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.
TOOLS FOR ADJUSTING AND ERECTING
[Illustration: Fig. 163.--Practical Hand Tools Useful in Dismantling and
Repairing Airplane Engines.]
A very complete outfit of small tools, some of which are furnished as
part of the tool equipment of various engines are shown in group at Fig.
163. This group includes all of the tools necessary to complete a very
practical kit and it is not unusual for the mechanic who is continually
dismantling and erecting engines to possess even a larger assortment
than indicated. The small bench vise provided is a useful auxiliary that
can be clamped to any convenient bench or table or even fuselage
longeron in an emergency and should have jaws at least three inches wide
and capable of opening four or five inches. It is especially useful in
that it will save trips to the bench vises, as it has adequate capacity
to handle practically any of the small parts that need to be worked on
when making repairs. A blow torch, tinner's snips and soldering copper
are very useful in sheet metal work and in making any repairs requiring
the use of solder. The torch can be used in any operation requiring a
source of heat. The large box wrench shown under the vise is used for
removing large special nuts and sometimes has one end of the proper size
to fit the valve chamber cap. The piston ring removers are easily made
from thin strips of sheet metal securely brazed or soldered to a light
wire handle. These are used in sets of three for removing and applying
piston rings in a manner to be indicated. The uses of the wrenches,
screw drivers, and pliers shown are known to all and the variety
outlined should be sufficient for all ordinary work of restoration. The
wrench equipment is very complete, including a set of open end
S-wrenches to fit all standard bolts, a spanner wrench, socket or box
wrenches for bolts that are inaccessible with the ordinary type,
adjustable end wrenches, a thin monkey wrench of medium size, a bicycle
wrench for handling small nuts and bolts, a Stillson wrench for pipe and
a large adjustable monkey wrench for the stubborn fastenings of large
size.
Four different types of pliers are shown, one being a parallel jaw type
with size cutting attachment, while the other illustrated near it is a
combination parallel jaw type adapted for use on round work as well as
in handling flat stock. The most popular form of pliers is the
combination pattern shown beneath the socket wrench set. This is made of
substantial drop forgings having a hinged joint that can be set so that
a very wide opening at the jaws is possible. These can be used on round
work and for wire cutting as well as for handling flat work. Round nose
pliers are very useful also.
A very complete set of files, including square, half round, mill, flat
bastard, three-cornered and rat tail are also necessary. A hacksaw frame
and a number of saws, some with fine teeth for tubing and others with
coarser teeth for bar or solid stock will be found almost indispensable.
A complete punch and chisel set should be provided, samples of which are
shown in the group while the complete outfit is outlined in another
illustration. A number of different forms and sizes of chisels are
necessary, as one type is not suitable for all classes of work. The
adjustable end wrenches can be used in many places where a monkey wrench
cannot be fitted and where it will be difficult to use a wrench having a
fixed opening. The Stillson pipe wrench is useful in turning studs,
round rods, and pipes that cannot be turned by any other means. A
complete shop kit must necessarily include various sizes for Stillson
and monkey wrenches, as no one size can be expected to handle the wide
range of work the engine repairman must cope with. Three sizes of each
form of wrench can be used, one, a 6 inch, is as small as is needed
while, a 12 inch tool will handle almost any piece of pipe or nut used
in engine construction.
Three or four sizes of hammers should be provided, according to
individual requirement, these being small riveting, medium and
heavyweight machinist's hammers. A very practical tool of this nature
for the repair shop can be used as a hammer, screw driver or pry iron.
It is known as the "Spartan" hammer and is a tool steel drop forging in
one piece having the working surfaces properly hardened and tempered
while the metal is distributed so as to give a good balance to the head
and a comfortable grip to the handle. The hammer head provides a
positive and comfortable T-handle when the tool is used as a screw
driver or "tommy" bar. Machinist's hammers are provided with three types
of heads, these being of various weights. The form most commonly used is
termed the "ball pein" on account of the shape of the portion used for
riveting. The straight pein is just the same as the cross pein, except
that in the latter the straight portion is at right angles to the hammer
handle, while in the former it is parallel to that member.
FORMS OF WRENCHES
Wrenches have been made in infinite variety and there are a score or
more patterns of different types of adjustable socket and off-set
wrenches. The various wrench types that differ from the more
conventional monkey wrenches or those of the Stillson pattern are shown
at Fig. 164. The "perfect handle" is a drop forged open end form
provided with a wooden handle similar to that used on a monkey wrench in
order to provide a better grip for the hand. The "Saxon" wrench is a
double alligator form, so called because the jaws are in the form of a
V-groove having one side of the V plain, while the other is serrated in
order to secure a tight grip on round objects. In the form shown, two
jaws of varying sizes are provided, one for large work, the other to
handle the smaller rods. One of the novel features in connection with
this wrench is the provision of a triple die block in the centre of the
handle which is provided with three most commonly used of the standard
threads including 5/16-inch-18, 3/8-inch-16, and 1/2-inch-13. This is
useful in cleaning up burred threads on bolts before they are replaced,
as burring is unavoidable if it has been necessary to drive them out
with a hammer. The "Lakeside" wrench has an adjustable pawl engaging
with one of a series of notches by which the opening may be held in any
desired position.
[Illustration: Fig. 164.--Wrenches are Offered in Many Forms.]
Ever since the socket wrench was invented it has been a popular form
because it can be used in many places where the ordinary open end or
monkey wrench cannot be applied owing to lack of room for the head of
the wrench. A typical set which has been made to fit in a very small
space is shown at D. It consists of a handle, which is nickel-plated and
highly polished, a long extension bar, a universal joint and a number of
case hardened cold drawn steel sockets to fit all commonly used standard
nuts and bolt heads. Two screw-driver bits, one small and the other
large to fit the handle, and a long socket to fit spark-plugs are also
included in this outfit. The universal joint permits one to remove nuts
in a position that would be inaccessible to any other form of wrench, as
it enables the socket to be turned even if the handle is at one side of
an intervening obstruction.
The "Pick-up" wrench, shown at E, is used for spark-plugs and the upper
end of the socket is provided with a series of grooves into which a
suitable blade carried by the handle can be dropped. The handle is
pivoted to the top of the socket in such a way that the blades may be
picked up out of the grooves by lifting on the end of the handle and
dropped in again when the handle is swung around to the proper point to
get another hold on the socket. The "Miller" wrench shown at F, is a
combination socket and open end type, made especially for use with
spark-plugs. Both the open end and the socket are convenient. The
"Handy" set shown at G, consists of a number of thin stamped wrenches of
steel held together in a group by a simple clamp fitting, which enables
either end of any one of the four double wrenches to be brought into
play according to the size of the nut to be turned. The "Cronk" wrench
shown at H, is a simple stamping having an alligator opening at one end
and a stepped opening capable of handling four different sizes of
standard nuts or bolt heads at the other. Such wrenches are very cheap
and are worth many times their small cost, especially for fitting nuts
where there is not sufficient room to admit the more conventional
pattern. The "Starrett" wrench set, which is shown at I, consists of a
ratchet handle together with an extension bar and universal joint, a
spark-plug socket, a drilling attachment which takes standard square
shank drills from 1/8-inch to 1/2-inch in diameter, a double ended
screw-driver bit and several adjustments to go with the drilling
attachment. Twenty-eight assorted cold drawn steel sockets similar in
design to those shown at D, to fit all standard sizes of square and
hexagonal headed nuts are also included. The reversible ratchet handle,
which may be slipped over the extension bar or the universal joint and
which is also adapted to take the squared end of any one of the sockets
is exceptionally useful in permitting, as it does, the instant release
of pressure when it is desired to swing the handle back to get another
hold on the nut. The socket wrench sets are usually supplied in hard
wood cases or in leather bags so that they may be kept together and
protected against loss or damage. With a properly selected socket wrench
set, either of the ratchet handle or T-handle form, any nut on the
engine may be reached and end wrenches will not be necessary.
USE AND CARE OF FILES
Mention has been previously made of the importance of providing a
complete set of files and suitable handles. These should be in various
grades or degrees of fineness and three of each kind should be provided.
In the flat and half round files three grades are necessary, one with
coarse teeth for roughing, and others with medium and fine teeth for the
finishing cuts. The round or rat tail file is necessary in filing out
small holes, the half round for finishing the interior of large ones.
Half round files are also well adapted for finishing surfaces of
peculiar contour, such as the inside of bearing boxes, connecting rod
and main bearing caps, etc. Square files are useful in finishing keyways
or cleaning out burred splines, while the triangular section or
three-cornered file is of value in cleaning out burred threads and
sharp corners. Flat files are used on all plane surfaces.
[Illustration: Fig. 165.--Illustrating Use and Care of Files.]
The file brush shown at Fig. 165, A, consists of a large number of wire
bristles attached to a substantial wood back having a handle of
convenient form so that the bristles may be drawn through the
interstices between the teeth of the file to remove dirt and grease. If
the teeth are filled with pieces of soft metal, such as solder or
babbitt, it may be necessary to remove this accumulation with a piece of
sheet metal as indicated at Fig. 165, B. The method of holding a file
for working on plain surfaces when it is fitted with the regular form of
wooden handle is shown at C, while two types of handles enabling the
mechanic to use the flat file on plain surfaces of such size that the
handle type indicated at C, could not be used on account of interfering
with the surface finished are shown at D. The method of using a file
when surfaces are finished by draw filing is shown at E. This differs
from the usual method of filing and is only used when surfaces are to be
polished and very little metal removed.
SPLIT PIN REMOVAL AND INSERTION
One of the most widely used of the locking means to prevent nuts or
bolts from becoming loose is the simple split pin, sometimes called a
"cotter pin." These can be handled very easily if the special pliers
shown at Fig. 166, A, are used. They have a curved jaw that permits of
grasping the pin firmly and inserting it in the hole ready to receive
it. It is not easy to insert these split pins by other means because the
ends are usually spread out and it is hard to enter the pin in the hole.
With the cotter pin pliers the ends may be brought close together and as
the plier jaws are small the pin may be easily pushed in place. Another
use of this plier, also indicated, is to bend over the ends of the split
pin in order to prevent it from falling out. To remove these pins a
simple curved lever, as shown at Fig. 166, B, is used. This has one end
tapering to a point and is intended to be inserted in the eye of the
cotter pin, the purchase offered by the handle permitting of ready
removal of the pin after the ends have been closed by the cotter pin
pliers.
COMPLETE CHISEL SET
[Illustration: Fig. 166.--Outlining Use of Cotter Pin Pliers, Spring
Winder, and Showing Practical Outfit of Chisels.]
A complete chisel set suitable for repair shop use is also shown at Fig.
166. The type at C is known as a "cape" chisel and has a narrow cutting
point and is intended to chip keyways, remove metal out of corners and
for all other work where the broad cutting edge chisel, shown at D,
cannot be used. The form with the wide cutting edge is used in chipping,
cutting sheet metal, etc. At E, a round nose chisel used in making oil
ways is outlined, while a similar tool having a pointed cutting edge and
often used for the same purpose is shown at F. The centre punch depicted
at G, is very useful for marking parts either for identification or for
drilling. In addition to the chisels shown, a number of solid punches
or drifts resembling very much that shown at E, except that the point is
blunt should be provided to drive out taper pins, bolts, rivets, and
other fastenings of this nature. These should be provided in the common
sizes. A complete set of real value would start at 1/8-inch and increase
by increments of 1/32-inch up to 1/2-inch. A simple spring winder is
shown at Fig. 166, H, this making it possible for the repairman to wind
coil springs, either on the lathe or in the vise. It will handle a
number of different sizes of wire and can be set to space the coils as
desired.
DRILLING MACHINES
[Illustration: Fig. 167.--Forms of Hand Operated Drilling Machines.]
Drilling machines may be of two kinds, hand or power operated. For
drilling small holes in metal it is necessary to run the drill fast,
therefore the drill chuck is usually driven by gearing in order to
produce high drill speed without turning the handle too fast. A small
hand drill is shown at Fig. 167, A. As will be observed, the chuck
spindle is driven by a small bevel pinion, which in turn, is operated by
a large bevel gear turned by a crank. The gear ratio is such that one
turn of the handle will turn the chuck five or six revolutions. A drill
of this design is not suited for drills any larger than one-quarter
inch. For use with drills ranging from one-eighth to three-eighths, or
even half-inch the hand drill presses shown at C and D are used. These
have a pad at the upper end by which pressure may be exerted with the
chest in order to feed the drill into the work, and for this reason they
are termed "breast drills." The form at C has compound gearing, the
drill chuck being driven by the usual form of bevel pinion in mesh with
a larger bevel gear at one end of a countershaft. A small helical spur
pinion at the other end of this countershaft receives its motion from a
larger gear turned by the hand crank. This arrangement of gearing
permits of high spindle speed without the use of large gears, as would
be necessary if but two were used. The form at D gives two speeds, one
for use with small drills is obtained by engaging the lower bevel pinion
with the chuck spindle and driving it by the large ring gear. The slow
speed is obtained by shifting the clutch so that the top bevel pinion
drives the drill chuck. As this meshes with a gear but slightly larger
in diameter, a slow speed of the drill chuck is possible. Breast drills
are provided with a handle screwed into the side of the frame, these
are used to steady the drill press. For drilling extremely large holes
which are beyond the capacity of the usual form of drill press the
ratchet form shown at B, may be used or the bit brace outlined at E. The
drills used with either of these have square shanks, whereas those used
in the drill presses have round shanks. The bit brace is also used
widely in wood work and the form shown is provided with a ratchet by
which the bit chuck may be turned through only a portion of a revolution
in either direction if desired.
DRILLS, REAMERS, TAPS AND DIES
In addition to the larger machine tools and the simple hand tools
previously described, an essential item of equipment of any engine or
plane repair shop, even in cases where the ordinary machine tools are
not provided, is a complete outfit of drills, reamers, and threading
tools. Drills are of two general classes, the flat and the twist drills.
The flat drill has an angle between cutting edges of about 110 degrees
and is usually made from special steel commercially known as drill rod.
A flat drill cannot be fed into the work very fast because it removes
metal by a scraping, rather than a cutting process. The twist drill in
its simplest form is cylindrical throughout the entire length and has
spiral flutes which are ground off at the end to form the cutting lip
and which also serve to carry the metal chips out of the holes. The
simplest form of twist drill used is shown at Fig. 168, C, and is known
as a "chuck" drill, because it must be placed in a suitable chuck to
turn it. A twist drill removes metal by cutting and it is not necessary
to use a heavy feed as the drill will tend to feed itself into the work.
[Illustration: Fig. 168.--Forms of Drills Used in Hand and Power
Drilling Machines.]
Larger drills than 3/4-inch are usually made with a tapered shank as
shown at Fig. 168, B. At the end of the taper a tongue is formed which
engages with a suitable opening in the collet, as the piece used to
support the drill is called. The object of this tongue is to relieve
the tapered portion of the drill from the stress of driving by
frictional contact alone, as this would not turn the drill positively
and the resulting slippage would wear the socket, this depreciation
changing the taper and making it unfit for other drills. The tongue is
usually proportioned so it is adequate to drive the drill under any
condition. A small keyway is provided in the collet into which a
tapering key of flat stock may be driven against the end of the tongue
to drive the drill from the spindle. A standard taper for drill shanks
generally accepted by the machine trade is known as the Morse and is a
taper of five-eighths of an inch to the foot. The Brown and Sharp form
tapers six-tenths of an inch to the foot. Care must be taken, therefore,
when purchasing drills and collets, to make sure that the tapers
coincide, as no attempt should be made to run a Morse taper in a Brown
and Sharp collet, or vice versa.
Sometimes cylindrical drills have straight flutes, as outlined at Fig.
168, A. Such drills are used with soft metals and are of value when the
drill is to pass entirely through the work. The trouble with a drill
with spiral flutes is that it will tend to draw itself through as the
cutting lips break through. This catching of the drill may break it or
move the work from its position. With a straight flute drill the cutting
action is practically the same as with the flat drill shown at Fig. 168,
E and F.
If a drill is employed in boring holes through close-grained, tough
metals, as wrought or malleable iron and steel, the operation will be
facilitated by lubricating the drill with plenty of lard oil or a
solution of soda and water. Either of these materials will effectually
remove the heat caused by the friction of the metal removed against the
lips of the drill, and the danger of heating the drill to a temperature
that will soften it by drawing the temper is minimized. In drilling
large or deep holes it is good practice to apply the lubricating medium
directly at the drill point. Special drills of the form shown at Fig.
168, B, having a spiral oil tube running in a suitably formed channel,
provides communication between the point of the drill and a suitable
receiving hole on a drilled shank. The oil is supplied by a pump and its
pressure not only promotes positive circulation and removal of heat, but
also assists in keeping the hole free of chips. In drilling steel or
wrought iron, lard oil applied to the point of the drill will facilitate
the drilling, but this material should never be used with either brass
or cast iron.
The sizes to be provided depend upon the nature of the work and the
amount of money that can be invested in drills. It is common practice to
provide a set of drills, such as shown at Fig. 169, which are carried in
a suitable metal stand, these being known as number drills on account
of conforming to the wire gauge standards. Number drills do not usually
run higher than 5/16 inch in diameter. Beyond this point drills are
usually sold by the diameter. A set of chuck drills, ranging from 3/8 to
3/4 inch, advancing by 1/32 inch, and a set of Morse taper shank drills
ranging from 3/4 to 1-1/4 inches, by increments of 1/16 inch, will be
all that is needed for the most pretentious repair shop, as it is
cheaper to bore holes larger than 1-1/4 inches with a boring tool than
it is to carry a number of large drills in stock that would be used very
seldom, perhaps not enough to justify their cost.
[Illustration: Fig. 169.--Useful Set of Number Drills, Showing Stand for
Keeping These in an Orderly Manner.]
In grinding drills, care must be taken to have the lips of the same
length, so that they will form the same angle with the axis. If one lip
is longer than the other, as shown in the flat drill at Fig. 168, E, the
hole will be larger than the drill size, and all the work of cutting
will come upon the longest lip. The drill ends should be symmetrical, as
shown at Fig. 168, F.
[Illustration: Fig. 170.--Illustrating Standard Forms of Hand and
Machine Reamers.]
It is considered very difficult to drill a hole to an exact diameter,
but for the most work a variation of a few thousandths of an inch is of
no great moment. Where accuracy is necessary, holes must be reamed out
to the required size. In reaming, a hole is drilled about 1/32 inch
smaller than is required, and is enlarged with a cutting tool known as
the reamer. Reamers are usually of the fluted form shown at Fig. 170, A.
Tools of this nature are not designed to remove considerable amounts of
metal, but are intended to augment the diameter of the drill hole by
only a small fraction of an inch. Reamers are tapered slightly at the
point in order that they will enter the hole easily, but the greater
portion of the fluted part is straight, all cutting edges being
parallel. Hand reamers are made in either the straight or taper forms,
that at A, Fig. 170, being straight, while B has tapering flutes. They
are intended to be turned by a wrench similar to that employed in
turning a tap, as shown at Fig. 172, C. The reamer shown at Fig. 170,
C, is a hand reamer. The form at D has spiral flutes similar to a twist
drill, and as it is provided with a taper shank it is intended to be
turned by power through the medium of a suitable collet.
As the solid reamers must become reduced in size when sharpened, various
forms of inserted blade reamers have been designed. One of these is
shown at E, and as the cutting surfaces become reduced in diameter it is
possible to replace the worn blades with others of proper size.
Expanding reamers are of the form shown at F. These have a bolt passing
through that fits into a tapering hole in the interior of the split
reamer portion of the tool. If the hole is to be enlarged a few
thousandths of an inch, it is possible to draw up on the nut just above
the squared end of the shank, and by drawing the tapering wedge farther
into the reamer body, the cutting portion will be expanded and will cut
a larger hole.
Reamers must be very carefully sharpened or there will be a tendency
toward chattering with a consequent production of a rough surface. There
are several methods of preventing this chattering, one being to separate
the cutting edges by irregular spaces, while the most common method, and
that to be preferred on machine reamers, is to use spiral flutes, as
shown at Fig. 170, D. Special taper reamers are made to conform to the
various taper pin sizes which are sometimes used in holding parts
together in an engine. A taper of 1/16 inch per foot is intended for
holes where a pin, once driven in, is to remain in place. When it is
desired that the pin be driven out, the taper is made steeper, generally
1/4 inch per foot, which is the standard taper used on taper pins.
[Illustration: Fig. 171.--Tools for Thread Cutting.]
When threads are to be cut in a small hole, it will be apparent that it
will be difficult to perform this operation economically on a lathe,
therefore when internal threading is called for, a simple device known
as a "tap" is used. There are many styles of taps, all conforming to
different standards. Some are for metric or foreign threads, some
conform to the American standards, while others are used for pipe and
tubing. Hand taps are the form most used in repair shops, these being
outlined at Fig. 171, A and B. They are usually sold in sets of three,
known respectively as taper, plug, and bottoming. The taper tap is the
one first put into the hole, and is then followed by the plug tap which
cuts the threads deeper. If it is imperative that the thread should be
full size clear to the bottom of the hole, the third tap of the set,
which is straight-sided, is used. It would be difficult to start a
bottoming tap into a hole because it would be larger in diameter at its
point than the hole. The taper tap, as shown at A, Fig. 171, has a
portion of the cutting lands ground away at the point in order that it
will enter the hole. The manipulation of a tap is not hard, as it does
not need to be forced into the work, as the thread will draw it into
the hole as the tap is turned. The tapering of a tap is done so that no
one thread is called upon to remove all of the metal, as for about half
way up the length of the tap each succeeding thread is cut a little
larger by the cutting edge until the full thread enters the hole. Care
must be taken to always enter a tap straight in order to have the thread
at correct angles to the surface.
In cutting external threads on small rods or on small pieces, such as
bolts and studs, it is not always economical to do this work in the
lathe, especially in repair work. Dies are used to cut threads on pieces
that are to be placed in tapped holes that have been threaded by the
corresponding size of tap. Dies for small work are often made solid, as
shown at Fig. 171, C, but solid dies are usually limited to sizes below
1/2 inch. Sometimes the solid die is cylindrical in shape, with a slot
through one side which enables one to obtain a slight degree of
adjustment by squeezing the slotted portion together. Large dies, or the
sizes over 1/2 inch, are usually made in two pieces in order that the
halves may be closed up or brought nearer together. The advantage of
this form of die is that either of the two pieces may be easily
sharpened, and as it may be adjusted very easily the thread may be cut
by easy stages. For example, the die may be adjusted to cut large, which
will produce a shallow thread that will act as an accurate guide when
the die is closed up and a deeper thread cut.
[Illustration: Fig. 172.--Showing Holder Designs for One- and Two-Piece
Thread Cutting Dies.]
A common form of die holder for an adjustable die is shown at Fig. 172,
A. As will be apparent, it consists of a central body portion having
guide members to keep the die pieces from falling out and levers at each
end in order to permit the operator to exert sufficient force to remove
the metal. The method of adjusting the depth of thread with a clamp
screw when a two-piece die is employed is also clearly outlined. The
diestock shown at B is used for the smaller dies of the one-piece
pattern, having a slot in order that they may be closed up slightly by
the clamp screw. The reverse side of the diestock shown at B is outlined
below it, and the guide pieces, which may be easily moved in or out,
according to the size of the piece to be threaded by means of
eccentrically disposed semi-circular slots in the adjustment plate, are
shown. These movable guide members have small pins let into their
surface which engage the slots, and they may be moved in or out, as
desired, according to the position of the adjusting plate. The use of
the guide pieces makes for accurate positioning or centering of the rod
to be threaded. Dies are usually sold in sets, and are commonly
furnished as a portion of a complete outfit such as outlined at Fig.
173. That shown has two sizes of diestock, a tap wrench, eight assorted
dies, eight assorted taps, and a small screw driver for adjusting the
die. An automobile repair shop should be provided with three different
sets of taps and dies, as three different standards for the bolts and
nuts are used in fastening automobile components. These are the
American, metric (used on foreign engines), and the S. A. E. standard
threads. A set of pipe dies and taps will also be found useful.
[Illustration: Fig. 173.--Useful Outfit of Taps and Dies for the Engine
Repair Shop.]
MEASURING TOOLS
The tool outfit of the machinist or the mechanic who aspires to do
machine work must include a number of measuring tools which are not
needed by the floor man or one who merely assembles and takes apart the
finished pieces. The machinist who must convert raw material into
finished products requires a number of measuring tools, some of which
are used for taking only approximate measurements, such as calipers and
scales, while others are intended to take very accurate measurements,
such as the Vernier and the micrometer. A number of common forms of
calipers are shown at Fig. 174. These are known as inside or outside
calipers, depending upon the measurements they are intended to take.
That at A is an inside caliper, consisting of two legs, A and D, and a
gauging piece, B, which can be locked to leg A, or released from that
member by the screw, C. The object of this construction is to permit of
measurements being taken at the bottom of a two diameter hole, where the
point to be measured is of larger diameter than the portion of the hole
through which the calipers entered. It will be apparent that the legs A
and D must be brought close together to pass through the smaller holes.
This may be done without losing the setting, as the guide bar B will
remain in one position as determined by the size of the hole to be
measured, while the leg A may be swung in to clear the obstruction as
the calipers are lifted out. When it is desired to ascertain the
measurements the leg A is pushed back into place into the slotted
portion of the guide B, and locked by the clamp screw C. A tool of this
form is known as an internal transfer caliper.
[Illustration: Fig. 174.--Common Forms of Inside and Outside Calipers.]
The form of caliper shown at B is an outside caliper. Those at C and D
are special forms for inside and outside work, the former being used,
if desired, as a divider, while the latter may be employed for measuring
the walls of tubing. The calipers at E are simple forms, having a
friction joint to distinguish them from the spring calipers shown at B,
C and D. In order to permit of ready adjustment of a spring caliper, a
split nut as shown at G is sometimes used. A solid nut caliper can only
be adjusted by screwing the nut in or out on the screw, which may be a
tedious process if the caliper is to be set from one extreme to the
other several times in succession. With a slip nut as shown at G it is
possible to slip it from one end of the thread to the other without
turning it, and of locking it in place at any desired point by simply
allowing the caliper leg to come in contact with it. The method of
adjusting a spring caliper is shown at Fig. 174, H.
Among the most common of the machinist's tools are those used for linear
measurements. The usual forms are shown in group, Fig. 175. The most
common tool, which is widely known, is the carpenter's folding two-foot
rule or the yardstick. While these are very convenient for taking
measurements where great accuracy is not required, the machinist must
work much more accurately than the carpenter, and the standard steel
scale which is shown at D, is a popular tool for the machinist. The
steel scale is in reality a graduated straight edge and forms an
important part of various measuring tools. These are made of high grade
steel and vary from 1 to 48 inches in length. They are carefully
hardened in order to preserve the graduations, and all surfaces and
edges are accurately ground to insure absolute parallelism. The
graduations on the high grade scales are produced with a special device
known as a dividing engine, but on cheaper scales, etching suffices to
provide a fairly accurate graduation. The steel scales may be very thin
and flexible, or may be about an eighth of an inch thick on the
twelve-inch size, which is that commonly used with combination squares,
protractors and other tools of that nature. The repairman's scale
should be graduated both with the English system, in which the inches
are divided into eighths, sixteenths, thirty-secondths and
sixty-fourths, and also in the metric system, divided into millimeters
and centimeters. Some machinists use scales graduated in tenths,
twentieths, fiftieths and hundredths. This is not as good a system of
graduation as the more conventional one first described.
[Illustration: Fig. 175.--Measuring Appliances for the Machinist and
Floor Man.]
Some steel scales are provided with a slot or groove cut the entire
length on one side and about the center of the scales. This permits the
attachment of various fittings such as the protractor head, which
enables the machinist to measure angles, or in addition the heads
convert the scale into a square or a tool permitting the accurate
bisecting of pieces of circular section. Two scales are sometimes joined
together to form a right angle, such as shown at Fig. 175, C. This is
known as a square and is very valuable in ascertaining the truth of
vertical pieces that are supposed to form a right angle with a base
piece.
The Vernier is a device for reading finer divisions on a scale than
those into which the scale is divided. Sixty-fourths of an inch are
about the finest division that can be read accurately with the naked
eye. When fine work is necessary a Vernier is employed. This consists
essentially of two rules so graduated that the true scale has each inch
divided into ten equal parts, the upper or Vernier portion has ten
divisions occupying the same space as nine of the divisions of the true
scale. It is evident, therefore, that one of the divisions of the
Vernier is equal to nine-tenths of one of those on the true scale. If
the Vernier scale is moved to the right so that the graduations marked
"1" shall coincide, it will have moved one-tenth of a division on the
scale or one-hundredth of an inch. When the graduations numbered 5
coincide the Vernier will have moved five-hundredths of an inch; when
the lines marked 0 and 10 coincide, the Vernier will have moved
nine-hundredths of an inch, and when 10 on the Vernier comes opposite 10
on the scales, the upper rule will have moved ten-hundredths of an inch,
or the whole of one division on the scale. By this means the scale,
though it may be graduated only to tenths of an inch, may be accurately
set at points with positions expressed in hundredths of an inch. When
graduated to read in thousandths, the true scale is divided into fifty
parts and the Vernier into twenty parts. Each division of the Vernier
is therefore equal to nineteen-twentieths of one of the true scale. If
the Vernier be moved so the lines of the first division coincide, it
will have moved one-twentieth of one-fiftieth, or .001 inch. The Vernier
principle can be readily grasped by studying the section of the Vernier
scale and true scale shown at Fig. 176, A.
[Illustration: Fig. 176.--At Left, Special Form of Vernier Caliper for
Measuring Gear Teeth; at Right, Micrometer for Accurate Internal
Measurements.]
The caliper scale which is shown at Fig. 175, A, permits of taking the
over-all dimension of any parts that will go between the jaws. This
scale can be adjusted very accurately by means of a fine thread screw
attached to a movable jaw and the divisions may be divided by eye into
two parts if one sixty-fourth is the smallest of the divisions. A line
is indicated on the movable jaw and coincides with the graduations on
the scale. As will be apparent, if the line does not coincide exactly
with one of the graduations it will be at some point between the lines
and the true measurement may be approximated without trouble.
A group of various other measuring tools of value to the machinist is
shown at Fig. 177. The small scale at A is termed a "center gauge,"
because it can be used to test the truth of the taper of either a male
or female lathe center. The two smaller nicks, or v's, indicate the
shape of a standard thread, and may be used as a guide for grinding the
point of a thread-cutting tool. The cross level which is shown at B is
of marked utility in erecting, as it will indicate absolutely if the
piece it is used to test is level. It will indicate if the piece is
level along its width as well as its length.
[Illustration: Fig. 177.--Measuring Appliances of Value in Airplane
Repair Work.]
A very simple attachment for use with a scale that enables the machinist
to scribe lines along the length of a cylindrical piece is shown at Fig.
177, C. These are merely small wedge-shaped clamps having an angular
face to rest upon the bars. The thread pitch gauge which is shown at
Fig. 177, D, is an excellent pocket tool for the mechanic, as it is
often necessary to determine without loss of time the pitch of the
thread on a bolt or in a nut. This consists of a number of leaves having
serrations on one edge corresponding to the standard thread it is to be
used in measuring. The tool shown gives all pitches up to 48 threads per
inch. The leaves may be folded in out of the way when not in use, and
their shape admits of their being used in any position without the
remainder of the set interfering with the one in use. The fine pitch
gauges have slim, tapering leaves of the correct shape to be used in
finding the pitch of small nuts. As the tool is round when the leaves
are folded back out of the way, it is an excellent pocket tool, as there
are no sharp corners to wear out the pocket. Practical application of a
Vernier having measuring heads of special form for measuring gear teeth
is shown at Fig. 176, A. As the action of this tool has been previously
explained, it will not be necessary to describe it further.
MICROMETER CALIPERS AND THEIR USE
Where great accuracy is necessary in taking measurements the micrometer
caliper, which in the simple form will measure easily .001 inch
(one-thousandth part of an inch) and when fitted with a Vernier that
will measure .0001 inch (one ten-thousandth part of an inch), is used.
The micrometer may be of the caliper form for measuring outside
diameters or it may be of the form shown at Fig. 176, B, for measuring
internal diameters. The operation of both forms is identical except that
the internal micrometer is placed inside of the bore to be measured
while the external form is used just the same as a caliper. The form
outlined will measure from one and one-half to six and a half inches as
extension points are provided to increase the range of the instrument.
The screw has a movement of one-half inch and a hardened anvil is placed
in the end of the thimble in order to prevent undue wear at that point.
The extension points or rods are accurately made in standard lengths and
are screwed into the body of the instrument instead of being pushed in,
this insuring firmness and accuracy. Two forms of micrometers for
external measurements are shown at Fig. 178. The top one is graduated
to read in thousandths of an inch, while the lower one is graduated to
indicate hundredths of a millimeter. The mechanical principle involved
in the construction of a micrometer is that of a screw free to move in a
fixed nut. An opening to receive the work to be measured is provided by
the backward movement of the thimble which turns the screw and the size
of the opening is indicated by the graduations on the barrel.
[Illustration: Fig. 178.--Standard Forms of Micrometer Caliper for
External Measurements.]
The article to be measured is placed between the anvil and spindle, the
frame being held stationary while the thimble is revolved by the thumb
and finger. The pitch of the screw thread on the concealed part of the
spindle is 40 to an inch. One complete revolution of the spindle,
therefore, moves it longitudinally one-fortieth, or twenty-five
thousandths of an inch. As will be evident from the development of the
scale on the barrel of the inch micrometer, the sleeve is marked with
forty lines to the inch, each of these lines indicating twenty-five
thousandths. The thimble has a beveled edge which is graduated into
twenty-five parts. When the instrument is closed the graduation on the
beveled edge of the thimble marked 0 should correspond to the 0 line on
the barrel. If the micrometer is rotated one full turn the opening
between the spindle and anvil will be .025 inch. If the thimble is
turned only one graduation, or one twenty-fifth of a revolution, the
opening between the spindle and anvil will be increased only by .001
inch (one-thousandth of an inch).
As many of the dimensions of the airplane parts, especially of those of
foreign manufacture or such parts as ball and roller bearings, are based
on the metric system, the competent repairman should possess both inch
and metric micrometers in order to avoid continual reference to a table
of metric equivalents. With a metric micrometer there are fifty
graduations on the barrel, these representing .01 of a millimeter, or
approximately .004 inch. One full turn of the barrel means an increase
of half a millimeter, or .50 mm. (fifty one-hundredths). As it takes two
turns to augment the space between the anvil and the stem by increments
of one millimeter, it will be evident that it would not be difficult to
divide the spaces on the metric micrometer thimble in halves by the eye,
and thus the average workman can measure to .0002 inch plus or minus
without difficulty. As set in the illustration, the metric micrometers
show a space of 13.5 mm., or about one millimeter more than half an
inch. The inch micrometer shown is set to five-tenths or five hundred
one-thousandths or one-half inch. A little study of the foregoing matter
will make it easy to understand the action of either the inch or metric
micrometer.
Both of the micrometers shown have a small knurled knob at the end of
the barrel. This controls the ratchet stop, which is a device that
permits a ratchet to slip by a pawl when more than a certain amount of
pressure is applied, thereby preventing the measuring spindle from
turning further and perhaps springing the instrument. A simple rule that
can be easily memorized for reading the inch micrometer is to multiply
the number of vertical divisions on the sleeve by 25 and add to that the
number of divisions on the bevel of the thimble reading from the zero to
the line which coincides with the horizontal line on the sleeve. For
example: if there are ten divisions visible on the sleeve, multiply this
number by 25, then add the number of divisions shown on the bevel of the
thimble, which is 10. The micrometer is therefore opened 10 x 25 equals
250 plus 10 equals 260 thousandths.
Micrometers are made in many sizes, ranging from those having a maximum
opening of one inch to special large forms that will measure forty or
more inches. While it is not to be expected that the repairman will have
use for the big sizes, if a caliper having a maximum opening of six
inches is provided with a number of extension rods enabling one to
measure smaller objects, practically all of the measuring needed in
repairing engine parts can be made accurately. Two or three smaller
micrometers having a maximum range of two or three inches will also be
found valuable, as most of the measurements will be made with these
tools which will be much easier to handle than the larger sizes.
TYPICAL TOOL OUTFITS
The equipment of tools necessary for repairing airplane engines depends
entirely upon the type of the power plant and while the common hand
tools can be used on all forms, the work is always facilitated by having
special tools adapted for reaching the nuts and screws that would be
hard to reach otherwise. Special spanners and socket wrenches are very
desirable. Then again, the nature of the work to be performed must be
taken into consideration. Rebuilding or overhauling an engine calls for
considerably more tools than are furnished for making field repairs or
minor adjustments. A complete set of tools supplied to men working on
Curtiss OX-2 engines and JN-4 training biplanes is shown at Fig. 179.
The tools are placed in a special box provided with a hinged cover and
are arranged in the systematic manner outlined. The various tools and
supplies shown are: A, hacksaw blades; B, special socket wrenches for
engine bolts and nuts; C, ball pein hammers, four sizes; D, five
assorted sizes of screw drivers ranging from very long for heavy work to
short and small for fine work; E, seven pairs of pliers including
combination in three sizes, two pairs of cutting pliers and one round
nose; F, two split pin extractors and spreaders; G, wrench set including
three adjustable monkey wrenches, one Stillson or pipe wrench, five
sizes adjustable end wrenches and ten double end S wrenches; H, set of
files, including flat, three cornered and half round; I, file brush; J,
chisel and drift pin; K, three small punches or drifts; L, hacksaw
frame; M, soldering copper; N, special spanners for propeller retaining
nuts; O, special spanners; P, socket wrenches, long handle; Q, long
handle, stiff bristle brushes for cleaning motor; R, gasoline blow
torch; S, hand drill; T, spools of safety wire; U, flash lamp; V,
special puller and castle wrenches; W, oil can; X, large adjustable
monkey wrench; Y, washer and gasket cutter; Z, ball of heavy twine. In
addition to the tools, various supplies, such as soldering acid, solder,
shellac, valve grinding compound, bolts and nuts, split pins, washers,
wood screws, etc., are provided.
[Illustration: Fig. 179.--Special Tools for Maintaining Curtiss OX-2
Motor Used in Curtiss JN-4 Training Biplane.]
SPECIAL HALL-SCOTT TOOLS
NO. TOOL DIRECTIONS FOR USE
1 Engine hoisting hook, 6-cylinder Hook under cam-shaft housing,
when hoisting engine.
2 Engine hoisting hook, 4-cylinder Hook under cam-shaft housing,
when hoisting engine.
3 Water plug wrench For use on water plugs on top
and end of cylinders.
4 Vertical shaft flange puller For pulling lower pinion shaft
flange from shaft. (Used on A-5
and A-7 engines only.)
5 Oil gun For general lubrication use.
6 Magneto gear puller For pulling magneto gears from
magneto shaft.
7 Socket wrench, 1/4" A.L.A.M. For use on bolts and nuts on
crank cases.
8 Socket wrench, 1/4" A.L.A.M For use on crank cases and
magneto gear housings.
9 Socket wrench, 1/4" A.L.A.M. For use on magneto gear
housings.
10 Socket wrench, 3/8" standard For bolts and nuts which fasten
magnetos to crank-case.
11 Socket wrench, 1/4" A.L.A.M. For use on magneto gear
housings.
12 Vertical shaft gear puller For removing water pump and
magneto drive gear.
13 Brace and facing cutter For facing lugs on cylinders for
cylinder hold down stud washers.
14 Handle for brace Use with brace.
15 Valve grinding brace For grinding in valves.
16 Socket wrench base, 3/8" A.L.A.M. For thrust bearing cap screws.
17 Brace and facing cutter, 5/16" For facing lugs on rocker arm
A.L.A.M. covers.
18 Valve grinding screw driver For grinding in valves.
19 Valve spring tool For putting on and taking off
valve springs.
20 Block-valve spring tool For use with valve spring tool.
21 Socket wrench, 5/8" A.L.A.M. For main bearing nuts.
22 Socket wrench, 1/4" A.L.A.M. For use on cam-shaft housing.
23 Socket wrench, 5/16" A.L.A.M. For cam-shaft housing hold down
stud nuts.
24 Socket wrench, 1/2" A.L.A.M. For cylinder hold down stud
nuts.
25 Socket wrench, 5/16" A.L.A.M. For carburetor and water pump
bolts and nuts.
26 Socket wrench, 5/16" A.L.A.M. For carburetor and water pump
bolts and nuts.
27 Socket wrench For use on carburetor jets.
28 Magneto screw driver For general magneto use.
29 Brass bar, 1" diameter x 7" long For driving piston pins from
pistons.
30 Hack saw For general use.
31 Oil can For cam-shaft housing
lubrication.
32 Gasoline or distillate can For priming or other use.
33 Oil can For magneto gear lubrication.
34 Shellac can For rubber hose connections and
gaskets.
35 Magneto cleaner For use on magnetos.
36 Clamps For holding cylinder hold down
studs, when fitting main
bearings.
37 Piston guards For use in pistons, when out of
engine, to protect them.
38 Screw driver For general use.
39 Vertical shaft clamps For clamping vertical shaft
flanges, when timing engine.
40 Thrust adjusting nut wrench For adjusting propeller thrust
bearing.
41 Stuffing box spanner wrench For adjusting stuffing box nut
on vertical shaft.
42 Water pump spanner wrench For adjusting water pump
stuffing nut.
43 Wrench For use on cylinder relief cocks
and cylinder priming cocks.
44 Hose clamp wrench For use on hose clamps.
45 Scraper For cleaning piston ring grooves
on pistons.
46 Crank-shaft nut wrench For adjusting crank-shaft nut.
47 Spark-plug wrench For putting in and taking out
spark-plugs in cylinders.
48 Timing disc (single disc) For use on crank-shaft to time
engine.
Specify type motor disc should be made for. If double disc is
required, specify the two types of motors the disc is to be made
for. Double disc.
49 Main bearing scraper For scraping in bearings.
50 Cylinder carbon scraper For removing carbon from heads
of cylinders.
51 Valve seating tool For seating valves in cylinder
heads.
52 Scraper, small For general bearing use.
53 Scraper, large For general bearing use.
54 Crank-shaft flange puller For pulling crank-shaft flange
from crank-shaft.
55 Piston and connecting rod racks.
56 Main bearing stud nuts and shim
rack.
57 Main bearing board rack.
58 Rocker arm and cover rack.
The special tools and fixtures recommended by the Hall-Scott Company for
work on their engines are clearly shown at Fig. 180. All tools are
numbered and their uses may be clearly understood by reference to the
illustration and explanatory list given on pages 410 and 411.
OVERHAULING AIRPLANE ENGINES
After an airplane engine has been in use for a period ranging from 60 to
80 hours, depending upon the type, it is necessary to give it a thorough
overhauling before it is returned to service. To do this properly, the
engine is removed from the fuselage and placed on a special supporting
stand, such as shown at Fig. 181, so it can be placed in any position
and completely dismantled. With a stand of this kind it is as easy to
work on the bottom of the engine as on the top and every part can be
instantly reached. The crank-case shown in place in illustration is in a
very convenient position for scraping in the crank-shaft bearings.
[Illustration: Fig. 180.--Special Tools and Appliances to Facilitate
Overhauling Work on Hall-Scott Airplane Engines.]
In order to look over the parts of an engine and to restore the worn or
defective components it is necessary to take the engine entirely apart,
as it is only when the power plant is thoroughly dismantled that the
parts can be inspected or measured to determine defects or wear. If one
is not familiar with the engine to be inspected, even though the work is
done by a repairman of experience, it will be found of value to take
certain precautions when dismantling the engine in order to insure that
all parts will be replaced in the same position they occupied before
removal. There are a number of ways of identifying the parts, one of the
simplest and surest being to mark them with steel numbers or letters or
with a series of center punch marks in order to retain the proper
relation when reassembling. This is of special importance in connection
with dismantling multiple cylinder engines as it is vital that pistons,
piston rings, connecting rods, valves, and other cylinder parts be
always replaced in the same cylinder from which they were removed,
because it is uncommon to find equal depreciation in all cylinders. Some
repairmen use small shipping tags to identify the pieces. This can be
criticised because the tags may become detached and lost and the
identity of the piece mistaken. If the repairing is being done in a shop
where other engines of the same make are being worked on, the repairman
should be provided with a large chest fitted with a lock and key in
which all of the smaller parts, such as rods, bolts and nuts, valves,
gears, valve springs, cam-shafts, etc., may be stored to prevent the
possibility of confusion with similar members of other engines. All
parts should be thoroughly cleaned with gasoline or in the potash kettle
as removed, and wiped clean and dry. This is necessary to show wear
which will be evidenced by easily identified indications in cases where
the machine has been used for a time, but in others, the deterioration
can only be detected by delicate measuring instruments.
[Illustration: Fig. 181.--Special Stand to Make Motor Overhauling Work
Easier.]
In taking down a motor the smaller parts and fittings such as
spark-plugs, manifolds and wiring should be removed first. Then the more
important members such as cylinders may be removed from the crank-case
to give access to the interior and make possible the examination of the
pistons, rings and connecting rods. After the cylinders are removed the
next operation is to disconnect the connecting rods from the crank-shaft
and to remove them and the pistons attached as a unit. Then the
crank-case is dismembered, in most cases by removing the bottom half or
oil sump, thus exposing the main bearings and crank-shaft. The first
operation is the removal of the inlet and exhaust manifolds. In some
cases the manifolds are cored integral with the cylinder head casting
and it is merely necessary to remove a short pipe leading from the
carburetor to one inlet opening and the exhaust pipe from the outlet
opening common to all cylinders. In order to remove the carburetor it is
necessary to shut off the gasoline supply at the tank and to remove the
pipe coupling at the float chamber. It is also necessary to disconnect
the throttle operating rod. After the cylinders are removed and before
taking the crank-case apart it is well to remove the water pump and
magneto. The wiring on most engines of modern development is carried in
conduits and usually releasing two or three minor fastenings will permit
one to take off the plug wiring as a unit. The wire should be
disconnected from both spark-plugs and magneto distributor before its
removal. When the cylinders are removed, the pistons, piston rings, and
connecting rods are clearly exposed and their condition may be readily
noticed.
Before disturbing the arrangement of the timing gears, it is important
that these be marked so that they will be replaced in exactly the same
relation as intended by the engine designer. If the gears are properly
marked the valve timing and magneto setting will be undisturbed when the
parts are replaced after overhauling. With the cylinders off, it is
possible to ascertain if there is any undue wear present in the
connecting rod bearings at either the wrist pin or crank-pin ends and
also to form some idea of the amount of carbon deposits on the piston
top and back of the piston rings. Any wear of the timing gears can also
be determined. The removal of the bottom plate of the engine enables the
repairman to see if the main bearings are worn unduly. Often bearings
may be taken up sufficiently to eliminate all looseness. In other cases
they may be worn enough so that careful refitting will be necessary.
Where the crank-case is divided horizontally into two portions, the
upper one serving as an engine base to which the cylinders and in fact
all important working parts are attached, the lower portion performs the
functions of an oil container and cover for the internal mechanism. This
is the construction generally followed.
DEFECTS IN CYLINDERS
After the cylinders have been removed and stripped of all fittings, they
should be thoroughly cleaned and then carefully examined for defects.
The interior or bore should be looked at with a view of finding score
marks, grooves, cuts or scratches in the interior, because there are
many faults that may be ascribed to depreciation at this point. The
cylinder bore may be worn out of round, which can only be determined by
measuring with an internal caliper or dial indicator even if the
cylinder bore shows no sign of wear. The flange at the bottom of the
cylinder by which it is held to the engine base may be cracked. The
water jacket wall may have opened up due to freezing of the jacket
water at some time or other or it may be filled with scale and sediment
due to the use of impure cooling water. The valve seat may be scored or
pitted, while the threads holding the valve chamber cap may be worn so
that the cap will not be a tight fit. The detachable head construction
makes it possible to remove that member and obtain ready access to the
piston tops for scraping out carbon without taking the main cylinder
portion from the crank-case. When the valves need grinding the head may
be removed and carried to the bench where the work may be performed with
absolute assurance that none of the valve grinding compound will
penetrate into the interior of the cylinder as is sometimes unavoidable
with the I-head cylinder. If the cylinder should be scored, the water
jacket and combustion head may be saved and a new cylinder casting
purchased at considerably less cost than that of the complete unit
cylinder.
The detachable head construction has only recently been applied on
airplane engines, though it was one of the earliest forms of automobile
engine construction. In the early days it was difficult to procure
gaskets or packings that would be both gas and water tight. The sheet
asbestos commonly used was too soft and blew out readily. Besides a new
gasket had to be made every time the cylinder head was removed. Woven
wire and asbestos packings impregnated with rubber, red lead, graphite
and other filling materials were more satisfactory than the soft sheet
asbestos, but were prone to burn out if the water supply became low.
Materials such as sheet copper or brass proved to be too hard to form a
sufficiently yielding packing medium that would allow for the inevitable
slight inaccuracies in machining the cylinder head and cylinder. The
invention of the copper-asbestos gasket, which is composed of two sheets
of very thin, soft copper bound together by a thin edging of the same
material and having a piece of sheet asbestos interposed solved this
problem. Copper-asbestos packings form an effective seal against leakage
of water and a positive retention means for keeping the explosion
pressure in the cylinder. The great advantage of the detachable head is
that it permits of very easy inspection of the piston tops and
combustion chamber and ready removal of carbon deposits.
CARBON DEPOSITS, THEIR CAUSE AND PREVENTION
Most authorities agree that carbon is the result of imperfect combustion
of the fuel and air mixture as well as the use of lubricating oils of
improper flash point. Lubricating oils that work by the piston rings may
become decomposed by the great heat in the combustion chamber, but at
the same time one cannot blame the lubricating oil for all of the carbon
deposits. There is little reason to suspect that pure petroleum oil of
proper body will deposit excessive amounts of carbon, though if the oil
is mixed with castor oil, which is of vegetable origin, there would be
much carbon left in the interior of the combustion chamber. Fuel
mixtures that are too rich in gasoline also produce these undesirable
accumulations.