electric motor

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charley Leight

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Hi!! I am new I have been considering building a cam grinding machine project, have a question on motor to rum the grinding wheel. I don't want to go big for weight. a 110 volt 1/3 hp. 1750 rpm I was considering. I am having some difficulty finding what I was looking for maybe I have been to fussy. Any suggestions would be appreciated. I have looked at some of the work and projects members have done. They are built with love and knowledge. I am still learning at 75 and I love it. keep up the work. Charley
 

Tim Wescott

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Unless you're sticking on wanting exactly 1750 RPM, that should be almost as common as dirt. What you're really looking for is "a bit slower than 1800 RPM", because that's how those induction machines work. You probably want to settle for a nameplate RPM anywhere between 1700 and 1800.

Granger has a ton of them, but even here in Oregon, which is a no-sales-tax state you need a commercial account with them: https://www.grainger.com/category/motors/ac-motors?attrs=HP|1/3~~RPM+Range|1,701-1,800&filters=attrs. It may be worthwhile doing a web search for industrial supply houses in your area, or if you have any friends associated with a small buisiness that might have an account with Granger, get one through them.

McMaster-Carr has them, but they're The Most Expensive Source of Stuff on the Internet -- shopping around will definitely benefit you. But now you know they're out there. You might try MSC as well -- they usually have what McMaster has, only at a (generally) significantly lower price, more chance that it's from India or China, and slightly less immediate availability.

I got a ton of hits on eBay, but that's not the sort of thing I'd trust eBay for. Craigslist an Facebook Marketplace will probably be good for stuff that may have the motor in it, but then you'll end up with a perfectly good table saw or industrial sewing machine or whatever that just needs a little bit of TLC before it's perfect, and you won't be building engines for a while.

Or look for a clapped out table saw, or, or, or...
 

charley Leight

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thanks Tim. the rpm was a figure pulley size can change the rpm. the pictures don't always relate to dimension size of the motor. But I may have to accept the size to get the good results. Thanks I will eat the extra weight. I have had really good results with purchases from e-bay. Any thing used is a gamble. There was a few new units I'll check them out. Thanks again
 

pat_pending

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Hi. There’s always a big selection of motors on Machine Mart (Harbor Freight I think it’s called in your neck of the woods). Lots of pulleys and stuff to match I seem to recall. Else fleabay is definitely your friend,

Patrick
 

almega

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Referring to Grainger, you do not have to be a commercial account to buy from them but they are pricey. They have a less commercial entity called Zoro, where you could purchase a 1/3 hp motor like you need for reasonable pricing and in some cases you can get free shipping. Just go to their online site (Zoro.com: 1,000s of Brands, Millions of Products) and search for what you need. You might also check craigslist for used motors that would fit your needs.
 

ignator

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You can find these on ebay, but searching keywords need to be thought through.
I searched for "induction motor 4 pole", which brought up many hits. (4 pole gets you RPMs in the 1800 range). Then 1/3HP is 250watts, so keep that in mind.
To zero in on your motor, you need to reduce the category that ebay is searching through to "general purpose industrial electric motors". Then it's easy to find something in your $ range and motor specifications.
Note that my example with 4 pole has to be in the description, and not all sellers put the correct detail in their titles. So try other keywords. These words really can point you down the wrong 'rabbit hole' fast. My search for AC induction motor came up with total different results, and much higher prices.
 

Gordon

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I would try Craigslist. 1/3 HP NEMA 48 frame electric motors were common on many of the older furnace blowers and even older washers and dryers. That category should be cheap. If this is just for personal use who cares?
 

almega

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I would try Craigslist. 1/3 HP NEMA 48 frame electric motors were common on many of the older furnace blowers and even older washers and dryers. That category should be cheap. If this is just for personal use who cares?
I believe this was to be for a grinder and if that is the case, an open frame motor such as a furnace or washing machine motor would not be advisable. Grit and metal grindings could get inside and cause catastrophic damage. A totally enclosed motor would be more appropriate. I have seen good used ones on Craigslist for $35 or new could be purchased for $150-$200.
 

Tim Wescott

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Oh, now what could possibly go wrong with filling an electrical device full of metal powder?
 

almega

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Oh, now what could possibly go wrong with filling an electrical device full of metal powder?
Good point. The fireworks might be fun to watch.
1614125353623.png
 

almega

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All kidding aside, for most applications in machines, TEFC motors are the best for the applications. My old lathe does have an open frame motor, but it is protected from actual shavings. When it fails, I will replace it with a TEFC motor. All other stationary motors in my shop are totally enclosed.
 

awake

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Hmm ... certainly there is no doubt that a TEFC is the best choice in a metal shop. But I'm going to take a contrarian view here.

With regard to sparks and fireworks, I'm not sure how that would happen with an induction motor, unless you left open the box or plate where the connections are made - nothing else is going to expose un-insulated electrical current. The concern I would have is not sparks and fireworks, but rather grit leading to premature wear of the bearings.

But even that may be a solution in search of a problem, in actual practice in a hobby shop, so long as reasonable precautions are taken. Two personal examples:

1) I have been using a washing machine motor to power my home-built grinder for 15 years; no problems yet. Of course I didn't leave it completely exposed; I partially enclosed it to keep out the majority of the grit. If it burns up tomorrow, no worries - the original motor cost me $0.00, and I have two more just like it in the drawer, both of which also cost $0.00.

2) I acquired my Cincinnati 12.5 x 30 TrayTop lathe with a re-fitted single-phase motor - an ancient repulsion-induction motor. If you are not familiar with this type of motor, it uses a starting circuit very different from the usual split phase or capacitor start; rather it is a system that vaguely resembles a universal motor, with brushes - only in circuit until the motor starts. Part of this design is that one can reverse the motor by rotating the position of the brushes - which means that there is an opening in the motor with a lever to connect to this starting circuit. Surely this ought to be a disaster waiting to happen - not just an open-frame induction motor, but one that uses brushes, powering a lathe off of which comes all sorts of metal slivers. Perhaps it is ... but I've been using it for 20 years now, and I don't know how long it was used before that ... and so far it is all going strong.

Again, I certainly cannot contest that a TEFC is the best option. But given the number of 1/3 and 1/2 hp motors that get thrown out every single day, it seems a shame to me not to give them a chance at a second life, even if that second life might be measured in a just a few decades ... :)

Here are a couple of pictures of the grinder to show the motor and how it is partially enclosed - open at the bottom for ventilation, but no easy way for grit to get into it:

Picture13.jpg
Picture16.jpg

And here is an image of the lathe motor - it is labeled "Motor repair" because I had to fab up the reversing lever and rewire it for 110, but no other repair was actually involved. The closest end in the picture sits just to the left of the chuck, about a foot down - totally exposed! In my case, this is a TEFC = "Totally Exposed Fan Cooled." :)

Motor repair 4.jpg
 
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Gordon

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I also have an open frame motor on my belt sander. It has been working for probably 10 years. Being a home shop it does not get a lot of use but it gets run 2 to 3 times per day. The only thing I do is keep an eye on it and blow it out from time to time.

An interesting note: I just looked on Craigslist and some folks are nuts. Who is going to pay $175 for a used blower motor? In the same search it came up with several furnace blowers for $30 each and a new 1/2 HP for $75.
 

EMF

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you could also consider a DC PM (Direct Current, Permanent magnet) motor. You would need a speed control but I have them on my small bandsaw and a grinder and they work fine. Motors on treadmills are heavy duty and usually cheap (free if you find a treadmill). I put a 1/2 horse DCPM motor on my bandsaw with a reduction drive as an experiment and the variable speed was great.

Using open frame motors on wood machines is done and usually you can get decent life out of them but metal dust environments can get exciting. Metal dust getting into an electric motor cause a number of faults. First is the metal dust gets into the centrifugal switch ( on all single phase motors) in the end bell and when that happens and the switch shorts closed, the start windings do not disconnect resulting in all the factory installed smoke escaping from the start windings. Second is the bearings altho most motors have double sealed bearings so this is less a problem than you might imagine. The last is related to the fact that a motor is a big electromagnet when running. The iron filings begin to build up like they do on any magnet and if they build up between the rotor and the stator and you begin to grind down or lock up the rotor to the point that either the motor will not start or the gap between the rotor and the stator get wider and hp goes down. Once you grind this gap, its goodbye motor.

I saw a lot of open frame motors and none that I got from a metal dust environment survived. Use a TEFC (totally enclosed fan cooled).
 

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