© 2018 Boiler & Engineering Skills Training Trust
Axleboxes support the steel axles of the locomotive within the structure of the frames. Generally the axleboxes sit just inside the wheels. In UK locomotives there is vertical movement of the box within the guides in the frame called Hornblocks to allow for uneven track. Springs to transmit the load through to the frames are arranged above or below the axlebox.
Axleboxes on coupled wheels not only transmit the weight of the locomotive beween frames and wheels but they also have to transmit horizontal forces. Firstly as the locomotive rounds a corner the force comes through the wheels into the axleboxes and thence to the frames.It is essential for the axlebox to be able to cater for both these scenarios. White metal is invariably used to carry the cornering thrust and special lubrication provision in the form of felt pads have to be installed within the thrust face to ensure efficient lubrication
In addition to the above, bronze thrust faces are installed within the axlebox on the horizontal centreline to resist and transmit the force of the piston rod under steam when the locomotive is working hard..The small contact found at the crown cannot be expected to carry this load
The William Stanier designed axlebox which was designed for the Duchess class in 1938 for the LMS. Several features noteworthy here: The serrated face to key the white metal into the bronze shell. The off set machining of the crown to avoid hand scraping and the Mechanical oil feed into the horizontal centreline of the bearing.
This shows the axlebox within the frames and hornblock The width presented by the hornblock to the axlebox spreads the horizontal loads load evenly across the frames. The vertical loads are transmitted to the frames by the ends of the springs into the frames also.
Once a bearing overheats the lubrication breaks down friction is created which causes heat. Thus” Hot Box.” Of course there is enough power in the locomotive to drag the resisting axle round against its wishes causing massive damage unless it is detected. In the worst cases the end of the axle gets so hot it becomes plastic and shears off leading to a derailment as the load comes off the end of the axle
The axleboxes stripped from 60007 during overhaul at the NRM by the A4 Locomotive Trust. The thrust faces of the driving axleboxes can be seen together with the cavity for the lubricating felt
This shows an example of the “Cannon-box” design of bearing assembly where rolling contact bearings in the form of back to back taper roller bearings tied together by a central tube. This example is from the front bogie of 71000 “Duke of Gloucester” undergoing overhaul at Tyseley Locomotive Works.The central tube maintains the alignment of the bearing assembly, as well as maintaining the lubrication where it is needed. It also stops the ingress of dirt and contamination thus ensuring a long and potentially trouble free axlebox life
A brand new Armstrong Oiler bearing pad prior to being soaked in oil ready for use. The spring steel frame sits in the bottom of the underkeep in the oil and the tails of worsted wool hanging down wick up the oil to the surface of the pad resting against the rotating axle journal providing a fresh supply of oil to the underside of the bearing which carries up into the narrow wedge to separate the two metal surfaces.
The “Collett Wedge” showing the cleverly different shape between the bearing and the axle which encourages the oil into the ever decreasing gap and allows the bearing to ride up on the shaft free of metal to metal contact.
Boring the axlebox in a vertical borer. The white metal crown is first bored out at exactly the same size as the axle. Then the tool centre is moved slightly (about 0.020”and the cut increased (about 0.010”) so as to create two wedges in the whitemetal which entrain the oil
Worker using a syringe to sample the oil in the bottom of the underkeep to check that no water is present. All the water can be sucked out from the bottom and fresh oil topped up
LNER Wedge hornblock/axlebox assembly allowing the fit of the axlebox sliding vertically within the hornblock to be adjusted to eliminate knock.and free play
Manganese steel facings on the sliding surfaces of the axlebox hornguides. This surface mated with another Manganese steel facing allows work hardening of the sliding surfaces to take place which presents an almost maintenance free friction pair!
Frame and cylinder alignment taking place at Swindon Works using the Carl Zeiss Optical alignment Gear. The telescope shown on the stand will be positioned accurately in the centre of the cylinder bore as assembly of the locomotive progresses. The purpose of the instrument is to get the alignment of the cylinder bores exactly at right angles to the fully parallel axles