Future Trends

If the business of providing proper lubrication for  gears and transmissions were a  static one, people  would  lose  interest in it, and  there  would  be no  purpose  in this volume. However, as indicated by the just preceding, there are problems in connection with gear lubrication and gear lubricants. While  the immediate reaction  to a complaint  or a  problem  of this  sort  is to  blame  the lubricant, it  should be  again  pointed  out  that  perhaps  only  ten  per cent  of   such  complaints are due to  deficiencies  in either  the lubricant or the  application. In spite of this , the  industry  does  have problems and since they  will not  always solve  themselves, it  is necessary  to give  thought  to the  future  when  solution of  the  immediate  problems will be possible  but new  ones  will be  confronted.

Since a little  adversity is good  for the soul, these  problems stimulate  thought  and are the  cause  of many  improvements  and  advancements  in   all industry. In the lubrication of   gearing, the problems do not always take the form of complaints but often of suggestions. Whatever the form,  such  questions do indicate that  modification of  not  only  present  products  but  also  present  thought may be  necessary if the  lubrication industry  is  to  play  a part  in continually improving  the world.

No matter how  did  wild  dreams about providing  different  or better lubricants for gears may  be,  they  would  come  to naught  if  practical considerations are not  kept  in mind. These  include  the economy  of   the suggestion,  the  availability  of  the  necessary  components of the  composition, the  ease of  application, compatibility  with other  materials, and  acceptance  by  other industries  and  by the public. Any or all of these factors may change with time; hence, it is well to dream.    

Freedom from separation in gear oils

Precipitation or settling of some components in gear oils is sometimes noted. This most often occurs in mixtures containing EP additives. The separation may be due to lack of solubility or to reaction of ingredients resulting in formation of sludge. Since such additives are often present in concentrations of 9 per cent or more, the base oil must keep a high proportion of heavy chemical compounds in dispersion or suspension. Both additive manufacturers and oil blenders select ingredients which will keep any separation of such agents at a minimum.  

Fletcher^23 selected three SAE 90 hypoid gear lubricants and three multipurpose SAE 90 oils meeting MIL-L-002105A specification. By precipitation tests, the first three oils showed some sludge in the unused oil which increased after a service test in two of the lubricants. In the multi-purpose oils there was only a trace of sludge before use but measurable amounts up to 7 per cent after the tests.

Of course, settling or sludge formation in gear lubricants results in loss from the action zone of valuable active ingredients, but the greatest concern is the effect sludge may have on operating mechanisms. Thus, Fletcher^23 mentions that precipitation of sludge out of oil due to centrifuging in transmission cases may result in carbon like deposits in pocket bearing positions, internal clutch teeth, and in some cases in oil grooves  and synchronizer grooves. It is conceivable that such deposits could adversely affect the operation of the unit. This fact was probably recognized by one tractor manufacturer who specified that oils used in their equipment should be filterable, thus, indicating that sludge should not separate during  normal operation.

Where sludge is formed in EP gear oils the action is accelerated by increasing temperature. It is therefore probably a result of reaction of the chemical compounds which constitute the EP additives. Detergent agents do not seem to be a correction for such sludge separation, and any improvement in the condition probably lies in selection of the EP additives.