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Thread: OK, dumb motor question coming

  1. #1
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    OK, dumb motor question coming

    Ok,

    so, here's the idea: take an underpowered but otherwise solidly built tool, and add a new motor. Like, say, this one:

    "Brand new
    Baldor 1 HP Electric Motor 1725 RPM CM3546

    Don't miss a great deal on this electric motor! Great for use with Pumps, fans, conveyors, machine tools, gear reducers and much more.

    Features:
    # Pressure cast aluminum end plates with ribbed design for rigidity
    # Ball bearings
    # Locked drive end bearing
    # Heavy gauge steel frame"

    Yes, well, but maybe I don't want to run it at 1725 rpm. Maybe that's just not my style.

    So I get to thinking (always dangerous!). What about one of them new-fangled router speed controls. Like, say, this one:

    http://www.mlcswoodworking.com/order.../speedcon.html

    with these features: "# Adjustable speed from 0 RPM to full speed
    # 3 position rocker switch- Variable / Off / Full Speed
    # Full power and torque at all speeds Go back and forth from any preset speed to full speed at the flip of a switch
    # Works with all routers 3-1/4 HP or less
    # 120V 15AMP "

    Hmmm... there *must* be a reason why this won't work, but I'm danged if I can figure it out. I know, I know... it's just another crazy idea. But why not, he asked, all innocent-like...

    Thanks,

    Bill

  2. #2
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    Hey Bill,

    This question comes up from time to time. It actually has to do with the type of motor it is. It sounds like you're considering an 'induction' motor. This type of motor operates a certain way.

    A router motor is what's called a "universal" motor. So named, I suspect, becasue they're able to run both on AC or DC power. They operate using brushes that need to be periodically replaced.

    The speed controllers are designed for use on universal motors only. That is, the speed controllers that you can buy for under 35 bucks that are used for routers. They make speed controllers for induction motors, but they're quite expensive.

    Basically the induction motor's speed is based on two factors: The frequency of the AC power (60hz, in the US) and the number of distinct windings. The latter is almost always 2 or 4 windings and is obviously not trivial to change. The frequency of the power is adjustable, but takes some fairly spendy circuitry to do so.

    The universal motor's speed relies mostly on the amperage being supplied to it. These speed controllers have a meaty rheostat that that adjusts this amperage. But, it also reduces the operating power of the motor as well.


    That's basically why it won't work, as far as I understand it. Hopefully someone who knows more than I do will come along and fill in any details I've missed.
    Last edited by Jason Beam; 06-13-2007 at 04:05 PM.
    Jason Beam
    Sacramento, CA

  3. #3
    Jason is right

  4. #4
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    Bill, you could probably pick up a used 3 phase motor and a VFD for it for about the same as a new single phase motor, then you have the ultimate speed controlled set up and no start capacitors to fail.

  5. #5
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    Gentlemen,

    Thanks for your replies. My first thought was: "rats!" My second thought was.. hmmm... I do have a router motor (I made the mistake early on of buying one of these: http://www.mlcswoodworking.com/order...marvel3hp.html ) And I loath the thing... I could take the motor out of that. But no... I'm not sure I'd want something that would spin at 26,000 rpm...

    Then I read John's post and thought... hmmm... but I don't even have 220 to the shop, much less anything like three phase. Then I started doing the research. I guess we're looking at something like this: http://cgi.ebay.com/3-HP-Rotary-Phas...QQcmdZViewItem
    to run a 1-2 hp motor. Then I'd still need a motor (yes, those seem cheap) and a VFD?

    Really, this is just research at this point. But I've been told the kind of drive that's on my lathe tends to give out after a while, and I'd really like the thing to spin down around 200, rather than the 600 present slowest speed. Still, it's starting to look like it might be cheaper to just buy new... Or am I getting something wrong?

    Thanks,

    Bill

  6. #6
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    The problem with using a universal motor and one of those speed controllers is that they cut the electricity to the motor, which means they have drastically reduced power in the slower speeds. You're not just slowing it down, you're also making it weaker. So the combination you're considering (and just about everyone does, at first) would yield a lathe that has no oomph when it really needs it.

    One other option that you may consider - and it depends on the size of your application, of course - is that many treadmills use a DC motor with variable speed on them. They're much much quieter running than universal motors and their controllers strive to provide adequate power in all speed ranges.

    This is the option I would explore if I were looking to convert my lathe to variable speed. Many folks have done so with salvaged treadmills that they got for free off craigslist or freecycle. The whole setup is included, which is what makes the treadmill so attractive. You just keep all the wiring intact and mount the motor.

    The biggest trick is converting the pulley/belts. My Jet mini happens to use a belt that fits into the grooved pulley on my salvaged DC treadmill motor. Lucky, no? :P

    Buying new, you will probably be better off buying a whole lathe attached to a fancy variable speed motor. But if you can find the parts surplus for a deal, then it can be worthwhile.

    Be sure to peruse http://www.surpluscenter.com/ a bit - they will give you an idea of what the surplus market prices are for some of the components. You'd need a DC motor (usually 90 or 110v) and a controller board for it. Preferably one with a built in potentiometer, otherwise you'll need that, too. The controller board will specify the correct "pot" to use.
    Last edited by Jason Beam; 06-13-2007 at 06:23 PM.
    Jason Beam
    Sacramento, CA

  7. #7
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    Quote Originally Posted by Bill Lantry View Post
    ...Still, it's starting to look like it might be cheaper to just buy new...
    I think you nailed it there, Bill. Sorta like putting a Formula 1 engine in a Chevy Nova. Overkill for the platform, IMHO.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

    workingwoods.com

  8. #8
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    Actually, what I meant was no phase converter needed, but you might need 220 single, depends on what kind of drives are availible. A VFD is a variable frequency drive, that will run an induction motor at adjustable speed by adjusting the frequency of the AC going to it. There are a lot of different ones out there for a lot of different uses, among them turning 220 single phase into 3 phase along with a variable frequency, real slick, but used to be too expensive to do for more than about 3 hp, but that may have changed for all I know. You might be able to find something along these lines to do 110 to 110 variable freq and just use it with your existing lathe motor.

    Just went and looked at some, 110V single to 220V 3 phase is do-able, if you ever change the motor, thats something to think about.
    Last edited by John Dow; 06-13-2007 at 07:07 PM.

  9. #9
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    Bill,
    I'm not sure exactly what you're looking to put that motor on, but you might be better off with the 3 phase motor idea. Depending on the tool and your ability to fab up mounts and such, you could go with a 1hp 3ph motor and a 115v VFD like this one http://www.factorymation.com/s.nl/it.A/id.193/.f. if you only have 115v avaliable. A 1hp 3ph motor should be cheap, check junk yards and surplus places along with the local classifieds. You can probably find one for $25-$50 if you look a bit.

    Mike

  10. #10
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    Dear John and Mike,

    I think this is seeping into my dim brain, but isn't quite there yet...

    With, say, a $50 used three phase 1 hp motor, and this guy:
    I'm home for this side of $170. plus wiring and some way to spin the pulley?

    By the way, Mike, I don't know if the people here have seen the kind of work you do, but I found this on your site:

    http://members.cox.net/toupink/graphics/cradle04.jpg

    Very nice!

    Jason's idea is also attractive... I can't believe I gave away a treadmill a few years back...

    Thanks,

    Bill

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