Increasing rpm on my 10EE
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  1. #1
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    Default Increasing rpm on my 10EE

    I have a 1942 round dial 10EE currently running on an AC variable speed drive. The top speed of the drive seems to be much lower than what the lathe was designed to do. Can I increase the size of the pulley on the gearbox or decrease the size of the one on the spindle to increase the rpms of this lathe? Could it be that simple? Any advice or opinions are appreciated. Thanks

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    Quote Originally Posted by Fourierseries View Post
    I have a 1942 round dial 10EE currently running on an AC variable speed drive. The top speed of the drive seems to be much lower than what the lathe was designed to do. Can I increase the size of the pulley on the gearbox or decrease the size of the one on the spindle to increase the rpms of this lathe? Could it be that simple? Any advice or opinions are appreciated. Thanks
    What do you mean by "seems to be" in actual RPM?

    The VFD should be able to tell you, what the MOTOR RPM is, or grap a cheap tacho?

    If your OEM spindle tacho is working, 2500 RPM at rated load was the top for THE MOST COMMON of MG-era round-dials, (as-in both my '42 and '44).

    Top RPM of 4,000, 6,000, and even 8,000 are known.

    Motor was nominal 670 RPM @ nameplate Voltage & rated load, 2400 RPM with 400 ohms in series with a 115 VDC Field. That info per Reliance 3 HP large-fram DC motor nameplate. When run unloaded, both were higher

    Round-dial AC conversions with VFD usually go to HIGHER RPM than DC with ease as a higher "base" RPM is hard to avoid.

    What does your AC motor have as pole-count and/or name plate "base" RPM, and what are your pulley diameters, motor and spindle?
    Last edited by thermite; 07-30-2020 at 04:50 AM.

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    Quote Originally Posted by thermite View Post
    ...
    If your OEM spindle tacho is working, 2500 RPM at rated load was the top for normal MG-era round-dials, as-in both my '42 and '44.
    ...
    My "MG-era" round-dial shipped from the factory with a 4000 RPM spindle and tachometer. As an initial assumption, the machine should be able to reach whatever RPM the installed tachometer has as it's maximum speed, be it 2500, 3500 or 4000 RPM. It's just matter of what customer ordered.

    Cal
    ---

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    Quote Originally Posted by Cal Haines View Post
    My "MG-era" round-dial shipped from the factory with a 4000 RPM spindle and tachometer. As an initial assumption, the machine should be able to reach whatever RPM the installed tachometer has as it's maximum speed, be it 2500, 3500 or 4000 RPM. It's just matter of what customer ordered.
    Cal? Your one was not a previous-owner shop-fabbed VFD conversion last time I looked?

    This one IS such a conversion. No longer relevant what the "first" customer ordered with DC drive.

    We do not yet know enough about it.

    We need:

    Motor nameplate nominal RPM (@ 60 Hz)

    Motor nameplate "do not exceed" RPM .. that will give us max safe Hz for the VFD.

    Both pulley sizes.

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    The point is, 2500 RPM, IS NOT the maximum SPINDLE speed on FACTORY round-dial 10EEs. To suggest otherwise is incorrect. If this machine shipped with a 2500 RPM tach, then then that's what the VFD drive should be tuned for, assuming that it still has the original belts/pulleys. (I don't think he said what RPM tach he has.) And yes, he CAN change the maximum spindle speed by changing the belt ratio. I wouldn't go above 4000 RPM.

    Cal
    ---

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    Quote Originally Posted by Cal Haines View Post
    The point is, 2500 RPM, IS NOT the maximum SPINDLE speed on FACTORY round-dial 10EEs. To suggest otherwise is incorrect.
    So just don't suggest otherwise. Why would one? AFAIK they've shipped with 6,000 and even 8,000 RPM. 2500 was just the more common for round dials. Loose too much torque to run a higher ratio for the needs of most tasking of that earlier era.

    Notice the move to the "small frame" Reliance 3 HP with about double the base RPM, then again to 5 HP motors with more that double the original 3 HP large frame base RPM?


    Not germane. This one is AC powered.

    The problem is the OP hasn't said anything useful AT ALL!

    The top speed of the drive seems to be much lower than what the lathe was designed to do.
    Lower than "designed to do..." 8,000 RPM? 6,000 RPM? 4,000 RPM? Or lower than 2500 RPM?

    "Seems" or measured?
    "Much" is how big a number?

    I say again.. we need:

    Pole count / base RPM of the motor?
    UNKNOWN

    Do-not-exceed RPM? - if even labeled;
    UNKNOWN

    Gearbox retained?
    UNKNOWN

    Spindle pulley size?
    UNKNOWN

    Motor/gearbox pulley size?
    UNKNOWN

    AC motor HP?(a 3/4 HP ain't gonna cut it..)
    UNKNOWN

    VFD utilized, IF EVEN there IS a VFD?
    UNKNOWN

    Actual max RPM being observed?
    UNKNOWN

    WITH that .. one can know the VFD / motor combo max safe shaft RPM. UNKNOWN.

    Then calculate the pulley ratio needed to hit the OP's goal of.. some OTHER RPM at the spindle. UNKNOWN.

    How much of that information do we have to work with so far?

    Wudja believe "ZERO"?

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    While .. awaiting actual nameplates and numbers from the OP, here are some "possibilities".

    Presume that in order to minimize conversion work:

    - the OEM 1942 gearbox was utilized,

    - that a new pulley was NOT fabbed,

    - and that it had come from the same 10EE it is in, now

    - and that 10EE had been one of the most common 2500 RPM capable 1942 Round-Dial. Or MAYBE a 4,000 RPM one?

    - presume also the AC motor is comfortable at a 90 Hz (150%) VFD "overclock". , but not presently being pushed to the riskier 120 Hz (200%) overclock.

    - ignore the 50 to 70 RPM "slip" for the moment, lets run simpler "close enough" numbers at "synchronous" or nominal motor shaft RPM.

    - also for simplicity, let's take the pulley ratio at 1:1. They aren't, exactly, but "close enough" where a 3 HP large frame @ its nameplate max safe 2400 RPM was to deliver a Field-weakened spindle RPM of 2500.

    Possible AC motors include:

    - two-pole 3-Phase, 3600 RPM nominal @ 60 Hz, 5400 RPM @ 90 Hz.. we need no go further. Even if seeking 4,000 OEM RPM, not 2500? He would already HAVE that. So the OP probably does NOT have a 2-pole motor.

    - four pole 3-Phase, 1800 RPM nominal @ 60 Hz, 2700 RPM @ 90 Hz, 3600 RPM @ 120 Hz.

    Possible choice. Common, even. But unlikely in THIS case. A VFD tune-up and he would be already be above a 2,500 RPM OEM with OEM 2,500 RPM pulleys. IF the OEM "donor" had been a 4,000 RPM machine and the same pulleys for that had been retained? 90 Hz would have put him above the 4,000 RPM spindle RPM as well.

    Just a guess, but I doubt he has a 4 Pole motor. Or he would not be complaining.

    - six pole 3-Phase, 1200 RPM nominal @ 60 Hz, 1800RPM @ 90 Hz, 2400 RPM @ 120 Hz.

    THIS.. smoother than 4-pole - is a "not uncommon" selection. Even so, it should be able to reach OEM spindle RPM of 2500 with pulleys from a 2500 RPM host, or 4,000 RPM with pulleys from a 4,000 RPM host with no more than VFD tweaking.

    Possible. If 6-pole it is? Just tweak the VFD.

    Now .. the most probable culprit after an under-tuned 6-pole?

    The smoothest at low RPM, rather UNCOMMON, but often CHEAP off eBay because the NEED for them is also uncommon and they do not sell as fast?

    8-pole, 3-Phase motor.

    - eight-pole 3-Phase, 900 RPM nominal @ 60 Hz, 1350 RPM @ 90 Hz, 1800 RPM if yah dare 120 Hz.

    Yaz, Marathon "Black Max" inverter-duty (and not only) with dataplates the size of a cookie sheet listing all their options, limits, and "goodness" can go waay faster.

    But if yah HAD one of those, AND any decent VFD? It already WOULD be going waay faster, yah?



    An 8-pole motor can be a challenge as to hitting OEM RPM with either set of OEM pulleys. Shop-fab motor/gearbox end pulley - and a BIG f**ker at that, 'coz yah can't make the spindle one a great deal smaller and still fit, and still carry useful power - is pretty much unavoidable with an 8-pole motor.

    UNLESS.. the person who did the original conversion was more into larger-diameter chuck and faceplate working, and NOT so much into smaller diameter higher-RPM collet-working.

    If best performance at mid and low RPM were all they really wanted? IF HSS/Cobalt were good enough, carbides less commonly utilized and not a big deal?

    Performance would have "been there", and smoothly, even when going slowly.

    Should the OP swap to some other OEM pulleys? Or make new ones in calculated "custom" sizes"? The math was never hard. Metal can be purchased in large diameters.

    All that can still be an AVOIDABLE pain in the ass?
    So I might not bother. Lazy Iyam.

    If your TIME is worth a damn? It could be faster, easier, not all that expensive... to change the AC motor instead of messing with pulleys at all.

    Given I have the spares to do it, no new out-of-pocket spend nor any fab work?
    I'd go back to OEM Dee Cee. End of AC and its fragile, complicated, VFD problems, altogether.

    Or.. even LESS work?

    Just run what you GOT!


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    Bill, Fourierseries asked a simple question: "Can I increase the size of the pulley on the gearbox or decrease the size of the one on the spindle to increase the rpms of this lathe?"

    Quote Originally Posted by Fourierseries View Post
    I have a 1942 round dial 10EE currently running on an AC variable speed drive. The top speed of the drive seems to be much lower than what the lathe was designed to do. Can I increase the size of the pulley on the gearbox or decrease the size of the one on the spindle to increase the rpms of this lathe? Could it be that simple? Any advice or opinions are appreciated. Thanks
    The answer is yes.

    All this other stuff is just noise and goes way beyond answering his question. It's a perfect example of why I get so many complaints about you. Please concentrate on being more concise.

    Fourierseries, If you have other questions about your VFD drive, please start another thread.

    Cal
    ---

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