Lathe Motor problem

[max bayliss]

Hi all
New to posting on the forum but have viewed many usful posts in the past in the past.

I have an axminster C4B lathe that has been working very well up till now.
i was doing some thread cutting this after noon and i went to reverss the lathe and got nothing but a buzzing sound.
i stopped it and tried again and it reversed fine, did another cut and it did it again, this time it never started again.
the motor works in the forward position still but dosnt reverse at all now.
After stripping it down a to do a bit of testing i found that if i spin the motor in reverse and turn it on it does run at full speed if i stop it and try turning it on it wont run. i have a look at both the capacitors on the motor but they habe no connectors and are hard wired i was going to swap them around to test. not sure if taking the motor apart will give me the chance to unwire them.
anyone got any ideas what may have died? i dont think its the winding as it still turns one way. im not sure how the centrifugal could be the problem but my thought is it wouldnt work at all.
Any one got any hints tips ideas of what to do. a new one is looking around 100 GBP so not keen on that.
motor spec is.
single phase ac induction
Type YLA 7134
No: 1100615
550w
240v
3.8amp
c1 100uF 250v
c2 20uF 450v
1400rpm
Rating: S1

 

[slim_boy_fat]

Welcome to the forum.

I'm not too hot with electrics [I don't like anything I can't see but still has the ability to kill me ], but are you sure the problem doesn't lie in the forward/reverse swith on the lathe?

Just a thought.........

 

[max bayliss]

I had thought that but if i turn it on with no belts attached it moves slowley and if i spin it it will then kick in full speed, i rulled the switch out with that ( it was the first thing i took apart to look at so your not the only one thinking it!)

Thanks for the input through

 

[brightspark]

Welcome to the forum.

I'm not too hot with electrics [I don't like anything I can't see but still has the ability to kill me ], but are you sure the problem doesn't lie in the forward/reverse swith on the lathe?

Just a thought.........

more than likely. if it runs forward ok there's nothing wrong with the motor possibly the reversing switch contacts burnt or loose

 

[ukracer]

more than likely. if it runs forward ok there's nothing wrong with the motor possibly the reversing switch contacts burnt or loose

Does it not use a capacitor one in each Direction??

 

[brightspark]

test the voltage in motor on the starting windings and running with a meter if 240v on each in forward position u should get the same in reverse if u haven't its the switch if u pull it over by hand backwards and it runs it means the starting windings aren't kicking in

 

[brightspark]

Does it not use a capacitor one in each Direction??

no it just swaps the polarity of the starting windings

 

[max bayliss]

test the voltage in motor on the starting windings and running with a meter if 240v on each in forward position u should get the same in reverse if u haven't its the switch if u pull it over by hand backwards and it runs it means the starting windings aren't kicking in

you have to excuse me im not to bad with electrical/ electronics but i havent touched motors in years, i know how to test for voltage and have a multi meter but where would i be testing on the motor? there are 2 round external cylinders (i think there capacitors) but i took one off and its hard wired no conectors its a little hard to get to the motor but ive come to the conclusion that i will have to take it off the lathe tomorrow as i cant get to the cover of the electrical conectors and thers a shed load of wires in the box (might look more complicated than it is)
how can i tell if its a 2 or 4 pole motor ive read a bit about them but it seems both have only 2 wire? not sure on that at all

 

[brightspark]

you have to excuse me im not to bad with electrical/ electronics but i havent touched motors in years, i know how to test for voltage and have a multi meter but where would i be testing on the motor? there are 2 round external cylinders (i think there capacitors) but i took one off and its hard wired no conectors its a little hard to get to the motor but ive come to the conclusion that i will have to take it off the lathe tomorrow as i cant get to the cover of the electrical conectors and thers a shed load of wires in the box (might look more complicated than it is)
how can i tell if its a 2 or 4 pole motor ive read a bit about them but it seems both have only 2 wire? not sure on that at all

speed of motor makes no difference either 1450 rpm or 2800 rpm there will be 4 wires in to the motor. a pair for starting windings and a pair for the running

 

[max bayliss]

Hi Brightspark

couldnt resist went back out and took more panels and covers off the motor has 6 terminals but only have the 4 wire u mention there marked V1 V2 U1 U2, its a little late at night to start it up so going to test it in the morning and see what happens any thought on which terminals i need to test at? the cabels are marked well so ill have to have a better look in good light looks complicated this time of night.

Thanks every one for the input.

 

[Turbo]

It sounds like a switch problem to me, for some reason when you hit the reverse button it isn't sending power to the start windings.

 

[max bayliss]

Thanks every one after a lot of googleing I think I have my head around how the motor works and I can see why people are saying the switch looks to be the issue. From my understanding if the motor works in one direction it should work in the other just by swapping the current flow of 2 of the wire. So if it isn't working switch or spring looks at fault? Back in the garage today having a good look. Will let you know how it goes

 

[max bayliss]

no it just swaps the polarity of the starting windings

Thanks brightspark this bit helped a lot!
I did a load of testing and swapped the polarity and then started the lathe with the switch in the forward position and bingo it goes backward! So it's a dead switch for now i'll just have to swap the connectors to run backwards but will try and find a new switch on eBay later.

Thank you every one you have been magic!