Why lubrication in gearbox

JavaScript seems to be disabled in your browser. For the best experience on our site, be sure to turn on Javascript in your browser. When it comes to the lubrication of machine components, especially gearboxes, things get tricky quickly.

Like other rotating machine parts, gearboxes depend on lubricants to function properly. In other words, lubrication forms an essential aspect of industrial gearboxes. Adequate lubrication levels help gearboxes decrease friction between their elements and produce the cooling required for optimal performance. They also improve mechanical efficiency and reliability, increase the equipment's lifespan, and reduce its maintenance requirements.

There are several ways to lubricate a gearbox. Manufacturing companies usually provide specifications and recommendations for which lubrication methods should be used and standard lubrication intervals.

However, the best gearbox lubrication procedure depends on the environmental conditions in which the gearbox operates, whether it is adequately maintained and whether it is experiencing overloading. Lubricant performance is ranked on the basis of overall level of friction, friction stability, and temperature and load dependence of friction.

Figure 2 A CVT push belt would have about of these elements scale 2. IVT toroidal traction drives can be traced back to an patent and the short lived Hayes transmission fitted to some Austin cars in the s. General Motors in the USA also experimented with double sided full toroidal variators in the s. Forbes Perry of Perbury Engineering developed the concept further in the s. In Rover Group, for which Mr Perry then worked as a consultant, sold its interest to what is now the British Technology Group and the Torotrak variator was born.

The transmission comprises two sets of tilting rollers running between discs with toroidal profile surfaces. It is a true infinitely variable transmission capable of providing all ratios from full reverse to high overdrive.

Unlike the Van Doorne CVT it does not need a clutch or torque converter for starting, making for simplicity, reduced weight and lower cost. The properties of the fluid are critical to the success of the drive; in particular a high traction coefficient is needed.

Familiar names such as Santotrac 50 and the naphthenic oil based Sternol Hydratorque are fluids with the necessary high traction coefficients which have been used successfully in industrial applications and in the Harrier constant speed generator drive.

However, they have proved unable to cope with the range of operating temperatures and the complex demands made on an automotive transmission fluid. Synthetic lubricants like polyalphaolefins PAO are notable for having low traction coefficients and are therefore not suitable. The availability of effective traction fluids is essential to the success of this revolutionary transmission technology. Shell are using Shell's fluids are currently being supplied to a diverse range of prototype applications Constant velocity joints CVJ are the joints in drive shafts which do not impose the cyclic velocity change of the Hooke type universal joint noticeable at larger articulation angles.

Constant velocity joints are now used on almost all front wheel drive cars and on many rear wheel drives. These joints take several forms. There are the fixed ball joint or Rzeppa joint, the plunging ball joint with either straight tracks double offset joints or crossed tracks VL joints , all with six balls running in cylindrical grooves.

Tripod joints, both fixed and plunging, the latter GI joint having needle roller bearings on each of the three-legged inner part, are popular alternative designs of CVJ Figure 3. Front wheel drive cars have four CVJs. A fixed joint at each of the front wheels which can be turned through up to 45 degrees for steering and a plunging joint mounted at the gearbox end of each drive shaft.

Plunging joints permit axial movement between the inner and outer race of the joint which is needed to allow for the variation in length of the drive shafts as the vehicle suspension moves up and down. As well as two CVJs on each drive half shaft, many rear wheel drive cars have had the Hooke-type universal joints on the propshaft replaced by CVJs to reduce the significant vibration which occurs at angles greater than 3 degrees.

Again, one of these would be of the plunging type to accommodate changes in propshaft length. Four wheel drive cars can have as many as 14 CVJs of different types.

Figure 3 Some CV-joints shown in part section. The early fixed ball CVJs as found on the Austin Mini from were first lubricated with standard lithium soap thickened extreme pressure mineral oil grease but soon suffered wear, evidenced by a pronounced clicking sound on going round corners as the balls in the joints oscillated over the worn bearing grooves.

The replacement grease was a number 2 modified clay thickened oil containing 20 per cent molybdenum disulphide. Gear oil has generally proved a better lubricant for CVJs but sealing difficulties, ease of assembly and noise and vibration considerations have persuaded most manufacturers to prefer grease. The tripod joints in use in France from the s are lubricated with calcium complex thickened mixed base paraffinic and naphthenic oils.

Tripod joints need a lubricant free of solids which could prevent the free movement of the needle rollers. The s saw the use of still popular lithium hydroxystearate thickened greases with 3 per cent molybdenum disulphide and other additives such as polyethylene, lead naphthenate or lead dithiocarbamate.

Polyurea thickened mineral oil based greases were first used in The increasing demands on some joints have meant higher loads, greater installed angles and higher temperatures which can exceed the limits of lithium thickened mineral oil greases.

This has meant the use of polymer or complex soap thickened synthetic or semi-synthetic base oils and substantially higher lubricant costs. CVJ oils contain numerous additives to improve their physical properties such as tackiness, pour point and viscosity index. Solid lubricant additives include graphite, molybdenum disulphide, polytetrafluoroethylene and polyethylene. While effective in reducing wear, solid lubricants can be centrifuged out of high speed joints and can cause clogging of needle roller bearings.

Chemically active additives range from anti-oxidants and corrosion inhibitors to anti-wear, extreme pressure and friction modifying compounds. Friction reducers are particularly valuable in joints operating at large installation angles where the efficiency of the joint can drop below 99 per cent, causing substantial internal heat generation.

Lead additives give excellent wear resistance but are being phased out on environmental grounds. Various grades of modified polychloroprene have been used as the rubber boot material protecting CVJs since the introduction of the Mini. There is considerable interaction between the rubber and the grease with the plasticiser and protective agents being leached out and replaced by oil from the grease.

Installation of Des-Case breathers at these critical ingression points is a cost-effective means to prevent contaminants from entering the fluid reservoirs as differential pressures occur.

Plus they are an aid in eliminating any water contamination from the gear reservoir, as the water can be seen in the sight glass and drained off periodically. This plant—located in Calera, Alabama—has a SEW Eurodrive helical right angle separator gearbox on the top of a raw mill. It is driven by a hp electric motor and is constantly exposed to the elements, which are dusty, wet, cold, heat along with a lot of vibration.

This particular gearbox was also suffering from foaming and seal leakage. Figure 2. Figure 3. While using a commercial grade lubricant, the plant had to change the oil every six months.

They were also experiencing foaming, degradation of additives, and the units were running hot. Maintenance Manager Bill Tiller wanted a gear lubricant that would last longer and help reduce overheating and wear. In addition, the units stopped foaming and are now running cooler. The oil change interval is approaching three years, as opposed to the original six months.

Lubrication Engineers provides consultative support for our valued customers worldwide via a global team in more than 60 countries. Industrial clients are enjoying increasing profits due to the reduced maintenance and operating costs relating to their gearboxes and many other applications. High performance lubricants alone cannot provide these savings; it is vital to prevent the contamination of gearboxes in plants in order to remove any possibility of expensive downtime.

Reliable gearboxes result in increased profits. Log in to leave a comment. Sign in Join. Sign in. Log into your account. Sign up. Password recovery. Recover your password. Friday, November 12, Media kit Contact. Forgot your password? Get help. Gear Solutions magazine. Different methods of aqueous polymer concentration control. You can also Contact Us by email and view the regions we service.

We will be happy to give you the answers you need to ensure your gearbox or operations do not come to a halt. Grease lubrication Grease lubrication can be used for industrial gearbox systems that are open or closed, as long as they run at low speeds.

Splash lubrication Helical, spur, and bevel gearboxes are typically lubricated using splash lubrication. Spray lubrication High speed industrial gearboxes are lubricated through spray lubrication. Professional gearbox maintenance services At Amarillo Gear Service, we work with our clients to ensure their gearboxes remain operational for the duration of their intended lifespan. Comments are closed.