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LONGER ON THE TRAIL

3rd September 1976
Page 42
Page 42, 3rd September 1976 — LONGER ON THE TRAIL
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Better seals treble bearing life

WHEEL-BEARING life on some trailers has been considerably increased since they have been fitted with oil-filled bearing housings.

Conventionally lubricated bearings suffer from problems because the grease used doesn't always reach every part of the bearing, and so wear can be accelerated. With oil lubrication these problems are removed.

The oil finds its way into. every crevice of the bearing, providing a continuous film over the components. Without doubt the biggest problem is to keep the oil in and this is where the Stemco oil seal comes in

Made from a leather impregnated with polymers and encased in a pressed steel outer shell, the seal is said to be completely impervious to all lubricating oil additives. However, the lip of the seal is designed to absorb a small amount of oil to ensure that the edge doesn't become torn owing to drag between the seal and the rubbing surface.

As the leather section of the seal is pre-formed, it exerts a high and constant pressure at the lip and thus allows a degree. of eccentricity and run out within the hub assembly. A further advantage of using leather, says Stemco's manufacturer, Garlock (Great Britain) Ltd of Bone Lane, Newbury, Berkshire, is that the material is much more forgiving than rubber and can therefore tolerate more abuse, especially during assembly and dismantling.

The same seal can be used over again if the lip is in good condition. In order to ensure a good contact between the lip of the seal and the stub axle, an axle ring is fitted.

This is an 18-gauge pressed steel ring with a coined surface finish, which is an interference fit on the stub axle.

Fitting is simple. The ring is positioned on the axle and tapped into place using a special axle tool. When the ring is in its correct position, it should be flush with the bearing shoulder and so can be easily checked.

Assembly of the bearings in the hub follows normal practice, and the seal is installed with another special tool. An extra steel guard can be supplied by Garlock which, when fitted between the hub and back plate, prevents water and dirt ingress.

When the hub and inner bearings have been fitted to the stub, oil is added in between the bearings up to the level of the outside bearing cap. The outer bearing is fitted and the assembly adjusted.according to the manufacturer's recommendations.

Finally, a special outer cover is fitted. This consists of a cast aluminium casing with a shatterproof transparent glass centre window. The cover is bolted on to the outside of the hub with a paper gasket. A filler hole in the casing allows the oil level to be topped up to a line on the sight gauge, and the oil level can be later checked without the need for dismantling.

A substantial number of trailer axles are now running in the UK with oil-filled bearings and in some cases are trebling bearing life. The Stemco conversion can add as little as E5 to the cost of each axle. Stemco is currently working on a differential pinion oil seal although it is unlikely that it will be made from leather.

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