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Terms and Terminology

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.

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 blade.

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 bed.

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 rams.

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 the valves.

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 superchargers.

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.

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