PETROLEUM — FIELD 241 



engine and fuel development work on the other parts of the automo- 

 bile and on petroleum-product requirements for these parts. In- 

 creasing the power output of the engines produced greater loads on 

 the engine connecting rod and main bearings with the result that many 

 engine designers developed engines in which alloys of cadmium-silver 

 and copper-lead were used for bearings instead of the conventional tin- 

 lead (babbitt) which had been used heretofore. From the standpoint 

 of bearing loads these materials were excellent but they immediately 

 gave the petroleum refiners many headaches. The sulfur compounds 

 present in the lubricating oil, the condensate from combustion cham- 

 ber "blow-by" to the crankcase, and the acids produced by normal 

 oxidation of the lubricating oil caused severe and rapid bearing dete- 

 rioration. The corrosion attacked the lead and cadmium in these bear- 

 ings, resulting in weakening of the bearing alloy, high wear, and early 

 noisy operation of the engine. 



Protection of these bearing materials was critical and the challenge 

 to the petroleum research laboratories started a new trend in lubricat- 

 ing-oil development. This trend has resulted in the progressive addi- 

 tion to lubricating oils of a long series of additives. Initially additives 

 were used to take care of bearing-corrosion problems. Later, additives 

 were developed to add higher film strength characteristics. Presently, 

 additives are being incorporated to furnish, in addition to the pre- 

 vious benefits, properties to prevent build-up of sludge deposits in the 

 crankcase and to increase engine life heretofore shortened by internal 

 rusting between periods of operation. 



As engines increased in power and the streamlining of automobiles 

 resulted in smaller wheels and lower floorboards, a redesign of the dif- 

 ferential drive in the rear axle came about in efforts to lower the drive- 

 shaft to avoid the necessity for a tunnel in the rear floor. This gave 

 rise to the use of hypoid gearing to drop the driveshaft below the cen- 

 ter line of the rear axle. Hypoid gearing worked out very admirably 

 from the standpoint of chassis design but necessitated an extensive 

 amount of research in petroleum laboratories to develop a rear-axle 

 lubricant for these new-type gears. The previous type of gearing, 

 namely, spiral bevel gears, operated on the principle of rolling fric- 

 tion and a conventional heavy lubricant protected the faces of the gear 

 teeth quite satisfactorily. The hypoid gear, on the other hand, oper- 

 ates on the principle of sliding friction and conventional lubricants 

 could not give protection, with the result that the hypoid rear axles 

 were scuffing severely because of failure of the oil to stay between the 

 gear teeth. By the use of additives especially developed for the pur- 

 pose, the oil companies quite promptly were able to furnish lubricants 

 which had the proper combination of surface tension and wetting 

 properties to stay in place on the gear teeth of heavily loaded hypoid 

 gears. 



