Thread: Lathe has burnt-out motor

i am there.. my motor still works but it eats capacitors real fast. It don´t line up no matter what i do, it don´t give me the 2000 rpm´s any more, i wobbles like hell... I have been looking at the cost and the time i had to spend on getting things to line up, and run smoothly. I also looked at how good i would be able to get the late running with my metalworking skills. I ended with making the decision to buy a better lathe.
I have gone all the way because i have the money to do so, but if money had been an issue i would still have bought a better lathe, something used, something smaller, but something that didn't eat 50% of my time in repairs. I want to turn wood, not make machines...
I don't know if you have access to a better lathe or have tried something better, if you haven't i sure someone on the forum will help. (you can come try mine in denmark i 3 weeks)

So my advice would be save the money (quick) and get something better, a small jet or vicmarc or what ever, get something used thats i working order...

Well after taking the lathe to a motor rewinding place, got the worst possible news, the starter windings are burnt out . I had thought and stated in a previous post that the capacitor had failed me, maybe it triggered this problem, don't know. To fix the motor, minimum $250. A new motor from Hare and Forbes would be $165 when they're in stock. To install a better motor would cost upward of $350 (most of that is labour), reason being that the current mount is all wrong plus the Reeves pulley that the WL 18 operates on has a long shaft, so it would need the motor to be taken apart and a new shaft machined in. Carbatec have the MC900 with a 3/4 motor for $148 for what is really the same machine.

Interestingly both motor places that I took the motor to said that it was a poor motor just by looking at it and stated that it would be more like 1/2 HP than the 1 HP that it claims it has.

Leaves me a bit at the crossroads, my lathe has given me more trouble than any of my other tools and consumed more time fixing/modifying it than anything else. Feel like dropping woodturning and concentrating on other areas. Am a bit too depressed at the moment to think straight but would like to hear from anyone else who has been through this, I would like to know how hard they found it to change motors, would you bother or just save up for a better one if you wanted to continue turning?

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Tiger,
This is the problem with clones......... I have a MC1100 and very quickly I realised that it was not so crash hot.It ran so hot I could not leave my hand on it.

If you can get a motor for $148 take it. This is a good price, I realised when I pulled mine down that the long shaft was going to be a stumbling block. So as soon as it was feasible I went over to a 3phase motor with variable speed.

What you can do when install the Carbatec motor is cut away the grill on the fan at the back of the motor. Don't touch the cowling just the grill. When you have done this it will increase the air flow over the motor body.

Then take some light sheet metal or cardboard and fashion an extension of the existing cowl further down the motor body. This will force the air flow around the body. Leave about a 10-12mm gap to give the air a chance to flow.

Ask Carbatec if the new motor has a ali body to it. As the earlier models did not and had a bad habit of burning out. So they changed the design to a ribbed or finned body out of cast ali on the outer casing. If so, then you will most likely not have to do any mods to it.

The only thing I used to do was make sure the dust and chips etc were swept off the motor so as not incourage any extra heat build up.

how long is the shaft from the motor endplate?

I had two old matching tanners for a while but in the end I realised it would be cheaper and easier in the long run to buy a newer well supported second hand machine. In the end I ended up with a 5 year old teknatool lathe. For around $600 or so. Next step is to build a lathe stand for it and get it off the floor and into being used. I think Teknatool is such a great company that if one of their motor burt out they would make sure I was well looked after.

Killerbeast, it is so frustrating, you buy a machine and just spend so much time adjusting it so that you can finally use it for what you bought it for which is turning wood. If it's eating capacitors fast, you may need to try a higher rated capacitor, that's what one motor place told me today.

Hughie, you're right about these clones. The H and F motor is rated 1 HP and the Carbatec is rated 3/4 HP, do you think the Carbatec one would fit my lathe no problems and have you a picture of your set up where you cut away the grille?

Bob, the shaft protrudes about 100 mm.

Kiwi, will now gladly pay $600 for a better lathe but I will have to sell some things first in order to pay for it. I'm considering selling my diy, woodwork and metalwork books to help finance this.

Be carefull with the bigger capasitors, might burn out the motor... Well i am in the process of spending way to much money on a bigger lathe (Jet/powermatic 3520B) so im set. The old one might get converted into a disksander/buffing station might just be sold..

I have a WL18HD that i am changing to EVS in about 3 months. The motor on it now will be for sale then.

Also i think the Hafco has the motor on the other side o the other mc900

Tiger, the motor will be a switched cap start type by the sound of it. They have a set of run windings which do the normal work with the motor, plus a second higher current winding set, which connect via a capacitor and an output shaft activated centrifugal switch. This is the start winding.

With a three phase motor there are three sets of windings, which produce a rotating magnetic field around the motor armature (core around the output shaft). With the rotating field, the motor is guaranteed to start and run in a particular direction when powered up.

With a single phase motor, there is an alternating (not rotating) magnetic field from the run winding when power is applied. This will make the shaft buzz and rattle but not rotate. If the spindle and hence the motor shaft can be given a brisk part turn immediately before or during switch on, the motor should start and run in the direction it is lead. I think that I recall earlier posts from you a fair while ago about the motor indicating the stall/buzz issue.

The start winding connected through the start cap and switch generates a stronger magnetic field than the run winding, and offset from that of the run winding. This effectively simulates a multiphase system and kickstarts the shaft in the correct direction. Once kickstarted, the motor should continue to run until switched off.

Because the start winding is only needed for a very short time to kick start the motor, it is connected through the centrifugal switch, and typically is disconnected once the motor achieves about 50RPM. The start winding is often formed with the same size wire as the run winding, but much fewer turns. This means that it draws a lot more current than the run windings, but is normally only active for less than 1/2 second, so does not get a chance to overheat. The capacitor has two roles, it helps limit the current in the start winding, and reacts with the winding to introduce a phase shift or offset into the magnetic field, relative to that of the run winding. The greater the strength and offset of the start winding, the greater the kickstart effect and the better the motor will start.

To burn the windings there are a number of possibilities.

If the capacitor fails to low impedance, the start winding current increases accordingly but the kickstart effect reduces because the phase offset reduces to near zero. The motor might start unloaded but start will be sluggish so the centrifugal switch will not isolate the winding within the intended time. The result will be a toasted start winding.

If the motor is stalled due to overload when starting, the cap will still supply a phase shift and the motor will try to start. If the stall is allowed to linger, the cap will be damaged due to overload, and will create winding damage on subsequent start attempts even if the stall has been cleared.

If the cap fails to a high impedance, it will limit the current in the start winding and protect it, but the motor will buzz and not rotate on startup. If this is allowed to continued for long, or through a series of closely timed short attempts at starting, the run winding can overheat and be damaged.

In your situation, you should probably assess the machine as a whole. If the rest of the machine is fettled to be adequate for your current and future needs, I would suggest rewinding the motor rather than transplanting another motor, even a new one from from a similar machine.

The primary difference between a motor costing $x dollars and an apparently identical one costing $2x is either quality or margin. Because the Chinese are masters of the art of reducing costs to a minimum, they will often scimp on winding sizes, insulation temp, etc to produce the cheapest possible unit that will work under average conditions for the warranty period. Replacing the motor with a very similar one may result in better, worse, or similar reliability, depending on the manufacturers cost base for the production run. This is very difficult to assess prior to using the unit for an extended period.

However, if a rewinder is confident enough of the outcome to rewind the motor, they generally do so to industrial standards and the unit is normally significantly more reliable than the original. From that perspective, rewinding the motor is often the better alternative to replacing with another Chinese one. However the cost effectiveness overall depends on your assessment of whether you would be better to dispose of the lathe and upgrade, or retain and reburbsh the existing unit.

Hughie, you're right about these clones. The H and F motor is rated 1 HP and the Carbatec is rated 3/4 HP, do you think the Carbatec one would fit my lathe no problems and have you a picture of your set up where you cut away the grille?

Bob, the shaft protrudes about 100 mm.

Tiger,
If the shaft is the right length, as this is the bug bear on the MC motors.Carbatec hopefully would be able shed some light on the motor suitability. ie motor mounts etc

Pics, will try and get some up before the weekend, after that I am gone for a week. yeeeehaaaa north queensland..........warmth

Originally Posted by Tiger

Leaves me a bit at the crossroads, my lathe has given me more trouble than any of my other tools and consumed more time fixing/modifying it than anything else. Feel like dropping woodturning and concentrating on other areas. Am a bit too depressed at the moment to think straight but would like to hear from anyone else who has been through this, I would like to know how hard they found it to change motors, would you bother or just save up for a better one if you wanted to continue turning?

Hey tiger, before you tie a cement block to it and push it off the bridge??? I was at the same crossroads a number of years ago...... a wise old(er) friend of mine heard my complaining and asked me a very simple question..."if you treated your wife like you have treated that lathe, what would she do"?? I looked at him kinda funny and he reminded me about the 12 kilo chunk of walnut that I had to turn outboard because of the size...and all of that weird, off center stuff that I love to work with......needless to say, I don't look at my table saw or my lathe the same way anymore....all of that being said, I am in the U.S. I have a motor I am willing to donate to your cause, here is the bad part I am sure...this motor is wired 120/220 Volts, 60 cycle AC, SINGLE PHASE.....you haven't really said but I am thinking you need 3 phase?? And I am also thinking the voltage "down under" is something other than 120/220??? The good news is, I still have a 3 phase motor sitting in limbo in a friend's shop. I took it off of a piece of equipment that I had purchased, he runs 3 phase, he has it sitting as a spare. If you would be willing to pay parcel/postage/shipping, I can get some particulars....As I recall, it is a Rockwell motor with a flat foot/mounting bracket on the side of the housing....holler at me, I hate to see a brother give up his lathe work!!!
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Mobjack68. you are so right !! if it fails i have access to several motors god ones, danish made, old style, but build to last...

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Malb, thank you for your description of what happens with these windings, it was detailed and I'm appreciative of the time you've taken to explain this. My motor had no centrifugal switch according to the motor rewinder, he said what I had was a run capacitor and these don't require a switch or something to that effect. I didn't run the lathe much after it started humming, so not sure whether the failing capacitor damaged the motor or vice-versa.

mobjack68, I appreciate your kind offer about the motor but have been told that unless it is a perfect match, it won't engage the pulley and thus I would lose the variable speed (ie being able to shift speeds without manually changing pulleys). I do have a motor that was pulled out of a washing machine but then I would need matching pulleys, different belt and not sure that I'm skilled enough to do all that. I have contemplated doing this but in order that I can keep turning will probably buy another motor. The rest of the lathe is fine and has been tuned up but someday I would like to upgrade....
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