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Message started by DragBikeMike on 03/28/20 at 22:50:19

Title: Help!!!
Post by DragBikeMike on 03/28/20 at 22:50:19

I’m hoping that some of you are electricians, or have lots of experience with motors. My lathe motor just died. I was in the middle of a Savage project when the lathe motor would not start. At first, I got it to run by spinning the chuck and then flipping the switch. After a while, that wouldn’t work. One interesting thing that it does is when I turn the switch “off” it will momentarily rotate about ¼ turn.

For a long time now, the switch has been getting hot. I know I should have investigated that, but you know how it is. If I was doing a job that took more than a few minutes, the switch would get hot. Hot enough that I started paying attention to it and would shut down periodically for it to cool off.

I took a picture of the data plate.

Title: Re: Help!!!
Post by DragBikeMike on 03/28/20 at 22:51:02

When I went to remove the motor one of the wires would not pull out of the connector block. I had to cut the wire. When I could see it better the connector block was melted to the wire. Could a loose connection here cause the switch upstream to overheat too? The wires between the terminal block and switch are about 24” long.

Title: Re: Help!!!
Post by DragBikeMike on 03/28/20 at 22:51:48

The capacitors look OK but I have no idea how to check them. Anyone know how to do that?

Title: Re: Help!!!
Post by DragBikeMike on 03/28/20 at 22:52:50

When I got the end bell off, I could see that the starting contacts were burned. Is it OK to clean the contacts up with a points file or abrasive material? If these contacts aren’t conducting well, will it cause the switch to run hot or the terminal block to overheat?

Title: Re: Help!!!
Post by DragBikeMike on 03/28/20 at 22:53:30

Another view of the contacts. Do you think I can salvage this?

Title: Re: Help!!!
Post by DragBikeMike on 03/28/20 at 22:54:12

The centrifugal throw-out mechanism that operates the starting contacts tends to hang up occasionally. It feels a bit like residual magnetism holding it in the running position. It only does it every now & then, and lasts about 30 seconds, maybe one-minute. Its not dirty or sticky. The action seems smooth. It just seems to hang up a bit. Any ideas on this?

Title: Re: Help!!!
Post by DragBikeMike on 03/28/20 at 22:54:47

I would be really appreciate any help I can get on this problem.

Best regards, Mike

Title: Re: Help!!!
Post by Fast 650 on 03/29/20 at 08:00:23

6D6B64181A1D19290 wrote:

I think that is the culprit. It sounds like the start windings are remaining energized after the motor is up to speed, which will make the motor run very hot and eventually burn up the windings.

Title: Re: Help!!!
Post by justin_o_guy2 on 03/29/20 at 08:08:04

Cleaned up my starter contacts with a diamond fingernail file.

Title: Re: Help!!!
Post by Hiko on 03/29/20 at 23:50:13

This from my Electrician Son

I am certainly not a cap start motor expert but I am an electrician and know how they work.

The cap shifts the phase of a start winding to give the motor direction and a rotating field to actually start moving rather than a solenoid.

If the cap is blown or not connecting via the switch then the motor would just sit there and hum[like a solenoid ;]

The switch disconnects the cap and start winding when the motor is spinning fast enough to throw the centrifugal switch

Test the resistance of your start winding as if that is gone then the motor will need to be rewound The heat melts the insulation and that is what destroys them

You could disconnect the switch and the cap,the motor should still run if you give it a start flick Be aware it will run in either direction if you start it this way

If this test works then it is definitely your start switch or start winding
Yes you can file and clean your contacts but better to replace when you can as they may not last too long

Unfortunately I would say the start switch contacts became welded and
now cooked the start winding . If you can hand start it it should run all day and not get hot

Good luck!

Title: Re: Help!!!
Post by DragBikeMike on 03/29/20 at 23:58:21

Thanks guys (and Hiko please thank your son also). I fixed the terminal block, cleaned the burned contacts, lubricated the centrifugal switch actuator. Still didn't work. Then I zeroed in on the switch. That screwy rotation when I cycled the switch to "off" made me focus on the switch. It's fried. A quick check with an ohmmeter verified it's not making good contact and you can see the terminal lug is raised up from melted plastic. Have to round up a new switch. Melted connections in three places??? Could they all be related?

BTW, I checked amperage with the motor running (took a lot of juggling to get it to lite off). The black wire pulled 11.2 amps, but the white wire was less at 10.6 amps. Shouldn't both wires have the same current flowing?

Title: Re: Help!!!
Post by Matchless G11 on 03/30/20 at 05:24:40

17111E62606763530 wrote:

The capacitors look OK but I have no idea how to check them. Anyone know how to do that?

Best thing to do with capacitors is to replace them.
Just make sure the voltage rating is the same or higher.

Title: Re: Help!!!
Post by SpamyToo on 03/30/20 at 07:02:10

Like Matchless said, probably just replace the capacitor. You cant check those big ones with a normal meter you have to have a special one. Probably any A/C repair shops in the area could check it. But its likely just 6 to 12 bucks to replace anyways and more often than not they are the culprit when it just wont start up. Sometimes they look messed up, but other times they look perfectly normal but are bad.

Loose connections can also lead to heat, which might be why the connectors got hot enough to melt. Otherwise a large amperage draw was the culprit, but I imagine you would have noticed the lathe laboring.

Those contactors dont look that trashed to me. Just clean gently and they should be ok.

But like you saw that switch has got to be replaced too. Its probably not easy to get replacement parts for a Chinese lathe either, just gotta get what you can. If you need any translation I actually speak Chinese. ha ha.

Bummer, its always one thing after the other isnt it. And way to often around tax return time. >:(

Title: Re: Help!!!
Post by Matchless G11 on 03/30/20 at 07:35:02

4B525C5C0A0A495E4F5E5850080F0E3B0 wrote:

[quote author=17111E62606763530 link=1585461020/0#2 date=1585461108]The capacitors look OK but I have no idea how to check them. Anyone know how to do that?

Best thing to do with capacitors is to replace them.
Just make sure the voltage rating is the same or higher.
[/quote]

All so the value might be difficult to find, 300uF. Most caps are 330uF
I don't think that will be a problem. (May be some one with more experience with caps on motors can tell us.) My cap replacement knowledge comes form fixing vintage shortwave/ ham receivers.
It looks like the tolerance is 50% so might not be a problem.
But I would not go much higher then 330uF for one might have problems with current inrush.

Dragbike mike I might have a switch like that. You live near by in Jersey?

Title: Re: Help!!!
Post by justin_o_guy2 on 03/30/20 at 08:39:15

Theres a motor shop in Longview,, They can fix stuff like that.. and give an estimate first. If its gonna be almost the cost of new,, well,,
You might be ahead to Hire it fixed,, You might throw a few hours and dollars at it and hoope first..

Title: Re: Help!!!
Post by DragBikeMike on 03/30/20 at 15:12:52

Thanks again to all of you. I have a lot more confidence after getting your advice. I ordered a new switch. I should have it within a week or so. I'm pretty sure that once that switch is installed the lathe will be operational. I'll let you know how it works out.

Matchless, thanks for the offer of the switch. If the one I ordered falls through, I will get in touch with you. These DPST toggle switches are really a poor selection for starting a motor. It really needs something more on the order of a spring loaded contact that slams the contacts closed. But this DPST switch has been working good for about 20 years.

The lathe was delivered with a rotary switch that incorporated a spring loaded contact system. It self destructed in short order. That thing had killer springs. I replaced it with a system that uses two DPDT switches to select direction of rotation, and the one DPST switch to energize the system.

Again, thanks. I appreciate the help. Electrons are not my forte. ;)

Title: Re: Help!!!
Post by Matchless G11 on 03/31/20 at 10:12:50

while you are in there. I would replace the capacitor too.

here is a suggestion
https://www.grainger.com/product/PACKARD-Round-Motor-Start-Capacitor-44ZU53

It look like the cap date code 8 -88 meaning 8 week 1988.
old caps may be leaky and pass more current, That "might" have cooked your switch.
Just like a burnt exhaust valve, one has to look else where for why it failed.

Title: Re: Help!!!
Post by DragBikeMike on 03/31/20 at 23:57:04

Thanks for the link on the capacitors. I'll measure the dimensions on mine and see if these Grainger units will fit. The ones on there now don't have the resistor, is that a problem?

Aren't the caps out of the loop almost as soon as the rotor starts turning? The centrifugal switch seems to cycle almost instantaneously.

Title: Re: Help!!!
Post by Matchless G11 on 04/01/20 at 10:56:56

4C4A45393B3C38080 wrote:

I think the resistor may be a large value to bleed down the cap after use.
(safety issue)

But not sure, and for the second question not sure either, But I do know quite a but of current can be pulled by bad caps in a very short time.
(I run into this quite often.)