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Thread: Northfield Jointer Throwing Belts

  1. #1

    Northfield Jointer Throwing Belts

    I have a 1953 Northfield 12HD jointer. It has been a great machine with one exception. I got it with a 5 hp three phase motor. I swapped it out with a new 3 hp Baldor single phase motor and Furnace starter. It works fine except on shut down. Something happens to the motor that causes a brief shutter that throws the belts. The folks at Northfield suggested that this is characteristic of single phase motors. They also recommended I use double 3/8" belts when I did the motor swap. Once running the belts work fine. I asked them if I could switch to 5/8" belts and pulleys in order to stop the belts being thrown at shut down. They are suggesting against it. I don't remember why. They are now suggesting I put the original 5 hp/3 phase motor back on with a vfd. I wouldn't mind doing this, but I don't know the condition of the 68 year old motor, a proper name brand vfd will cost close to $1,000.00 with tax and shipping, and the vfd will require a 50 amp/220 volt circuit, which I am capable of providing, but it's a big job. This seems to be a very expensive and labor intensive way of preventing the belts from being thrown. The current 3 hp motor works great and I have yet in all the years I have owned the jointer, been able to bog it down. I've adjusted the belt tension and checked the pulley alignment. The distance between the motor shaft and the cutterhead shaft is 37 1/2 " OC, making for long belts. Any suggestions? What about idler pulleys to reduce the flex on the long stretch of belts?

  2. #2
    Have you been to the motor shop? Could be a problem with the centrifugal switch, definitely worth having it checked out.

  3. #3
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    What's a furnace starter?

  4. #4
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    I would not use an idler pulley, not really their application. Speed might also be limiting factor. Brian
    Brian

  5. #5
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    Quote Originally Posted by Richard Coers View Post
    What's a furnace starter?
    I suspect OP mean a "furnas" starter, it's a brand name.
    --Certainty is the refuge of a small mind--

  6. #6
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    When does it throw the belt? Right when you shut it off, or a little while later during spin down?
    --Certainty is the refuge of a small mind--

  7. #7
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    That’s a weird one . My first thought is the belt isn’t the correct side for the pulley. I’ve ran odd sizes before on my Davis and wells table saw and never had one come off it’s a single phase motor. It would have to be very far off in sizes
    Good Luck
    Aj

  8. #8
    Quote Originally Posted by Richard Coers View Post
    What's a furnace starter?
    I meant Furnas brand manual starter for the motor. I really could use a Spellcheck for Woodworkers app.

  9. #9
    Quote Originally Posted by Paul F Franklin View Post
    When does it throw the belt? Right when you shut it off, or a little while later during spin down?
    It will throw the belt 8 to 10 seconds after shutting down the machine. There is a slight click and the motor drops into a lower rpm range. At that point the belts vibrate momentarily and more often than not, one or both will either flip over upside down, or occasionally fall off the motor pully.

  10. #10
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    Quote Originally Posted by Rob Sack View Post
    I have a 1953 Northfield 12HD jointer. It has been a great machine with one exception. I got it with a 5 hp three phase motor. I swapped it out with a new 3 hp Baldor single phase motor and Furnace starter. It works fine except on shut down. Something happens to the motor that causes a brief shutter that throws the belts. The folks at Northfield suggested that this is characteristic of single phase motors. They also recommended I use double 3/8" belts when I did the motor swap. Once running the belts work fine. I asked them if I could switch to 5/8" belts and pulleys in order to stop the belts being thrown at shut down. They are suggesting against it. I don't remember why. They are now suggesting I put the original 5 hp/3 phase motor back on with a vfd. I wouldn't mind doing this, but I don't know the condition of the 68 year old motor, a proper name brand vfd will cost close to $1,000.00 with tax and shipping, and the vfd will require a 50 amp/220 volt circuit, which I am capable of providing, but it's a big job. This seems to be a very expensive and labor intensive way of preventing the belts from being thrown. The current 3 hp motor works great and I have yet in all the years I have owned the jointer, been able to bog it down. I've adjusted the belt tension and checked the pulley alignment. The distance between the motor shaft and the cutterhead shaft is 37 1/2 " OC, making for long belts. Any suggestions? What about idler pulleys to reduce the flex on the long stretch of belts?
    A 20amp 240v circuit should be more than enough for a 5hp VFD. The last Chinese 5hp VFD I purchased was about $100. The Last Hitachi 5hp VFD (SJ200) I purchased was a little over $200 (Used SJ200 off ebay). Not much need for a fancier WJ200 Hitachi VFD on a jointer. A 68yo 3ph motor is still practically a baby, I have a ~100yo 3ph motor with its original bearings running on a Chinese VFD just fine. 3ph motors will way outlast most single phase motors.

    I have no clue why the single phase motor is causing the jointer to throw belts? Are you sure the pulleys are lined up correctly? Are you using the original motor pulley off the original 3ph motor? I might try a link belt. How is the motor tentioning the belt (a photo or two might help). But I would go with the original motor and a Chinese VFD.
    Last edited by Michael Schuch; 01-06-2022 at 12:05 AM.

  11. #11
    Quote Originally Posted by Rob Sack View Post
    It will throw the belt 8 to 10 seconds after shutting down the machine. There is a slight click and the motor drops into a lower rpm range. At that point the belts vibrate momentarily and more often than not, one or both will either flip over upside down, or occasionally fall off the motor pully.
    The click definitely sounds like the centrifugal switch. Does the motor vibrate at that point?
    Last edited by Kevin Jenness; 01-06-2022 at 7:53 AM.

  12. #12
    Chances are you have damage belt already I would replace your belts. Once they've rolled there's a good chance that the cords have been damaged and they will continue to roll off. Next take a straight edge and make sure that you are aligned from sheeve to sheeve. Then I suggest you check the tightness of the belts the belts I don't know what the span is between the motor and the top sheeve. But I can say that you probably should have about a 1/2 inch of deflection it's been a deflection on the belt mid span.

    You don't have to look at the electrical it has nothing to do with the belts rolling off. It's like saying your car doesn't start and you check the air pressure in the tires.

    You are hitting a harmonic on slow down and that is causing your belt to jump off but but you already have some issues that are allowing the belts off.

  13. #13
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    Explore getting a banded V-Belt. They are one piece with 2 or more Vee's. Here is a link to an example. It's guaranteed they won't flip over. In my experience once a belt "turns" over it is no longer dependable. That may be why you are having more issues after tightening. We had an application that ran 5 belts side by side. They seemed to even when "matched" to never all tighten evenly. Switched to these and belt issues became a non factor.

    https://www.vbeltsupply.com/banded-w...apped-belts/3v

  14. #14
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    I agree with George. Things I'd look at are:
    - not enough tension on the belts and/or wrong size belts.
    - making sure the pullyes are coplanar.

    Single phase/3phase should have nothing to do with this, unless the motor is damaged and makes extra ordinary vibration.

  15. #15
    Quote Originally Posted by Michael Schuch View Post
    A 20amp 240v circuit should be more than enough for a 5hp VFD. The last Chinese 5hp VFD I purchased was about $100. The Last Hitachi 5hp VFD (SJ200) I purchased was a little over $200 (Used SJ200 off ebay). Not much need for a fancier WJ200 Hitachi VFD on a jointer. A 68yo 3ph motor is still practically a baby, I have a ~100yo 3ph motor with its original bearings running on a Chinese VFD just fine. 3ph motors will way outlast most single phase motors.

    I have no clue why the single phase motor is causing the jointer to throw belts? Are you sure the pulleys are lined up correctly? Are you using the original motor pulley off the original 3ph motor? I might try a link belt. How is the motor tentioning the belt (a photo or two might help). But I would go with the original motor and a Chinese VFD.
    This solution certainly is cheaper and much less labor intensive. However, the folks at Wolfautomation, which is a highly regarded supplier of quality VFD's, recommend a supplying electrical circuit twice amperage of the motor plus 50%, bring the total to 42 amps, hence a 50 amp circuit.

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