One stumbling block to working on a tractor and sometimes even using it is that the terminology can be perplexing.
For those of you that grew up with internal combustion engines and maybe even tractors it may be hard to relate
to the need for covering the basics at this level. But for those that have grown up in the last thirty years (and
not with a shop handy) when the prevailing opinion was "Don't do it yourself", even the basic systems
of the engine may have many foreign terms. Couple this attitude with the fact that older tractors may have engine
components that have not been present on automobiles and trucks for nearly forty years, and you end up having to
deal with instructions that may as well be written in a foreign language. Manuals often expect that you are already
acquainted with these terms or you would not be working on your machine.
In addition to the component terms, we have also included terms associated with implements and their components.
Alternator - Alternators are used on later model tractors and are frequently retrofitted on old working
tractors to improve battery charging. The primary difference is the alternator has better charging characteristics
throughout the RPM range. Though both Generators and Alternators would generate AC, the alternator actually generates
AC and diodes are used to convert it to DC. Contrast this with Generators.
Baler - an implement that can collect, compress and tie wire or string around grasses such as Alfalfa,
Oat Straw, etc. Square Balers have a pickup to bring the grasses up into an auger that moves them into position
to be pressed by a piston. When the pressed grass reaches a configurable length a mechanism is tripped to cause
the string to be tied and cut. The bale is then ejected and a new one started. There are also balers that generate
large round bales that are more resistant to rain damage.
Battery Ignition - A battery ignition differs from the Magneto ignition in that it does not generate
its own voltage. It modifies the voltage it takes from the Battery and Charging system and delivers it at the correct
time to fire the spark plugs.
BDC - Before Top Dead Center. Use in timing to show the number of degrees prior to the piston reaching
the top of its stroke.
Block - The major casting of the engine. Holds the cylinders, crankshaft, and camshaft (through the 1960s).
When you look at an engine, most of what you see is the block.
Blade - A cutting edge and moldboard for pulling or rearranging dirt, manure, bedding, or snow. On wheel
tractors these are mounted on the rear or middle of the tractor to allow effective use while on crawler tractors
they are mounted on the front.
Bottom - Refers to a single plow share and moldboard. If a plow has two bottoms it has two shares and
moldboards. Some be call this type of plow a "bottom plow".
bulldozer - A blade that goes on front of a tractor (usually a crawler) to push dirt.
Brush Hog/Bush Hog - Many companies make a rotary flailing blade mower that is commonly referred to as
a brush hog. One of these companies calls their product a bush hog.
Butterfly - valves in the carburetor to control the level of mixture provided to the Intake valves (Throttle
Butterfly) and the ratio of fuel to air mixture for starting (Choke Butterfly).
Camshaft - A secondary shaft that causes the valves to open and close via the push rods or even directly
pushes them open and closed in flathead and overhead cam (modern tractors only) engines. This shaft is connected
(usually via a gear) and timed to the turning of the Crankshaft. The camshaft will frequently drive the oil pump
and occasionally drive the hydraulic pump and distributor.
Camshaft Lobes - There is a lobe for each valve on the camshaft. The lobe is a non-concentric surface
and thus can cause the valve to be open or closed depending on the position of the shaft in its rotation.
Choke - A valve in the carburetor to allow the intake of air to be reduced for cold starting. Reducing
the air intake, increases or richens the fuel mixture (more gas, less air).
Combustion Chamber - When the piston is at the top of its compression stroke with the valves closed,
the resulting sealed area contains a compressed mixture of fuel and air. When the spark plug fires, this mixture
is "Combusted" or ignited to push the piston back down. That area that the mixture is compressed into
is the combustion chamber.
Connecting Rods - The rods that connect the crankshaft to the piston. The piston pin or wrist pin holds
the piston to the top of the connecting rod. The rod bearings isolate the bottom of the connecting rod from the
Crankshaft - Also called the bottom end. This is the shaft at the bottom of the engine that turns as
the Pistons fire (the pistons force it to rotate in circular motion) and has a connection to the flywheel, clutch,
and eventually the main shaft of the transmission, torque convertor and possibly Belt Pulley or PTO. Other components
that the crankshaft will drive are the water pump, generator, oil pump, camshaft (and thus valves), and hydraulic
pump (some older models instead had hydraulic pumps connected to the PTO or Belt Pulley system). On some machines,
it also either directly or indirectly drives superchargers, air port intakes (2 stroke diesels), and air conditioning
pumps (late model tractors only).
Crawler - A tractor that uses tracks in place of wheels. Crawlers exhibit superior floatation and traction
compared to wheel tractors since their weight is spread over significantly more surface area. They are more maintenance
intensive and costly. Crawlers are critical for operations requiring floatation such as areas where soil compaction
is a problem. They are also critical to operations where serious traction is required such as using a bulldozer
Creeper Gear - A very low low gear used to pull implements that must move slower than standard first
gear would allow.
Cutout Relay - A relay that keeps the battery from discharging through the generator when the generator
output is lower than that required to charge the battery. All regulators have a cutout relay. Some earlier tractors
had no regulator but had merely a cutout relay.
Disc Harrow - A harrow that uses Discs to accomplish the breaking up and smoothing of soil. Disc harrows
may have 1 or 2 rows of discs which may be angled or straight depending on desired outcome.
Disc Plow - A plow that uses a disc instead of a bottom (share and moldboard). Disc plows are capable
of turning over more difficult soil but cover less width on a single pass.
Distributor - Ignoring the fuel distributor on diesels, the distributor commonly refers to the device
that distributes spark to each of the spark plug wires at the right time. Both Magnetos and Battery Ignitions have
a distributor. The distributor consists of a rotating shaft (timed ultimately to the crankshaft via the camshaft
or a gear) that turns the rotor. The rotor makes and breaks contact with the spark plug wires via the distributor
cap. Simultaneously the same shaft opens and closes the points.
Dual Fuel - See Two Fuel.
EROPS - Enclosed Roll Over Protection System. EROPSs add weather tight enclosures including doors and
windows to a ROPS.
Flathead - Engines that have no moving components in the head. These engines have simply a heavy casting,
with holes for the spark plugs and indentations on the bottom that make up the combustion chamber for each cylinder,
covering the top of the block. Contrast this with Overhead Valve heads.
Flyball - Small steel balls in the governor that push on a plate to close the carburetor butterfly depending
on centrifugal force.
Flyweight - Hinged weights that move outward depending on centrifugal force to close the carburetor butterfly.
Conceptually the same as Flyball. Flyweights replaced Flyballs in later governors.
Four Stroke - Tractor engines will mostly be 4 stroke gas or diesel or 2 stroke diesel. On the four stroke,
each stroke is one half of a crankshaft revolution.
- First stroke (Intake Stroke) - the piston is pulled down to draw fuel and air in through the Intake valve which
is open during this stroke. Exhaust valve is closed.
- Second stroke (Compression Stroke) - compresses the fuel and air mixture by pushing the piston upward. Both
valves are closed.
- Third stroke (Power Stroke) - the piston is push down by the explosion of the compressed mixture when the spark
plug fires. Both valves are closed.
- Fourth stroke (Exhaust Stroke) - The piston is pushed back up by the crankshaft to push the now burned exhaust
gases out the Exhaust Valve which is open during this stroke. Intake valve is closed.
Four Stroke diesels are similar only the mixture ignites due to compression rather than a spark plug.
Gear Pump - Gear Pumps are used for some engine oil pumps and hydraulic pumps. The concept involves generating
oil flow by two gears meshing together in a relatively tight enclosure. The size of the gears and the tightness
of the enclosure will determine what the pump is capable of generating.
Generator - The generator generates voltage to charge the battery. Generators have one set of brushes
grounded to avoid generating AC and thus actually generate cyclic pulses of DC from the other brush. There are
two types of generators found on tractors; 2 brush and 3 brush.
Governor - an integral component of the engine that maintains a certain RPM based on the setting of your
throttle. If your throttle is set for 1200 RPM and you place a load on the engine which begins to slow it down,
the governor will compensate by opening the carburetor and allow extra gas and air in. Most tractors have a governor
between the throttle and the carburetor, i.e., You set the Governor with the throttle, the Governor sets the carburetor.
Harrow - an implement to break up and smooth plowed or clumped soil in preparation for creating a seed
Hay Rake - this is an implement that is used to rake up the grass into windrows so it can be baled. Older
rakes generate a single windrow on a pass whereas newer large rakes can build two windrows on one pass.
Head - The casting that is bolted to the top of the block. See overhead valve and flathead.
I Head - See Overhead Valve. Head named for the shape of the combustion chamber as related to the piston
to valve positioning. Probably should have been called T Head (but I wont argue with the engineers of the 1930s).
Ignition Timing - Assembling the ignition components (either Magneto or Distributor) ignition such that
the spark is delivered to each cylinder at nearly the top of its compression stroke. The timing will usually be
at slightly beyond TDC. The terms Advancing and Retarding the timing refers to the relationship of when the spark
plug fires to TDC. Ignition timing is different at different RPMs. There is usually a device to advance the timing
as the RPMs increase. The faster the engine spins the sooner it needs to fire.
Industrial Loader - refers to a loader built with heavy duty steel, large bucket, and hydraulic bucket
IPTO - Independent PTO. Prior to the concept of Independent PTOs, either the tractor needed to be moving
or the transmission in neutral to keep the PTO turning. This was primarily accomplished by disassociating the PTO
shaft from the transmission though other methods used hand clutches or shuttle-style clutches such that forward
motion could be stopped without stopping the PTO.
Journals - These are machines mating surfaces. The Camshaft and Crankshaft have journal to allow them
to ride in the block. The crankshaft has additional journals for the connecting rod to ride on. Journals are the
surfaces that Rod, Main, and Camshaft Bearings are are against. All that separates them is a thin coating of oil.
L Head - See Flathead. Head named for the shape of the combustion chamber since valves are offset to
the side in relation to the piston. This forms and upside down L.
Lean - carburetor setting are called lean when the mixture of fuel and air are biased toward more air
than would be used in the standard mixture.
Lifters - See Rocker Arms. Slang for Rocker Arms (... or are Rocker Arms slang for Lifters??)
Loader - An implement to pick up and dump dirt, manure, fresh bedding etc.
Magneto - A device to generate spark and direct it to the spark plugs. It is similar to a Battery ignition
except rather than getting its voltage from the battery, it creates it internally by using magnets and a rotor.
It is an electricity generator coupled with a distributor delivering spark to the plugs at the appropriate time
to explode the gas and air mixture in the combustion chamber.
Main and Rod Bearings - Replaceable metal inserts that ride on the crankshaft journals. Many people might
think of these more as bushings since there are no roller or ball bearings but the term bearing simply refers to
the bearing surface that isolates the bottom of the connecting rod from the Crankshaft journals and the similar
arrangement for the attachment points of the crankshaft to the block.
Manure Spreader - A trailer that when filled with manure and driven across a field will chop and spread
the manure out.
NFE - Narrow Front End. Two types of narrow front ends were used through the fifties. The dual wheel
and single wheel. The greater maneuverability of the NFE was eventually put aside in favor of the slight less tippy
and stronger Wide Front End. Aside from basic safety, the NFE did not adapt well to the explosion of loader usage
since placing a load high in the air required greater lateral stability.
Oil Pickup - The oil pump draws oil out of the oil pan through the oil pickup. On some tractors it is
in a fixed position below the "low" mark on the dipstick while others used a floating pickup to avoid
the larger sediments and contaminants that would be found lower in the pan. Both types have a screen to keep large
particles of grime from being circulate back in to the oiling system.
Overhead Cam - An overhead valve engine with the Camshaft in the head. Not seen until the 1970s on tractors.
Overhead Valve - The head contains the valves, spark plugs, rocker arms and push rods.
PAW - Power Adjust Wheels. Rims that would allow spacing to be adjusted laterally without removal or
jacking. Allis Chalmers brought out a rim style in the early 50s with spiral bars that would allow this movement
by simply loosening the lock bolts and releasing the clutch while the opposite brake was on. Thus the power of
the engine would pull or push the rim in or out. This became common on all machines until the size requirements
of upper-end tractors and the shift to chemical-based "cultivating" made spacing adjustments somewhat
moot. This capability is still extremely viable and appreciated where manual cultivating is practiced.
Piston - The piston is a "plug" that moves up and down in the cylinder depending on the position
of the crankshaft in its rotation. During 3 strokes of a 4 stroke engine the piston is pulled or pushed by the
crankshaft while during the compression stroke it is pushed by the explosion of the air / fuel mixture.
Piston Pump - A type of hydraulic pump that uses cam lobe action against pistons to generate hydraulic
fluid flow for the lifting of implements. Though superior in their characteristics and longer lasting, excessive
numbers of parts (meaning expense) limited their use to only a couple of manufacturers.
Pittman Arm - An arm that is used in combination with a offset flywheel to convert circular motion to
back and forth motion. The most common use on tractor implements is the sickle bar mower. When used thusly, the
pittman arm connecting rod is normally made of wood to allow its own destruction in the event of binding such as
contact with rocks. Pitmann arms can also be used on implements where vibration is needed.
Post Driver - Hydraulic device that pounds or pushes fence posts into the ground with first digging a
hole. Fence posts used are normally sharpened on the downside to go in easily and straight.
Post Hole Digger - A PTO driven auger that digs a hole for a fence post.
PTO - Power Take Off. A separate method of using the tractors horsepower for running various implements.
Usually a shaft is connected between the PTO and the implement to turn whatever gearbox the implement may have.
A good example would be a post hole digger with an auger that must turn to dig the hole. PTOs turn at 540 or 1000
RPM. 540 was the common standard until the late 50s. Various sizes and spline configurations of PTO shafts exist
though older tractors primarily used 1 3/8 and 1 1/8 inch shafts with 6 splines.
Push Rods - The rods that link the tappets (pushed by the camshaft lobes) to the rocker arms that actuate
Regulator - Cutout relay and Voltage/Current relay in a single case. Rarely, some tractor models had
3 relays in the case; the Cutout relay, a separate Voltage relay, and separate Current relay. On earlier machines,
the cases containing only a cutout relay were not called Regulators since they did not regulate generator output.
Rich - carburetor settings are called Rich when the mixture of fuel and air are biased toward more fuel
than would be used in the standard mixture.
Rings - These are metal bands that encircle the piston with multiple functions of keeping the compression
chamber pressure out of the crankcase, providing a good enough seal to generate compression, and oiling the cylinder
wall to keep down wear of the piston and cylinder.
Rocker Arms - These levers that are pushed by the push rods to cause the valves to open.
Rods - Slang for Connecting Rod. Not to be confused with Push Rods.
ROPS - Roll Over Protection System. ROPSs are found on later model tractors and were made mandatory on
tractors over a certain weight.
Roto or Rotating Valves - Valves that are designed to turn as they are opened and closed. Causes even
wear and theoretically longer valve life.
Rototiller - An implement that chops the soil be tines rotating on a shaft running parallel to the ground.
To effectively use a rototiller requires that a tractor have a creeper gear to allow it to move along very slowly.
RPM - Stands for Revolutions Per Minute. When the engine crankshaft turns 360 degrees it is one Revolution.
The number of times the engine does this in a minute is the RPM it is set to.
Sickle Mower - A mower that uses a bar of cutting blades, pulled back and forth with a pittman arm, that
slides in a fixed position bar to cut grass crops on relatively smooth surfaces. The Sickle mower was used extensively
through the 60s.
Sleeve - A replaceable cylinder that can be removed from the block. Sleeves are never bored out. Tractors
were commonly made with sleeved engines. Contrast this with most automobiles where the block and cylinders are
integral. Sleeves are sealed at the top and bottom since coolant circulates by their sides but the top and bottom
are open to the combustion chamber and crankcase respectively.
Spike Tooth Harrow - A harrow that uses downward spikes to accomplish the breaking up and smoothing of
soil. The spikes are reminiscent of railroad spikes.
Spring Tooth Harrow - A harrow that uses spring steel bars shaped in half-moons to accomplish the breaking
up and smoothing of soil.
Tappets - These ride on the camshaft and actuate the valves. On a flathead, they directly open the valves,
on an overhead valve engine they push rocker arms via the push rods to perform the same function.
TDC - Top Dead Center. Refers to the position being at the very top of its travel in the cylinder. On
a four stroke, TDC will occur at the top of the compression stroke and the top of the exhaust stroke.
Three Brush - Refers to the type of generator that uses a 3rd brush to limit output. These had poor characteristics
for generating voltage at low and high RPMs and are found on earlier tractors into the 50s.
Tri-cycle - See NFE.
Trip Bucket Loader - Loaders that use a locking latch that when released will allow the bucket to dump.
The dumping of such loaders may depend on having a load in the bucket. Usually some spring mechanism is provided
to help nudge the bucket back to its locked position or at least to bring it part of way such that locking can
be accomplished by lowering it to the ground.
Two Brush - Refers to the type of generator that has external means for limiting the current generated.
One brush provides the output and the other brush is grounded to eliminate the generation of AC.
Two Fuel - Engine systems designed to run on tractor fuel, kerosene, or gasoline. These systems have
a small tank for gasoline to get the engine to operating temperature at which time the larger tank (containing
the second type of cheaper fuel) is opened and the gas tank closed. Common differences are that the dome of the
pistons will have a flatter profile to reduce compressions, the Intake manifold will have shrouding to help it
heat the fuel to a hotter temperature, a different thermostat is used to keep the temperature up, and a radiator
shutter is used to limit the amount of coolant cooling. As gasoline became cheaper, most two fuel tractors were
converted to simply gas. Running the tractor on gas generates more horsepower.
Two Stroke - Only a small number of tractors used two stroke engines and these were all diesels. Chain
saws, dirt bikes, leaf blowers, and weed eaters commonly use gas 2 strokes. The primary difference is that the
cycle is completed in half the revolutions of the crankshaft (one full turn versus the two full turns of the 4
stroke). To accomplish this, the cylinders will have ports (valved holes in the side of the cylinders) in them
that are open depending on the position of the piston. Gas 2 strokes do not have normal valves in the combustion
chamber but the most common diesel tractors strokes do. To gain efficiency, old 2 stroke diesel tractors needed
Valves - Many types of valves are on tractors including valves in the hydraulic pump, carburetor, and
oil pump but when used alone the term "Valve" refers to the Intake and Exhaust Valves. These open and
close based on the action and timing of the camshaft to allow air and fuel to be drawn in and burnt exhaust gases
to be push out.
Valve Springs - Springs that cause the valves to close when the rocker arms (or tappets on a flathead)
are not pushing them open.
Valve Timing - Assembling the engine such that the Valves open and close when they should to allow mixture
in, compression, and allow burned gases out. See Four Stroke for a description of the timing. Valve timing is usually
accomplished by lining up the gear that drives the camshaft to the correct marks on the crankshaft gear.
Vane Pump - Vane pumps are used for some engine oil and hydraulic pumps. Generation characteristics are
superior to gear pumps but wear characteristics and expense is worse. Vane pumps use two or more spring loaded
vanes spinning within an eccentric enclosed space to generate flow.
WFE - Wide Front End. Refers to any non-tri-cycle front end configuration. All tractors from the early
60's on used WFEs exclusively.