If you want to get the most value out of your equipment, lubrication is key.
Here are a few other Shop Talk Blog posts you might find of use:
- Lubricants: An Investment in Your Equipment
- Most Common Failure Items on a Final Drive
- Guidelines to Final Drive Maintenance
What is Lubrication?
According to Machinery Lubrication Magazine,
"Lubrication is the control of friction and wear by the introduction of a friction-reducing film between moving surfaces in contact."
You'll notice two keywords in this definition: wear and friction.
Wear and Final Drives
Wear occurs when metal surfaces come into contact with each other. It is going to be more pronounced when there are high forces involved (such as at the gear teeth in your planetary drive). Some degree of wear is always going to be unavoidable, even with the best lubrication possible. Regardless, wear inevitably leads to parts that aren't as efficient.
If you've ever pulled a hydraulic filter (like the case drain filter) and saw bits of metal in it, that is likely the result of wear. As parts experience wear, slivers, chunks, and particles of metal are displaced. This is referred to as internally generated contamination, and once that starts developing it leads to even more wear in a cycle of continuing damage. In the image below, you can see a disturbing amount of metal that fell out of a case drain filter.
Hydraulic fluid and gear oil should never look like it has glitter in it. Shiny particles are signs of accelerated wear and can lead to even more problems in not just your final drive motor but your system as a whole.
There are certain parts in a drive motor that experience more intense wear, such as the bearings. Once the bearings reach a certain level of wear, they need to be replaced or other components can end up damaged. However, without enough lubrication, the result is accelerated wear. Parts wear out sooner than they should, and that adds internally generated contamination to your final drive motor. That contamination, which is usually abrasive, leads to more damage and wear.
Friction and Final Drives
When friction is present, whether we're talking about bearing in a final drive motor a pin in the boom on a mini-excavator, it means more work is needed to get something done. Friction leads to energy and power losses, which reduces the performance of your equipment. Friction can also lead to worsening surface damage, again leading to a destructive cycle of damage.
One of the key tasks of lubricants lies in reducing friction. Think about the gear teeth in the planetary gear set. These teeth are transferring extremely high forces to produce the torque your machine needs to move. When those gear teeth contact each other, a lubricant (in this case, gear oil) is present so that they move across each other as smoothly as possible. Without enough lubricant, or in the presence of old, contaminated gear oil, friction will make it harder for these teeth to interact with each other.
Gear oil in this condition is only increasing friction and causing more damage.
Another complication resulting from friction is the generation of heat. One of the secondary tasks of lubricants is to conduct heat away from critical components. When there is not enough lubricant to dissipate the heat, parts will begin to change in size. Components in a final drive motor to expand, cutting off necessary clearances or increasing the chances of damaging metal-on-metal contact. This, again, further reduces the performance of your equipment.
Conclusion
Proper lubrication reduces wear and conducts heat away from critical components. In fact, that's why we put so much emphasis on checking and changing the gear oil in your planetary hub and ensuring that the hydraulic fluid you use is appropriate for your machine. Lubrication will extend the life of your equipment, including the final drive motors.
