Some Causes of Bearing Failure
Page 42
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THE most serious bearing failures
were caused by dirt getting between the housing and the back of the bearing, said Mr. P. P. Love, technical manager, Glacier Metal Co., Ltd., in a talk to the Leeds Centre of the Institute of the Motor Industry.
Such dirt, he said, caused extra load to be carried locally and prevented heat due to that load, from being carried away through the housing. Dirt that became embedded in the metal of the bearing could also cause serious trouble and might, in certain cases, lead to a " run" bearing.
An interference fit was required for two reasons. In the first place, it was important to have fairly intimate contact between the back of the bearing and its housing in order that some of the heat generated in the bearing could be carried away through the housing.
Secondly, there must be a fairly substantial pressure between the housing and the back of the bearing in order that the tendency of the bearing to rotate was restricy.
For these reasons, thin-wall bearings were made with a certain amount of excess length, so that when the hearing was assembled the tightening of the holts compressed the excess length of the bearing to give the necessary interference fit in the housing.
When examining a bearing that had failed, said Mr. Love, one should always look at the back, because it often provided evidence of the cause of failure. Defective bonding of the bearing metal and the steel shell could often be denoted by a dark line running along the joint face.
Where a crankshaft had been reground, it was important to ensure that the radii had been properly finished. If it were not, when the bearing was assembled, the load would be carried on the fillet radii instead of over the parallel portion of the journal. In such a cause, almost immediate failure and possibly serious trouble would result.
On the subject of crankshaft whip and bearing failure, Mr. Love said that in some American engines the centre • main bearing had been omitted. In the case of six-cylindered units these were being made with five bearings instead of seven, because the omission of the second-front and second-rear main bearings gave room for better engine balance.
radius restriction was help to be partly responsible for his getting into debt.
IN A LINE OR TWO
A reduction of 3d. in rates by West 13rid.g1ord is partly attributed to the transport department's paling its way.
Liverpool Transport Department arc to convert the Pier Head-Muirhead Avenue tram route to motorbps operation.
A £500,000 factory for the production of synthetic rubber is to be built at Birmingham by the Dunlop Rubber Co., Ltd.
The sum of 100m. escudos (about £1.25m.) has been allocated for road construction in Portuguese West Africa this year.
A bonus of £10 is to be paid to employees of the Ford Motor Co.. Ltd., to celebrate 25 years' working at Dagenham and last year's good results.
The transport department of Joseph Terry and Sons, Ltd., Bishopthorpe Road, York, have copies of The Commercial Motor for 1950-53 of which they wish to dispose.
Trams are to be replaced by motorbuses on the Durham Road-Town Centre route of Sunderland Transport Department next Monday, when the tram fleet will be depleted to 20.