I am doing an experiment testing different types of gears, the gears are fairly small, with gear 1 being approx. 35mm in diameter and gear 2 being 45mm in diameter, and both are meshed together, there are also around 15mm wide. the gears will be rotating at a max speed of 2000 RPM also. I want to test a lot of the same gears with different constrains, but want the lubrication to remain the same, since these gears tangential velocity are not that fast, many suggest Grease as lubrication, but I want to use the exact same amount of grease each time I test the gears so it does not affect the results, another maybe the oil bath method, which will allow me to put an exact amount of oil each time however might seem a bit overkill for gears which are so small.

does anyone know Which method of lubrication will be better and if it is grease, what are the suggestions to make sure I use the exact same amount each time so It does not affect the results.



1 Answer 1


one solution would be to spray the lubricant (provided it's fluid enough) on the gears

enter image description here

Figure 1: source machinery lubrication

By spraying you can make sure that you control the flow of the lubricant, and therefore you can control parameters like:

  • heat abduction
  • estimated thickness of film on the gears
  • etc

Splash lubrication

Another solution is Splash lubrication (but not optimal for the parameters you have provided).

enter image description here

Figure 2: Splash lubrication addinol

The advantage is that it is more cost effective. The only problem is that with the dimensions of the gear only at the maximum rpm you are at the low end of the recommended velocity.

I.e. Assuming that the 45[mm] is rotating at 2000[rpm], then the velocity will be about 4.7[m/s]. (if the 35 mm is @2000[rpm] then the velocity is about 3.67[m/s]).

The recommended range velocities for the different types of lubrication can be seen in the following image

enter image description here

Figure 3: Ranges of tangential speed (m-s) for spur gears and bevel gears source KHK gears

  • $\begingroup$ Hi thanks for answering, would this method require constant spraying or could I spray once before the start of testing and leave it. $\endgroup$
    – mikey5512
    Jun 2, 2021 at 7:17
  • $\begingroup$ The best case (if you can afford it because it has an added cost), is to continuously apply the lubricant. $\endgroup$
    – NMech
    Jun 2, 2021 at 7:20
  • $\begingroup$ each test will only be operating for around 90 minutes, does this impact how much should be used? $\endgroup$
    – mikey5512
    Jun 2, 2021 at 7:22
  • $\begingroup$ Actually no, because you can re-circulate the oil (maybe with a small filter to remove the particles). There are ready systems, with the pump, filter, sprayer you can look at. $\endgroup$
    – NMech
    Jun 2, 2021 at 7:25
  • $\begingroup$ Do you have any suggestions if I use grease lubricant because it is on low end of speed to make sure the grease amount stays constant each test? $\endgroup$
    – mikey5512
    Jun 2, 2021 at 7:45

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