I have tested a gear box for many hours. Where the gears are made of a hardened steel alloy and the housing is 7000 series aluminum. Now I drained the gear box of its gear oil and I need to weight the metal shavings in that oil. So I can put in fresh oil and test the gear box for a couple more hours. And then do the test all over again. Can anyone give me a good idea as to how I can accurately separate the oil with out losing the tiny pieces of metal? I thought I could filter the oil through coffee filters then give it a thorough cleaning with hot water and soap, then drying it in the oven. Can anyone tell me if this is a good idea or can you come up with a better one?

  • $\begingroup$ If the gears are made of steel, the usual solution would be to run the oil over a small magnet. $\endgroup$
    – Ethan48
    Jul 29 '16 at 16:30
  • $\begingroup$ The problem is that half the metal is aluminum. I will update my post. Thank you for your suggestion. $\endgroup$
    – RoboChris
    Jul 29 '16 at 16:35
  • $\begingroup$ You could use a centrifuge, but I would think that your solution would work as well and would be cheaper (unless you already have a centrifuge at hand). $\endgroup$
    – fibonatic
    Jul 29 '16 at 16:46
  • $\begingroup$ Yea I don't have access to one. Thank You $\endgroup$
    – RoboChris
    Jul 29 '16 at 16:56
  • $\begingroup$ If only the housing is aluminum, what is removing the metal from it? Do you know that "half the metal" in the oil is aluminum, or is that just a guess? $\endgroup$
    – alephzero
    Jul 29 '16 at 21:04

Standard lab approach is vacuum filtration: Get a Buchner funnel and filter paper sized to capture the smallest particles you care to measure. Now:

  1. Weigh filter.
  2. Place filter in funnel and wet with solvent.
  3. Connect funnel to vacuum filter flask.
  4. Turn on vacuum.
  5. Pour sample into funnel.
  6. Continue to rinse sample with a volatile solvent until it is clean. For rinsing off oil you could use acetone.
  7. Wait a few moments for solvent to evaporate.
  8. Weigh filter with sample.
  • $\begingroup$ Only problem is that I do not have access to that equipment. But I will find out if I can use the chem lab at my university. Thank You $\endgroup$
    – RoboChris
    Jul 30 '16 at 18:27
  • $\begingroup$ @Chris: Not expensive stuff. You can get a funnel, flask, and filters for a few tens of dollars. If you're patient enough (and the oil isn't too viscous) you don't even need the vacuum; you can just wait for it to drain through the filter on its own. For vacuum you might already have a hand vacuum pump (e.g., for bleeding brakes) in your shop, or you can assemble a water-powered aspirator like this. $\endgroup$
    – feetwet
    Jul 30 '16 at 18:31
  • $\begingroup$ I needed it done asap. So here is what I did, and tell me if you can help me solve this. I went and bought some coffee filters and ran the solution through the coffee filter. The solution is a mixture of Aluminum and Steal alloys, Purple Power Degreaser and water. I left the solution to filter for about an hour then I put the filter and the residue into the oven at 215F to left the water and some of the oil to evaporate. Now I am left over with metal and this gray powder and some of it is still in a sludge form. What do you suggest I can do to accurately weight the metal $\endgroup$
    – RoboChris
    Jul 30 '16 at 19:13
  • $\begingroup$ Here is a picture of the residue $\endgroup$
    – RoboChris
    Jul 30 '16 at 19:15
  • 2
    $\begingroup$ I would mix a liberal quantity of solvent with the oil before hitting the filter. $\endgroup$
    – agentp
    Jul 31 '16 at 14:20

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