Grouser
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Grousers are devices intended to increase the traction of
continuous track Continuous track or tracked treads are a system of vehicle propulsion used in tracked vehicles, running on a continuous band of treads or track plates driven by two or more wheels. The large surface area of the tracks distributes the w ...
s, especially in loose material such as
soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...
or
snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...
. This is done by increasing contact with the ground with protrusions, similar to conventional tire treads, and analogous to athletes' cleated shoes. On tanks and armoured vehicles, grousers are usually pads attached to the tracks; but on construction vehicles they may take the form of flat plates or bars. Similar traction-improving patterns have been implemented on the surface of the
wheel A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machin ...
s on tractors. These include strakes, where material is removed from the surface of the wheel to achieve protrusion; cleats, with spikes instead of straight bars; and lugs with raised rubber on a
tire tread The tread of a tire or track refers to the rubber on its circumference that makes contact with the road or the ground. As tires are used, the tread is worn off, limiting its effectiveness in providing traction. A worn tire can often be retr ...
.


Variations

Developed during
World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
, external track extensions – often called "grousers" or "duckbills" – were added to the outside edges of the trackshoes on armored fighting vehicles such as
tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and battlefield mobility provided by tracks and a powerful engine; ...
s, widening the track for improved performance in snow or mud. Track segments (i.e., trackshoes) that incorporate grouser bars are known as ''grouser shoes'', and typically include one to three grousers. Grousers are commonly used on construction vehicles such as
bulldozer A bulldozer or dozer (also called a crawler) is a large tractor equipped with a metal #Blade, blade at the front for pushing material (soil, sand, snow, rubble, or rock) during construction work. It travels most commonly on continuous tracks, ...
s,
loader Loader can refer to: * Loader (equipment) * Loader (computing) ** LOADER.EXE, an auto-start program loader optionally used in the startup process of Microsoft Windows ME * Loader (surname) * Fast loader * Speedloader * Boot loader ** LOADER.COM ...
s, and
excavator Excavators are heavy equipment (construction), heavy construction equipment primarily consisting of a backhoe, boom, dipper (or stick), Bucket (machine part), bucket, and cab on a rotating platform known as the "house". The modern excavator's ...
s. Grousers may be permanently attached to, or formed as a single piece with, the track shoe, or they may be bolted onto the track shoe for ease of replacement as they become worn. While grousers are usually straight, they may have more complex shapes, including spikes and
involute In mathematics, an involute (also known as an evolvent) is a particular type of curve that is dependent on another shape or curve. An involute of a curve is the Locus (mathematics), locus of a point on a piece of taut string as the string is eith ...
curves, depending on the type of terrain and the performance requirements of the vehicle. Grousers are typically made of metal, such as
forged Forging is a manufacturing process involving the shaping of metal using localized compression (physics), compressive forces. The blows are delivered with a hammer (often a power hammer) or a die (manufacturing), die. Forging is often classif ...
steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...
, and are not designed for use on paved roads. Various devices, with names such as road bands, have been developed to temporarily cover grousers/cleats in order to allow a vehicle to travel on paved roads. Grousers have been used in such exotic environments as the
deep sea The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low tempe ...
floor A floor is the bottom surface of a room or vehicle. Floors vary from wikt:hovel, simple dirt in a cave to many layered surfaces made with modern technology. Floors may be stone, wood, bamboo, metal or any other material that can support the ex ...
, and the surfaces of the
Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
and
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
.
Snowmobile A snowmobile, also known as a snowmachine (chiefly Alaskan), motor sled (chiefly Canadian), motor sledge, skimobile, snow scooter, or simply a sled is a motorized vehicle designed for winter travel and recreation on snow. Their engines normally ...
s once used cleated tracks, but racing snowmobiles are banned from using cleated track for safety reasons and instead use rubber tracks. Protrusions molded into rubber tractor tire treads are known as lugs, as are cleats for round wheels, which perform a similar function. Unlike metal grousers, these rubber tire treads or crawler-track shoes/pads may be more suitable for driving on roads.


Terramechanics

Grousers function by trapping soil against the contact area of the track. It is the
shearing Sheep shearing is the process by which the woollen fleece of a sheep is cut off. The person who removes the sheep's wool is called a '' shearer''. Typically each adult sheep is shorn once each year (depending upon dialect, a sheep may be sai ...
of the soil against itself that generates tractive force. The gross tractive effort, or soil thrust, of a vehicle may be calculated from the equation: H = blc \left ( 1 + \frac \right ) + W \tan \phi \left ( 1 + 0.64 \left \left ( \frac \right ) \cot^ \left ( \frac \right ) \right \right ) where: :H = soil thrust :b = track width :l = contact length :c = coefficient of cohesion (a soil property) :h = grouser height :W = gross vehicle weight :\phi =
angle of repose The angle of repose, or critical angle of repose, of a granular material is the steepest angle of descent or Strike and dip, dip relative to the horizontal plane on which the material can be piled without slumping. At this angle, the material ...
(a soil property)


Gallery

File:British Sherman Firefly Namur.jpg, A British
Sherman Firefly The Sherman Firefly was a medium tank used by the United Kingdom and some armoured formations of other Allies in World War II, Allies in the Second World War. It was based on the US M4 Sherman but was fitted with the more powerful British cal ...
tank fitted with track grousers File:T29.Fort Knox.0007x8yr.jpg, An experimental American T29 heavy tank of 1945 with grousers to widen the track File:Farmall regular web.JPG, Cleats on the drive wheel of a
Farmall Farmall was a model name and later a brand name for tractors manufactured by International Harvester (IH), an American truck, tractor, and construction equipment company. The Farmall name was usually presented as McCormick-Deering Farmall and l ...
tractor File:Old Farmall.jpg, A Farmall tractor with road bands fitted to facilitate driving on paved roads File:Fordon Tractor ModelF.jpg, A
Fordson tractor Fordson was a brand name of tractors and trucks. It was used on a range of mass-produced general-purpose tractors manufactured by Henry Ford & Son Inc from 1917 to 1920, by Ford Motor Company (U.S.) and Ford Motor Company Ltd (U.K.) from 1920 t ...
displaying another style of cleats, made of angle stock File:Left-Front Wheel of Curiosity Rover, Approaching Three Miles.jpg, Grousers on the wheel of the mars rover
Curiosity Curiosity (from Latin , from "careful, diligent, curious", akin to "care") is a quality related to inquisitive thinking, such as exploration, investigation, and learning, evident in humans and other animals. Curiosity helps Developmental psyc ...


See also

* Bar grip tyre *
Heavy equipment (construction) Heavy equipment, heavy machinery, earthmovers, construction vehicles, or construction equipment, refers to heavy-duty vehicles specially designed to execute construction tasks, most frequently involving earthwork operations or other large con ...
*
Soil mechanics Soil mechanics is a branch of soil physics and applied mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a heterogeneous mixture of fluids (usually air and ...
* Terramechanics


References

{{reflist Vehicle parts Tracked vehicles Soil mechanics