A cavalry is a cylindrical protrusion used as a mounting or pivoting point. First associated with guns, they are an important military development. Alternatively, a trunnion is a shaft that positions and supports an inclined plate. This is a misnomer, as it is actually the cradle of the true trunnion.

Trunnions are protrusions from the side of the barrel that the carriage rests on.

In mechanical engineering (see trunnion bearing section below), it is a part of a reciprocating joint where a shaft (trunnion) is inserted (and turned in) into a complete or partial cylinder.

Trunnion position saw table and provides a pivot point.

Medieval history

A cannon has two trunnions that are inserted just ahead of the center of mass of the cannon and fixed to a two-wheeled movable gun carriage . [3] Since they allowed the muzzle to be raised and lowered smoothly, the integral casting of the trunnion is seen by military historians as one of the most significant advances in early field artillery .

With the creation of larger and more powerful siege guns in the early 15th century , a new way of mounting them became necessary. Stouter gun carriages were built with reinforced wheels, axles, and “trails” that extended into the rear of the gun. The guns were now eight feet long and were capable of shooting iron projectiles weighing between twenty-five to fifty pounds. When discharged, these wrought iron shells were comparable in range and accuracy with stone-firing bombers . [4]

Trunnions were mounted near the center of mass to allow the barrel to be elevated to any desired angle, without descending from the carriage on which it was resting. Some guns had a second set of trunnions placed several feet behind the first pair, which could be used to allow for easier transport. [5] The gun would recoil, causing the carriage to retreat several feet, but a team of men or horses could bring it back to the firing position. These large siege cannons became easy to transport rapidly, moved them from transport mode to firing position, and a team of men or horses could drag them wherever they went.

Initial importance

Because of its capabilities, the French- and Burgundy-designed siege gun, which was equipped with its trunnion, required little significant modification from about 1465 to the 1840s.
King Charles VIII and the French army used this new gun in the invasion of Italy in 1494 . Although considered masters of war and artillery at the time, the Italians did not anticipate innovations in French siege weapons. Prior to this, field artillery guns were giant, large-caliber bombards: superguns that, with giant stones or other projectiles, were pulled from destination to destination. These behemoths could only be used effectively in sieges, and often did not provide just a psychological effect on the battlefield; of these giant mortarsBeing a boss does not guarantee victory for any army. The French saw the limitations of these massive weapons and focused their efforts on improving their smaller and lighter guns, using smaller, more manageable projectiles with larger amounts of gunpowder. Equipping them with trunnions was important for two reasons: teams of horses could now move these guns fast enough to keep up with their armies, without stopping and firing them from their carriages to achieve proper range. Take it down Francesco Guiciardini, an Italian historian and statesman, sometimes referred to as the “Father of History”, wrote that the cannons were placed so quickly against the city walls, together so closely and so rapidly and Shot with such force that the amount of damage done for a significant amount of time went from just a few days (with bombings) to a matter of hours. [4] For the first time in history, as seen in the 1512 Battle of Ravenna and the Battle of Marignano , artillery weapons played a very decisive part in the victory of the invading army over the besieged city. [7] Cities that had proudly laid siege for seven years fell rapidly with the advent of these new weapons.

Defensive tactics and fortifications had to change because these new weapons could be carried so rapidly and aimed with greater precision at strategic locations. Two important changes were the addition of a moat and low, sloping ramparts of packed earth ( glacis ) that surrounded the city and absorbed the impact of cannonballs, and the replacement of round watchtowers with angular bastions . These towers would be considered the Italian Trace . [8]

Anyone who could purchase these new weapons had a strategic advantage over their neighbors and small sovereigns, who could not enlist them in their army. Smaller states, such as the principalities of Italy, began to converge. Pre-existing strong entities, such as France or the Habsburg emperors, were able to expand their territories and maintain tight control over the lands they had already captured. With their lands and palaces in potential danger of being confiscated, the nobility began to pay their taxes and more closely followed the orders of their ruler. With siege guns, stronger and larger states were formed, but because of this, conflicts broke out between neighboring governments with consolidated power and would continue to plague Europe for the next few centuries.


In dams

A common watercourse used in dams and canal locks is the Tainter Gate . This gate opens and closes by pivoting on a tunnel extending across the mass of the dam or lock. Tenter gates are used around the world in water control dams and locks. The Upper Mississippi River basin alone is the Tainter Gate 321, and the Columbia River basin is 195.

In vehicles

  • In older cars, the trunnion is part of the suspension and either allows free movement of the rear wheel hub with respect to the chassis [10] or allows the front wheel hub to rotate with the steering. On many cars (such as those made by Triumph [11] ) trunnions are machined from brass or bronze casting and fail if not greased properly . [12] American Motors recommends lubrication of its prepackaged front suspension trunnions using sodium base grease every 32,000 miles (51,000 km) or three years. [13] It later incorporated molded rubber “claveblock” bushings on the upper trunnion to draw out dirt and retain the silicone lubricant for the life of the car.[14]
  • In aviation, the term refers to the structural component that connects the chassis or landing gear to the airframe. [15] For aircraft equipped with retractable landing gear, the trunnion is pivoted to allow rotation of the entire gear assembly. [16]
  • In heavy equipment, such as a bulldozer, the term refers to the bulge on the frame of the vehicle, to which the blade frame is attached and allows vertical motion.
  • In Chevrolet GMC C/K pickup trucks, the term tailgate refers to the combination points. Instead of using traditional tailgate hinges, trunnions are used to allow quick toolless removal and installation of the pickup tailgate.
  • In axles, the term refers to the type of suspension used on multi-axle configurations. It is a “short axle” transverse to its center line about a horizontal axis at or near its mid-point, usually in pairs in conjunction with a beam moving to achieve oscillation of the two axes. is used to .” [17] This type of suspension allows 60,000 pounds (27,000 kg) to be loaded onto a single axle group. [18]
  • In trailers, the leveling jack may have trunnion mounts. [19]
  • In the valve train of a pushrod engine, the term refers to the fixed axle that serves as a pivot point for the valve rocker.

In other technology

  • In steam engines, they are supporting axle pins on either side of an oscillating steam cylinder. They are usually tubular and give off steam.
  • On communications satellites, antennas are usually placed on a pair of trunnions in geostationary orbit to allow the beam pattern to be accurately stated on Earth.
  • On stage lighting devices, a bracket mounted to both ends of a striplight allows the striplight to be mounted on the floor. Trunnions are sometimes also equipped with casters to allow the striplight to be moved easily.
  • In woodworking, they are the assembly that holds a saw’s arbor to the bottom of the saw table.
  • In garbage collection, a trunnion is the bar on the front of a dumpster that attaches to the back of a garbage truck.
  • On the Space Shuttle, mounted pins are affixed to the side of payload items allowing them to secure receivers mounted on the sills of the payload bay. These receivers can be commanded remotely to secure and release selected items. Similar keel pins protrude from the nadir side of the payload item into the matching hole in the bottom of the payload bay.
  • On hydraulic cylinders, a mount (featuring either an external pin or internal pocket), as opposed to a flange or pin eye, may be an alternative body mounting type.
  • In steelmaking, on the Bessemer converter. There are trunnions on both sides to be able to take out the molten steel.
  • In total surveyed stations and theodolites, the mounted axis is about the axis which is the telescopic transit. It is parallel to the horizontal axis defined by the tubular spirit bubble.
  • In Dobsonian telescopic design, commonly known as altitude bearings.
  • In structural engineering, a type of bascule bridge consisting of a road deck on one side of a trunnion, and a counterweight on the other.
  • In laboratory centrifuges, trunnions are used to pivot the sample bucket in swinging-bucket rotors.
  • In nuclear power plants, when steam generators are replaced, trunnions are used to lift them up, to get them out of control, to get them onto the rail system.
  • 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) that allow limited speed due to torque variations and allow the drive-train to be remote and An accessible way to do service. ,

Trunnion bearings

In mechanical engineering, it is a part of a rotating joint where a shaft (trunnion) is inserted into (and turned in) a complete or partial cylinder. Often used in opposing pairs, this joint allows tighter tolerances and strength from a larger 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 ​​steering.

The term is also used to describe the wheel on which a rotating cylinder moves. For example, a lapidary (stone-polishing) cylinder moves on a pair of rollers similar to a trunnion. The sugar industry uses rotating cylinders up to 22 feet (7 m) in diameter, 131 feet (40 m) long and weighing about 1,000 tons [ which? ] . They make about 30 revolutions per hour. They are supported on the Pathway, which runs on trains. Similar equipment called rotary kilns are used in cement manufacturing.

In mining, some refining plants use drum scrubbers in this process which are supported by a large trunnion and associated trunnion bearings at each end.