A cannon bearing or cannon box bearing is an arrangement of bearings on a shaft, usually an

axle An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearing ...

, where two bearings are mounted in an enclosed tube. The function of the cannon box is to preserve the alignment of the two bearings, even if the overall tube is allowed to move. The two bearings will retain their same relative position. The bearing tube can be attached to the vehicle frame through either a pivot or springs. The name 'cannon box' derives from the appearance of the hollow tube. Also from the boring machines used to machine the accurately aligned bearing seats, the same machines developed for the boring of

cannon A cannon is a large- caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder ...

and also used for machining the

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infin ...

s of steam engines. Cannon box bearings are still found today, although much of the need for them was removed by the development of

self-aligning ball bearing A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races. The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this ...

s. These allow the inner race of a bearing to move independently of its outer, so that each bearing can align to both shaft and housing simultaneously, even if the housing moves around.

Railway use

The 'cannon box' bearing was introduced by

George Stephenson George Stephenson (9 June 1781 – 12 August 1848) was a British civil engineer and mechanical engineer. Renowned as the "Father of Railways", Stephenson was considered by the Victorians a great example of diligent application and thirst for ...

on his locomotive ''Locomotion'' of 1825 for the

Stockton and Darlington Railway The Stockton and Darlington Railway (S&DR) was a railway company that operated in north-east England from 1825 to 1863. The world's first public railway to use steam locomotives, its first line connected collieries near Shildon with Darl ...

. One of the axles was carried in a 'cannon box' bearing that was pivoted centrally and could tilt from side to side. Unlike Stephenson's earlier locomotives and their steam springs, this new suspension had no springing but was a compensated suspension: as one side was raised, the bearing tube pivoted and the other side was pushed downwards. Although not giving a stable ride for the locomotive, it did allow the wheels to follow uneven track.

Rail Rail or rails may refer to: Rail transport *Rail transport and related matters *Rail (rail transport) or railway lines, the running surface of a railway Arts and media Film * ''Rails'' (film), a 1929 Italian film by Mario Camerini * ''Rail'' ( ...

s of this period were short pieces of

cast iron Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...

rather than lengths of rolled steel and had frequent, often misaligned, joints. A side-effect of the cannon box is that the centre of the shaft is now enclosed and inaccessible. Previously Stephenson had coupled the driving axles of his locomotives with a central

chain A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A c ...

. The need for an alternate system spurred the development of the

coupling rod A coupling rod or side rod connects the driving wheels of a locomotive. Steam locomotives in particular usually have them, but some diesel and electric locomotives, especially older ones and shunters, also have them. The coupling rods transfer t ...

s, where the drive was connected on the outside face of the wheels. The enclosure of the shaft and bearing also had advantages for enclosing the bearings to exclude dirt and to contain lubricating oil. Francis Webb's form of

radial axle A radial axle is an axle on a railway locomotive or carriage which has been designed to move laterally, along the arc of a circle, when entering a curve in order to reduce the flange and rail wear. William Bridges Adams was an early developer of rad ...

design for the

LNWR The London and North Western Railway (LNWR, L&NWR) was a British railway company between 1846 and 1922. In the late 19th century, the L&NWR was the largest joint stock company in the United Kingdom. In 1923, it became a constituent of the Lond ...

used a cannon box. A radial axle is a form of single axle pony truck, where instead of a pivoted frame, the two axle bearings can slide sideways in a circular track. Webb's design placed them into a curved cannon box. David Joy, designer of the eponymous valvegear, described encountering these axleboxes on Webb's Precedent class. The earlier Adams design for a similar axle had relied on the axle and thrust-faces within the axle bearings to keep the hornblocks in position. In the 1920s, some electric locomotives used rigid frames with a leading and trailing truck, where a cannon bearing was a convenient inside-framed bearing for the truck. The Swiss '

Java bogie The Java bogie (german: Java-Drehgestell, Java-Gestell often in Swiss literature), was a bogie for electric locomotives manufactured by the Swiss Locomotive and Machine Works (SLM). It contained a driving wheel and a trailing wheel. It got its na ...

' design, developed by

Jakob Buchli Jakob Buchli (4 March 1876 – 1 April 1945) was a Swiss design engineer in the field of locomotive construction. Life Jakob Buchli was born in Chur, Switzerland, on 4 March 1876. After his training to be an engineer he worked from 1902 t ...

, even used this for a driving axle, with the drive provided by a one-sided

Buchli drive The Buchli drive is a transmission system used in electric locomotives. It was named after its inventor, Swiss engineer Jakob Buchli. The drive is a fully spring-loaded drive, in which each floating axle has an individual motor, that is placed in ...

outside the wheels. Roller bearings, and their enclosing cannon boxes, were used for the British Railways Standard classes, on bogie axles and also on the driving axles of some of the larger classes. This use was simplified, as the Standard classes (with the unique exception of the single Class 8) had just two outside cylinders. Railway use of such bearings continues today. The Peppercorn Class A1 ''Tornado'' replica uses roller bearings rather than the original plain bearings and these use cannon tube bearings for both the driving and bogie axles, although not for the central cylinder's crank axle. The rigidity of the cannon box also allows the faces of the axleboxes which move up and down in the hornguides to only need a single horn flange. Conventional axleboxes have a pair of flanges with the guide between them, so that they can move up and down for suspension without any axial movement. If they are both held at the correct spacing by the cannon tube, only one flange is needed. The thinner axlebox, without the external flange, can allow the hornguides and frames to be placed closer to the inner face of the wheel, giving better support for a heavily-loaded axle.

Traction engines

Traction engine A traction engine is a steam engine, steam-powered tractor used to move heavy loads on roads, plough ground or to provide power at a chosen location. The name derives from the Latin ''tractus'', meaning 'drawn', since the prime function of any t ...

s began as agricultural vehicles and ignored springing or suspension on their main wheels. As light steam tractors developed from 1896 for

road haulage Haulage is the business of transporting goods by road or rail between suppliers and large consumer outlets, factories, warehouses, or depots. This includes everything humans might wish to move in bulk - from vegetables and other foodstuffs, to cloth ...

though, locomotives with solid rubber tyres and suspension became favoured. The driving wheels of a traction engine are carried on a single axle, running closely behind the rear plate of the boiler firebox and carried in bearings fitted to the hornplates on either side of the boiler. Where springs were used, the cannon box bearing was favoured for maintaining the bearing alignment, with a further advantage of enclosing the axle away from the coal and ash from the firebox. Designs such as the Tasker ''Little Giant'' used another compensated suspension, where the tube was suspended from a single transverse

leaf spring A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, elliptical spring, or cart spring, it ...

References

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