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Craftex CX709 motor issue?

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DHHok

Active Member
Some of you may know I purchased a cx709 that BusyBee had on clearance because it had a problem.
BB's explanation of the issue on this machine was that it couldn't get to top speed, but everything else worked. The guy at BB stated that it actually would get to top speed, but it just took awhile.
I purchased the lathe, figuring it was a motor problem, and because I have a spare motor I wasn't concerned.
So I just got around to cleaning the machine and testing it. Turns out, it will not run on the 3 top speeds. (850, 1100 & 1650). On any of these settings, the speed fluctuates drastically for about 5 seconds then trips the breaker. I can't attach videos of the issue, but they can be seen here & here.

I have my theory as to what the problem is, but don't have time right now to check it out, so I thought I'd see what others think the problem may be. You may come up with something I didn't think of.
I have ruled out a mechanical problem because the lathe works fine at the 640rpm setting, but fails at the 850rpm setting. These two settings use the same gearset and is only a belt change, so nothing mechanical really changes. What I think happens is that as the speed setting increases, the torque requirement for the motor becomes greater and it just can't handle the increased torque load at the top 3 settings.
I have already checked the start & run capacitors and they seem ok. Granted, I only checked with an ohmmeter, but they did pass that test, and look perfectly fine.
What I don't have time to check right now (and what I think the problem is), is the centrifugal switch. I'm thinking it may be opening too quickly and dropping out the start capacitor before the motor has enough momentum/torque to be able to run on the Run capacitor.

That's where I'm headed next, but I am open to all opinions.
 
DHHok said:
Some of you may know I purchased a cx709 that BusyBee had on clearance because it had a problem.
BB's explanation of the issue on this machine was that it couldn't get to top speed, but everything else worked. The guy at BB stated that it actually would get to top speed, but it just took awhile.
I purchased the lathe, figuring it was a motor problem, and because I have a spare motor I wasn't concerned.
So I just got around to cleaning the machine and testing it. Turns out, it will not run on the 3 top speeds. (850, 1100 & 1650). On any of these settings, the speed fluctuates drastically for about 5 seconds then trips the breaker. I can't attach videos of the issue, but they can be seen here & here.

I have my theory as to what the problem is, but don't have time right now to check it out, so I thought I'd see what others think the problem may be. You may come up with something I didn't think of.
I have ruled out a mechanical problem because the lathe works fine at the 640rpm setting, but fails at the 850rpm setting. These two settings use the same gearset and is only a belt change, so nothing mechanical really changes. What I think happens is that as the speed setting increases, the torque requirement for the motor becomes greater and it just can't handle the increased torque load at the top 3 settings.
I have already checked the start & run capacitors and they seem ok. Granted, I only checked with an ohmmeter, but they did pass that test, and look perfectly fine.
What I don't have time to check right now (and what I think the problem is), is the centrifugal switch. I'm thinking it may be opening too quickly and dropping out the start capacitor before the motor has enough momentum/torque to be able to run on the Run capacitor.

That's where I'm headed next, but I am open to all opinions.
Click to expand...
You could take the motor to a local motor shop. The centrifugal switch can be changed or adjusted. I think you're on the right track though.
 
Quite a trick getting 1.5 horsepower out of 11A at 110V but that's neither here nor there.

I pulled the wiring diagram out of the online manual:
CX709 wiring diagram.jpg


Could you confirm that yours has the forward-reverse switch? I believe there are different styles of forward-reverse (aka drum) switches that have different patterns of connections. Conceivably, they put the wrong style of switch on a small number of machines?

Your theory about the centrifugal switch dropping out too soon sounds plausible to me. I'd also verify that the start and run windings are actually connected correctly.

I'd be very careful about the number of times I'd test the problem lest the magic smoke gets loose!

Craig
 
I appreciate the response guys.

The machine is not wired as per the wiring diagram, but I haven't assumed that it means the motor is wired incorrectly. The motor does run properly at 9 of the 12 speed settings.
So far, I have traced out all the wires as best I could and jotted down where each one goes. I still have to pull the Transfer Switch in order to see it better and then I will draw out a proper schematic so I can better understand if the motor is wired correctly.
I don't want to assume the Chinese wiring diagram is correct and wire it up as shown. Based on the rest of the manual, it's pretty obvious there wasn't much thought or attention put into it.

What I can tell so far, is it does have the same forward/reverse switch as shown and looks to be wired the same.
It does not have a 2 pole breaker as shown. The breaker is a single pole and wired (incorrectly) into the Neutral side. It should be on the Line side.
The Indicator Light is wired before the power switch, so as long as the machine is plug into power, it is always on. That will need to change.

When I'm out tomorrow, I am going to stop by the BusyBee and look at the one they have. I'll take some pictures of the wiring and compare to mine and the wiring diagram, then go from there.
 
Unless they are being changed when speeds are changed, I doubt that the issue is capacitors or the centrifugal switch. These components are used to start and run the motor. Normally, they should not know what gear the lathe is in. Since they work in the lower gears, they should work in the higher gears.

But I confess that your videos sure do look like it's a problem like the centrifugal switch!

Normally, a centrifugal switch is used to disconnect the start capacitor or a start winding in a single phase motor once the motor gets running. It does not carry load at the higher rpm, only at the lower startup rpm. But your video makes it look like it's a transition issue between start and run rpm.

If the motor is the problem, I think it will be in the windings or in that switch arrangement that is in the schematic.

Can you put an ac ampmeter on the mains? Higher load will draw higher amps. So you can check amps to check load in the high gears and in the middle gears.

I think you should try to eliminate the possibility of mechanical problems further in order to avoid making them worse.

You can try removing the drive belt and turning the lathe by hand in the various gears. This can be done both ways - turning the input pulley by hand or with a wrench, and turning the spindle with a t-wrench.

You can also try spinning the motor without the belts on too. In fact, you can also run the motor without the drive belts if you want.

These latter two evaluations are to try and determine if you have a sticking gear or bushing or bearing or something.

Just a guess, but if the motor does that when the drive belts are removed, then the actual load is not a factor and you can zero in on motor/switch problems.

I'd ask how hot the motor gets when running for a while on any of the three middle speeds, but I'd be leary of running it for any length of time for fear of overheating an internal gear or shaft that is sticking in a bushing or bearing. Hence the need to check for these conditions first.

Does your backup motor have all those windings too?

To improve my own understanding, it would help to have a theory paragraph that explains how the circuitry and gears all work together. Fir example, you had said that the only difference between the top gears and lower gears is a belt change. Can you explain what is all supposed to change as you change speeds? Since it's a 12 Spd and all three top speeds are not working, I am surmising that the motor is a 4 speed and there are three belt/gear changes?
 
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I looked up the motor as specified in the drawing.

Be very cautious about doing your own search. Two of the websites I found contained malicious scripts (viruses).

The motor is a 3 speed with three different sets of windings. So I'm guessing one of them is bad.

My guess is that the motor works on the start circuitry and then when the centrifugal switch kicks out the start capacitor or start windings and switches over to the highest speed set of windings, the bad winding fails and drops the speed enough to kick the start system back in and that's why the motor hunts like that.

Your video shows that motor torque goes down as the motor speed goes up. This again suggests a winding that isn't working as opposed to excessive load.
 
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There ought to be a label with a wiring diagram on the motor. Hopefully you can trust that. You might want to pull the motor and bench test it so you can isolate from any mechanical problems.

BTW, I just saw @Susquatch 's posting. I'm clearly not finding the same specs as he is. Searching for "Yl-90L4 electric motor 1.1 KW" leads me to what appears to be typical single-speed, dual capacitor motors. The only odd part is that they all seem to be 220 V; no option for 110V operation?

A WAG: if it is a 220V motor running on 110V, maybe the highest speed settings put on enough load to cause it to oscillate between the start and run windings?

Also, could you confirm how the speeds are configured? From the look of the controls, I'm guessing there are 2 gear levers giving you 6 gear-selected speeds. Then with a belt change, it switches between a high and low range? But that doesn't line up with what you said about only 3 of the 12 speeds causing a problem after a belt change.

Craig
 
trlvn said:
There ought to be a label with a wiring diagram on the motor. Hopefully you can trust that. You might want to pull the motor and bench test it so you can isolate from any mechanical problems.

BTW, I just saw @Susquatch 's posting. I'm clearly not finding the same specs as he is. Searching for "Yl-90L4 electric motor 1.1 KW" leads me to what appears to be typical single-speed, dual capacitor motors. The only odd part is that they all seem to be 220 V; no option for 110V operation?

A WAG: if it is a 220V motor running on 110V, maybe the highest speed settings put on enough load to cause it to oscillate between the start and run windings?

Also, could you confirm how the speeds are configured? From the look of the controls, I'm guessing there are 2 gear levers giving you 6 gear-selected speeds. Then with a belt change, it switches between a high and low range? But that doesn't line up with what you said about only 3 of the 12 speeds causing a problem after a belt change.

Craig
Click to expand...

Exactly why I would like to see a theory of operation or even just a description of the way all the speed changes are supposed to work.

I confirm that my search finds 3 different switch controlled speed settings each selecting 2 or 4 or 6 poles.

My search also says 115V.

But such confusion and conflicting info is the wonder of the internet!
 
Just some more info in case it helps. The number of poles usually determines motor speed as follows:

2 poles = 3600rpm
4 poles = 1800rpm
6 poles = 1200rpm

The wiring diagram that @trlvn provided also suggests 3 different pole configurations.

Doesn't mean that's what you have, but that's what I found.

As mentioned before. Be very careful searching in this info. My virus protection blocked malicious content on two websites.
 
Susquatch said:
Just some more info in case it helps

2 poles = 3600rpm
4 poles = 1800rpm
6 poles = 1200rpm

The wiring diagram that @trlvn provided also suggests 3 pole configurations.
Click to expand...
Um, no? I think it shows a typical forward-reverse scheme where two of the start capacitor leads are interchanged. On the section for the switch, the columns are labelled "F O R" for Forward, Off and Reverse.

Craig
 
trlvn said:
Um, no? I think it shows a typical forward-reverse scheme where two of the start capacitor leads are interchanged. On the section for the switch, the columns are labelled "F O R" for Forward, Off and Reverse.

Craig
Click to expand...

Yes, I saw that. But then there are various settings for each. Typically, the caps and centrifugal switch are internal and not affected by switch settings. I thought that's why there are four wires going into the motor. It would help to see the wiring diagram that is usually on the motor and know how the speeds are supposed to be selected and configured.

I gather that you think that the motor is a single speed motor and all the speeds are selected manually. I thought so too - hence my earlier concerns regarding a mechanical problem. But then I saw the poles in the motor specifications on line.

I guess I shouldn't speculate so much and just wait to see what @DHHok finds. Right now, I feel like I'm just throwing info out there excessively.
 
historicalarms said:
That lathe would be perfect for me...$hit can happen fast enough at 300 rpm....I never turn faster than that.
Click to expand...
The minimum speed on my lathe is 70rpm. I'd like 30 or 40 and would be thrilled with 50.


I've run my 14x40 at the max speed of 1400 just to make sure it worked. But I very rarely use it to cut anything in any gear set but the lowest speed range which is 70, 220, & 360.
 
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As a former owner of the lathe I can tell you that there is nothing wrong with the machine.

Drain all oil form the gearbox.

Fill it with ISO32 oil - fresh from Princess Auto.

Make sure room temperate is around 10C or above.

Start lathe in 700 rpm and run it for at least 15 min.

Then go up in speed for another 15min

Then top speed.

BTW, I had same identical issue.
 
Also your lathe is rather "anemic" i.e. it is not at all "powerful" - when running at mid speed say 700 rpm or so and you chuck in at least 2" or 3" bar you can stop the lathe with your hand when squishing the part hard with emery cloth.

I did the same on my chipmaster but no way I can stop it - I can hear motor working hard but it powers through, even with larger stuff like 6" face plate. On my big lathe it does not even break a sweat - I cannot even hear much change in motor pitch.

Due to above anemic behavior do not expect to take heavy cuts in say 2" - 3" sized pieces especially at high speed around 700.
 
Finally you can get some expensive ISO 32 oil that is "all season" or "winter grade" or "synthetic" etc. that stays more liquid in colder temperatures. If your workspace is not heated it will help a lot.

No issues in the summer!
 
Wow. Lots of discussion. This is good.
I haven't had time to dig into the problem and probably won't for a couple days, but to answer your questions:
The motor has 6 wires. W1/2, U1/2, V1/2. So 3 windings.
There are 6 different gear changes and a high/low belt change to get 12 speeds total. It will not run at 1100 or 1650 (same gears, high & low belt setting).
It will run at 640, but not at 850. This is the same gear set, with just a belt change.
It will run at every other speed.
This is why I do not think it is the actual motor, but the centrifugal switch dropping out too early.
How I view it is:
The centrifugal switch will drop out at the same rpm every time. Doesn't matter what gear speed is selected. However, the higher speeds will require more motor torque to get the spindle up to and maintain speed. At the lower speeds the required torque is not as high and when the Start cap drops out, the motor can maintain enough momentum to continue to turn the spindle. Somewhere between 640rpm & 850rpm is the threshold where it can not do this. At 850rpm (spindle speed) and above the motor can not reach a high enough rpm where it is able to produce enough torque (on the Run cap alone) to keep running once the Start cap drops out.
That being said, I can see that it could be a bad winding. My above "torque" reasoning/explanation could fit this situation also.

The quickest solution would be to install the 2hp motor I have laying around, but then I'd never know if the craftex motor is any good or not.

Tom, I know you feel it's the oil, but I have to respectfully disagree. This problem was only on a small batch of units that got shipped out last summer. This "batch" of units was identified by BusyBee as having a high speed issue and instead of determining the cause and fixing it, they sold them off (cheaper and without warranty) as CX709X's. Any that came before, or after don't have the problem. It appears I purchased the very last one, as the website no longer advertises these units. Fyi, I have changed the oil with the recommended ISO68 (20w) and the lathe is in a heated garage where the lowest temp seen is 60F.

I appreciate all the suggestions. I'll be able to check it out further in a couple days and see if I'm right or wrong on my theory.
 
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Wow. Talk about an interesting tale...... I cannot stop thinking about it! More importantly, I can't wait till it gets fixed.

As the old saying goes, "This problem too will be simple when solved."
 
Is there a model number on the centrifugal switch that can be compared to previous models? With the COVID supply shortage could it have been swapped out for a different model?
 
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