Trunnion
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A trunnion (from
Alternatively, a trunnion is a shaft that positions and supports a tilting plate. This is a misnomer, as in reality it is a cradle for the true trunnion.[citation needed]
In mechanical engineering (see the trunnion bearing section below), it is one part of a rotating joint where a shaft (the trunnion) is inserted into (and turns inside) a full or partial cylinder.
Medieval history
In a
With the creation of larger and more powerful
Trunnions were mounted near the center of mass to allow the barrel to be elevated to any desired angle, without having to dismount it from the carriage upon which it rested. Some guns had a second set of trunnions placed several feet back from the first pair, which could be used to allow for easier transportation.[5] The gun would recoil causing the carriage to move backwards several feet but men or a team of horses could put it back into firing position. It became easier to rapidly transport these large siege guns, maneuver them from transportation mode to firing position, and they could go wherever a team of men or horses could pull them.[6]
Initial significance
Due to its capabilities, the French- and Burgundy-designed siege gun, equipped with its trunnions, required little significant modification from around 1465 to the 1840s.
Defensive tactics and fortifications had to be altered since these new weapons could be transported so speedily and aimed with much more accuracy at strategic locations. Two significant changes were the additions of a ditch and low, sloping ramparts of packed earth (glacis) that would surround the city and absorb the impact of the cannonballs, and the replacement of round watchtowers with angular bastions. These towers would be deemed trace Italienne.[8]
Whoever could afford these new weapons had the tactical advantage over their neighbors and smaller sovereignties, which could not incorporate them into their army. Smaller states, such as the principalities of Italy, began to conglomerate. Preexisting stronger entities, such as France or the Habsburg emperors, were able to expand their territories and maintain a tighter control over the land they already occupied. With the potential threat of their land and castles being seized, the nobility began to pay their taxes and more closely follow their ruler’s mandates. With siege guns mounted on trunnions, stronger and larger states were formed, but because of this, struggles between neighboring governments with consolidated power began to ensue and would continue to plague Europe for the next few centuries.[6]
Usages
In dams
A common
In vehicles
- In older cars, the trunnion is part of the suspension and either allows free movement of the rear wheel hub in relation to the chassisAmerican Motors recommended lubrication of its pre-packed front suspension trunnions on some models using a sodium base grease every 32,000 miles (51,000 km) or three years.[13] In 1963 it incorporated molded rubber "Clevebloc" bushings on the upper trunnion of others to seal out dirt and retain silicone lubricant for the life of the car.[14]
- In aviation, the term refers to the structural component that attaches the undercarriage or landing gear to the airframe.[15] For aircraft equipped with retractable landing gear, the trunnion is pivoted to permit rotation of the entire gear assembly.[16]
- In heavy equipment, such as a bulldozer, the term refers to the protrusions on the vehicle frame on which the blade frame attaches and hinges allowing vertical movement.
- In Chevrolet GMC C/K pickup trucks, the term refers to the tailgate attachment points. Rather than using conventional tailgate hinges, trunnions are used to permit quick toolless removal and installation of the pickup tailgate.
- In axles, the term refers to the type of suspension used on a multi-axle configurations. It is a "short axle pivoted at or near its mid-point about a horizontal axis transverse to its own centerline, normally used in pairs in conjunction with a
- In trailers, leveling jacks may have trunnion mounts.[19]
- In the valve train of a pushrod engine, the term refers to the fixed axle that acts as a pivot point for the valve rocker.
In other technology
- In steam engines, they are supporting gudgeon pins on either side of an oscillating steam cylinder. They are usually tubular and convey steam.
- On communication satellites, the antennas are usually mounted on a pair of trunnions to allow the beam pattern to be correctly pointed on the Earth from the geostationary orbit.
- On stage lighting instruments, a trunnion is a bracket attached to both ends of a striplight that allows the striplight to be mounted on the floor. Sometimes trunnions are also equipped with casters to allow the striplight to be moved easily.
- In arborto the underside of the saw table.
- In waste collection, the trunnion is the bar on the front of a Dumpster that connects to the back of a garbage truck.
- On the Space Shuttle, trunnion pins are affixed to the sides of payload items allowing them to be secured to receivers mounted on the sills of the payload bay. These receivers can be remotely commanded to secure and release selected items. Similar keel pins protrude from the nadir side of payload items, into matching holes in the bottom of the payload bay.
- On hydraulic cylinders, a trunnion (either featuring external pins or internal pockets) can be an alternative body mounting type, as opposed to a flange or pin eye.
- In steelmaking, on the Bessemer converter. There are trunnions on either side to be able to pour out the molten steel.
- In surveying total stations and theodolites, the trunnion axis is the axis about which the telescope transits. It is parallel to the horizontal axis defined by the tubular spirit bubble.
- In Dobsoniantelescope designs, commonly known as altitude bearings.
- In structural engineering, a type of bascule bridge, with the road deck on one side of the trunnion, and the counterweight on the other.
- In laboratory centrifuges, trunnions are used to pivot sample buckets in swinging-bucket rotors.
- In nuclear power plants, when the steam generators are replaced, trunnions are used to upend them, to get them on the rail system, to shuttle them out of containment.
- In wind turbine generators, trunnions are used as two of three or more mounting points for the gearbox (transferring power from the rotor to the generator) which allows for limited movement due to torque variations and an accessible way to remote and service the drive-train .
Trunnion bearings
In mechanical engineering, it is one part of a rotating joint where a shaft (the trunnion) is inserted into (and turns inside) a full or partial cylinder. Often used in opposing pairs, this joint allows tight tolerances and strength from a large surface contact area between the trunnion and the cylinder.[20]
In airframe engineering, these are self-contained concentric bearings that are designed to offer fluid movement in a critical area of the steering.
The term is also used to describe the wheel that a rotating cylinder runs on. For example, a
In mining, some refining plants utilise drum scrubbers in the process that are supported by a large trunnion and associated trunnion bearings at each end.
See also
References
- ^ "trunnion". The Free Dictionary. Retrieved 2010-08-23.
- ISBN 978-0-679-73082-8.
- ISBN 0-415-14649-6
- ^ ISBN 0-415-14649-6
- ISBN 0-554-39597-5
- ^ ISBN 0-226-56158-5
- ISBN 0-308-60014-2
- ISBN 0-87413-906-6
- ^ "The Tainter Gate". Dunn County Historical Society.
- ^ Society of Automotive Engineers (1915). SAE transactions, Volume 10, Part 1. p. 180. Retrieved 22 April 2013.
- ISBN 978-0-7603-1738-9. Retrieved 22 April 2013.
- ISBN 978-0-7603-3576-5. Retrieved 22 April 2013.
- ^ Schultz, Morton J. (June 1965). "To lube or not to lube". Popular Mechanics. 123 (6): 162–167. Retrieved 22 April 2013.
- ^ "American Motors". Car Life. 10: 57. 1963. Retrieved 22 April 2013.
- ISBN 978-0-07-038603-7.
- ISBN 978-0-930403-41-6. Retrieved 22 April 2013.
- ^ "Trucking terms Glossary". Volkema Thomas Miller & Scott. Retrieved 22 April 2013.
- ^ "Spring Beam". Watson and Chalin. Retrieved 22 April 2013.
- ^ Operator's, Organizational, Direct Support, and General Support Maintenance Manual for Compressor, Rotary, Air, DED, 250 CFM, 100 Psi Trailer-mounted. Department of the Army Technical Manual. 1990. pp. 150–151. Retrieved 22 April 2013.
- ^ "BEARING, TRUNNION". Engineering-Dictionary.org. Archived from the original on 2016-03-04.
A bearing used as a pivot to swivel or turn an assembly.