Thrust Bearing Test

If we were perfect fishermen, our reels would not need any provision for thrust loads on the spool (i.e., loads in the direction of the spindle axis). A fish on the line creates a torque on the spool, which we counter with an appropriate force on the knob. But we are at times likely to get a little excited when playing a fish and then apply extra forces on the knob that really are not needed to bring in the line. Typically these extra forces will be in the direction of pushing the spool into the frame.

In my first “fixed spindle” reel design, I included a bronze thrust washer in the frame, which ran against the face of the acetal ratchet.
IMG_4035
But it was difficult to make the two faces of the washer parallel. I made several different fixtures to assist in this, but none were totally satisfactory.

When I created my most recent reel design, I left out the thrust washer. Now the thrust bearing is a raised face on the ratchet, running on the anodized inside end of the frame.
IMG_4204
Is this OK? I had to devise a test to help convince me.

Here is the fixture for my test. On the right is an anodized plate supporting a short spindle. On the left is a 200 rpm gearmotor with an acetal runner attached to the shaft.
IMG_4258
Where the two bearing surfaces meet, the aluminum was wet sanded to 2000 grit before anodization, and the acetal was sanded to 12000 grit with Micromesh pads.

Here the fixture is assembled. The gearmotor weighs 2.3 pounds and provides the thrust load for the test. A piece of wire carries the necessary torque.
IMG_4260
I ran the fixture for 4 days, over one million revolutions, and the anodize coating remained intact. Had it broken down, it would have been visible and it would have conducted electricity. My conclusion is that this is an adequate thrust bearing.

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3 Responses to Thrust Bearing Test

  1. Keenan says:

    I was wondering if you might be able to share some insight on how an appropriate load was determined. I’ve been trying to work that sort of thing out for similar situations mainly for building up an intuition for what seems “about right.”

  2. dave49 says:

    Keenan,
    I can only say that I made a guess. The load on the thrust bearing has little to do with mechanics and much to do with the amount of adrenaline injected into the fisherman’s bloodstream at the moment of fish strike.
    I puzzled for a while on how to make the fixture so that it would rotate the bearing under load. When I finally weighed the gearmotor, 2 pounds seemed like a very reasonable load.
    Dave

    • Keenan says:

      That’s good to know. Now I don’t feel so bad about the methods I have used. I’m not a fan of the “Guess and Check” method, but sometimes that’s the only method that will work. I don’t like to rely on it, though. When the only tool you use is a hammer, everything starts to look like a nail.

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