SOME IMPROVEMENTS IN PLAIN BEARINGS.
Page 20
If you've noticed an error in this article please click here to report it so we can fix it.
1'J ANY EFFORTS have been devoted .1.V to the perfecting of various kinds of bearing-material with a view to reducing wear both on the shaft and bearings, and also permitting -better lubrication and higher speeds. Efforts have also been directed towards the improvement of °thew bushingssbuts these have not proved quiteso satisfactory as was at first anticipated, and, they are now employed almost exclusively for those parts which do not have complete rotational movements, and, in which the surface sueeds are not of a high order. In very few engines are bronze bearings. atill employed. These were satisfactory from the bearing point of view, and did not wear to any great extent.,
538 but they were rather inclined to cause scoring of the shafts, and, if they
seized, serious breakages USlially occurred; on the other hand, whitemetal-lined brasses merely run out instead of seizing solid, and thus act on the same principle as the safety valve. Something has to go in such circumstances, and it is better that what goes will not cause undue damage, and can easily be replaced. Apart from this, white metal has the property of spreading slightly under load, so that it quickly beds itself to the shaft, all the high spots being pressed level with the low, and the slight porosity causes the bearings to assume a high degree of polish after
they have been running for a short time.
Following out this idea of a porous metal, General Motors Corporation recently developed a new copper-tin alloy called Durex. The pores in this material are numerous, and are uniformly distributed -throughout, the metal, and if a bearing of this type be soaked in oil and afterwards wiped free, a coating of oil reforms on it in a very short time— an obvious advantage which prevents the bearing running dry.
So porous is the new metal that, if fitted into an ordinary paraffin lamp in place of a cotton wick, it can be lighted, and will continuo to draw up the paraffin through capillary attraction.