The South African Railways began experimenting with polymer pedestal liners in the late 1970ís. Problems of cracking
when forming the steel liners had resulted in many rejects and high costs. Excessive wear occurred between the steel
pedestal liner and the axle box with the most wear occurring on the axle box. On average an axle box costs ten times
more than the pedestal liners.
Hilube 20 Pedestal Liners
VescoPolycap BMS was used to replace the spring steel pedestal liners used on many of their class E (Electric
Locomotives). It was hoped that a polymer liner would cause less wear to the axle box mating surface. This factor
alone would result in major savings.
The new polymer material would have to be tested for lateral and vertical resistance as well. Resistance could not be
too high or too low. The correct vertical and lateral resistance for optimal functioning had to be maintained.
Initial field tests revealed that the lower coefficient of friction of the BMS liner resulted in less wear to the axle box mating surface indicating that massive savings could be generated in this area. It was also postulated that less tyre flange and rail wear would result because of the smoother sliding movement generated between the truck frame and axle box. This was considered to be another major advantage.
These promising results led the Train Dynamics Division of the South African Railways to conclude that a still lower friction material would result in better axle box, tyre flange and rail life thereby reducing maintenance and replacement costs considerably.
A new material, Hilube 20, was specially formulated to give the lower friction characteristics required.
VescoPlastics was then requested to send samples to General Steel Industries (GSI) in the USA. GSI confirmed the South African test results in 1982.
Hilube 20 has been accepted as the pedestal liner of choice for a wide range of GE and GM locomotive bogies.
Over 10 years, more than 2 million kilometres have been achieved with individual Hilube 20 liners.
Hilube 20 - material of choice for pedestal liners
- also known as axle box guides, horn cheek liners, journal box liners
- available in Hilube 10 or 20 or VescoPolycap
Hilube 20 typical properties|
|Tensile strength (dry)||60 Mpa||8700 psi
|Flexural Modulus (dry)||2500 Mpa||362,500 psi
|Maximum design loading||20 Mpa||2,900 psi
|Deflection temperature at 1.8 Mpa||57oC||135oF
|Continuous temperature rating||100oC||212oF
|Coefficient of thermal expansion||10 x 10-5mm/mm/oC||5.6 x 10-5in/in/oF
|Maximum water absorption at 20oC||6 %||6 %
|Water absorption 24 hours||0.9 %||0.9 %
|Unlubricated friction at 4 MPa||0.06||0.06
The above data should be taken for indicative purposes. Physical properties may be altered to some extent by processing conditions.
Problems when forming steel liners result in many rejects and high costs. Metal to metal wear causes damage to the axle or journal box which is expensive to replace (the axle box is ten times the cost of a liner). Steel liners are prone to fatigue cracking after continued use. Cracked and loose steel liners cause damage to the pedestal jaws which are costly to repair.
- extended wear life over 10 years or 2000 000 kmís
- greatly reduced wear to expensive axle boxes
- smoother sliding movement between truck frame and axle box
- axle box is able to slide more freely relative to loco chassis
- noise reduction
- no fatigue cracking
- maintenance and operational cost savings on axle boxes, wheel and track