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Harman XXV "Squeal" Finally Solved!! No, Really!!!

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by Dale Breault, Sep 24, 2013.

  1. Dale Breault

    Dale Breault New Member

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    I have been plagued with the Harman XXV "squeal" for about three years now. I have tried everything that I could find online, but nothing worked. I am proudly announcing that I think that I finally figured it out, once and for all, and it is not at all related to anything that I have found in any forum.

    Forget about cleaning your stove, buying better pellets, oiling here, graphite there, tighting bolts, lostening bolts, and all of the other nonsense. This was an unintended design flaw in the auger that turned the auger into a tuning fork. Don't believe me? Check out the video that I made..............



    I plan on taking the auger to a welder to have some additional welds put on the shaft so that the vibration will go away.

    I would assume that this flaw is also the reason for the same noises in some other Harman stoves.

    I hope this helps other people. This has driven me crazy for the past few years, and I know that this will fix it.

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  2. P38X2

    P38X2 Minister of Fire

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    Holy crap, that's the noise! Lol. I've only heard it 3 times so far on my P38 for only about a couple revolutions of the auger, then it goes away. May have to look into your idea at the end of the heating season. I wonder if the spot welds, even if properly ground, would cause pellet binding issues?

    Jimmy Page/Nigel Tufnel ain't got nuthin on you! ;)
  3. Bioburner

    Bioburner Moderator Staff Member

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    Don't weld on the push side of the flights if worried about pellet binding. Use stainless to avoid rusting and stainless with higher nickel will also have lower density to possibly mute also.
  4. P38X2

    P38X2 Minister of Fire

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    Wonder why the XXV's often seem to have this issue. Different/longer auger?
  5. Bioburner

    Bioburner Moderator Staff Member

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    Did I see the flight taper in its thickness from the start to the end?
  6. Dale Breault

    Dale Breault New Member

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    Bioburner......Yes, the very end of the auger (nearest the firepot) broke off a few years ago due to some "aggresive" cleaning. It does not seem to have caused any issues. I modified the other end of the flight by grinding it to a point in my first attempt to "fix" this noise. My thought was that pellets and or dust were possibly binding back there and that by grinding the very end of the flight to a point, it would help to break the "bound mass" up a bit. That turned out to not be the cause of the noise, but the grinding has not caused any problems.

    I agree with you that the additional welds need to be on the non-push side of the auger, and that it should be a "neat" weld, with stainless if at all possible.
  7. Stovensen

    Stovensen Burning Hunk

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    On march 10. 2013 forum member geppapa posted a recording of his Harman P-61 making exactly the same noise:
    http://www.hearth.com/talk/threads/...nasty-high-pitched-sound.107305/#post-1403310

    And two other Harman owners reported having had the same noise issue in geppapa's thread.

    Forum member Dave Breault's video is very convincing and interesting, not only for Harman owners... the video had my full attention all the way through.

    Dave Breault, I have a couple of questions:

    The resin used for making the correct friction on a cello bow, isn't this the same resin as in softwood pellets? Spruce, fir or pine resin?
    And the frictional properties of this resin are highly unique, right?... good on a cello bow, but in a Harman stove, not so good::P

    Don't you think that this friction phenomena could be eliminated be spraying some lubricant on the auger now and then? For example forum member Don2222's Dry Moly spray?

    And another question: By welding some points on the auger screw you are altering the pitch of its self oscillation away from the audible range. Isn't there a risk that the oscillation might continue well up in the ultrasonic range so that cats and dogs will be able to hear it?
    Last edited: Sep 24, 2013
  8. P38X2

    P38X2 Minister of Fire

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    Why wouldn't the contact by the pellets at least highly mitigate the harmonic? I know they're not packed in there tightly, but I'd think it wouldn't take much contact at all....but obviously this isn't the case. Strange
  9. TheMightyMoe

    TheMightyMoe Minister of Fire

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    That sound is identical to what mine was, so I am sure you are probably right.

    To fix mine I pulled the auger and motor, took a long metal brush with a drill, and brushed the auger tube. Have not had a problem since.

    Keeping your fines box empty might also help with preventing squealing, as both times mine have squealed and the fines box was pretty full, letting the stuff that will build/clog up, into the tube. Even with a perfect auger install, if the pellets/dust bind up somewhere, your going to have the auger hitting the sidewalls at some point. Or if the auger gets jarred and the bolts aren't tight, it'll start hitting the side probably producing the exact sound we Harman owners fear.

    Good find.
  10. Dale Breault

    Dale Breault New Member

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    P38X2 You are correct. The rosin, which is rubbed on stringed instrument bows, is essentially hardened pine "pitch." So my guess is that any amount of this dried "pitch" that exists in the pellets/dust can help this vibration along. But.....I am not so sure that the pitch is even necessary. I think any item, sich as a fine wedged between the auger and the tube, could potentially cause the noise. I was actually able to "kind-of" make the noise by running the back of a butcher knife on the auger, but got much better results from the bow. I have burned both softwood and hardwood pellets, and the noise has happened with both, so I dont think that this should necessarily ignite the hardwood vs softwood battle.

    I have successfully used some graphite powder mixed in with the pellets to make the noise go away, but the most successful method was to bang on the very end of the shaft (center of the sprocket) in the back with a hammer. That would loosen up whatever was causing the friction and would make it go away for a while. These were always temporary measures and the noise would eventually come back, usually in the middle of the night.

    You are correct that there is a potential to just raise the pitch. Think of it this way.....when you fret a string on a guitar, you are making the string shorter, thus raising the pitch. By adding welds to the auger flight (just learned that word today) you are doing the same thing. I don't think it will be an issue though due to the thickness of the flight. As long as I have a spot weld placed every inch or so, the remaining "suspended" metal should be too short and thick to vibrate. Mind you, I have not studied acoustical engineering, so it's just my gut feeling at this point.

    Probably, the ideal thing to do would be to put a nice neat weld along the whole thing. When I take it to a fabrication shop, I'll see what they can do.....
    I don't think it was designed this way for flexibility, since the whole shaft can be moved slightly...
  11. Dale Breault

    Dale Breault New Member

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    To: TheMightyMoe

    You are right back where I started. I did all of those things...many many times, and it never solved the issue for long. One time I cleaned the whole thing right back to near factory shape (including removing auger and brushing tube with a drill and circular wire brush), and it "squealed" within a few hours. I am convinced that this is the real problem, and will keep you posted.

    I was sick of my $3,000 stove keeping me up at night while a friend's $900 "hardware store special" that he never cleans goes on like a champ.
  12. Bioburner

    Bioburner Moderator Staff Member

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    Could try and coat the auger flight with some graphite paint to help slip things along if worried about the welding causing additional friction.
  13. mikkeeh

    mikkeeh Burning Hunk

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    Wouldn't a small bead of high temp RTV on the flight stabilize it enough to break the harmonics??? Im sure some weld would be better...but not everyone has a welder....Just a thought.
  14. Lousyweather

    Lousyweather Guest

    nope
  15. krooser

    krooser Minister of Fire

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    It's blasphemy I tell you... pure blasphemy. Every enlightened stove owner knows that Harman stoves do not have any problems... they are flawless. Rumors of defects and design flaws are pure poppycock!

    You can expect to see the MIB in your neighborhood in short order... I hope the sounds of those black helicopters don't keep you awake at night. Watch out for the black Suburbans circling the block... it will be the Harman brown shirts planning your first trip to the re-education camp.

    To those of you who watched that video... expect your hard drive to implode any minute...
    Tedinski, briansol and stayfitz like this.
  16. Dale Breault

    Dale Breault New Member

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    Krooser: I haven't seen anyone yet.......I'll keep an eye open for them.

    Anyway, I looked in the yellow pages yesterday for a local welding/fabrication shop. I took the auger there and there was an awesome guy who did the job in 10 minutes for $10. See the two pics below.

    Anyway, I put everything back together and ran the stove all night last night. It did not make any noise. More importantly, it did not explode or do anything else dramatic due to the additional welds. Since the noise used to happen at random times, I will keep you posted to see how things go.


    photo 2.JPG photo 1.JPG
  17. krooser

    krooser Minister of Fire

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    BTW Dale... you did great job of thinking outside the box... congrats.

    I'd be building a reinforced castle for the end times... you never know when the zombie apocalypse will start...==c
  18. XXV-AK

    XXV-AK Member

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    Dale
    So any updated news on the pig iron squeal. It's funny now because I told the family that I might have a possible fix for the squeal. But I heard today "dad it's the pig iron I'm use to the sound and I know to come down stairs and watch the fire and be warmth"
  19. krooser

    krooser Minister of Fire

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    Maybe it's so quiet he can finally get some sleep...
  20. stayfitz

    stayfitz Feeling the Heat

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    Fantastic! Hackles are up in the Harman Cyborg Collective
  21. WoodPorn

    WoodPorn Minister of Fire

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    Yeah but the dogs in the neighborhood are freaking out.

    Outstanding job Dale, Nice kitchen too, I like the turned pepper mill and chopping block
  22. tsmith

    tsmith Minister of Fire

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    Why is this only happening on the XXV? Do the other stoves have augers that are welded together properly? I have never heard this with my Accentra. By the way good find, Harman needs to compensate you for correcting this problem for them.
  23. Lousyweather

    Lousyweather Guest

    *snicker*
  24. tsmith

    tsmith Minister of Fire

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    Yea, I know, Like that would ever happen. A co worker of mine invented a neat deck lift assist mechanism for ex-mark lazer Z mowers and submitted it to them. They liked it and patented it as their own and all he got was a jacket from them.
  25. Dale Breault

    Dale Breault New Member

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    Sorry that I have taken a while to update everyone on this.......

    I have good news and bad news. The noise is "almost" gone. The additional welds did stop the nose for the most part, but there was still an occasional high pitched ringing that was occuring. When I took the auger to the fabrication shop, I did not remove the sprocket and large bushing, so there was still a section of the flight that was overhanging the shaft past the last weld in the back. I could flick this section like a guitar string, and it would also ring, so, even before reinstalling the auger, I suspected that I might have a problem. The sprocket and bushing come off pretty easily, so if anyone else were to want to do this, I would highly recommend it. It will make welding the flight to the shaft much easier.

    Anyway, I made another video to explain all of this. Sorry that I'm so long-winded. Again, I'll let you know how I make out. BTW - I used JB Weld due to the fact that this was at the very back end of the auger. I would never use it or anything other than a solid weld if it were any farther forward, as the heat from the fire box would be too much.

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