed relative to crank shaft: 72.
Outside diameter of threads: % inch.
Pitch of threads: 18 U. S. F .
•
SUMMARY OF CLEARANCE-CURTISS D- 12
ENGINE
Mini- Maxi­mum
mum
Breaker gap __ ___ ____ __ _______ ___ ---- - _____ - __ -- ---- --- -
Cam follower, diametrical clearance in guide ____ ___ ___ _
Cam shaft, diametrical clearance ______ __ __ ___ ____ _____ _
Cam shaft, end play ________ ____ ___ ___ ___ __ ____ ______ _ _
Cam shalt dri,-e shaft lower bearing in housing, end play
Crank shaft, diametrical clearance ___ __ __ ____ __________ _
Crank shaft ball thrust bearing, end play in crank case __ _
Connecting rod, diametrical clearance on crank pin ___ __ _
Connecting rod, end play on crank pin _________ ____ __ Gears (all), backlash when cold __________________ ______ Gear case pump drive shalt, diametrical clearance _____ _ Gear gas pump drive shalt, end play __ _______ ___ ___ __ _
Oun control drive shaft upper ball bearing, end play in
housing ______ ____ ___ __ _________ __ ___ -- - --- -- - -- -- -- --
Gun control drive shaft,diametrical clearance in housing
Oun control drive shaft, end clearance at top of housing __
Hand starter drive bevel gear, diametrical clearance __ __ _
Hand starter driving shaft, diametrical clearance at
small end. __ ____ ____ ___ __ ----- - --- __ __ --- - ------ - -- --
Hand starter driving shalt, diametrical clearance at
large end _____ ______ ____ -- ---- -- -- - -- ---- -- -- · ---- -- --
Hand starter driving shalt, end play __ -- --- ----- ---- --­Hand
starter idler gear, diametrical clearance_ - - - -- - - __
Hapnladi ns tbaeraterri nmg a__g_n_e_t_o__ d_1_f_r_e_ _sh__a_f_t_, _d_ia__m_ e__tr_i_c_a_l_ c__le_a_ r-a-n__ce_ _
Hand starter magneto drive shaft ball hearing, outer
race end play in housing _ ____ __ _______ ___ ____ ___ __ __ _
Hand starter screw clutch gear hub, diametrical clear-ance
____ - - - - - - - - - - - - - - - - - - - - - - - -- -- - - - - - - - - -- - - - --- - -
Hand starter screw clutch gear, diametrical clearance __ _
Hand starter magneto spur gear, diametrical clearance _
Hand starter magneto worm gear, diametrical clearance_
Magneto Oldham coupling driving flange, clearance in
housing __ -- ---- ------------ ----- ---- -- ___ -- - -- --- __ _
Magneto drive shaft, ball hearing end play in housing __
Oil pump live shaft, diametrical clearance ____ ________ _
Oil pump gear, diametrical clearance in body ___ ______ Oil pump gear, end play in body _ ___ _______ __ _______ _ Oil pump gear, diametrical clearance on idler shaft __ __ _
Piston at top land ____ ______ __ _____________ ____________ _
Piston at bottom of skirt_ __ ___ ___________ ___ ____ ______ _
Piston pin in piston __ ____ _____ ___ ______ ____ ___ _______ _ _
Piston pin in connecting rod ______ _____ ____________ __ _ _
Piston ring in groove ____ __ ___ _______________ _______ __ _ _
Piston ring gaP-- -------- ---- ----- -- ---- -- ---- -- --- - - --_
Piston ring, diametrical clearance at root of groove. _____ _
Propeller hub, diametrical clearance at small end of
crank shalt when pushed on shaft by: hand ____ __ ______ _
Pump drive shalt, diametrical clearance in gear case ____ _
Pump dri\·e shalt, end play in gear case ___ ______ ____ __ _
Spark plug gap _________ --- ---- - ------- ---- _____ ______ _
Tachometer drive shalt, diametrical cle.arance _____ __ __ .
Tachometer drive shalt, end play _---------- -- -- -- --- --
Tappet gap ______ ------- -- -- -- -- -- - -- -- -- -- __ - -- --- - -__
Triplex gas pump shaft, diametrical clearance ____ __ __ _ Triplex gas pump shalt, end play ________ _____________ _
Triplex gas pump piston, end play on shalt __________ _ _
Triplex gas pump piston, diametrical clearance in bore __ _
Valve, diametrica clearance in guide ____ ___ _______ __ _ _
Vertical drive shalt, diametrical clearance at lower end __
Vertical drive shalt, end play in gear case _________ ___ __ _
Water pump shalt, end play __ --- --- -- - ----- --- ____ ___ _
Link pin, diametrical clearance in short connecting rod __
0.020
.0005
. 0015
. 001
. 001
.002
.0006
.002
.004
. 003
.0005
.002
. 001
. 001
.005
.0005
. 001
. 001
.003
. 001
. 0005
. 001
. 001
. 0005
.001
. 001
. 003
. 001
. 0005
. 001
.002
.oor
. 017
. 010
. 0005
.0000
.0007
.007
.044
. 002
. 001
. 006
. 015
. 001
. 005
.014
. 0005
.002
. 002
. 0005
. 0025
. OOl
. 007
. 003
. 0000
WEIGHT OF ENGINE AND PARTS
0. 024
. 0025
. 003
. 009
.003
. 0025
.018
.006
.0015
.004
. 006
·002
. 002
.003
. 010
. 002
. 0015
. 013
. 003
.0025
. 002
. 002
. 0065
. 0015
. 003
.005
. 002
. 021
. 014
.0005
. 0015
.0027
.009
. 004
.003
.008
. 018
. 003
. 010
. 016
.002
.004
. 0045
.0025
. 004
. 003
. 010
. 006
. 0015
Per
Cra11 k case gro11p, including bea rin ~. studs, nuts, etc.: Pounds rent
t'pper hall group ____ - -- __ ----- _ __ _______ ____ _ 85. 50
Lower half group_. _._--- -------- ------ -- -- --- -- -- - 14. 10
Gear ca>e __ ____________ ----- ------ _ __ ___ ___ _ _ ___ 12. 20
Total. _______ _ · ----- --- ---- ---- -- ---- -- -- -- -- ----
Crank .•t.rift. group, including shalt, t h1·ust bearing, d rh·c
gear, oil plugs, and oil rings ______ _ ·-- ___ -- - -- - - -- - -- -
P ropeller h11b assembly, includ ing hub, flanges, bolt s,
pins, nuts, etc ___ _____ _____ __ _____ _______ ____ _______ _
Lock nut_ __ _ - -- -- - ------ ----- - --- ------ ----- -- - - ..
Total. __ __ ___ ---- ---- __ --- -- --- _______________ __ C0111ucti11g rod group, includ ing rod assemblies, with
bolts, studs, nuts, bea rings, etc ___ __ ------- ---- - - - ---
Piston grouv, i11cluding-
Pistons:
L . C., 12 at i.64 each _______ __________ ____ ____ _
H. C., l2at l.74 each ____ ___________ ____ ___ ____ _
Piston rings __ __ __ __ __ ____________________ ______ __ _
Piston pins, with retainers _________ ____ _____ __ ___ _ _
111.80
68. 50
16. 70
1. 11
Ji. 81
36. 00
19. 68
20. 89
l.80
6.00
16.15
9. 89
2. 57
5. 20
7
Per
Cylinder group, including- Pounds cent
Bare cylinder blocks, with studs, nuts, etc __ _______ 203. 00
Exhaust valves ·- ·- -- - ---- --- ------------ ---- -- --- - 18. 7.5
Intake valves_- - -- - - --- - . ------------------·- ------ 18. 75
Valve springs, with collars nnd retaining nuts __ ____ 7. 60
TotaL. ---------- --- --- ---------- --- - --- -- -- - --- 248. 10 35. 80
Driving gear group:
Cam shaft inclined drive shaft, gears, and housings_ 9. 38
Upper vertical drive shaft _______________ -----_ ____ 2. 50
Lower vertical drive shaft_ ______ __ _____ ___ ___ ___ ___ 1. 40
Magneto drive gear, bearinr, etc__ _______ __ __ ______ 2. 76
Total. __ ------- -- - --- - --------·--- - -- --- -- --- --- - 16. 04 2. 31
Cam .•haft group, including-
Cam shafts, with gears and hearings_____ ___ __ _____ 32. 40
Cam shalt housings, with covers, nuts, etc .. - ---- -- 8. 40
Cam follow ers __ _____ __________ _______ __ __ ___ __ __ __ 7. 70
Total_ - - - -------- - ----- · - ---- - ·-- - ---- -- -- ·- -- - -- 48. 50 7. oo
Lubrication group, including-
Oil pump assemblies.- - ---- --- ---- - --- -- - -- -- -- - __ . 6. 90
Oil strainer_·------------------ --- --- - -- - ---------- .10
Oil pipes ___ ___ --- - ----------- ------- --- -- ---- - ----- 2. 49
Total __ - ----- -- ---- - - --- · - ---- - -· --- -- ---- --- - --- 9.49 l.37
Cooling svstem group, including-
Water pump assembly_ __ _______ __ ____ ____ ____ ____ 4. 40
Water manifolds and piping ____ -- -------- -- -- --- -- 9. 50
Tota!_ ___ ___ _____ _____ _ ----- - --- -------- - -- - - -- __ 13. 90 2. 00
Induction gro11p, including-
Carburetor assemblies, complete__ __ ________ ____ ___ 25.03
Intake manifolds, complete_______ ___ __ ____________ 18.35
TotaL _ --- -------- - --- ------ ---- ----- --- - - - --- -- - 43. 38 6. 26
Ignition group, including-
M agnetos and cottpling __________ --- -------- -----· _ 29. 60
Wire, manifolds, and distributors . • -· -- - -- -- - -- -- · 6. 00
Spark plugs. ----- - ---- -------- ----- ---- --- -- -- - -- __ 8. 20
TotaL __ ------ -- ----- - -- - -------- -- -- ----- ---- - -- 43. 80 6. 32
MU.cellaneous:
Cotter pins, lock wire, nuts, etc ___ ____ _______ __ ___ 1. 00 . 14
Auxiliaries:
Gasoline pumps ___ __ -- -- ------ -- --- - - ------ ---- --- 4. 58
Synchronizer drives____________ __ ___ __ _____ ___ _____ 2. 48
Total. __ ----- _ -- - -- -- - --- --- - -- --- -- -- -- -- -- -- -- - 7. 06 1.02
T o t a 1e ngm· ewe1·g h t w1· th all.I ni·a n·e s _____ ___ ___ ____ {' 692. 86}, 00
694
_
06
100.
Weight of water in engine _____ __ ________ ____ __ __ _ _
Reciprocating and centrifugal weights:
Piston, complete with rings, pin, etc.{~·. ~---~ :: : : :
Upper end, main connecting rod __ ---- --- -- - --- --- -
Upper end, secondary connecting rod ____ ___ ___ ___ _
Lower end of complete connecting rods ____ ________ _
Total weight, main rod complete __ ____ ___ ______ __ _
Total weight, secondary rod and pin, complete ___ _
Intake >alve, without spring ___ __ ____ ___ __ --- --- --
Exhaust valve, without spring _-- --- --- - ----- - --- --
Valve springs for one valve ___ _________ ______ _____ Upper spring collar and nut _ ___ ____ __ ___ _________ Cam follower ___ _ ---- -- ----- ---- -- -- - -- -- --- - --- ---
42. 0
2. 0
2. 35
.9
. 7
3.6
4. 3
1. 70
1. 6
1. 6
. 140
.03
. 321
RECORD OF ENGINE TEST- INTRODUCTION
This report has been compiled from tests which
have been run in the power plant laboratory since the
first engine was received; in May, 1923. The results
are an average of eight high and eight low compression
runs. A few changes in design have been made, but
these have not affected the power results.
Little carburetion information has been included in
this report, inasmuch as there is another report devoted
to that subject. (Eng. Div. Report Serial- No. 2426.)
'l'otal __ __ ______________ _________ _________ ___ ____ _
'l7. 48
1 With low-compression pistons.
3. 97 I ' Percentages figured with low-compression pistons.
8
METHOD OF TEST
All runs were made on engines which were connected
to Sprague electric cradle dynamometers. The power
was determined by measuring the torque reaction of
the field housing on indicating scales. The following
runs, which are included in the report, were made
according to the detailed methods set forth in the
Engineering Division Report, Serial No. 1507.
High-compression engines (6.0:1)
Engine Nos.
A. S. Mfg.
No. I No.
Power runs R.p.m.
range
~~1-~~~~~1-~~~-
23-157 I 128
23-155
23-154 1
23-218
68869
68870
1 full rich ______ _
1 best setting.
126 1 best setting __ _
1 full rich.
125 1 best setting ___ _
15 1 full rich ____ __ 14 1 full rich ______ _
1 best setting.
•
1, 800-2, 500
1, 800-2, 500
1, 700-2, 300
1, 700-2, 300
1, 700-2, 300
13 _______ ___________
1
1, 201H,OOO
Miscellaneous runs
Friction run.
Friction.
Do.
Friction; beat rejection;
water and oil pump
capacity run; 1 hour
fuel and oil consump-tion.
Propeller load .
Low compression (.5.3:1)
Engine Nos.
A.s. \Mrg.
No. No.
Power runs R.p.m.
range
23-144 93 1 full ricb ________ 1 1, 800-2, 500
1 best setting.
23-173 180 lfullricb _______ 1,600-2,200
23-115 53 lfullricb __ __ ___ 1,400-2,200
1 best setting.
23-123 112 1 lull rich_______ 1, 600-2, 800
1 best setting ___ 1, 600-2, 500
23- 112 22 1 full rich _____ __ 1, 700-2, 300
llliscellaneous runs
Friction; beat rejection.
Friction.
Propeller load.
Friction.
Friction; beat rejection;
pump capacity run; 1
hour fuel and oil con­sumption.
The low-compression engines were tested with a fuel
mixture of 20 per cent benzol and 80 per cent gasoline, ·
by volume. In the high-compression engines the quan­tity
of benzol was increased to 50 per cent. The gaso­line
used conformed to War Department Specification
2-40. All oil used was grade 2 of War Department
Specification 2-23D.
OBSERVATIONS DURING TEST
The fuel mixture distribution generally throughout
all the tests was rather poor. On all the engines the
extreme end cylinders (Nos. 1 and 6) seem to run
richest, with Nos. 2 and 5 leanest. The vibration on
the dynamometer stands seemed to be a maximum at
about 2,500 revolutions per minute. At no point,
however, did it appear serious, although at times some­what
uncomfortable to observers.
RESULTS OF TEST
The results of tests are tabulated and plott.ed on
pages 9 to 15, inclusive. Engine performance varies
considerably, as shown by the curves on figures 2 and
3. The curve on figure 1 gives average performance
of the engines tested. This variation is undoubtedly
due to the poor distribution, which also causes a high
specific fuel consumption. In spite of -the poor dis­tribution
an unusually high B. M. E. P. is obtained.
The friction horsepower is low, resulting in high
mechanical efficiency. This is shown by the curves on
figures 4 and 5.
A.nalysis of per/ ormance
Cumbailc sipnecehdes _ _o_f_ p__is_t_o_n__ d_i_s_p_l_a_c__e_m__e_n_t _p_e_r_ _B_._ _h__. p__. _a_t_ _n_o_r_- _
B.s pbe. epd. _p__e_r_ c_u__b_i_c_ i_n_c_h__ o_f_ p__i_s_to_n_ _d__is -p-l_a_c_e_m_ _e_n__t_ a_t_ n__o_r_m__a_l _
P iston speed in feet per minute at normal speed ____ ___ __ _
Indicated mean effective pressure at normal speed ___ ___ _
Friction mean efiective pressure at normal speed __ __ __ . __
Brake thermal efficiency at normal speed _ ____ per cent__
Indicated thermal efficiency at normal speed ______ do __ _
Air standard efficiency __ ________ . ____ .. __ ________ do __ _
Efficiency ratio (indicated thermal to theoretical air
standard) ___ --------------- __ ___ ______ . ____ per cent__
Efficiency ratio, based on brake thermal efficiency_ do .. __
CONCLUSIONS
DESIGN
Compression
ratio
6.0:1 5.3:1
2. 618 2. 689
o. 382 0. 372
2, 200 2, 200
155. 5 151. 8
18.0 17.8
26. 0 24. 09
29. 54 27. 06
52. 22 49. 55
56. 6 54.6
49. 8 48. 6
The design in general is distinctly superior to that of
contemporary engines. The relatively low weight has
been obtained largely by compact arrangement and
careful proportion of parts, and by the extensive use of
light alloys. Among the admirable design features of
the engine the following are outstanding:
Light, stiff crank shaft, · with large bearings
and broad crank cheeks.
Light pistons, with excellent wearing qualities.
Induction system providing high volumetric
effi ciency , and consequently high mean effec­tive
pressures.
Reduction of reciprocating and rotating loads,
resulting in exceptional freedom from vibra ­tion.
Liberal strength and area of bearings.
Several design faults also have been disclosed since
the adoption of the engine as a service type. A large
portion of these faults have already been corrected
by design changes. The diameter of the link pin
bolts has been increased from lif inch to % inch to
eliminate failures which have occurred at that point.
The slot in the link pin boss on the master rod has '
been eliminated . A cast duralumin water jacket
with enlarged fillets has been substituted for the
original aluminum jacket to reduce water jacket leaks.
A built-up steel main bearing oil manifold with
brazed joints has been substituted for the original
one-piece pipe with welded flanges. A tapered collar
has been added at the splined joint between the
vertical shafts and upper gears to reduce trouble
caused by wear and shear of the splines resulting from
poor fits.
The thrust bearing nut locking wire has been re­designed
to permit joining of the ends by wire to
prevent throwing loose by centrifugal force at high
speeds.
Intake cam back faces are being drilled for better
lubrication of cams and followers.
The oil supply . spiral groove in ,the tachometer
drive shaft at the rear of the valve cover is now filled
with solder to prevent oil flooding of the tachometer.
ew shafts are made without the spiral groove. A
depression spring has also been added to prevent
injury to the housing during assembly.
Die cast piston, released for production at engine
manufacturer's o. 138, has the same weight as the
original piston and is interchangeable with it.
Piston pin material changed from Curtiss material
201 oil hardened to 211 casehardened. Material 211
composition is:
Carbon __ ___ __ ________ 0. 17 maximum.
Manganese____ _ _ 0. 30-0. 60.
Phosphorus____ ________ 0. 04 maximum.
9
Sulphur ____ ________ __ 0. 04 maximum.
Chromium ____________ 1. 25--1. 75.
NickeL _____ ____ ______ 3. 25--3. 75.
Shape of oil pressure line pump to crank case changed
to make room for socket wrench.
In ·addition several faults still remain to be corrected.
Fillets should be cut at the bottom of the grooves,
now square, which carry the main- bearing cap aligning
bars. Cracks have occurred at that point in several
engines.
Galling of the propeller hubs and crank shaft tapers
has occurred frequently. This trouble has often
been caused by improper hub fitting, but has occurred
several times when the hub was very carefully fitted
in accordance with manufacturer's instructions. Either
the hub or the installation method should be modified,
therefore, to prevent further such trouble.
Oil leakage at the magneto drive shafts should
also be eliminated.
PRODUCTION
For general production the engine should offer few
serious difficulties. In case of emergency, however,
if it were found desirable to manufacture the engine
in very large quantities and at several plants, the
intricate light alloy castings used in the engine would
probably cause delays.
PERFORMANCE
In performance the Curtiss D-12 by far excels
contemporary engines. The mean effective pressure
is considerably above ~he average and holds up well
at high speeds. The power peaks at 700 revolutions
per minute above the designed speed. Its fuel con­sumption,
however, is excessive, as a result of poor
distribution. The oil consumption is below average.
In maneuvers, also, the carburetor shows undesirable
characteristics, causing "cutting out" of the engine
in sudden " bumps," "nose overs," .and other maneuvers
which tend to throw the fuel away from the float
chamber outlet.
The endurance of the engine, as indicated by several
successful 50-hour tests at speeds up to 2,450 revolu­tions
per minute, is excellent.
SUITABILITY FOR AIRPLANE INSTALLATION
The small frontal area and general compactness of
the engine are particularly desirable for purposes of
installation. Its mounting flanges and control con­nections
are simple and readily accessible.
MAINTENANCE
The engine presents one serious difficulty for main­tenance
while installed in the matter of the inacces­sibility
of parts in the vee, principally spark plugs,
carburetor adjustments, and control settings. The
pressure oil line also is at present too close to the
crank case to permit the use of a socket wrench on the
inner flange nut, but, as noted above, that trouble is
being corrected by a change in the shape of the pipe.
For shop overhaul the engine presents few difficulties.
The auxiliary gear housing can be removed without
disturbing the rest of the engine. The blocks, oil
pan, and case are easily removed to give access to
main and rod bearings, but the block construction
makes necessary the removal of a complete block for
the inspection of one rod or to grind valves in one
cylinder. The use of retaining screws instead of dowels
to secure the bearings makes replacement of bearings
slightly more difficult.
Considerable time is required in setting tappet clear­ances.
Special tools are necessary for that adjust­ment.
Special apparatus is required also for the in­stallation
of new cylinders.
Propeller load run, Curtiss D-12 low-compression engine
Actual Water Oil Fuel consumption
R.P.M.
Brake
load B.H.P.
---------
Pounds
2, 210 552. 0 407.0
2,000 457. 0 305. 0
1, 780 368. 5 218.5
1,610 292. 0 156. 7
1,400 223.0 104. 2
1, 200 167.0 66.8
Date: February 9, 1925.
Brake arm length: 21 inches.
Cor-rected
H.P.
---
418.0
313. 2
224. 6
161.0
106. 9
68. 6
I
Tern-
Temperature pera-ture
In Out In
-------
o F. o F. o F.
148 162 139
146 160 138
148 160 138
146 160 140
146 160 138
146 160 134
Oil used: 2-23E, grade 4, viscosity 120 sec. (Saybolt) at 210° F.
---- Carb. air Man. Vac. Mixture
tern- In. control
Pres- pera· Lb./ Hg. position
sure ture Lb./hr. H.P./
hr.
--- -------1----
Pounds
Pf! sq.
in. o F.
144 133 60 F. R. 229. 5 o. 564
144 130 60 F.R. 153. 5 • 503
144 122 60 F. R. 115. 5 . 528
146 116 60 F.R. 86.0 • 546
140 108 60 F.R. 59.4 . 570
138 106 60 F.R. I 39.4 . 592
Fuel used: 20 per cent benzol, specific gravity 0.735 at 64° F.
Spark plugs: A. C.
Barometer: 29.11 In. Hg.
10
One-hour f uel and oil consumption run, Curtiss D-12, A. S. No. 23-112, manufacturer's No. 22
Compression rat io 5.3:I
I Fuel I Oil I
Actual Corrected Water Oil I . consumption consumption Carb . Man. - I
R. P . Temper- I air Vac. Oil
Time M. T emper- tern- In. I scale
Brake B.H. B. M. ature ature I Pres- pera- Hg. Lb. / Lb . .' I rdg. Lb./ Lb./ I
load P . H.P. E. P. --1sure
ture hr. H.P./ hr. H.P./br. br.
In Out In Out
- - - ------- - - ---- - - ---- ------,- - 1----- !
Lbs. Lbs. I pe_r o " per
Lbs. sq.in. l'. o F. o F. o F. sq.in. o F.
o ____ ____ --- ---- , fI~s5 -~-b_•:-1 ---~-b_s: ___ 5 ___ ___ _ -- --- -- 567. 0 380. 0 391.1 I34. 6 156 I<O I32 137 I06 59 1. 2 ---- - -- 2, 010 568.5 381.0 392. 1 135. 0 I57 170 134 138 106 60 I. 2 I94. 4 0
10 _______ 1, 978 567. 5 374. I 385. 0 1 134. 6 ' 156 170 135 140 110 60 u1rnu : ~i~ ~ij :::::r:::::::: 15 __ __ __, I, 992 567. 5 376. 8 387. 9 I34. 6 I56 170 I36 140 1 110 60 . 516 IO. 5 - --- - -1- -- - - ----- 20 __ ____ _ 1,998 568.5 378. 7 389. 9 I35. 0 156 170 138
25 ___ ____ 2,000 567. 5 378. 2 389. 3 134. 6 I56 170 139 114412 I I11l3l 6600 11.. 22 1 119938.. 02 .. 552130 1100.. 02 ---- ---- -- -- -------- ---- ---- -- -- 30 __ _____ 2, 004 568.5 379. 8 391. 0 135. 0 I56 I70 139 142 114 60 I. 2 194. 4 344Q55 ______ _______________ 11l ,,,999999646 555666788... 505 333777688... 844 333888997... 955 111333444... 995 1II555666 II177700I 111344900 11I444323 111111444 665009 t ~ ,-i87.-2- --:~~~- !: ~ :::::r:::::::: 50 _______ 2, 000 568. 5 379. 0 390. 1 134. 9 156 I70 139 142 114 59 11.. 22 1 119906.. 88 .504 I 8.8 -- ---- ---- ------ 55 ____ ___ .517 1 8.4 -- ---- ------- --- 60 ____ __ _ 1,998 567. 0 377. 5 388. 6 I34. 5 I56 I70 139 141 114 59 1. 2 190.8 . 506 8. 0 ---- -- ---- -- --- - 2,008 567. 0 379. 4 390. 5 134. 5 156 170 138 140 114 59 1.2 200.4 . 528 7. 7 -- -- -- -- - - -- -- -- ---
567. 8 378. 2 1 389. 4 I34. 8 1= 1= =1=:==1~1==1 193· 6 1---:5121==
- - ----
Average_ 1, 998
Oil us3d: 2-230 , grade No. 2, v isc)sity 120 sec. (Say b olt) at 210° F.
F uel used: Domestic avia t ion gasoline (2-40), specific gravity 0.700 at 79° F .
Spark plugs: A. C .
Barometer: 29.065.
Da te: August 23, 1923.
3. 8 0. 01005
One-hour fu gl and oil conrnmption run, CurUss D- 12, A. S. No. 68869, manufacturer's No. 14
Compression ratio 6.0 :1
Actual Corrected Water Oil
Carb. IMan
Fuel I Oil consumpt ion I consumption I
R. P. air · I Oil
Lb.f l Lb./
I Time M. Temper- Temper-I tern- Vac. scale Brake B.H. B. M. ature ature Pres- pera- In. Lb I Lb./ rdg.
load P. HP. E. P. ---- sure ture Hg.
hr: Hhr/ hr. H.P./hr.
In Out In Out
',----1--- ----------- -- -- ---- ------ -- ------ -
Lbs. I Lbs.
per p er
Lbs.
o ____ ____ 1, 991 598.o 397. o 408.3 141. 8 150 168 140 144 99 66 o.8 ___ __ __ ______ _ 10.4 ____ __ __ __ ____ _ _
Lbs. sq. in. \ ° F. ° F. ° F. ° F. sq. in. ° F . Lbs. Lbs.
5 ______ __ l, 99I 598.0 397. 0 408.3 141.8 I56 172 144 146 100 66 .8 0.523 9.8 -- ---- 0.01814
10 ____ __ _ 1,991 598.0 397.0 408.3 141.8 152 170 144 146 100 66 .8 . 505 9.5
15 ...... . 1,990 595. 5 395.0 406. 2 141.l 154 170 144 148 99 66 .8 . 509 8.9 : : : ::: : : : :::::: : ·
20 __ _____ 2,004 596.5 398.4 409.9 141.4 154 170 144 148 99 66 . 8 .511 8.3 -- - - -- -- - -- -- -- -
25 ____ ___ 1,991 597.0 396. 2 407.8 141.5 154 172 144 148 99 66 .8 . 515 7.9 --- --- -- - ------ -
30 ____ ___ 1, 980 596.5 394.0 405.2 141.4 154 170 144 148 99 66 .8 .518 7.4 - -- --- - - - - ---- --
35 ___ ____ 1,990 596.5 396.0 407.8 141.4 154 170 144 148 99 66 . 8 - - -- - - - - -- ---- 6.9 - - - --- ,-- -- -- - -- -
40 __ ___ __ 1,971 597.0 392.0 403. l 141. 5 154 170 144 148 98 66 . 7 . 527 6. 5 - - - --- -- --- --- -- '
45 ___ ____ 1,971 597.0 392. 0 403. l 141. 5 1 156 1 172 144 148 98 66 .8 - .506 6.0 ----- -,---- - ----
55 _______ 2, 004 596.5 398.8 410.0 141.4 156 172 144 148 98 66 .8 -- -- --- .508 5. 0 - - -- -- ---- -----
50 _____ __ 1,970 597.0 391.9 403.0 141.5 156 172 144 148 98 66 .7 - -- --- . 508 5.4 ----·-1·---------
60 ___ __ __ ~ 595. 5 393. 2 404.8 14i.1 --~~-T~-~~~~~--·1_::.:.:=.:..:.~~ .:..:..:..:.::.~I
Average l, 986 596.8 395.1 406.7 141.5 1--- --
1
____ _ -----1----- ---- --1-------1-- ---- 202. 6 1 . 513 5.8 1 . 01468 ,
Oil u sed: 2-230, grade No. 2, viscosity 120 sec. (Saybolt) at 210° F.
Fuel used: 50 per cent benzol, specific gravity 0.765 at 93° F .
Spark plugs: B. G. lXB.
Barometer: 29.10 In. Hg.
Date: August 8, 1923.
11
Heat rejection run, Curtiss D-12 engine, A. S. No. 28-144, man­ufacturer's
No. 93, September 12, 1914
- Water Average Heat re-
R. .P J\1. Weight Weight Weight Time through temper- jected to
before after of water engine ature dif- cooling ference water
- - - ------------ ---- - -----------
I Pounds I B.t. u.
per :per
I
Pounds Pound.• I Pounds Seconds minute op. nunute
2,000 109.0 257.0 148 15.0 592 14. 90 I 8,820
2, 100 65.0 216. 0 151 14. 8 612 15. 03 9, 195
2,200 61.0 216. 0 155 14. 6 637 14. 85 9,460
2,300 64. 0 230.0 166 14. 8 674 14.30 9,640
2,400 I 64. 5 231. 5 167 14. 8 677 14.00 9,480
I I - '
Barometer: 29.41 In. Hg.
Carburetors and setting: Stromberg NA Y-5A; throttle position, full open; mix­ture
control position, lull rich.
Fuel: 40 per cent benzol, 60 per cent domestic aviation gasoline.
Oil: 2-230, grade 2.
Water pump capacity run (through engine), Curtiss D-12, A. S .
No. 68869, manufacturer's No. 14
Compression ratio 6.00:1
Water I Scale readings Water flow
R.P.M. T emperature Total
Before After pounds L' Jm•o. IG.. . /m' o.
I for 15
In Out seconds
------ --------- ------- --------
oF. oF.
l , 770 166 170 42. 75 164. 00 121. 25 485. 0 58.5
l, 780 168 172 42. 50 165.00 122.50 490.0 59. l
2,010 172 172 42. 50 182. 25 139. 75 559. 0 67. 4
2,010 168 154 43. 25 184. 50 141. 25 565. 0 68. l
2, 190 170 172 42.25 200. 75 151.50 606.0 73.0
2,200 164 170 43.00 201.50 151. 50 606.0 73.0
Oil pump capacity run (through engine)
Oil Oil flow I I
R. P.M. T emperature Pounds Seconds
Lb./min. Gal./min.
In Out
-----
oF. op_
1, 770 137 140 10 20. 4 29.40 3. 94
l , 780 137 148 10 20.0 30.00 4.02
2, 010 135 148 10 20.8 28.85 3.86
2, 010 136 149 10 20. 8 28. 85 I 3.86
2, 190 138 152 10 19. 2 31.25 ! 4.18
2, 200 140 154 10 19. 2 31. 25 I 4. 18
2-ZIC grade No. 2.
-- -,_I __ ~~
_HQ_
I r-+::::: :-...( HIGH co,..,k ~~
~~ _.f.JJ2._
I :-,..;:-
LO/, -- -........... ~~ /20
'-'V.-.;; , J..J.._J .£1•/,< J- 1 0.V.JIU . .:.. r-........ I 4-70 t'.~RA~/.ft'g'j'~Ca;$.~tY3-S //0
460 I/ _,.,
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•AA v v
l:rl / v .4.fil_ !:i
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AOA I" -- - -LJEST S£1Tl/Y6'
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4 10 ~ / / FUEL - ;i '{,W..
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W' M &7"/Q>YS PD' MIY OF £iYGl/Y£
16W 11\xJ "lr/1 -"*'° ,.J,y, >tlr.n Pih?
FIG. 1
Ct/R 77SS .0-/Z LOff t:<:'HP,Pc.SS/ON C'N6"/AIE.J
,,,.~... . . ·-- 1460
400 ~ r>-JV/'1~ /, ~>·
/. /
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4SO ~ v
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420 ~ J / ..
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~~ .L
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~ I/ ;~ ;; l.2'.2Q. ~ • I 13 ~~ I~ / j
~~ "'t 1 I Ji
~ !1~I I '160 ~
->->o '/J
340 I v
330 l;I/
I Q?/> ), r ..
REVOLUTIO/'t5' PER N1/'ll!r£ OF EIYG//YE
16'1'"1 ;~bo ,2,..h.-, z-<loo ,,,,1,,., Ri'Y'l .a'ill
FIG. 2
13
Cl/R T/SS D ·/.2 H / GH
470 CO/'V"'R.G~S/OH EH~N.!'J /
/ / .
A£:0 ,~ <· --- -
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440~ I v J ,,
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4-10 ti
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G // ~;
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w:;o I / J
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.9.x1
REVOL.L/T/O/VS PL!'R /'?//Vt/TE Or ENtS//VE
.? <:>/'\ /'1, ,.,,., /~ 20L-.,., zpl,,n ~ 2D ~o
FIG. 3
CORT/SS .012 EMi/lr'E·L/7,V Cl4'fr'HS.f/'2'Y
PERFORM41'/CE Cl/RPES ~ - ~VEP 6£ ti" ,,.,,,,.. .e., ~IN,:~ "" I~
q~; --=
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REJ/tJ,!.UT/OA'J PfR h'/.N. o,.,- .£.N6'/#E
16~ /,!;oo I zob,, 2ko 2<"1.,, 26 l?o
FIG. 4
75863-26t-3
14
Cltl<T!SS LNZ HIGH a:l'ffeRLX57QY ~.Q')Z" iii;
PERFORHAl'/CE CO.RV£$ In
Wff,P, 'GE OF Flff EM:Jl/'iES
~
............
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:...
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v ~ ~ ......... ~Wll- v"" ~
./ ~ __4Q._ v ~
~ REYtJLl/l'7t7A<f PL'/i' H /Nl/T.£ O_., EKIS/NE ~ 30
16 r:>o /.Ano 2L I 2.A.o ~l.o ..!!b ot> I
FIG. 5
. (
Ml!TURE CONTROL SET Ft/LL RICH
EAR 29.JJ IN. HG.
AIR TE/'U' 60' F.
ir1L1n 20Z.BEN.ZOL SP.G.R.7.:J..5A T 64°.F.
400 )
P.Rl?PEL LeR LOALJ R t//V / ~i;j Cl/RT /.5S .D-/2 LO»' COH Plf'EJJ/Olt/E,YtiJIYt.
~ i/ ~'l
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Sl /
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.........
Al?
---- ~ la.6'l:l .......__ t-:i :i:: ...... ) ?;; A; ~ ~ ~ ----l"'-<t. v t;j cq r--~ ./
HE:VOLUT/ONJ Pc.Ii' ,Y/.N.OF .. 6¥6/H.S ~~ ~
/2hn /4bo I '"b., .2;0 22 ~~ I
/8 ~ "o
FIG. 6
15
HEAT REJECTIC¥Y Rl§Y
CVRTISS .lN2 E/'LJ. AS IY023-/14 NFRSl'IO. -9.'.! .9/~
...C~ "!/ HT· hf7
A~GE AIR TENP. .57" F.
THROTTLE FaSIT/O/Y, FOLL OPEIY
HJXT!IRE Ca"YT-©L FWfffO/'l fl/l.l RICH ,_, lrCHPRESSION RA770 S.8'1
,
-~
~ ~ ~
3l2Q ~
._... ~TA !&/El TC.[} roai U.U>C WAT~D ~
.,...... e:l>--
- ~ q::
~ _.22._
o~~ ar.u. IP£<>, ~P.Pl eMh r--... r-.._ ~'-2L
::s
1&i ?n
"""
--- ~
~i...-
~ l>QlTl "' n. ow ~
-~
'ii:!
!:'1
K~
N;
,-'E - B£Tk, !UV
~ "'
PYLE. AN£; oon ;,<:Th f4Ta
~-J
~
~' ~ 'LOT!O/YS PER Ml/YlJTE CY' £Iler/ff£
.,c.,,.. .,!,.,,, • .J,.,,., .k, ~ ·.,,,,
FIG. 7
WAT~.R Pl/HP CAPAC/TY RUN
(THROl/Gh' EN6/NL:)
Cl/,,..T/ .SS LJ-/2 £,lf/6/NE Av.Na68869 ;V,t:NJ.ht?..,/f.
_M_ ~
._ZQ_ ~ -
' -
~ ~ ....--
60 ~ - ------ !-"--- ~ _,.
~
~~
~
OIL PUMP CAPACITY ,RUN
(77-z'ROWH EJYGINE)
~
~ ~
~ ~ - __.,. - hl l-4.- - <i::
> ~ d
R.EVOJ.UT/OMS_ P.ER N/Nl/Tt:' O,t: EN6/H,t ~
17'0tJ 18 0 J.9L 20 0 .z1k Z2 '(Jo
FIG. 8
16
CURT/Jc5 L>-/2 EA/6'/#E
' LI. YALYE OPEN/No P/AuffA.#
/ ........ -........
I -----EXHt wsr ~!<"'" "' \
~ « I\
I /
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t---1.l'f, 'AKE U<!LY'.2 I\ \ ~ ~ l;J ~
~ I \ \ ~ ~ 1 ~ J
~ I I ' \ ~ ~ \
II' 1~ \ \
J ~,, / r-...
CRANK .POS/7'/0N-.DEGREES ~ t'O} /2 ,tJ l~ iO ~'O !BD It::> ,e< ro sc. !O ,(~ ~ .2c IO 24 r :z~ p ~ p .XI? .s
~ ~ v I;.)
""' I lo...i ./
~
'CRANK POSJ770JY-.lJ£(;Pf?Ji'9
' ~h ""f'.) cb th 1do ab Jo 1~ IO !tb ,a: to 2 l'D ,2; ~ :z~ o
FIG. 9
FIG. 10.-Three-quarter front view
17
FIG. 11.-Three-qnarter rear view
Fro. 12.-Top view
18
FIG. 13.-Side view
Fm. 14.-0ear end view
19
FIG. 15.- Longitudinal. section view
Fm. 16.-Cross-section view
20
Fm. lS.-Crankcase (inside)
21
FIG. 19.-Crankshaft
FIG.. 20.-Comparison or Curtiss and Liberty crankshafts
22
FIG. 21.-Connecting rods an~ pistons
FIG. 22.-Sectional views of pist.ons
23
F IG. 23.- Cylinder block assembly
F IG. 24 .- Gear housing assembly
24
CURTISS IJ ·l2 A.S. /Vo. 23-IS4
!1FG. No. 12 5
COl"IP~ISS/ON HAT/() S: 8 : I
So·HR. T"A'<JVE .3TANP f.+'PV-'AIW'~ HS'T
I 2 3 4
CYL/NDE.R NO.
S/11.C'H~O/l(E .STl:El
EXHRvsr VHLV.ES
.$EllT CtJNDITltJh'
F10. 25.-Exhaust valves showing seat condition after 50 hours
CURTISS 0-12 A.$. /(o.23-IS4
/"fF6.llo. JRS"
CO/"IP~ESS/OH HAT/() 5;8: I
SO·Hli TOA'~.SUND FMNl~Mal7.fT
CYL/NOEK BANX
511.Cl-IHOHE S7tEL
INrAKE VALVe.S
SEAT CtJNOIT/ON .
FIG. 26.-Intake valves showing seat condition after 50 hours
6
25
CU.l?T/SS 0-/2 A.S. No. 23-/54
~-4!'"G. /Vo./25 ~
COHPREsSION RAT/O S.8: I
.SO·HR.TO~DUE .ST-4,Nb E#DU/l?AIVCE 'T"ESr.
.S/LCNHONe ST.EEL E-XHAVJ"T J/4L.VES. sr~M CON0/7/0N
FIG. 27.-Exhaust valves showing stem condition after 50 hou rs
FIG. 28 .-Cam shafts
26
CllRTISS-012
FIG. 29.-Curtiss water pump
· FIG. 30.-Carburetors and manifolds
27
F10 . 31.- Jntake manifold assembly
FIG. 32.- Side ·dew of Stromberg l\A-Y5 carburetor
28
FIG . 33.- Thrcc-quarter view or Stromberg NA-Y5 carburetor
29
S7ROMBERG IYA-Y5 CARBURETOR
F rG. 34.- Sectional view of Stromberg N A-Y5 carbure tor
FIG. 35.-Magneto coupling
30
IJ TC rl?o lrROI TOR :
I rt7 1'1.:SClftJCrtGtnG PUr1PS TO" OIL.
QJJ.. Llf1C TO Tli'IPJ..CX Gl'IS PUl1P.
PL UG IF'" JOU/"fPI.$ nor u~co . 01/.. . PlfC~~(JfiC!lCLIC.r Vl'ILtlC.t
T£11PCtrf'ITURC HCGtJJ..ATOli' 'Y-V O. 0 .
noT£: PRES.SUR£ 111 T Hl5J.ln£0FTC!f
11TTl111Y.5 t00 LOS.PER SQ.trTCH
!ff COLD l./Cl9THC/i'.
SHRR/O BCIYOS t f'f TliC!i'/'10/"JCTCIP O/f'
P/1C.5SUIPC G/'16£ Llf1CS t1flY Rl.lllY ·
t/t STRtJl1£f'fT. r11rOrTU1'1 l?flDIUS OF
(JCITO /'f'J:,COl11"/Cl1DCD IS /.S 117CHCS .
! Ff(Of'I T SUl1P DRfllf1 PJ..VG
FIG. 36 -Oil line installation diagram
INLET FRD~_!l!l,,.Y_Afll~
FIG. 37.-"0il passage through engine (longitudinal section)
Oil.. Tl'lnl( FIJ...LC!f
PL/IC£ .so £XPRn.510n .JPl9CC CRl1f10T
/JC TILi.CO J.J/Tlf OU • . C¥Plff'IS!Oh .:JfflCC
~00 cu 111. JJITH L/1Glf'IC 1?Unn1nG.
'Rh IJ171ft/1 .
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OEl..OIJ OIJ.. PUl'1P.
31
TOOIL
THERMOMETER
ATURE REGULATOR
'.J-_____ OIL PREllURE RELIEF
FIG. 38.- 0il passage through engine (cross sect ion)
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C-tAt?a (AHi( L IH£tJ -o/a !!:£.:....
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FIG. 39.-Fuel line installation diagram
L E w LE FT E?C.!=WJST
LI • LEFT INTAKE
R . E R IGl4T £l<r\AUS T
R. I . : RIGHT INTAKE
TC. ~TOP CEf:f\'ER.
C .5 :::. CRAhKSt\l'..FT SPtl:p
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LETTEQ5 C ? · Q.E~!'\T -~~ Sw.HG£ ltl
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Of f \Tt'E3 C..EbS Qf' JI=\£ PAIR IN QUfi:;T!QN
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FIG. 40.-Splitdorf switcn and wiring diagram
t-'.Mi!K K \.-1.A.l="T
ANt> GE~ !?"\\NEC::. .
VIE.Wl'~M 1¢ffi·f>ROP'E\.\...ER.. ENO
FIG. 41.-Marking for timing
R\6K! ~1oe ~R\5 AR.£ \O'&Y.. Ml'\~l<'C.0 \ol\"''rto\. -t
Lt:.'Fl s.a:e
INLET OPEN5. 5° ST. C
INLET CL05E!;. 35° A.Q.C. •
E.XHAU5TOP~;t. .ss8 e. e.c:..•
EXHAU5Tc.LO~. 108 A .T.C.
LEFT MAG ADVANCC. u;.0
Rl6HTMAG. ADV-"NU:.. 3Z~
33
• .:>f:T f;}Y INLET CL051N6 C.. EXHAUST OPENING
Fm. 42.-Timing data
EXHAU5T OPEN5
AFTER ASSEMBUNG VALVC Gu1DE::t, LA? Vi\LYES ONT\L T ISHT 'NI-\™ TESTED IN "THREE
Pec~Tl (INS W ITH PORT FULL OF GASOL.ENE. VALVE SEATS IN CY UNDERS TO BE
AST IN BY H AND P IL OT ING FROM \.AL VE GUIDES .
AFIER LAPPING THE Vr"'-LVt:° SC. TtiAT \T SEA IS FOR \TS FULL W\DTf-\ l<?'CL\t:"VE
THE .SEAT IN THE' CYLINDER '25° INSIDE AND 25° OUTSIDE ~THl'.T THE LAPPED SURFACE'
CF THE Y&fi WILL El'.TE.ND l/<Q4 O'IER THE LAPPED S ll!?fACE OF T>-\E SC"-\ IN T HE C'fUNDER
RE·A55EMB LE AND REPE.,A,T IE§> 'Tt-IS:N IF NECE SSA.B,"'( RELA? (,)!:ft"\L AB50\..LlJ"ELY
"TIGHT
Fm. 43:-Seating operation for valves
0