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From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Research abstract on the composition, properties, and failures of various engine bearing alloys.

Identifier  ExFiles\Box 115\2\  scan0439
Date  1st April 1939
  
1020.

I.A.E. AUTOMOBILE RESEARCH COMMITTEE

Research Department,
Great West Road,
Brentford, Middx.

No. 9317. Class 278, 57.

April, 1939.

Engine Bearings

C.F. Smart,
S.A.E. and A.S.M. Reprint, December, 1938, 21 pp.

The usual method of testing the bond between the bearing metal and the back is to chisel babbitt from the back, a rough appearance with babbitt adhering to the back being assumed to indicate best bond strength. Tensile tests showed the fallacy of this assumption, rough fractures and low bond strength being obtained with over-heated babbitt or too slow a cooling rate. In order to obtain information on the effect of composition on the physical properties of tin-base babbitts, various alloys were examined for hardness, impact, compression, and bending, and the results are summarised in a table. Lead, in amounts of 1% and 1¾%, was detrimental to hot toughness. High copper resulted in increased hardness but greater brittleness. The most desirable composition appeared to be 89¾% tin, 2¼% copper and 8% antimony, without lead. Engine tests with this alloy showed considerable improvement in fatigue life over the harder and more brittle babbitt, and scrap losses were reduced. This alloy also made an excellent tinning material, with some saving in cost. The results of bending tests are given which show that rapid cooling is necessary for best physical properties.

Lead-tin-antimony alloys, with additions of arsenic, are claimed to have as good a fatigue life as tin base alloys. Certain test results showed that, under conditions of high speed, high load and high operating temperature, these alloys did not give as good service as tin-base bearings. The chief reason for the use of lead-base alloys is said to be economy, but enquiries for quotations resulted in two refusals, while two quotations were identical in price with tin-base bearings. Many bearing tests have shown that cadmium-silver-copper alloys have several times the fatigue life of any tin-base babbitt bearings.

Bearing failures due to load generally start directly below the rod in the top half, while failures due to deflection start from 15º to 45º from the parting line.

C.G.W.
  
  


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