Spoornet’s HS self steering bogies as well as the Barber type bogies were originally fitted with centre bowl pieces made from steel. This led to high wear on the horizontal face of the bolster centre bowl as well as on the wagon top centre casing.

A VescoPolycap flat liner was introduced to overcome the high wear experienced. The friction characteristics required were such that the correct rotational resistance for the bogie had to be maintained. The material also had to withstand loads in excess of 50 tons.

Subsequent to the introduction of the flat liner, a VescoPolycap cup liner was also introduced. This was to eliminate the wear that occurred between the vertical faces of the bolster centre bowl and the top centre casting.

Over ten years of wear life have been experienced with VescoPolycap centre bowl liners.

The need for an even lower friction material to cope with the extremey cold temperatures in the Nordic countries led to the formulation of Hilube 10 which in tests conducted by the Spoornet Engineering Development Centre registered a coefficient of friction of 0.11.

Nylon, Hilube 10 and Hilube 20 bogie centre liners were tested simulating a 25 ton axle load condition and an 80 meter radius curve. Data was obtained after a run in period of 10 000 cycles.

The coefficient of friction of the nylon liner increased rapidly after the run-in period due to increased stick-slip phenomenon whereas the coefficient of Hilube 10 and 20 remained constant.

The static coefficient of friction Hilube 10 and 20 materials was found to be very similar to the dynamic coefficient of friction hence the reduction in the stick-slip effect between the bolster and frame which is vitally important when operating in sub-zero temperatures. The low coefficient of friction resulted in a reduction in the vertical force operating on the bolster leading to a smoother and quieter operation.

The low coefficient of friction of Hilube 20 was confirmed by General Steel Industries in 1982.

Hilube 10 - material of choice for bogie centre bowl liners

• flat liners, cup liners and centre rings produced
• available in Hilube 10 or 20 or VescoPolycap

Hilube 10 typical properties
Specific gravity	1.25
Tensile strength (dry)	60 MPa	8700 psi
Flexural Modulus (dry)	2500 MPa	362,500 psi
Maximum design loading	20 MPa	2900 psi
Deflection temperature at 1.8 MPa (261 psi)	57oC	135oF
Continuous temperature rating	100oC	212oF
Coefficient of thermal expansion	10 x 10-5 mm/mm/oC	5.6 x 10-5 in/in/oF
Maximum water absorption at 20oC (68oF)	6 %
Water absorption 24 hours	0.9 %
Friction at 4 MPa (580 psi)	0.11

The above data should be taken for indicative purposes. Physical properties may be altered to some extent by processing conditions.

Excessive wear on the horizontal centre bowl as well as on the wagon top centre casing increases the vertical force between the bolster and the frame resulting in greater wear at the rail-wheel interface. Time consuming to fit because of the welding involved. Lubrication can be lost forced out under high loads or lost due to tipping of freight wagons when releasing load.

• extended wear life, over 10 years
• greatly reduced wear to horizontal face of bolster centre bowl and wagon top centre casing
• self-lubricating, no oil or grease required
• smoother operation due to low static and dynamic co-efficients of friction
• reduction in the vertical force operating between bolster and frame
• easy and quick drop-in installation
• noise reduction
• maintenance and operational cost savings on bolster, wheel and track

Bogie Centre Liners are known throughout the industry as Bolster bowl wear liner / liners, Bolster center plate ring / rings, Bolster centre plate rings, Center plate wear protector / protectors, pivot center liner / liners, pivot centre liner / liners, Bogies, Bogey and Bogeys