Leblond Regal 15 servo shift problem (1969)
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  1. #1
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    Question Leblond Regal 15 servo shift problem (1969)

    Hi,

    I have a Leblond Regal 15 built in 1969, with some issues.

    The lathe is one of the servo-shift units. However, sometime between the summer of love and today, the servo shift function broke & was "fixed" by attaching the shifting gears to a linkage connected to exterior handles. Two handles, one shifts the rightmost larger gears between three positions and the other shifts the high speed gears between four positions.

    After disconnecting the shifter unit on the top of the headstock gearbox, I have an issue with the four high speed modes: 654, 937, 1282, 1800 RPM. In these modes, especially 1800, I can easily stop the chuck with my hands, I am not getting the right torque. There is not even enough torque to bring the spindle up to the proper speed. I've checked, there doesn't seem to be an electric issue, my VFD reads 7.4 amperes output on power-on. I suspect the brake stuck engaged somehow. I am wondering if anyone might have an idea of what to try to rectify this. I'll attach some photos at the end of this post, but if there is something specific you'd like to see, let me know and I'll snap a photo and post it here.

    Any help is extremely appreciated.

    -Ian







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    If your brake was stuck engaged it would start to smell very rapidly at speed. I think your problem lies elsewhere.

    I would start by disconnecting power from the lathe. Then I would put the lathe in high gear and block the chuck so it can't turn. Then turn the motor pulley and see what happens. You shouldn't be able to turn the motor pulley at all. If you can, see where the motion stops and that is your problem.

    It is also possible your motor has an internal short. The motor pulls nameplate amps but won't develop any power. If you remove the cover from the peckerhead and smell the windings a burnt smell will greatly increase the likelihood of this being your problem. It could also be incorrectly wired windings for your voltage. Double check all the leads are correctly configured.

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    I see the whole servo shift assembly has been removed...

    I'd suspect your don't have a solid drive connection in your top speeds. Just like the previous post, check if it will lock up tight with the spindle blocked from rotation.

    Then, you will know if its electrical or mechanical.


    DAMNED SHAME. the servo shift is a really nice lathe. Why someone would emasculate it rather than doing a proper repair is terrible.

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    Quote Originally Posted by gbent View Post
    If your brake was stuck engaged it would start to smell very rapidly at speed. I think your problem lies elsewhere.

    I would start by disconnecting power from the lathe. Then I would put the lathe in high gear and block the chuck so it can't turn. Then turn the motor pulley and see what happens. You shouldn't be able to turn the motor pulley at all. If you can, see where the motion stops and that is your problem.

    It is also possible your motor has an internal short. The motor pulls nameplate amps but won't develop any power. If you remove the cover from the peckerhead and smell the windings a burnt smell will greatly increase the likelihood of this being your problem. It could also be incorrectly wired windings for your voltage. Double check all the leads are correctly configured.
    Thank you both for the replies. I blocked the chuck with some wood blocks and tried to turn the pulley attached immediately to the motor's rotor. It would not budge. I had the gearing set to 1800 RPM (highest, belt driven). Starting to get nervous.

    Quote Originally Posted by Karl_T View Post
    I see the whole servo shift assembly has been removed...

    I'd suspect your don't have a solid drive connection in your top speeds. Just like the previous post, check if it will lock up tight with the spindle blocked from rotation.

    Then, you will know if its electrical or mechanical.


    DAMNED SHAME. the servo shift is a really nice lathe. Why someone would emasculate it rather than doing a proper repair is terrible.
    It really is. I plan on trying to fix it.

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    Is that the original motor? I have never seen a 3hp on a 15 Regal. Normally 5 or 7.5hp. The electric brake is behind the big pulley driven by the motor. If you think the brake is dragging just unplug it. I would power the motor directly without the VFD and see if the problem improves. Shame about the servo shift, I love mine and it has been flawless for years.

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    Quote Originally Posted by moonlight machine View Post
    Is that the original motor? I have never seen a 3hp on a 15 Regal. Normally 5 or 7.5hp. The electric brake is behind the big pulley driven by the motor. If you think the brake is dragging just unplug it. I would power the motor directly without the VFD and see if the problem improves. Shame about the servo shift, I love mine and it has been flawless for years.
    I've been trying to do this -- those gears behind the V belts aren't turning, but I'm not convinced the brake is disengaged. Not having a lot of luck finding the connection to open either, seems like every time I disconnect something I lose a phase.

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    One other thing that comes to mind is there doesn't seem to be an extreme amount of tension on the V belts (pully) driven immediately by the motor. I am almost certain that the V belts aren't slipping, but it seems odd that I can pretty easily loop them on and off with my hands.

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    just disconnected the brake to no effect, still seeing crap torque on high speeds

    i think my next step will be to crank the turnbuckle connected to the motor's mounting plate, to further tension the V belts. if that doesn't do it, looks like im in for a new motor

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    A buddy has a FLIR thermal camera -- am thinking I will also use this to try and spot any points of internal friction that'd be robbing the spindle of torque. If that shows up clean, I'm afraid I'm in for a new motor..

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    Said buddy, here.

    Kremlin, I doubt slipping belts would be the issue. If they were, you'd hear a wretched squealing when it runs.

    Are you able to prop a camera up to watch the motor while you grab the chuck and bring it to a halt? Do that and see what's happening.

    Also, if you had something that was causing enough friction to rob that much torque, you wouldn't be able to spin the chuck by hand with the motor off.

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    The spindle is driven by the timing belt in high speed.I can see the tb pulley on the spindle(yellow paint) and it looks like it hasn't been slipping but the other one?
    When you blocked the chuck to test did you have it in high gear? Did you try it in all three high gear positions?What about the small pinion on the timing belt shaft?
    There is no way with a 3hp motor you could stop the spindle by hand although as moonlight says it should have a 7.5.

    The way it works is the right hand three positions select the three ranges(the two lower ranges are direct to the spindle;high is through the timing belt shaft).The four ratios in each range are the same and are the lh set.So the only thing different is the power is directed from the four speed shaft up to the small pinion tb shaft as your picture shows,it is in hi gear.
    Try hooking the brake up and turning the chuck in high as in the picture.You should be able to find any slipping.If none then its got to be the motor or a badly worn pulley.That is a small dia and see if the belts are bottomed out,not gripping the v-sides.

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    Quote Originally Posted by ratbldr427 View Post
    The spindle is driven by the timing belt in high speed.I can see the tb pulley on the spindle(yellow paint) and it looks like it hasn't been slipping but the other one?
    When you blocked the chuck to test did you have it in high gear? Did you try it in all three high gear positions?What about the small pinion on the timing belt shaft?
    There is no way with a 3hp motor you could stop the spindle by hand although as moonlight says it should have a 7.5.

    The way it works is the right hand three positions select the three ranges(the two lower ranges are direct to the spindle;high is through the timing belt shaft).The four ratios in each range are the same and are the lh set.So the only thing different is the power is directed from the four speed shaft up to the small pinion tb shaft as your picture shows,it is in hi gear.
    Try hooking the brake up and turning the chuck in high as in the picture.You should be able to find any slipping.If none then its got to be the motor or a badly worn pulley.That is a small dia and see if the belts are bottomed out,not gripping the v-sides.


    I had it in high gear but I didn't test the other positions. I'll try what you said -- I am also using a pal's winding test kit to check the motor windings.

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    Your test with the chuck blocked and trying to turn the motor pulley only tested the brake holding(if the brake was engaged;power on).That's why I suggested engaging the brake and trying to turn the chuck;you then isolate the motor and if in hi range the torque you apply to the chuck will flow through the spindle through the timing belt and pulleys through the small pinion and then held by the large gear attached to the input shaft.If that is a solid connection then it has to be on the other side of the brake;motor pulley to shaft or a loose rotor(never seen that but who knows!)

    The torque multiplication in the lower ranges could be enough that while you can stop it in high you won't be able to in lower ranges.


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