Import Motors - Your Experiences?

[Frank Hagan]

In my quest for a new DC, I've run across a few comments from people about the import motors. One person said they had trouble with import motors on Grizzly equipment (specifically a table saw purchased a few years ago), while another had bad experiences with some Jet and General motors.

My Jet table saw is still running fine with its TEFC import motor in its fifth or sixth year, so I'm not really that gun-shy. But I was wondering what your experiences are with the motors on Grizzly equipment especially, and then also generally on other import equipment.

I'm already busting the budget on my plan to buy either a Oneida 2 HP DG or a Grizzly G0440, but Oneida has an upgrade path to a Baldor US made motor for another $150.

[Dev Emch]

Most import motors come from semi automated, overseas plants and are made as cheaply as possible. I personally consider most of these junk and when issues show up, it costs me in terms of my time (time == $MONEY$) to resolve their issues. I personally can no longer afford to track down and debug their problems. So usually pursue Baldor or Seimens when buying new and I prefer the Louis Allis DMD types when restoring old iron. Its a formula that works for us.

[Frank Hagan]

During the early 1990's, I dealt with the move from US manufacturing to the maquiladoras in Mexico, and it was a mess. Magnetek, AOSmith, Century and Franklin were all having all sorts of problems with quality issues. They eventually sorted themselves out.

Around that same time, there was an exact copy of an AOSmith design, at least cosmetically, coupled to an exact cosmetic copy of one of our pumps (they even copied the defects in the older mold we had). The motor was absolute junk and unsafe, but my experience with the import motor on my Jet table saw has been very good (as all the rest of my tool motors have been).

Does anyone compile stats on failures on these motors?

[Steve Clardy]

Only one problem with an import motor over the years.
Off-the-wall drill press I have, motor smoked. Got to squeaking, then let go. Come to find out it didn't even have a lower bearing in it. Shaft was fitted to the end cover. Replaced it with a dayton motor 1hp.

All my other equipment, 3 griz included, never had any bad problems.
I just did replace the centrifugual switch on the motor on my griz 1023 cabinet saw, after 11 years.
I'm happy.

[Mark Rios]

I just did replace the centrifugual switch on the motor on my griz 1023 cabinet saw, after 11 years.
I'm happy.


Wow...11 years on the 1023? that's a real saw. I'm really impressed. That puts Grizzly up another couple on notches in my book. I didn't realize a (seemingly to me) mid-price saw would have such longevity. Shows what I know. :D Makes me want to upgrade more now. I'll have to wait till after my BS and Jointer purchase though.

[Dev Emch]

Wow...11 years on the 1023? that's a real saw. I'm really impressed. That puts Grizzly up another couple on notches in my book. I didn't realize a (seemingly to me) mid-price saw would have such longevity. Shows what I know. :D Makes me want to upgrade more now. I'll have to wait till after my BS and Jointer purchase though.
Mark... Some of the old US motors are like Diesel Engines. They take a licking and keep on ticking. 11 years on a Louis Allis motor doesnt even show wear! I have seen GE motors used in early 1914 wallace jointers that are still running like a clock today. Just needed a drop of oil and a clean out. Since these older single phase motors were repulsion motors, you get some brush dust on the inside that needs to be cleaned out. The brushes were still serviceable and the commutator was factory new. Did not need to be turned and slited. My oliver jointer has a delta wind, 10 HP, 440 volt Louis Allis and the stator windings are mint and original!

My 1951 DeWalt RAS has a 7.5 HP motor which was under water for a few years. The bearings were shot and I needed to do a skim cut on the lower 1/3 of the rotor to remove about 9/10 ths of 1 thousandandths to true it up. The stator pack was steam cleaned and then baked out in my kitchen oven overnight. Installed new bearings and hooked it up. I figured that the stator windings were a gonner and I was prepared to fail my growler test and drag out the check book for a rebuilt motor from Wolfe or Original. NOPE! The motor jumped to life and purrrrrrssss ohhh sooooo smooth. Being careful on the rotor work on the metal lathe helped keep everything in crisp balance. But the stator windings were just fine after the steam cleaning and bake out. The DeWalt motor is unique which is why you just cannt slap any old motor into one of these saws. Hence the effort to rehab the old one.

I have rewound a few three phase motors and have been impressed by the quality of the older US motors. The single phase motors dont rock my boat because they tend to be a bit kludgy and often have what is called a tein winding (sp?). I dont know how to do tein windings and have no ambition to learn.

[Steve Clardy]

Wow...11 years on the 1023? that's a real saw. I'm really impressed. That puts Grizzly up another couple on notches in my book. I didn't realize a (seemingly to me) mid-price saw would have such longevity. Shows what I know. :D Makes me want to upgrade more now. I'll have to wait till after my BS and Jointer purchase though.

Yes. Used daily in my cabinet shop.
1 on=off switch
1 set of belts
and the centrifugal switch on the motor. [IMPORT motor]:)

[lou sansone]

any folks out there that work in the motor rewinding business. I think they would provide some good insight into this question. Even with domestic mfg there is a large variation of motor quality. Going further, even with the same mfg ( say reliance ) there are a variety of grades of motors.
lou

[tod evans]

i do not work in the motor industry but i did pay an old guy to educate me for a day several years ago.....in a nut shell he told me that the varnish used on the windings is what will make or break a loaded motor. if a person runs a motor at 70% or less of its rated amp draw even the cheep taiwan motors will be long lived, but the fellow who works his equipment will be best served by a motor constructed with high quality componants.

[Curt Harms]

I'm doing this from memory. Forrest seems to know what he's talking about-had a series of articles in a home machinist magazine that got good reviews. The gist is that import motors sometimes omit the final varnish dip & bake step.The wires of the windings vibrate, rub thru the too thin varnish, short out and that's it. His recommendation was to partially disassemble the motor and if you can get a thumbnail to move a wire in the winding, have it dipped & baked by a motor shop.

Again, I'm doing this strictly from memory.

Curt

[Ken Garlock]

Curt, I believe you have the correct information from Forrest Addy regarding additional varnish on the import motors. I don't know that Forrest ever gave an estimate of the cost of having the motor 'dipped.' However, it must be less than a new motor.

[Jim Becker]

This is a subject that is so easy to generalize...the source of manufacture isn't what is important. The quality and ratings of the particular motor is. And consider the warranty, too. I have never had a problem with the motors in any of the motors on the Jet, Grizzly or Delta machines I have owned. Do I prefer Leeson or Baldor or AEG (what is in my Mini Max machines)...yes...I know that the particular versions of these motors in my shop are really good. But even these companies make lower-end products... ;)

[lou sansone]

This is a subject that is so easy to generalize...the source of manufacture isn't what is important. The quality and ratings of the particular motor is. And consider the warranty, too. I have never had a problem with the motors in any of the motors on the Jet, Grizzly or Delta machines I have owned. Do I prefer Leeson or Baldor or AEG (what is in my Mini Max machines)...yes...I know that the particular versions of these motors in my shop are really good. But even these companies make lower-end products... ;)

that was exactly my point and why I hoped someone who works in the motor rewinding business would weigh in on this topic.
regards
lou

[Frank Hagan]

This is a subject that is so easy to generalize...the source of manufacture isn't what is important. The quality and ratings of the particular motor is. And consider the warranty, too. I have never had a problem with the motors in any of the motors on the Jet, Grizzly or Delta machines I have owned. Do I prefer Leeson or Baldor or AEG (what is in my Mini Max machines)...yes...I know that the particular versions of these motors in my shop are really good. But even these companies make lower-end products... ;)

I think you're right on this. My experience with motors in the swimming pool pump industry was that manufacturers had several different price points for motors, with different ratings, etc.

In my research on cyclone DCs, it looks like only Oneida and Grizzly are offering class F rated insulation motors (rated at 311F ambient temperature), and most others are offering motors rated at class E (insulation rated at 248F ambient). Surprisingly, Jet's new cyclone dust collectors have just a class A rating ... 104F ... according American Woodworker.

My understanding is that the varnish on the windings is one of the elements that contributes to a higher insulation rating. So maybe the motors with an "F" rating have a higher probability of having the windings protected better.

Oneida says they have a two year warranty on their DG; does anyone know if that includes the motor? I suspect it is a standard 1 year warranty.

[Don Baer]

OK having worked in the motor and control industry for over 30 years I have found many instances where people simply don't understand about motors and there temperature rating. Rather then writing a tomb on the subject I'll just post this link for those who are interested in the subject.

http://www.motorsanddrives.com/cowern/motorterms4.html

If after raeding the link anyone has any further questions I'll be glad to anwer them.

[tod evans]

thanks don, very well written article.

[scott spencer]

I suspect all of the motors on my wwing equipment are imports. I've had no problems to date with any of them, but I'm a weekend warrior too, and don't put a ton of hours on them. Grizzly 2hp DC, Grizzly 1hp jointer, Craftsman 1-3/4hp TS, 1/2hp BS, DP, mortiser and sander. All ~1-5 years old.

I did have a centrifigal switch stick on an American made pump motor that was two years old a while back though. ...I suppose the switch may have been imported...:rolleyes:

[Dev Emch]

In my previous life, I worked in hydro power. Namely, smaller horizontal type plants still run today. Even had a chance to help restore the power plant used by Mr. Stanley to run the first electrified resort mountain hotel. That was the hotel used in the filming of The Shining.

My electrical engineering training was in power. And I have tons of experience working with controls and some rebuilding of three phase machines. As said, I understand the principle of tein windings for single phase but would rather not deal with it. When a single phase motor goes south, just buy a new one.

When motors of the same HP get smaller, they get harder to rewind. They also use thinner gage wire if possible. This allows the builder to stuff the coils from the various phase groups into the stator slots with greater ease. But the penalty for the thinner wire is NON-CONTINOUS duty cycle which means that the motor must be run for no more than its duty cycle before it must be shut down and cooled.

Here is an excerpt from my motor repair supplies catalog (Essex Brownell) regarding extra stator insultation.

* Purpose of Varnish and Varnishing Systems.
1). Bonding the wire together to form a solid mass.
2). Healing wire damage due to handling and winding.
3). Providing chemical and moisture resistance.
4). Adding additional insulation from wire and from metal.
5). Sealing the unit to resist moisture, dust and chemical contamination.
6). Preventing rust on metal parts.
7). Filling the voids in the slots, between layers of insulutation, to promote better heat transfer.

As most of you know, its not the voltage or the power that hurts you, its the amperage. All wire size is size according to how many amps it can carry and pushing to many amps will overheat that wire. It has nothing to do directly with voltage or power althrough its all related. So if I converted my house to run on 220 volts instead of 110 volts, I could reduce the size of wire used to wire the house. One reason the europeans use 220 volts.... to save precious copper.

So in order to run a motor hard but keep it cool and allow it to run continous, you need to get the heat off those stator windings! That is why the older machines had much larger motors and why the Louis Allis motors I have worked on have FAT windings. Deeper stator packs and cast iron housings also help here as do ventilated stators. So bad is the removal of stator winding heat that on some of the alternators I have seen, the windings were hollow and water cooled!

Heat is the arch enemy of all motors because it ruins your stator winding insulation. Here is a good rule of thumb worth keeping in mind. EACH TIME YOU OVERHEAT YOUR MOTOR, YOU REDUCE ITS EFFECTIVE REMAINING LIFE EXPECTANCY BY HALF. So given a motor with 100 hours of life expectancy that is overheated once but still works, your now down to 50 hours. Pull that stunt again, and your now down to 25 hours. Then 12.5 hours and so fourth.

So Todd's comment about pushing motors to 70 perent is right on the money on both points. Learning to rewind motors is not something you learn in college or even todays tradeschools. Its knowlege gleened from old timers and its a dying artform.

As to Forrest's comments on chafing. That to is correct. The insulation on motor wire is very thin and delicate and easy to damage. Most motors under 10 or 15 HP do not use preformed coils. The coils we put into those 30 to 60 KVA alternators were preformed. Double Diamonds. You wind each coil in a coil form and then wrap the coil with glass tape and then impregnate this tape with an expoxy varnish. These coils are then inserted into the stator slots and then dozens of connections are made to hook up each final phase group. All connections are covered with glass tubing and varnished.

Smaller motors like a 5 to 15 HP motor are different. Here, you wind each phase group as a unit lightly taping each coil together to retain the wires. Each coil is round and loose. You then insert a piece of insulation into each stator slot using something like fish paper. Then, using a poking tool, you work each coil into the bottom of the slot that goes in the bottom. At first, only one side of the coil is inserted. Depending on how many poles you have, you need to work one sided coils until you can insert the top of a predessor coil. So each slot contains two coils. One on the bottom and one on the top. Their position depends on how many coils are in a group, how many turns to each coil, how many slots your stator has and how many poles your motor has. Exact information about this can be found in Robert Rosenbergs book Electric Motor Repair.

As I work my way around the stator, stuffing lower and upper coils into the slots, I have wire hanging out both ends of the stator. These are the coil loop ends. Each time I complete the filling of one stator slot, I drive in the stator retainer wedge. In the old days, these were made from wood. Today, you see wood or plastics of various sorts. A leather mallet amoung other hand tools are used to artisticly mould the coil loops into a similar looking shape found on the double diamond preformed coils. Then these loops are often tied off using a nomex thread product.

So the working portion of the coils are packed so tightly into their slots that any vibration chafing is virtually impossible. But the mallet formed end loops are an entirely different story. But when all is said and done, does it matter where a coil failure occurs? A failure is a failure. So by dipping and baking the stator into varnish, you create one homongenous mass of wire, stator plates and fish paper that is almost water proof and not going anywhere and can transmit extra heat from the coil loops to the stator plates where it can be removed quickly.

Another thing to consider is the rotor. Rotors are both simple and complex. They are made by packing cookie like discs together on a rotor shaft. These discs are covered with an electrical insulation to reduce the size of inductive eddy currents within each of the discs. If those eddy currents can circulate in more than one disc, the temperature goes up. This is how induction furnaces and inductive bearing heaters work. They use the principle a bit differently to maximize heat whereas the motor's stator and rotor packs use the principles to minimize heat.

There are either grooves, slots or holes punched in these cookies or wafers that are lined up during assembly. The assembly is then placed into an injection moulding machine that injects molten aluminum into the mould. The aluminum fills these slots or holes forming the venerable rotor bars. But it also creates the front and aft end caps for the rotor which frequently also contains the cooling fan blades. Some rotors have cast in place cooling fans whereas others have fans that attach to the shaft with a set screw. I have seen both.

When these rotors are taxed beyond reason, some bad things can happen. First, if a rotor contains a bit of moisture that has worked itself between the wafers, very low freezing temperatures can exapand these wafers as freezing water expands. This can POP the connections between the rotor bars and the end caps taking the rotor bar offline. The disconnect is fracture in the injected aluminum. Clearly, the rotor is ruined. The effective way to determine how good your rotor is is to have a growler test done on it.

Another failure I have come accross is rotor wafer delamination. Here excessive heat expands the wafer pack and this also causes a fracture in one or more of your rotor bars. I personally have not seen this but have been explained this by Jeff M. whose family owns northfield woodworking. Apparently, some of the #4 table saws that were shipped with Doerr motors and were run very hard and put away wet had this failure. These saws were being used with power feeders as striaight line rip saws feeding a bank of heavy duty moulding machines (moulders). They were cranking out thousands of feet of moulding per day. The saw motors were just not up to it and the rotors failed.


Should you be worried with your grizzly table saw? Not really. A table saw used in a cabinet shop or more so, in a hobby shop never sees the violent use that some motors do. The more important thing is to make sure that your heaters are up to the task. Here, should you leave the lock pin in the arbor shaft while changing blades or if you get a hunk of lumber jammed into the saw that it creates a ROTOR LOCK UP condition, then your motor is at risk if the safety system does not take it offline. Of course, if your using your tiny table saw as straight line rip saw cutting teak or koa with a power feeder, you may need to call papa grizz and order a new motor.