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  1. #1
    Silver Member
    Join Date
    Feb 2009
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    224
    Location
    south western michigan
    Tractor
    pt 425, JI Case, Gravely Comm.10A

    Default broken stump grinder

    yesterday I was clearing out trees most averaging 4-6'' diameter when the grinder made a unusual sound pulled back and the grinding wheel/with motor shaft was leaning against the stump does anyone know the specifications on the motor? the shaft the hub was mounted to twisted off inside the motor, did not bend it, just glad it did not go freewheeling into the next county

  2. #2
    Gold Member
    Join Date
    Oct 2000
    Posts
    359
    Location
    Rutledge, GA
    Tractor
    Kubota L3710DT

    Default Re: broken stump grinder

    Make? Model? This post needs pictures of the carnage.

    SimS

  3. #3
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
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    17,328
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: broken stump grinder

    Quote Originally Posted by washita View Post
    yesterday I was clearing out trees most averaging 4-6'' diameter when the grinder made a unusual sound pulled back and the grinding wheel/with motor shaft was leaning against the stump does anyone know the specifications on the motor? the shaft the hub was mounted to twisted off inside the motor, did not bend it, just glad it did not go freewheeling into the next county
    Did you perhaps stall out the hyd motor several times before that happened.

    If the relief is not working in that circuit, and you were grinding real hard, and the wheel stopped suddenly, then it is possible that the motor could twist the shaft off.

    Did the engine labor any more than mormal.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  4. #4
    Silver Member
    Join Date
    Feb 2009
    Posts
    224
    Location
    south western michigan
    Tractor
    pt 425, JI Case, Gravely Comm.10A

    Default Re: broken stump grinder

    I might have around 5-6 hours on the stump grinder I will have to look at the model but it is the one that was sized for the 425 tractor the motor did not stall anymore than typical actually it did not stall the motor it just simply twisted off the hollow pipe/tube that the hub and cutting disk was bolted to the break is at roughly 15-20 degree angle of a 90 degree shear typically seen when a shaft twists off I will take pictures and post them, now since the heat of the moment is over, and the thinking is a clearer, if powertrac does stand behind it I will rebuild it myself and make it so the cutting disk cannot escape and injure somone, I feel that the stump grinder is a indispensible tool to have

  5. #5
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
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    17,328
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: broken stump grinder

    washita. Doesn't your hydraulic motor have solid taper shaft, and held on by a large nut and pin? I can't imagine a 1 1/4 in shaft twisting off. Pictures please. Does your stump grinder look like this, or does it have the bolt on blade? The second picture shows the wheel that can be turned around. Does anyone have a price on the wheel and hub?
    Attached Thumbnails Attached Thumbnails -stump-grinder-jpg   -stump_grinder_tbn_b_-jpg  
    Last edited by J_J; 05-24-2009 at 08:44 PM.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  6. #6
    Silver Member
    Join Date
    Feb 2009
    Posts
    224
    Location
    south western michigan
    Tractor
    pt 425, JI Case, Gravely Comm.10A

    Default Re: broken stump grinder

    pictures looks like potmetal to me whats your opinion
    Attached Thumbnails Attached Thumbnails -oops-broke-001-jpg   -oops-broke-002-jpg   -oops-broke-003-jpg   -oops-broke-004-jpg  

  7. #7
    Silver Member
    Join Date
    Feb 2009
    Posts
    224
    Location
    south western michigan
    Tractor
    pt 425, JI Case, Gravely Comm.10A

    Default Re: broken stump grinder

    before any one asks the bolts on the teeth are not original I had problems with the bolts stretching and the nuts backing off so after a trip to my local bolt supplier I now have grade 8 bolts and metal locking nuts on the teeth only drawback is if I change teeth the bolts will have to be replaced they are not reusable I was informed that was a common upgrade locally the local sharpening center also claims to sharpen the top of the teeth also in a wedge shape I have not done that modification yet but might in the future but first to fix the motor issue 4 acres of stumps to grind

  8. #8
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
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    17,328
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: broken stump grinder

    Well, that is a first for me. I haven't heard about or seen anything like this before. Do you think the wheel/teeth assemble might be out of balance. The only support for that shaft would be at the bearing, and the longevity would depend on how the stump grinder was used. Are you going to rebuild it or purchase a new motor? I didn't know those shafts were hollow either.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  9. #9
    Silver Member
    Join Date
    Feb 2009
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    224
    Location
    south western michigan
    Tractor
    pt 425, JI Case, Gravely Comm.10A

    Default Re: broken stump grinder

    my train of thought for now is 1 check to see if the wheel is balanced 2 replace motor with additional bearing support on shaft 3 move cutting wheel away from motor with bearing support on each side of it 4 make it belt drive/cogged like on a car motor 5 build it so wheel cannot escape if a bearing would fail 6 call terry at tazewell and see what they can do for me, good, bad, otherwise 7 research some other stump grinders to see what they have designed into their machines, bearing size, drive system, fpm of cutting wheel, etc. etc.

  10. #10
    Silver Member
    Join Date
    Feb 2009
    Posts
    224
    Location
    south western michigan
    Tractor
    pt 425, JI Case, Gravely Comm.10A

    Default Re: broken stump grinder

    most trees I grind out are either pine or 4-6'' saplings and muliflower rose, only removed one hardwood stump and it was a sugar maple, so I do not feel that I am overworking the grinder

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