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+-----------------------------------------------------------------+
AVIATION ENGINES
Design--Construction--Operation and Repair
by
FIRST LIEUT. VICTOR W. PAGE, A. S. S. C., U. S. R.
* * * * *
~JUST PUBLISHED~
=AVIATION ENGINES. Their Design, Construction, Operation and Repair.=
By Lieut. VICTOR W. PAGE, Aviation Section, S.C.U.S.R.
A practical work containing valuable instructions for aviation
students, mechanicians, squadron engineering officers and all
interested in the construction and upkeep of airplane power
plants. 576 octavo pages. 250 illustrations. Price $3.00.
=AVIATION CHART, or the Location of Airplane Power Plant Troubles Made
Easy.=
By Lieut. VICTOR W. PAGE, A.S., S.C.U.S.R.
A large chart outlining all parts of a typical airplane power
plant, showing the points where trouble is apt to occur and
suggesting remedies for the common defects. Intended especially
for aviators and aviation mechanics on school and field duty.
Price 50 cents.
=GLOSSARY OF AVIATION TERMS.=
Compiled by Lieuts. VICTOR W. PAGE, A.S., S.C.U.S.R. and PAUL
MONTARIOL of the French Flying Corps on duty at Signal Corps
Aviation School, Mineola, L. I.
A complete glossary of practically all terms used in aviation,
having lists in both French and English, with equivalents in
either language. A very valuable book for all who are about to
leave for duty overseas. Price, cloth, $1.00.
=THE NORMAN W. HENLEY PUBLISHING COMPANY=
2 WEST 45TH ST., NEW YORK
* * * * *
[Illustration: Part Sectional View of Hall-Scott Airplane Motor, Showing
Principal Parts.]
* * * * *
CENSORED
This Book Entitled
AVIATION ENGINES
By LIEUT. VICTOR W. PAGE
has been censored by the United States Government, and pages and
parts of pages have been omitted by special instructions from
Washington.
The book has been passed by THE COMMITTEE ON PUBLIC INFORMATION
and is as complete as we can furnish it, and we so advise the
purchaser of it.
THE NORMAN W. HENLEY PUBLISHING COMPANY
* * * * *
AVIATION ENGINES
Design--Construction--Operation and Repair
A Complete, Practical Treatise Outlining Clearly
the Elements of Internal Combustion Engineering
with Special Reference to the Design, Construction,
Operation and Repair of Airplane Power
Plants; Also the Auxiliary Engine Systems, Such
as Lubrication, Carburetion, Ignition and Cooling.
It Includes Complete Instructions for Engine
Repairing and Systematic Location of Troubles,
Tool Equipment and Use of Tools, Also Outlines
the Latest Mechanical Processes.
by
FIRST LIEUT. VICTOR W. PAGE, A. S. S. C., U. S. R.
Assistant Engineering Officer, Signal Corps Aviation School,
Mineola, L. I.
Author of "The Modern Gasoline Automobile," Etc.
[Illustration]
Contains Valuable Instructions for All Aviation Students,
Mechanicians, Squadron Engineering Officers and All Interested in
the Construction and Upkeep of Airplane Power Plants.
New York
The Norman W. Henley Publishing Company
2 West 45th Street
1917
Copyrighted, 1917
By
The Norman W. Henley Publishing Co.
Printed in U. S. A.
All Illustrations in This Book Have Been
Specially Made by the Publishers, and Their
Use, Without Permission, Is Strictly Prohibited
Composition, Electrotyping and Presswork
by the Publishers Printing Co., New York
PREFACE
In presenting this treatise on "Aviation Engines," the writer realizes
that the rapidly developing art makes it difficult to outline all latest
forms or describe all current engineering practice. This exposition has
been prepared primarily for instruction purposes and is adapted for men
in the Aviation Section, Signal Corps, and students who wish to become
aviators or aviation mechanicians. Every effort has been made to have
the engineering information accurate, but owing to the diversity of
authorities consulted and use of data translated from foreign language
periodicals, it is expected that some slight errors will be present. The
writer wishes to acknowledge his indebtedness to such firms as the
Curtiss Aeroplane and Motor Co., Hall-Scott Company, Thomas-Morse
Aircraft Corporation and General Vehicle Company for photographs and
helpful descriptive matter. Special attention has been paid to
instructions on tool equipment, use of tools, trouble "shooting" and
engine repairs, as it is on these points that the average aviation
student is weakest. Only such theoretical consideration of
thermo-dynamics as was deemed absolutely necessary to secure a proper
understanding of engine action after consulting several instructors is
included, the writer's efforts having been confined to the preparation
of a practical series of instructions that would be of the greatest
value to those who need a diversified knowledge of internal-combustion
engine operation and repair, and who must acquire it quickly. The
engines described and illustrated are all practical forms that have been
fitted to airplanes capable of making flights and may be considered
fairly representative of the present state of the art.
VICTOR W. PAGE,
_1st Lieut. A. S. S. C., U. S. R_.
MINEOLA, L. I.,
October, 1917.
CONTENTS
PAGES
CHAPTER I
Brief Consideration of Aircraft Types--Essential Requirements of
Aerial Motors--Aviation Engines Must Be Light--Factors Influencing
Power Needed--Why Explosive Motors Are Best--Historical--Main
Types of Internal Combustion Engines 17-36
CHAPTER II
Operating Principles of Two- and Four-Stroke Engines--Four-cycle
Action--Two-cycle Action--Comparing Two- and Four-cycle Types--
Theory of Gas and Gasoline Engine--Early Gas-Engine Forms--
Isothermal Law--Adiabatic Law--Temperature Computations--Heat and
Its Work--Conversion of Heat to Power--Requisites for Best Power
Effect 37-59
CHAPTER III
Efficiency of Internal Combustion Engines--Various Measures of
Efficiency--Temperatures and Pressures--Factors Governing Economy
--Losses in Wall Cooling--Value of Indicator Cards--Compression in
Explosive Motors--Factors Limiting Compression--Causes of Heat
Losses and Inefficiency--Heat Losses to Cooling Water 60-79
CHAPTER IV
Engine Parts and Functions--Why Multiple Cylinder Engines Are Best
--Describing Sequence of Operations--Simple Engines--Four and Six
Cylinder Vertical Tandem Engines--Eight and Twelve Cylinder V
Engines--Radial Cylinder Arrangement--Rotary Cylinder Forms 80-109
CHAPTER V
Properties of Liquid Fuels--Distillates of Crude Petroleum--
Principles of Carburetion Outlined--Air Needed to Burn Gasoline--
What a Carburetor Should Do--Liquid Fuel Storage and Supply--
Vacuum Fuel Feed--Early Vaporizer Forms--Development of Float Feed
Carburetor--Maybach's Early Design--Concentric Float and Jet Type
--Schebler Carburetor--Claudel Carburetor--Stewart Metering Pin
Type--Multiple Nozzle Vaporizers--Two-Stage Carburetor--Master
Multiple Jet Type--Compound Nozzle Zenith Carburetor--Utility of
Gasoline Strainers--Intake Manifold Design and Construction--
Compensating for Various Atmospheric Conditions--How High
Altitude Affects Power--The Diesel System--Notes on Carburetor
Installation--Notes on Carburetor Adjustment 110-154
CHAPTER VI
Early Ignition Systems--Electrical Ignition Best--Fundamentals of
Magnetism Outlined--Forms of Magneto--Zones of Magnetic Influence
--How Magnets are Made--Electricity and Magnetism Related--Basic
Principles of Magneto Action--Essential Parts of Magneto and
Functions--Transformer Coil Systems--True High Tension Type--The
Berling Magneto--Timing and Care--The Dixie Magneto--Spark-Plug
Design and Application--Two-Spark Ignition--Special Airplane
Plug 155-200
CHAPTER VII
Why Lubrication Is Necessary--Friction Defined--Theory of
Lubrication--Derivation of Lubricants--Properties of Cylinder Oils
--Factors Influencing Lubrication System Selection--Gnome Type
Engines Use Castor Oil--Hall-Scott Lubrication System--Oil Supply
by Constant Level Splash System--Dry Crank-Case System Best for
Airplane Engines--Why Cooling Systems Are Necessary--Cooling
Systems Generally Applied--Cooling by Positive Pump Circulation--
Thermo-Syphon System--Direct Air-Cooling Methods--Air-Cooled
Engine Design Considerations 201-232
CHAPTER VIII
Methods of Cylinder Construction--Block Castings--Influence on
Crank-Shaft Design--Combustion Chamber Design--Bore and Stroke
Ratio--Meaning of Piston Speed--Advantage of Off-Set Cylinders--
Valve Location of Vital Import--Valve Installation Practice--Valve
Design and Construction--Valve Operation--Methods of Driving
Cam-Shaft--Valve Springs--Valve Timing--Blowing Back--Lead Given
Exhaust Valve--Exhaust Closing, Inlet Opening--Closing the
Inlet Valve--Time of Ignition--How an Engine is Timed--Gnome
"Monosoupape" Valve Timing--Springless Valves--Four Valves per
Cylinder 233-286
CHAPTER IX
Constructional Details of Pistons--Aluminum Cylinders and Pistons
--Piston Ring Construction--Leak Proof Piston Rings--Keeping Oil
Out of Combustion Chamber--Connecting Rod Forms--Connecting Rods
for Vee Engines--Cam-Shaft and Crank-Shaft Designs--Ball Bearing
Crank-Shafts--Engine Base Construction 287-323
CHAPTER X
Power Plant Installation--Curtiss OX-2 Engine Mounting and
Operating Rules--Standard S. A. E. Engine Bed Dimensions--
Hall-Scott Engine Installation and Operation--Fuel System Rules
--Ignition System--Water System--Preparations to Start Engine--
Mounting Radial and Rotary Engines--Practical Hints to Locate
Engine Troubles--All Engine Troubles Summarized--Location of
Engine Troubles Made Easy 324-375
CHAPTER XI
Tools for Adjusting and Erecting--Forms of Wrenches--Use and Care
of Files--Split Pin Removal and Installation--Complete Chisel Set
--Drilling Machines--Drills, Reamers, Taps and Dies--Measuring
Tools--Micrometer Calipers and Their Use--Typical Tool Outfits
--Special Hall-Scott Tools--Overhauling Airplane Engines--Taking
Engine Down--Defects in Cylinders--Carbon Deposits, Cause and
Prevention--Use of Carbon Scrapers--Burning Out Carbon with
Oxygen --Repairing Scored Cylinders--Valve Removal and Inspection
--Reseating and Truing Valves--Valve Grinding Processes--
Depreciation in Valve Operating System--Piston Troubles--Piston
Ring Manipulation--Fitting Piston Rings--Wrist-Pin Wear--
Inspection and Refitting of Engine Bearings--Scraping Brasses to
Fit--Fitting Connecting Rods--Testing for Bearing Parallelism--
Cam-Shafts and Timing Gears--Precautions in Reassembling Parts 376-456
CHAPTER XII
Aviation Engine Types--Division in Classes--Anzani Engines--Canton
and Unne Engine--Construction of Gnome Engines--"Monosoupape"
Gnome--German "Gnome" Type--Le Rhone Engine--Renault Air-Cooled
Engine--Simplex Model "A" Hispano-Suiza--Curtiss Aviation Motors--
Thomas-Morse Model 88 Engine--Duesenberg Engine--Aeromarine
Six-Cylinder--Wisconsin Aviation Engines--Hall-Scott Engines--
Mercedes Motor--Benz Motor--Austro-Daimler Engine--Sunbeam-Coatalen
--Indicating and Measuring Instruments--Air Starting Systems--
Electric Starting--Battery Ignition 457-571
INDEX 573
LIST OF ILLUSTRATIONS
AVIATION ENGINES
DESIGN--CONSTRUCTION--REPAIR
CHAPTER I
Brief Consideration of Aircraft Types--Essential Requirements of
Aerial Motors--Aviation Engines Must Be Light--Factors
Influencing Power Needed--Why Explosive Motors Are Best--
Historical--Main Types of Internal Combustion Engines.
BRIEF CONSIDERATION OF AIRCRAFT TYPES
The conquest of the air is one of the most stupendous achievements of
the ages. Human flight opens the sky to man as a new road, and because
it is a road free of all obstructions and leads everywhere, affording
the shortest distance to any place, it offers to man the prospect of
unlimited freedom. The aircraft promises to span continents like
railroads, to bridge seas like ships, to go over mountains and forests
like birds, and to quicken and simplify the problems of transportation.
While the actual conquest of the air is an accomplishment just being
realized in our days, the idea and yearning to conquer the air are old,
possibly as old as intellect itself. The myths of different races tell
of winged gods and flying men, and show that for ages to fly was the
highest conception of the sublime. No other agent is more responsible
for sustained flight than the internal combustion motor, and it was only
when this form of prime mover had been fully developed that it was
possible for man to leave the ground and alight at will, not depending
upon the caprices of the winds or lifting power of gases as with the
balloon. It is safe to say that the solution of the problem of flight
would have been attained many years ago if the proper source of power
had been available as all the essential elements of the modern
aeroplane and dirigible balloon, other than the power plant, were known
to early philosophers and scientists.
Aeronautics is divided into two fundamentally different
branches--aviatics and aerostatics. The first comprises all types of
aeroplanes and heavier than air flying machines such as the helicopters,
kites, etc.; the second includes dirigible balloons, passive balloons
and all craft which rise in the air by utilizing the lifting force of
gases. Aeroplanes are the only practical form of heavier-than-air
machines, as the helicopters (machines intended to be lifted directly
into the air by propellers, without the sustaining effect of planes),
and ornithopters, or flapping wing types, have not been thoroughly
developed, and in fact, there are so many serious mechanical problems to
be solved before either of these types of air craft will function
properly that experts express grave doubts regarding the practicability
of either. Aeroplanes are divided into two main types--monoplanes or
single surface forms, and bi-planes or machines having two sets of
lifting surfaces, one suspended over the other. A third type, the
triplane, is not very widely used.
Dirigible balloons are divided into three classes: the rigid, the
semi-rigid, and the non-rigid. The rigid has a frame or skeleton of
either wood or metal inside of the bag, to stiffen it; the semi-rigid is
reinforced by a wire net and metal attachments; while the non-rigid is
just a bag filled with gas. The aeroplane, more than the dirigible and
balloon, stands as the emblem of the conquest of the air. Two reasons
for this are that power flight is a real conquest of the air, a real
victory over the battling elements; secondly, because the aeroplane, or
any flying machine that may follow, brings air travel within the reach
of everybody. In practical development, the dirigible may be the
steamship of the air, which will render invaluable services of a certain
kind, and the aeroplane will be the automobile of the air, to be used by
the multitude, perhaps for as many purposes as the automobile is now
being used.
ESSENTIAL REQUIREMENTS OF AERIAL MOTORS
One of the marked features of aircraft development has been the effect
it has had upon the refinement and perfection of the internal combustion
motor. Without question gasoline-motors intended for aircraft are the
nearest to perfection of any other type yet evolved. Because of the
peculiar demands imposed upon the aeronautical motor it must possess all
the features of reliability, economy and efficiency now present with
automobile or marine engines and then must have distinctive points of
its own. Owing to the unstable nature of the medium through which it is
operated and the fact that heavier-than-air machines can maintain flight
only as long as the power plant is functioning properly, an airship
motor must be more reliable than any used on either land or water. While
a few pounds of metal more or less makes practically no difference in a
marine motor and has very little effect upon the speed or hill-climbing
ability of an automobile, an airship motor must be as light as it is
possible to make it because every pound counts, whether the motor is to
be fitted into an aeroplane or in a dirigible balloon.
Airship motors, as a rule, must operate constantly at high speeds in
order to obtain a maximum power delivery with a minimum piston
displacement. In automobiles, or motor boats, motors are not required to
run constantly at their maximum speed. Most aircraft motors must
function for extended periods at speed as nearly the maximum as
possible. Another thing that militates against the aircraft motor is the
more or less unsteady foundation to which it is attached. The
necessarily light framework of the aeroplane makes it hard for a motor
to perform at maximum efficiency on account of the vibration of its
foundation while the craft is in flight. Marine and motor car engines,
while not placed on foundations as firm as those provided for stationary
power plants, are installed on bases of much more stability than the
light structure of an aeroplane. The aircraft motor, therefore, must be
balanced to a nicety and must run steadily under the most unfavorable
conditions.
AERIAL MOTORS MUST BE LIGHT
The capacity of light motors designed for aerial work per unit of mass
is surprising to those not fully conversant with the possibilities that
a thorough knowledge of proportions of parts and the use of special
metals developed by the automobile industry make possible. Activity in
the development of light motors has been more pronounced in France than
in any other country. Some of these motors have been complicated types
made light by the skillful proportioning of parts, others are of the
refined simpler form modified from current automobile practice. There is
a tendency to depart from the freakish or unconventional construction
and to adhere more closely to standard forms because it is necessary to
have the parts of such size that every quality making for reliability,
efficiency and endurance are incorporated in the design. Aeroplane
motors range from two cylinders to forms having fourteen and sixteen
cylinders and the arrangement of these members varies from the
conventional vertical tandem and opposed placing to the V form or the
more unusual radial motors having either fixed or rotary cylinders. The
weight has been reduced so it is possible to obtain a complete power
plant of the revolving cylinder air-cooled type that will not weigh more
than three pounds per actual horse-power and in some cases less than
this.
If we give brief consideration to the requirements of the aviator it
will be evident that one of the most important is securing maximum power
with minimum mass, and it is desirable to conserve all of the good
qualities existing in standard automobile motors. These are certainty of
operation, good mechanical balance and uniform delivery of
power--fundamental conditions which must be attained before a power
plant can be considered practical. There are in addition, secondary
considerations, none the less desirable, if not absolutely essential.
These are minimum consumption of fuel and lubricating oil, which is
really a factor of import, for upon the economy depends the capacity and
flying radius. As the amount of liquid fuel must be limited the most
suitable motor will be that which is powerful and at the same time
economical. Another important feature is to secure accessibility of
components in order to make easy repair or adjustment of parts possible.
It is possible to obtain sufficiently light-weight motors without
radical departure from established practice. Water-cooled power plants
have been designed that will weigh but four or five pounds per
horse-power and in these forms we have a practical power plant capable
of extended operation.
FACTORS INFLUENCING POWER NEEDED
Work is performed whenever an object is moved against a resistance, and
the amount of work performed depends not only on the amount of
resistance overcome but also upon the amount of time utilized in
accomplishing a given task. Work is measured in horse-power for
convenience. It will take one horse-power to move 33,000 pounds one foot
in one minute or 550 pounds one foot in one second. The same work would
be done if 330 pounds were moved 100 feet in one minute. It requires a
definite amount of power to move a vehicle over the ground at a certain
speed, so it must take power to overcome resistance of an airplane in
the air. Disregarding the factor of air density, it will take more power
as the speed increases if the weight or resistance remains constant, or
more power if the speed remains constant and the resistance increases.
The airplane is supported by air reaction under the planes or lifting
surfaces and the value of this reaction depends upon the shape of the
aerofoil, the amount it is tilted and the speed at which it is drawn
through the air. The angle of incidence or degree of wing tilt regulates
the power required to a certain degree as this affects the speed of
horizontal flight as well as the resistance. Resistance may be of two
kinds, one that is necessary and the other that it is desirable to
reduce to the lowest point possible. There is the wing resistance and
the sum of the resistances of the rest of the machine such as fuselage,
struts, wires, landing gear, etc. If we assume that a certain airplane
offered a total resistance of 300 pounds and we wished to drive it
through the air at a speed of sixty miles per hour, we can find the
horse-power needed by a very simple computation as follows:
The product of 300 pounds resistance times speed of
88 feet per second times 60 seconds in a minute
----------------------------------------------------- = H.P. needed.
divided by 33,000 foot pounds per minute
in one horse-power
The result is the horse-power needed, or
300 x 88 x 60
--------------- = 48 H.P.
33,000
Just as it takes more power to climb a hill than it does to run a car on
the level, it takes more power to climb in the air with an airplane than
it does to fly on the level. The more rapid the climb, the more power it
will take. If the resistance remains 300 pounds and it is necessary to
drive the plane at 90 miles per hour, we merely substitute proper values
in the above formula and we have
300 pounds times 132 feet per second times 60
seconds in a minute
----------------------------------------------- = 72 H.P.
33,000 foot pounds per minute in one
horse-power
The same results can be obtained by dividing the product of the
resistance in pounds times speed in feet per second by 550, which is the
foot-pounds of work done in one second to equal one horse-power.
Naturally, the amount of propeller thrust measured in pounds necessary
to drive an airplane must be greater than the resistance by a
substantial margin if the plane is to fly and climb as well. The
following formulae were given in "The Aeroplane" of London and can be
used to advantage by those desiring to make computations to ascertain
power requirements:
[Illustration: Fig. 1.--Diagrams Illustrating Computations for
Horse-Power Required for Airplane Flight.]
The thrust of the propeller depends on the power of the motor, and on
the diameter and pitch of the propeller. If the required thrust to a
certain machine is known, the calculation for the horse-power of the
motor should be an easy matter.
The required thrust is the sum of three different "resistances." The
first is the "drift" (dynamical head resistance of the aerofoils), i.e.,
tan [alpha] x lift (_L_), lift being equal to the total weight of
machine (_W_) for horizontal flight and [alpha] equal to the angle of
incidence. Certainly we must take the tan [alpha] at the maximum _K_{y}_
value for minimum speed, as then the drift is the greatest (Fig. 1, A).
Another method for finding the drift is _D_ = _K_ x _AV_^{2}, when we
take the drift again so as to be greatest.
The second "resistance" is the total head resistance of the machine, at
its maximum velocity. And the third is the thrust for climbing. The
horse-power for climbing can be found out in two different ways. I first
propose to deal with the method, where we find out the actual
horse-power wanted for a certain climbing speed to our machine, where
climbing speed/sec. x _W_
H.P. = ---------------------------
550
In this case we know already the horse-power for climbing, and we can
proceed with our calculation.
With the other method we shall find out the "thrust" in pounds or
kilograms wanted for climbing and add it to drift and total head
resistance, and we shall have the total "thrust" of our machine and we
shall denote it with _T_, while thrust for climbing shall be _T_{c}_.
The following calculation is at our service to find out
_V_{c}_ x _W_
this thrust for climbing --------------- = H.P.,
550
H.P. x 550
thence _V_{c}_ = ------------ (1)
_W_
_T_{c}_ x _V_
H.P. = --------------, then from
550
_T_{c}_ x _V_
--------------- x 550
550 _T_{c}_ x _V_
(1) _V_{c}_ = ----------------------- = ---------------, thence,
_W_ _W_
_V_{c}_ x _W_
T_{c} = ---------------.
_V_
Whether _T_ means drifts, head resistance and thrust for climbing, or
drift and head resistance only, the following calculation is the same,
only in the latter case, of course, we must add the horse-power required
for climbing to the result to obtain the total horse-power.
Now, when we know the total thrust, we shall find the horse-power in the
following manner:
_Pr_2[pi]_R_
We know that the H.P. = -------------- in kilograms, or in
75 x 60
_Pr_2[pi]_R_
English measure, H.P. = -------------- (Fig. 1, B)
33,000
where _P_ = pressure in klgs. or lbs.
_r_ = radius on which _P_ is acting.
_R_ = Revolution/min.
_M.R._2[pi]
When _P_ x _r_ = _M_, then H.P. = -------------, thence,
4,500
H.P. x 4,500 716.2 H.P.
_M_ = -------------- = ------------ in meter kilograms,
_R_2[pi] _R_
H.P. 33,000 5253.1 H.P.
or in English system _M_ = ------------- = ------------- in
_R_2[pi] _R_
foot pounds.
Now the power on the circumference of the propeller will be reduced by
its radius, so it will be _M_/_r_ = _p_. A part of _p_ will be used for
counteracting the air and bearing friction, so that the total power on
the circumference of the propeller will be (_M_/_r_) x [eta] = _p_ where
[eta] is the mechanical efficiency of the propeller. Now
[eta]
--------------- = _T_, where [alpha] is taken on the tip of the
_tan_ [alpha]
propeller.
I take [alpha] at the tip, but it can be taken, of course, at any point,
but then in equation _p_ = _M_/_r_, _r_ must be taken only up to this
point, and not the whole radius; but it is more comfortable to take it
at the tip, as
Pitch
_tan_ [alpha] = ---------- (Fig. 1, C).
_r_2[pi]
Now we can write up the equation of the thrust:
716.2 H.P. [eta] 5253.1 H.P. [eta]
-------------------, or in English measure -------------------
_R r tan [alpha]_ _R r tan [alpha]_
_T_ x _R_ x _r tan_ [alpha]
thence H.P. = -----------------------------, or in English measure
716.2[eta]
_T_ x _R_ x _r tan_ [alpha]
-----------------------------.
5253.1[eta]
The computations and formulae given are of most value to the student
engineer rather than matters of general interest, but are given so that
a general idea may be secured of how airplane design influences power
needed to secure sustained flight. It will be apparent that the
resistance of an airplane depends upon numerous considerations of design
which require considerable research in aerodynamics to determine
accurately. It is obvious that the more resistance there is, the more
power needed to fly at a given speed. Light monoplanes have been flown
with as little as 15 horse-power for short distances, but most planes
now built use engines of 100 horse-power or more. Giant airplanes have
been constructed having 2,000 horse-power distributed in four power
units. The amount of power provided for an airplane of given design
varies widely as many conditions govern this, but it will range from
approximately one horse-power to each 8 pounds weight in the case of
very light, fast machines to one horse-power to 15 or 18 pounds of the
total weight in the case of medium speed machines. The development in
airplane and power plant design is so rapid, however, that the figures
given can be considered only in the light of general averages rather
than being typical of current practice.
WHY EXPLOSIVE MOTORS ARE BEST
Internal combustion engines are best for airplanes and all types of
aircraft for the same reasons that they are universally used as a source
of power for automobiles. The gasoline engine is the lightest known form
of prime mover and a more efficient one than a steam engine, especially
in the small powers used for airplane propulsion. It has been stated
that by very careful designing a steam plant an engine could be made
that would be practical for airplane propulsion, but even with the
latest development it is doubtful if steam power can be utilized in
aircraft to as good advantage as modern gasoline-engines are. While the
steam-engine is considered very much simpler than a gas-motor, the
latter is much more easily mastered by the non-technical aviator and
certainly requires less attention. A weight of 10 pounds per horse-power
is possible in a condensing steam plant but this figure is nearly double
or triple what is easily secured with a gas-motor which may weigh but 5
pounds per horse-power in the water cooled forms and but 2 or 3 pounds
in the air-cooled types. The fuel consumption is twice as great in a
steam-power plant (owing to heat losses) as would be the case in a
gasoline engine of equal power and much less weight.
The internal-combustion engine has come seemingly like an avalanche of a
decade; but it has come to stay, to take its well-deserved position
among the powers for aiding labor. Its ready adaptation to road, aerial
and marine service has made it a wonder of the age in the development of
speed not before dreamed of as a possibility; yet in so short a time,
its power for speed has taken rank on the common road against the
locomotive on the rail with its century's progress. It has made aerial
navigation possible and practical, it furnishes power for all marine
craft from the light canoe to the transatlantic liner. It operates the
machine tools of the mechanic, tills the soil for the farmer and
provides healthful recreation for thousands by furnishing an economical
means of transport by land and sea. It has been a universal mechanical
education for the masses, and in its present forms represents the great
refinement and development made possible by the concentration of the
world's master minds on the problems incidental to internal combustion
engineering.
HISTORICAL
Although the ideal principle of explosive power was conceived some two
hundred years ago, at which time experiments were made with gunpowder as
the explosive element, it was not until the last years of the eighteenth
century that the idea took a patentable shape, and not until about 1826
(Brown's gas-vacuum engine) that a further progress was made in England
by condensing the products of combustion by a jet of water, thus
creating a partial vacuum.
Brown's was probably the first explosive engine that did real work. It
was clumsy and unwieldy and was soon relegated to its place among the
failures of previous experiments. No approach to active explosive effect
in a cylinder was reached in practice, although many ingenious designs
were described, until about 1838 and the following years. Barnett's
engine in England was the first attempt to compress the charge before
exploding. From this time on to about 1860 many patents were issued in
Europe and a few in the United States for gas-engines, but the progress
was slow, and its practical introduction for power came with spasmodic
effect and low efficiency. From 1860 on, practical improvement seems to
have been made, and the Lenoir motor was produced in France and brought
to the United States. It failed to meet expectations, and was soon
followed by further improvements in the Hugon motor in France (1862),
followed by Beau de Rocha's four-cycle idea, which has been slowly
developed through a long series of experimental trials by different
inventors. In the hands of Otto and Langdon a further progress was made,
and numerous patents were issued in England, France, and Germany, and
followed up by an increasing interest in the United States, with a few
patents.
From 1870 improvements seem to have advanced at a steady rate, and
largely in the valve-gear and precision of governing for variable load.
The early idea of the necessity of slow combustion was a great drawback
in the advancement of efficiency, and the suggestion of de Rocha in 1862
did not take root as a prophetic truth until many failures and years of
experience had taught the fundamental axiom that rapidity of action in
both combustion and expansion was the basis of success in explosive
motors.
With this truth and the demand for small and safe prime movers, the
manufacture of gas-engines increased in Europe and America at a more
rapid rate, and improvements in perfecting the details of this cheap and
efficient prime mover have finally raised it to the dignity of a
standard motor and a dangerous rival of the steam-engine for small and
intermediate powers, with a prospect of largely increasing its
individual units to many hundred, if not to the thousand horse-power in
a single cylinder. The unit size in a single cylinder has now reached to
about 700 horse-power and by combining cylinders in the same machine,
powers of from 1,500 to 2,000 horse-power are now available for large
power-plants.
MAIN TYPES OF INTERNAL-COMBUSTION ENGINES
This form of prime mover has been built in so many different types, all
of which have operated with some degree of success that the diversity in
form will not be generally appreciated unless some attempt is made to
classify the various designs that have received practical application.
Obviously the same type of engine is not universally applicable, because
each class of work has individual peculiarities which can best be met by
an engine designed with the peculiar conditions present in view. The
following tabular synopsis will enable the reader to judge the extent of
the development of what is now the most popular prime mover for all
purposes.
A. Internal Combustion (Standard Type)
1. Single Acting (Standard Type)
2. Double Acting (For Large Power Only)
3. Simple (Universal Form)
4. Compound (Rarely Used)
5. Reciprocating Piston (Standard Type)
6. Turbine (Revolving Rotor, not fully developed)
A1. Two-Stroke Cycle
a. Two Port
b. Three Port
c. Combined Two and Three Port
d. Fourth Port Accelerator
e. Differential Piston Type
f. Distributor Valve System
A2. Four-Stroke Cycle
a. Automatic Inlet Valve
b. Mechanical Inlet Valve
c. Poppet or Mushroom Valve
d. Slide Valve
d 1. Sleeve Valve
d 2. Reciprocating Ring Valve
d 3. Piston Valve
e. Rotary Valves
e 1. Disc
e 2. Cylinder or Barrel
e 3. Single Cone
e 4. Double Cone
f. Two Piston (Balanced Explosion)
g. Rotary Cylinder, Fixed Crank (Aerial)
h. Fixed Cylinder, Rotary Crank (Standard Type)
A3. Six-Stroke Cycle
B. External Combustion (Practically Obsolete)
a. Turbine, Revolving Rotor
b. Reciprocating Piston
CLASSIFICATION BY CYLINDER ARRANGEMENT
Single Cylinder
a. Vertical
b. Horizontal
c. Inverted Vertical
Double Cylinder
a. Vertical
b. Horizontal (Side by Side)
c. Horizontal (Opposed)
d. 45 to 90 Degrees V (Angularly Disposed)
e. Horizontal Tandem (Double Acting)
Three Cylinder
a. Vertical
b. Horizontal
c. Rotary (Cylinders Spaced at 120 Degrees)
d. Radially Placed (Stationary Cylinders)
e. One Vertical, One Each Side at an Angle
f. Compound (Two High Pressure, One Low Pressure)
Four Cylinder
a. Vertical
b. Horizontal (Side by Side)
c. Horizontal (Two Pairs Opposed)
d. 45 to 90 Degrees V
e. Twin Tandem (Double Acting)
Five Cylinder
a. Vertical (Five Throw Crankshaft)
b. Radially Spaced at 72 Degrees (Stationary)
c. Radially Placed Above Crankshaft (Stationary)
d. Placed Around Rotary Crankcase (72 Degrees Spacing)
Six Cylinder
a. Vertical
b. Horizontal (Three Pairs Opposed)
c. 45 to 90 Degrees V
Seven Cylinder
a. Equally Spaced (Rotary)
Eight Cylinder
a. Vertical
b. Horizontal (Four Pairs Opposed)
c. 45 to 90 Degrees V
Nine Cylinder
a. Equally Spaced (Rotary)
Twelve Cylinder
a. Vertical
b. Horizontal (Six Pairs Opposed)
c. 45 to 90 Degrees V
Fourteen Cylinder
a. Rotary
Sixteen Cylinder
a. 45 to 90 Degrees V
b. Horizontal (Eight Pairs Opposed)
Eighteen Cylinder
a. Rotary Cylinder
[Illustration: Fig. 2.--Plate Showing Heavy, Slow Speed Internal
Combustion Engines Used Only for Stationary Power in Large Installations
Giving Weight to Horse-Power Ratio.]
[Illustration: Fig. 3.--Various Forms of Internal Combustion Engines
Showing Decrease in Weight to Horse-Power Ratio with Augmenting Speed of
Rotation.]
[Illustration: Fig. 4.--Internal Combustion Engine Types of Extremely
Fine Construction and Refined Design, Showing Great Power Outputs for
Very Small Weight, a Feature Very Much Desired in Airplane Power
Plants.]
Of all the types enumerated above engines having less than eight
cylinders are the most popular in everything but aircraft work. The
four-cylinder vertical is without doubt the most widely used of all
types owing to the large number employed as automobile power plants.
Stationary engines in small and medium powers are invariably of the
single or double form. Three-cylinder engines are seldom used at the
present time, except in marine work and in some stationary forms.
Eight- and twelve-cylinder motors have received but limited application
and practically always in automobiles, racing motor boats or in aircraft.
The only example of a fourteen-cylinder motor to be used to any extent
is incorporated in aeroplane construction. This is also true of the
sixteen- and eighteen-cylinder forms and of twenty-four-cylinder engines
now in process of development.
The duty an engine is designed for determines the weight per
horse-power. High powered engines intended for steady service are always
of the slow speed type and consequently are of very massive
construction. Various forms of heavy duty type stationary engines are
shown at Fig. 2. Some of these engines may weigh as much as 600 pounds
per horse-power. A further study is possible by consulting data given on
Figs. 3 and 4. As the crank-shaft speed increases and cylinders are
multiplied the engines become lighter. While the big stationary power
plants may run for years without attention, airplane engines require
rebuilding after about 60 to 80 hours air service for the fixed cylinder
types and 40 hours or less for the rotary cylinder air-cooled forms.
There is evidently a decrease in durability and reliability as the
weight is lessened. These illustrations also permit of obtaining a good
idea of the variety of forms internal combustion engines are made in.