source for big universal motors?

Discussion in 'General Electronics Chat' started by strantor, Jun 12, 2012.

  1. strantor

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    I've been planning on using a 3ph motor & VFD that I already have for my home lathe project. Problem is, I thought my VFD will accept 220V single phase; it will accept single phase, but minimum of 380VAC. So I need a big costly transformer after all. So I thought why not use a big universal motor? I think I can probably put an encoder on it, and design a phase angle firing power control circuit that will read the speed of the motor and adjust the applied power to maintain constant speed with varying load.

    I'm blanking on ideas where to get a large universal motor. I don't want to buy something brand new; I'm thinking what kind of machine uses one I could get for scrap price. A washing machine comes to mind, but I'm not sure if that's big enough. Anybody know generally what HP a washing machine motor is? I'm not sure how much HP I'll need, but I'm assuming (conjecture) that 3HP is about the smallest motor I could get away with. The lathe chuck + shaft weighs about 75lbs and needs to spin at least 500 rpm I think, plus I'll be adding additional rotating resistance later in the form of gears and a lead screw.

    Or if you have any other ideas (other than universal motor) I'm all ears.
     
  2. upand_at_them

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    Treadmill?
     
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  3. strantor

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    good idea, complete with speed control circuit & everything. IIRC from reading different treadmill troubleshooting threads here, the numbers I saw were 2HP. That might do, but not sure.
     
  4. #12

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    Wikipedia says you go from hand tools to locomotives in one step. Perhaps an elevator motor in between them. Looks like 3-5 hp universal motors are pretty rare.
     
  5. GetDeviceInfo

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  6. strantor

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    is that your auction?

    I've got plenty experience with powerflex and could probably have that set up in under an hour, but being as I don't have company funding, 260$ is a big number.
     
  7. strantor

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    perhaps a couple of these in series, mechanically coupled, with 220V across them? that would give me 3.5hp.
     
  8. BSomer

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    One note about the treadmill motor is that the majority of those I have come across are DC motors. If you do get the controller with the motor though I guess it is kind of irrelevant.

    Just so I can understand you better, what exactly is a "universal" motor?

    I may be able to come up with a drive for you that could need repairs. I'll have to check what I have on the shelf at work that customers decided not to repair and just left with me to do as I please. I'm guessing that going with a 3 hp motor and a single phase feed to the drive you would need a drive rated at least to 5 hp. True?
     
  9. strantor

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    yeah, DC if fine, even if it doesn't come with a speed control board. I just figured that a universal motor would be easier to find (cheaper) and easier to build a circuit for. I'd prefer to stay away from 12VDC stuff though if possible because of how many amps it's likely going to pull .
    basically just a series wound DC motor with low reluctance laminations so it can run on AC. universal motor. That what you'll find in drills, angle grinders, blenders, etc.
    Yes sir that sounds great, and 5hp sounds safe.
     
  10. shortbus

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    The one problem with a universal type AC motor is the high RPM. Even tread mill motors are high RPM ~7000. They do use a lot of treadmill motors in DIY CNC machines but them they can't use the same cutters or take very much of a cut.

    Look at work at the mills and lathes, the motors are only ~1725 RPM. and then they gear them down ~2 or 3:1. While a treadmill motor would be good for a wood working machine (needs high RPM) for metal working not so good, other than grinding.

    Washing machines and dryers for the most part have 1/3 -1/2 HP induction motors in them.
     
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  11. strantor

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    I've been going on the (perhaps mistaken) understanding that the HP of series wound motors was constant and the speed was inversely proportional to the load. So in an application like a mill, where the only load is a bit attached to its shaft, it would spin in thousands of RPM, but if you were to put a heavy load on it (or limit the power to it), it would slow way down.
    If I'm wrong about that, then I suppose I could always gear it way down, but that would probably require some good gears with high speed bearings (which I don't have).

    What type of motor would you suggest shortbus?
    I've tried looking at the motors on the mill & lathe at work but I would have to dismantle them to see the motor nameplates. All I could find when I googled the lathe is that it's got a 7.5hp motor, didn't say RPM.
     
  12. BSomer

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    I don't think that I have come across those before. Interesting motors though.


    I did look here at work and the only drives that I have are 480V. I have one that is 230V though it is just for parts if/when I need them. The main PCB has some serious damage to it, so it isn't really repairable. I can keep an eye out for one although most of the drives that I get for repair are repaired or totally screwed.
     
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  13. chuckey

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    how about a 110V 10" angle grinder, my one is 2KW ~ 3HP, but its a bit fast for you?
    Frank
     
  14. strantor

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    that's an idea, big universal motor. Probably the same as the table saw motor. It is up in the air now since recent comments by shortbus, as to whether it can be ran slow. I don't know, I'm looking into it.
     
  15. shortbus

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    A shopvac has a universal motor in it (or even most home vacs) listen to the speed they make. The treadmill motors have a brushed DC motor.

    Check the lathes at Grizzly tool heres one http://www.grizzly.com/products/12-x-24-Gear-Head-Cam-Lock-Spindle-Gap-Bed-Lathe/G4002

    Any commercial air conditioning companies in your area? A lot of times they will give you or sell cheaply a motor from an air handling unit. One like from a store will have a motor in the 2 - 5 HP range. The ones they take out from a retro-fit are scrapped. Check around those kind of places.

    What kind of bearings are you putting on your spindle?
     
  16. strantor

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    There's some old rusty 2" dodge pillow blocks bolted to a scrap machine outside with my name on them.
     
  17. strantor

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    Sorry for the partial reply. brain is in 3 places.
    have you used one? I've only just started delving into the world of hobby-sized/priced lathes and grizzly & taig are the 2 names I keep seeing. If my lathe project takes a turn for the worst I will probably start doing some consumer research on these. I'd rather build it if I can build it for less, and if not, I'd rather try to find a used American (south bend, et. al.) made one before I send my greenbacks off to taiwan. But if I cant find even that, then the grizzly does look pretty sleek for the price. (to someone who doesn't know what they're looking at - me)
    good idea. I'm sure I can find one in this metropolis.
     
  18. strantor

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    After 2 hrs of chipping rust and beating on stubborn old metal I got the bearings off. They aren't pillow blocks as I previously said. They're square flange mount bearings. So I got them off and got them cleaned up, only to find out that they're some stupid metric size (not 2") as the machine is french. They're 2.434" ID but sweet deal they came with an already hollow shaft and flange to mount my chuck on.
     
  19. shortbus

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    I just pointed you to the Grizzly site so you could get an idea on the motors that are used on "hobby" size lathes. That said I have one from ENCO that is very similar. But I agree with you on getting an old but still good USA one since I also have two of them. There should be at least one used machinery place in your area? With every one going to CNC, the manual stuff doesn't sell as good today. That makes things better for the home shop guy, cause you can get stuff reasonably priced.

    You got to watch what kind of bearings you use on a lathe spindle, to make a good one. Most times guys forget about the thrust/longitudinal force taking a cut puts on a lathe. So I was going to suggest using Timken style bearings to you. Doge does make some pillow blocks with timken bearings.

    How are you going to make all the other parts of a lathe? Bed, cross slide, carriage and tail stock? A older ready made one might in the long run be cheaper. Not meaning to shoot down making one(I love a challenge too). Ive made several machines over the years, metal cutting band saw, couple of belt grinders and others, but had full machine shop access. Boy I miss working. :(
     
  20. strantor

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    ah, gotcha. I totally missed the point and didn't even look what size motor the grizzly had :(. I'll check it out again.

    I haven't looked locally, other than craigslist. I saw an ad for a southbend lathe and a bridgeport mill together for 1500$ - compared to the prices I've seen on ebay, that's a steal even if they're in disrepair. But 1500$, steal or not, is just not possible.
    I'll post pics of the bearings later on get your opinion if you'll give one. In the application they were being used, they supported the lateral weight of a 200lb cast iron gimble, plus probably a 500lb reel inside.
    Every time this crosses my mind, my mind usually changes the subject. I guess that's not a good sign. I really don't know what order things are going to happen in, but I've got an old busted milwaukee mag drill I was also planning on turning into a mill. So I might get halfway through the lathe project, hit a wall, and have to start the mill project, and then hopefully I between the two half-ass machines I'll be able to fabricate parts for each until I have 2 complete machines. Also entertaining the idea of making them able to come together in such a way that the mill can be positioned over the lathe like one of these smithy machines. (in other words, I'm just going to "wing it", if that proves to be possible)

    specifically, for the bed, I was thinking an upside down piece of railroad track (already have) and the carriage could slide across it (somehow). For the carriage, I don't know. Might cast that (no, I've never casted before) or just mill it out of a solid piece of steel if possible. Same for the crosslide. When I think about the tailstock, my mind does a complete u-turn. I really don't know at the moment. I suspect the only is to cast it, but I think that would be a nightmare. Or maybe not. I could just use the lathe to mill it out, and it would automatically be perfectly centered ;).

    For just about anybody, that would probably be true. However I believe I am in a very small percentage of people who might just already have every part needed to cobble together a functioning machine. I've got one of just about everything, motors, gears, pulleys, belts, acme screws, slide bars, etc. Lets just hope I don't need 2 of any one thing :D.
     
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