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Tip for giving an auger motor extra life- bearing switcheroo trick

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by pete324rocket, Mar 24, 2013.

  1. pete324rocket

    pete324rocket Feeling the Heat

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    Symptoms: Pellet stove seemed to be giving less heat for the setting chosen.Also fire seemed to have periods of less intensity and oddly less pellets consumed than normal.

    Result: Auger motor has lots of play from wear and sometimes at certain points of rotation, instead of spinning when power is applied, the rotor gets "locked" and doesn't spin, but will free itself after a few cycles.

    The shows the bearing ends of the motor.The stove is a Drolet eco-45. Others may be similar. Simply, the bearings can be spun around in the socket, and there is generally less wear on the other side. If anyone has a source for these bearings, please contact me. Pretty stupid to have to throw out a perfectly good motor over some 50 cent bearings. I'll make some first.



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    Defiant, imacman and heat seeker like this.

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  2. heat seeker

    heat seeker Minister of Fire

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    Good point, and good pics!
  3. imacman

    imacman Guest

    And don't forget a couple drops of light oil (3 in 1 or equivalent) in each bearing.
  4. bill3rail

    bill3rail Feeling the Heat

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    Minor problem... There may be a hundred different sizes of bearings for different manufacturers.
    I will look into finding replacements for my spare MK auger motor if I get the chance to take it apart. I just need to make a phone call to see who sells replacement Bronze bearings. If I find them, I will post here.

    Bill
  5. smwilliamson

    smwilliamson Minister of Fire

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    Look at the coil on that thing. The cellophane covering the copper winding is yellow brown, should be milky clear. Yer motor is junk. Do a resistance check with a DMM, use Ohm's Law...115v / total watts and your reading should be +/- 10% for a good motor.

    For example, 115v/ 56w = 2.35
  6. heat seeker

    heat seeker Minister of Fire

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    Are you allowing for the inductance? I don't know if that's a factor on these small coils, though?
  7. smwilliamson

    smwilliamson Minister of Fire

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    +/- 10%
  8. heat seeker

    heat seeker Minister of Fire

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    Thanks, I learned something good to know.
  9. Stovensen

    Stovensen Burning Hunk

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    smwilliamson, are you suggesting to calculate the resistance by dividing the voltage with the wattage?? If so, your calculations are VERY wrong, and not in accordance with Ohm's law. Please see illustration below on how to calculate different unknown parameters depending on what parameters are known.

    Your equation must be corrected to:

    R = UxU/P = 115x115/56 = 236.16 Ohm

    This resistance of 236.16 Ohm is way too high compared to what we will find in a typical auger motor ( 18 Ohm in the following example ). On the illustration below ( from a Whitfield service manual ) we see the parameters of an ECM auger motor ( 120V/60Hz, 1 rpm. ). This type of motor is found in many pellet stoves, so the data will most likely be relevant to the auger motor we are talking about in this thread.

    Ohms lov.jpg ECM auger motor.jpg
    Defiant likes this.
  10. MButkus

    MButkus Member

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  11. smwilliamson

    smwilliamson Minister of Fire

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    Ok you're right, but doing the way I did it also shows whether a motor is good going or gone...move the decimal point
  12. TheMightyMoe

    TheMightyMoe Minister of Fire

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    When it comes to Torque, do you want a plastic gear stripping, a metal gear stripping, a bushing cracking, a cam shattering, or a auger bending?

    In a lot of small high torque operations there is a plastic gear to prevent anything else from breaking apart.

    I am not saying this is why, in this situation, but typically that is why from my understanding.

    The next question is:

    Can you get a replacement plastic gear?
  13. imacman

    imacman Guest

    Doubtful
  14. smwilliamson

    smwilliamson Minister of Fire

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    buy a 3 -D printer and print one off.
  15. flynfrfun

    flynfrfun Minister of Fire

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    If the OP gets a source for those bushings, I would like to know. My Gleason Avery auger motor uses a bushing at the gearbox side of the motor. I believe when the bushing wears that the motor hits the side of the housing causing a grinding noise.
  16. MButkus

    MButkus Member

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    The plastic gear is for $$$. With a metal gear there.. what would wear out ? the motors are simple, no motor bushing to wear out. My original Whitfield auger motor lasted 11 years (after a quick fix after 6 years). I can only guess my replacement was not right from the start, hence not lasting more then 14 months.
  17. pete324rocket

    pete324rocket Feeling the Heat

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    my "junky" motor is still running nicely and the post was made about a month after the "fix" when I got the time to post. I bet you charged a lot of customers a handsome sum for their old "junk" yellowy motors since then. I let you know when it breaks.
  18. pete324rocket

    pete324rocket Feeling the Heat

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    So it didn't last-well a year anyways. Then the rotor inside the motor started to drag and would just sit there rather than spin. I thought for sure I was going to have to shell out over 100 bucks for a new one and I really got pissed off-who would build such a piece of crap-(or as the garage boys would say "anyone who would build something like this would suck a @*&*". So I finally pulled the bearings out,I used a dremel on the drive end to cut a couple of the retaining tabs,since I didn't want to totally destroy the retainer-just in case. So,after visiting two bearing shops-the first one just wasn't in business long enough to know I guess....so in my case , bearing R3A-ZZ - NOT METRIC! had a 3/16 I.D , 3/16 wide and O.D. of 5/8". Now, I had to cut a spacer-a bushing I had, to make a spacer for one end to take up the slack-I had found a PEX plumbing ring at the hardware store that could have worked-a little wide but they only sold bags of 100.
    Anyways,this should last for a long time,runs soo smooth and really it would be so easy for all of these auger motors to use ball bearings---but then they wouldn't sell any would they. Total cost $13.00 and change, ebay sells them pretty cheap too. I hope this will help a few people, and you "service people" won't get too out of joint with your "oh your motor is burnt" cuz thats just wrong. By the way, these motors get plenty hot back there,no kidding things will turn brown. I'm going to leave the back shroud off and observe for a bit but all seems good.

    Oh,one more thing....this motor would run and it was tricky to diagnose because the rotor wouldn't always stay stopped and would free itself-I couldn't figure out why there was such less heat per setting. I had to observe it for some time.Also, what I'm holding in my hand is the old spherical bushing. The new bearings are already installed.


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    Last edited: Jan 30, 2014
  19. Harvey Schneider

    Harvey Schneider Minister of Fire

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    Interesting that even the motor manufacturer doesn't use correct terminology. You will see in the picture it says "18 Ohm impedance". That is actually the dc resistance. The impedance is equal to the operating Voltage divided by the operating current, which using the manufacturers numbers is 120/0.41 = 293 Ohms. That impedance is a combination of the dc resistance and the ac reactance (sq root of the sum of the squares). The reactance changes as the motor load changes and is largest when the motor is at no load and lowest when the motor is stalled.
    If you check for the 18 Ohms you will know if there are shorted turns. You don't need to calculate anything.
  20. Harvey Schneider

    Harvey Schneider Minister of Fire

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    The manufacturers claim that the plastic gear is there to reduce cogging noise from the motor.
  21. Harvey Schneider

    Harvey Schneider Minister of Fire

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    I'm trying to figure out what you did.
    The old bearing was a self aligning sintered bushing. It was held in place by a brass spring plate.
    You are somehow going to replace it with a sealed ball bearing.
    How is the new bearing held in place after you removed the spring plate? How do you keep the new bearing aligned and centered?
  22. pete324rocket

    pete324rocket Feeling the Heat

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    After you pull all that mess out,the new bearing fits snugly in the housing on one side of the rotor,the other side needs a spacer. All centered and true and running now very quietly,all probably will be for a long time. My only concern was the grade of grease in the bearing-it gets plenty hot. It was a little noisy at first but has settled down. You can see the rotor spinning much longer now after the cycle stops. There is so much less friction vs. the bushing.

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