Foam inhibition in gear oils

The rapid movements of gears tend to aerate oils and produce foam. This tendency may be aggravated by the presence of some additives, such as EP agents. Also, the higher the viscosity of the oil the more permanent the foam as a rule. Cases have been noted where foam became so great that it filled...

Detergent qualities of gear and transmission lubricants

Detergent additives are not required or included in most gear oils. However, in mechanisms where the lubricant serves both gears and control devices, such as clutches, some of the moving parts will not tolerate deposits. In such cases detergent additives are included in the lubricants. A good example...

Demulsibility of gear oils

Lubricating oils vary in their tendency to emulsify with water; therefore, if emulsification of gear oils is likely to be a problem, the base oil should be investigated. Any polar compounds remaining in the oil after refining, such as sulfonates, petroleum acids, and even asphaltic bodies, may help...

Oxidation stability of gear lubricants

Once a proper gear lubricant is selected for a given application it should suffer a minimum chemical and physical change during use. One of the changes most likely to occur is oxidation  of  the oil  which ultimately  will  lead  to the formation of undesirable ...

Oiliness of gear lubricants

As lubricating conditions in gear sets change from that of thick film to boundary lubrication, the oil benefits by the presence of additives. For conditions with spur gear lubrication, some agent which will provide increased lubricity or oiliness may prevent film rupture and thus maintain a low friction....

Minimum action of gear oils on components of mechanisms

Well refined mineral lubricating oils have little if any action on most metals, particularly ferrous metals. It is only upon prolonged use at elevated temperatures that such oils may from compounds which will act upon metals. Since such oil changes can be retarded or almost completely arrested by...

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...

Compatibility of gear oils

Gear lubricants consisting of straight mineral oils will mix in all proportions at normal ambient temperatures. The resulting physical characteristics of the mixtures will not be an exact proportional average but will approximate this.    On the other hand, gear lubricants containing additives...

Adhesion of gear and transmission lubricants

Adhesion is a comparative term, and what is in mind in this case is stickiness which will insure that the lubricant will resist the action of centrifugal force and thus remain on the gear teeth. This quality is most important in the case of open gears. Desirable adhesion is obtained by the use of...

Desirable characteristics in gear and transmission lubricants

A number of characteristics, which were not evident in the discussion of functions of gear lubricants, contribute to satisfactory application of such products. After listing some of these qualities, consideration will be given as to what contributes to such characteristics. Such qualities include: (a)   ...

Dissipation of heat by gear lubricants

Under the most ideal conditions of lubrication of two moving metal surfaces heat is developed. In fact Bowden and Tabor^11 found that, even though lubricating films are present, surface temperatures of metals  may exceed several hundred degrees Centigrade  at  relatively small loads...

Abrasive or cutting wear

Gear oils are not correctives for abrasive wear because here the action is due to hard particles between the gear face as they mesh. If the abrasive is due to loose metal, sand, etc; gear oils may wash the foreign particles from the moving areas, but unless the abrasives settle out they will continue...

Fatigue wear

Fatigue wear may take place even where gear oil provides a satisfactory lubricating film and there seems to be some question as to what quality of a gear lubricant is responsible for decreasing fatigue wear of gear sets. Hutt^30 presented data from an IAE machine which showed that a 190 per cent...

Corrosive wear

Corrosive   wear  in  the  presence of a gear  lubricant may  be  due to the  environment if air, water , or electrolytes  are  present. If gear cases are not tight and high humidity prevails, rusting may occur, not only on idle gears above the...

Functions of gear lubricants

By stating the necessary functions of gear lubricants there will be a basis for consideration of how these purposes are accomplished and what characteristics are desirable in satisfactory gear oil. While the relative importance of the qualities of such lubricants may vary with the specific use, the...

Corrosion prevention by gear lubricants

Ellis et al.^22 consider that staining, tarnishing, and rusting are all  indications of corrosion. The thought is that light stain or tarnish represents the early stages of corrosion since, unfortunately these  changes do not proceed very far before pitting starts. Unreactive gear oils,...

Reduction of wear in gear sets and transmissions

Wear has been defined by a Committee of the Institute  of  Mechanical Engineers as: “Progressive loss  of substance  from the surface of a body  brought  about by mechanical  action ( usually it  reduces the serviceability of  a  body  but ...

Gear lubricants as structural materials

Since gear sets would not function without a proper lubricant, it has been suggested that gear oils be given the status of structural materials. As early as 1942 Almen^1 stated that a gear lubricant in addition to being: “A lubricant in the usual accepted  sense of a liquid film separating two...

Reduction of noise,vibration and shock by gear lubricants

Gear lubricants, particularly those of high viscosity, will act as cushions and thus reduce noise, shock, and vibrations of meshing gears. However, it must be kept in mind that even the most viscous products are not correctives for poor mechanical conditions. Mention might be made that Cardillo,^14...

Reduction of friction in gear operation

Bowden  and  Tabor^11  have shown  that  the coefficient  of  friction  for  one lubricated  surface  moving relative  to  another  will  depend  upon  the material  used  in the two  surfaces, the type ...

Conditions under which gear lubricants operate

With meshing gears, both rolling and sliding motions are present. However, the  two  types  of  contacts  vary  both  with  the  type  of  gears  and  the  speed  of  operation. The  sliding  component  is ...

Types of gears to be lubricated

Where   gears  are  on  parallel  axes, either  spur  or  helical  gears  are  generally  employed. Either type can be used as external or internal drives.   The  herringbone  gear  is  similar  to ...

Designation and recommendation of gear lubricants

While  industrial  gear  lubricants  are  often  marketed  under  trade  names, information  is  always  available  as  to  how  these  products  conform  to  AGMA  numbers . Therefore, little  ...

History related to gear lubrication

We  are  little  concerned  with  the  first  gears, which   were   said  to  consist    of  wooden  wheels   with  wood  pegs   for   teeth, since  speeds  ...

Demands made on gear and transmission lubricants

Mention  of  some  of  the  demands  made  on  gear  and  transmission   lubricants  may  well  serve  as  a  further  justification  for  the  assembly   and   publication ...