# Lathe motor stopped



## mzetati (Sep 30, 2011)

Had the lathe motor refusing to re-start after being stopped during a cut, to say nothing about the smokes and smells.
A bit later, I could have it turning again, though intermittently. Unusual buzzing sounds coming from somewhere into the HS 
Sounds like that 50mm dia. steel rod (a un-machined remnant from sequential gearbox arbor blank of a well known Italian sport cars brand) was a bit too tough for the little thingy.
Decided to dismount it and have a closer look at the inside.
As usual with pulleys, this one wont come out easily: no point into trying to hammer it free (dont ask why I know that) better for me to use a suitable extractor. 
Of course, none of the ones I previously made could fit the task, though I could re-use part of the bike clutch extractor by machining an aluminium base from a portion of a once-too-long homemade lathe TS. 








Definitely weak, with that (already present) large hole in that position, but it got the job done.

And a picture of the partially dismounted HS.







When I finally managed to open the motor, everything inside of it was covered with a thick layer of black dust from the carbons, but the wires look- OK. The carbons themselves are still long enough to reach their contacts, but the springs are no more acting accordingly to their names. . Maybe I found where the problem was?
I still dunno: wanna clean it thoroughly before reapplying any power. I suppose soaking into alcohol and brushing should do, providing I let it dry before causing any spark in its proximity. 


The rotor, the old carbons and a new one (from an identical  never used before  motor).








Top motor casing, showing a couple of partially melted carbon holders: I suppose I can avoid hunting for replacements, providing I will find no shorts. Of course, should I happen to stumble upon a couple of suitable ones I would not let the occasion escape.







In the meanwhile, I will do with that spare motor. While I am at it, I have ideas about a few (mostly cosmetic) machine modifications, while I have it dismounted.

a)	A couple of risers for the entire machine: somewhere between 1 and 2 inches, to ease cleaning the chip tray (to say nothing about reducing the frequency of the task). That might involve reducing the height of the table it is sitting on. Will see..
b)	Some hinges for the gear cover to pivot on.
c)	A new splash screen (easier to remove than the current one) with a separate chip protection for the motor.
d)	A new, smaller, motor pulley to reduce the lowest speed and increase the torque. 

Marcello


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## Ken I (Sep 30, 2011)

Looks like the pigtail (flex wire) failed - then you start passing current down the spring - heavy load = red hot spring = no longer a spring.

2c   Ken


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## mzetati (Sep 30, 2011)

Ken I  said:
			
		

> Looks like the pigtail (flex wire) failed - then you start passing current down the spring - heavy load = red hot spring = no longer a spring.
> 2c   Ken



Ken,

that makes sense.

In fact, when lightly I pulled the carbon it was held by the spring only: the pigtail (thank You for the translation) came out from its hole with no efforts.
Soft soldering (the old tin/lead alloy) to eventually fix them? (Replacement are not so easy to find)

Marcello


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## Ken I (Sep 30, 2011)

Marcello, The pigtail is normally pressed into a driled hole using a solid wire insert (plug) to force an interference fit.
Optionally crimp on a bootlace ferrule and drill a suitable intereference fit hole in the brush.

Normally doesn't solder and not a good idea even if it does because of high brush temperatures.

There are normally plenty of places you can get brushes made - or try a dealer in Bosch, Ryobi etc. etc. - you can generally scare up something (or larger & skim down).

Ken


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## mzetati (Sep 30, 2011)

Ken,

that'll be some light force fit, then: just to see whether the motor runs or not. 
A dealer in Bosch or other branded tools can be a good idea: will try that. 
Marcello


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## EL-CORAZON (Oct 22, 2011)

Hi again Marcello .
Nice to see that you get it running again.
have you don any modifications on the speed of the motor... I am considering this lathe butt the motor/motor-controller 
on this type (all manufactures) holds me back.
Leaning a little towards the sieg sc2 with brushles motor even if it is smaller


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## Jasonb (Oct 22, 2011)

You should be able to buy the brushes as spares, if not from Optimum then the same lateh comes from many other makers like Warco and Chester in the UK.

Had a similar thing with my 280mm lathe, one brush wore more than the other and the sparking made it get hot and loose the spring tension






J


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## mzetati (Oct 24, 2011)

EL,

speed mods, here: http://www.homemodelenginemachinist.com/index.php?topic=16091.msg164270#msg164270.
I'm happy with them mods for now, time and use will tell whether the idea was good or not.
Another option I have in mind is about removing the tensioning pulley and replacing the intermediate pulley (the three stepped one) with a new one, where the inner step (the larger, the one that goes to the motor) was made of larger diameter.
IIRC, the new version of my lathe comes with brushless motor, too. But don't buy a 7x10: go bigger!!!
Marcello

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Jason,

thank You for the Warco/Chester idea.
Will check, but no hurry at the moment.
Marcello


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## mzetati (Oct 24, 2011)

I wasn't recalling correctly: sounds like the brushless motors are for the 'next size up' models only.

http://www.optimum-machines.com/products/lathes/index.html.

Marcello


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## MachineTom (Oct 24, 2011)

As you can see the sides of the brushes are worn. This is because the current is now being transfered from the hold to the brush, do to the tag wires poor fit in the brush (carbon) as the brushes get looser in the holder the timing of the motor is threw'n off. A similar condition happened with my wheelchair, motors ran like a 4 cylinder engine that had a bad sparkplug. So in your case the power was decreased at a time when you needed the max. Did the motor sound odd at slow speed, surging, skipping? that the brush timing.


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