Start capacitor failure?

[Chipmaster]

Over the last couple of weeks my Colchester Chipmaster motor has been increasingly reluctant to start. I have been able to tug the drive belt to encourage it but it refused to go yesterday and just growled at me until the thermal cut out - cut out. This appears to be symptomatic of a failed capacitor.

The motor on a Chipmaster is difficult to remove slung upside down beneath the Kopp Variator.

IMG_3494 (2) by Andy, on Flickr

IMG_3498 (2) by Andy, on Flickr

I bought the Brook Crompton 2.2kw single phase motor new 31 years ago just after I'd bought the lathe but couldn't afford a phase converter. Fitting it was a straight swap for the three phase motor which I still have, at the time I didn't imagine acquiring more machinery and a Transwave Converter as has happened as my salary increased.
It took some mauling to remove the variator and motor assembly, I was fitter then and don't relish having to repeat the exercise. By the way there is only this single capacitor on the motor.

So, I managed to remove the just the capacitor and felt quite pleased. However, The large clips that held the capacitor plus the manufacturer's paint job almost obliterated the specification on the sticker attached to the capacitor.

I think it reads 160 micro farad and a couple of sources reckon that is likely, can any MEM members confirm or suggest the spec for the start capacitor?

The capacitor 130mm long x 50mm diameter.
IMG_3496 (2) by Andy, on Flickr

A couple of zoomed in shots of the label,

 IMG_3495 (3) by Andy, on Flickr

 IMG_3497 (2) by Andy, on Flickr

The start capacitors aren't expensive and I assume the spec wouldn't be precise so reckon if I fit a new capacitor and the motor starts quickly that's ok. If it doesn't start quickly I turn it off before the capacitor explodes!

Andy

[Jo]

Tugging the belt 

Great news surgery has moved on greatly over the years  . I think Stuart had his finger go under a belt round a pulley he can give you the gory details   



Any part of the series circuit could have done what you describe. Have a measure of the windings while the caps off. On a 3HP motor it may well be a 160 UF Cap.

..... I hate to think how big the spike is that goes down the mains when that starts. Does it cause interference 

Jo

[Admiral_dk]

I read it as : 160µF -0/+25% (tolerance -> 160-200µF), 250-275Vac. 50-60Hz.

A new cap should be a cheap solution - and a VFD combined with the old 3 phase, would be the fancy solution.

I hope that you solve this to your satisfaction 

Per

[Chipmaster]

Ah yes I agree Jo, I should add that the motor wasn't turned on when I tugged the belt, I was only moving it a few inches before closing the cover and trying to start the motor again. The Chipmaster has a safety switch (plunger type) that disconnects the power when the large fibre glass end cover that protects all the belts and change gears is open. 

I haven't been aware of my motor causing interference, it used to dim the lights momentarily when I started it but it didn't cause any problems with computers. That was in a 1930's house I lived in until 2003, perhaps the electricity cabling to the house wasn't up to current standards. Where I live now in a thirty year old house there's no problem at all, my wife hasn't noticed the lights dimming.

So you think 160uf is likely, thanks.

Andy

[Chipmaster]

Thanks Per I feel I can order a 160-200µF tomorrow and be confident of a satisfactory result.

Andy

[MJM460]

Hi Chipmaster, my mill was a bit slow on starting particularly on high speed.  I replaced the capacitors after a little research and solved the problem very nicely.  My lathe is starting to show similar problems, but like yours, a pain to get at.  But that is next on the list when the weather warms up a bit.  I wrote it up recently on the tooling and machines board.  It does not seem like an uncommon problem, and replacing the capacitors seems the right place to start.

Will be interested to hear how it goes when your new capacitor arrives.

MJM460

[Jo]

I just wandered over to Brook Crompton website. They very helpfully provide lots of useful information in their booklet on single phase motors: http://www.brookcrompton.com/upload/files/products/2227e_1phase_v1.1e.pdf

Their modern 2.2KW single phase Capacitor Start Capacitor Run motors they identify them using  20OUF start and a 20UF running capacitor. Did you check is there a running capacitor?

I went there trying to find the starting current for single phase motors. I assume you have it on a 40A ring main 

Jo

[Chipmaster]

Hello Jo,
thanks for your interest, when we moved to this house five years ago I had professionals install a new power supply taken from the meter and routed underground to a new distribution board in our detached garage. I know that the board has a 100A circuit breaker then individual mcbs for radial circuits to the lathe and phase converter, there are further ring circuits for sockets, lighting, garage doors, outside lighting etc. I don't remember the rating of the circuit breaker dedicated to the lathe, perhaps 35A but it hasn't tripped in the last five years or the previous 25yrs in other locations where it was on its own 35A supply.
My 2.2kw single phase motor definitely only has one capacitor unless another one is cunningly concealed inside the motor casing  . 

I hope to report a successful conclusion if I can fit a replacement capacitor tomorrow.

Andy

[AOG]

If you don’t see a run capacitor it may be built into your start cap. The way to tell is the number of leads on the part. If it’s 2 it’s probably a pure start capacitor. If it has 3 separate leads it’s the start/run type.

Tony

[Chipmaster]

The Chipmaster lathe motor is back to normal, a new capacitor did the trick

A local Redditch firm 'Electrical Mechanical Solutions' ( http://e-m-s.uk/index.html ) who specialise in the repairing, servicing and supplying of electric motors didn't have start capacitors in stock, they suggested I contact Rush Industrial Sales in Sandy, Bedfordshire ( https://www.rushind.com/index.html ). Here I spoke with Andre who took time to discuss the problem motor and identified the appropriate capacitor by reference to his records of backdated GEC Brook Crompton specifications. The capacitor supplied and posted.....



The new capacitor was fitted this morning and I have started the lathe many times, it's running as it should, what a relief.

I recommend Rush Industrial Sales - Andre, to MEM members for the supply of capacitors.

Thanks to Jo, Per, MGM 460 and Tony for their input and advice.

Andy

[Jo]

 

[Chipmaster]

Oh dear, back to square one the motor is playing up again after an hours use 

Time to think about putting the original three phase 3hp motor back in the lathe and buy an inverter.

Andy

[Admiral_dk]

Oh dear - that is annoying .... there must be another reason it kills the caps, but probably not worth trying to discover why, as it most likely means another motor anyway ....

[Jo]

 

Did you measure the coil winding resistance? Did you measure the old capacitor to see if it was short circuit?

The other (relatively) cheap thing that may have gone wrong is the switch  .


Was there any "odd smell" and was the motor hot? (= possible cooked winding  )

Jo

[Chipmaster]

Hi Jo,

I don’t know what the coil winding resistance should be even if I was able to measure it. The motor is in such an awkward position that it’s not possible to access particular terminals on the motor. I had to use an inspection mirror to disconnect the capacitor but I was very lucky with the connections which happened to be on the two convenient to reach posts.
I feel that if I go to the trouble of removing the motor and Kopp variator I might as well opt for putting the original dual voltage three phase motor back, dispense with the variator and use an inverter, perhaps from Transwave who are only ten miles away.
A friend had his single phase motor from his Myford lathe repaired a couple of years ago, it was quite expensive, so repairing my 3hp single phase probably won’t be worthwhile.
This is the opportunity to have a smoother and quieter three phase motor driving the lathe....so any suggestions gratefully received.

How do you power your machine tools Jo ?

Andy

[Jo]

What you are measuring for is a short circuit 

How do you power your machine tools Jo ?

I have a Transwave Rotary (transformer) three phase converter to power all of my 3 phase machines. It is rated to enable me to run two machines at once if required - not that I ever have 

The cheapest way forward for you would be to put the original 3ph motor back and run with a VFD.

Personally I would keep the Variator: Because motors are designed to run at a specific speed and if you slow them down you are fiddling with both their cooling and their power output. It has the advantage that the Variator is already plumbed in and you will only have to replace the one belt with its original. You then have the option of modifying the speed on the VFD (if you really must  ) or on the control that you are already used to.

Jo

[Vixen]

+1 for keeping the Variator. 

The other major advantage of the Variator is that the shaft torque doubles as the spindle speed is halved. With a VFD the torque is reduced as the speed is reduced.

If your Variator is in good condition, keep it. Buy yourself another single phase motor.

Thats what I did with my Chippie

Mike

PS I had trouble with the original stop/ start /reverse switch contacts and replaced it with a contacter.

PPS It may be an idea to remove and get the duff motor checked out by a motor repairer.

[Chipmaster]

Ok the variator is sound so I'm halfway though removing the motor, it's quite a struggle.

 IMG_3504 by Andy, on Flickr

IMG_3505 by Andy, on Flickr

I had to slide the assembly out, couldn't lift it as I did 31 years ago. Another problem has surfaced, one of the three anti vibration motor mounts had become a mush and fell apart.

IMG_3506 (2) by Andy, on Flickr

Here's one that's ok

IMG_3511 (2) by Andy, on Flickr
IMG_3512 by Andy, on Flickr

Problem is the mounts are threaded 1/2" UNC into the base of the lathe and I think I won't be able to find a replacement, may have to do without the rubber or bodge it!

I hope to remove the variator and motor from the frame this evening and take the motor to the local motor repairer tomorrow.

Andy

[Chipmaster]

Variator and motor removed, the variator is incredibly heavy, my hydraulic lift table was key to moving these things about.

 IMG_3518 by Andy, on Flickr

Ready to take to the motor repair folk tomorrow.

Andy

[Vixen]

Andy,

I hope the motor man says there is nothing wrong with your motor, it's is a goody. That would narrow it down to the fwd/rev/on/off switch or the wiring connections. I have had problems with that old fashioned Dewhurst switch before and replaced it with a contacter.

Good luck

Mike

[Chipmaster]

Thanks  Mike. When I converted my Chipmaster to single phase I replaced the original three phase starter with a Crabtree starter which is controlled remotely by the original Craig & Derricott rotary switch on the end of the chrome on off forwards backwards lever with the illuminated knob. I visited the Craig & Derricott works in Walsall Wood and they gave me the necessary cams to modify their switch to reverse the single phase motor. So my motor has the three power supply leads plus a four core cable for reversing. I was far more resourceful then. Putting this lot  back together is going to be a struggle.
Andy

[Chipmaster]

Hi Mike, the motor man took my motor apart while I waited and showed me how the centrifugal switch contacts are very dirty. He said the rest of the motor is in beautiful condition, “just look at those windings and the rotor, we don’t see motors like it these days”, it was becoming quite emotional !

So the motor will be repaired by cleaning or replacing the centrifugal switch  .


Gosh I haven’t had this much tension since one of my library books was overdue.

Andy

[Jo]

Did he give you a price 

Jo

[Vixen]

Hello Andy,

If the motor man can find brand new replacement centrifugal switch contacts then you should be good for another forty years.   

Now all you have to do is get that heavy lump back into the machine. BTW I have wooden spacers in place of those rubber vibration mounts. OK it's a bit noisier but I dont care as I have become deaf.

Cheers

Mikw

[Chipmaster]

Hello Jo and Mike,

I asked about a price and was told it wouldn’t be much, it will depend on whether the centrifugal switch has to be replaced and whether a like for like replacement is obtainable. The motor man said modern motors have something other than centrifugal switches and he would fit one of those if necessary. I didn’t take all the details on board.
To me it’s worth paying out to have the lathe working again.

Mike Re the rubber mounts: two of the three are good and like you I’ve had a block of wood wedged alongside the mount at the front which I knew was rather soft and soggy for a couple of years

Andy

[Vixen]

Hello Andy

While you have the Variator out, now would be a good time to change the special oil inside.        I cannot recall the spec (Google it)  but I got a bottle off e-bay.

Cheers

Mike

[Alyn Foundry]

Hi Andy.

The virtues of being close to what was known as the " Workshop of the World " eh? You'd be hard pressed to find such firms in my locality these days.

My Denbigh was converted to single phase nearly 40 years ago. I fitted the bigger and older brother to your motor. It's a 4 HP Brooks with the centrifugal switch mounted in a little domed housing at the rear end. Everything is easy to access and it has given Sterling service despite being second hand when I got it.
Everyone knows when she's started, even the neighbors. ( 4 other properties on a 24KVA pole transformer for us all ) It used to put out the fluorescent lights in the workshop every time. Now we have LED lighting the problem isn't so noticeable.

I didn't really have any doubts about your motor being burnt out, they're really well made and as you didn't mention a smell, the smoke never left the box!!

Good luck with the refit.

Cheers Graham.

[Chipmaster]

Hi Graham,
At 14.25 this afternoon I received the phone call telling me that my motor was ready to collect, how about that for service?
They demonstrated the motor working for me and showed me pictures they had taken of the centrifugal switch before and after, it looks immaculate now.
The original capacitor had also been checked and passed the test. The motor will probably outlast me 

Jo - The cost was £60 for two hours work, I'm ok with that.

Mike - yes I'll change Variator oil, it was Shell Tellus R10 when I bought two five litre flagons of it 30 years ago. Draining the oil is rather a messy affair so I will take the opportunity to do some plumbing to avoid the Variator oil pouring out all over the cradle and motor in future. In the past I have cut up plastic ice cream cartons to catch most of the oil.

To refit the motor and variator I will buy some square steel tube to act as rails so the whole assembly can be slid along into place. I'll also take the opportunity to clean the oily mess off the interior of the lathe base.

Andy
 

[Jo]

£60 

Not long now and the swarf will be flying again 

Jo

[Vixen]

Mike - yes I'll change Variator oil, it was Shell Tellus R10 ...............
Andy

Great result Andy

Oh! Thanks for the reminder. Now I know (remember?) what that grotty old plastic bottle of Tellus R10 was being kept for.

Cheers

Mike

[john mills]

great result it will be good to have it running again as it was.  I would of thought you would be able to get rubber
mounts a range of them are obtainable as standard items here in melbourne.
my old horizontal mill has an old 2 hp single phase motor body would be twice the size  of yours  it came from a farm were it drove a water pump on a spring  .
It would not start but would run it it was given a spin.an electrical contractor that came in to were i was working
took it to have a look at it .the switch contacts were cleaned up and the insulation on the wires repaired.with a new capacitor it has been working ever since that was 40 years ago .
John

[Jo]

How we doing? Any Swarf sign?

Jo

[Chipmaster]

Gosh Jo, I've been slacking - had the day off relaxing but still thinking how to get the Variator & Motor assembly back inside the lathe without doing myself a mischief. I can hardly lift the Variator by itself let alone the assembled Variator, cast iron cradle and motor. I reckon I must be crocked, the best I can do is slide it about, a little at a time, it probably weighs 2cwt / 100kg ! The rubber mounts are a further complication, they could be badly damaged if I don't take care.... I could be damaged too !

IMG_3505 (2) by Andy, on Flickr

So, I'll be cleaning the interior of the lathe tomorrow, it's a nasty mess because of a slight oil leak from one of the headstock seals combined with rubber particles from the drive belts. Everything I touch inside the cabinet leaves a black gungy mark. My overalls and jeans were such a mess that've been in the wash today.

Andy     

[Chipmaster]

Hi Don,

I have searched for rubber sandwich mounts threaded 1/2” x 13tpi that would suit the lathe for a few years without success, all the bobbin style rubber or anti vibration mounts sold in the U.K.have metric threads. Over the years I have seen a few other Chipmaster owners writing on the Internet asking for help obtaining suitable mounts. They appear to be available in the USA but the articles said that the supplier ( McMasterI think) won’t post abroad.
I have considered making my own, obtaining the rubber isn’t a problem but there are no longer any firms that do Vulcanising in my vicinity and I don’t know whether there are any effective adhesives for bonding rubber to steel.

Andy

[Pete49]

I wonder if one our US members might be able to assist you in getting them and posting them over? It's been done before even Ihave done it on another forum.

[crueby]

According to McMaster-Carr's website, they will ship worldwide, though I have heard of some people saying they would not - worth trying the order, or just email them and ask - their customer service is usually a quick reply. Another company that is very similar to them is MSC,   https://www.mscdirect.com/   or Grainger,   https://www.grainger.com   both sell to individuals as well as business.

[Chipmaster]

 Spent this afternoon having a fairly difficult time returning the Motor and Variator assembly by sliding it in on two lengths of 25mm square steel tube which kept the assembly just above the rubber mounting pads to avoid damaging them. As the third rubber mount at the front of the lathe had perished I substituted a block of wood as a temporary measure.
My wife took quite a lot of pictures but as most were taken from behind me I think I'll leave those out , I don't know what she was thinking 

Fitting the toothed belt and pulley between the motor and Variator, thank goodness for the taper lock pulley on the motor shaft providing the necessary slack before it was tightened up.

IMG_3541 by Andy, on Flickr

IMG_3565 (2) by Andy, on Flickr

IMG_3540 by Andy, on Flickr

IMG_3564 (2) by Andy, on Flickr

IMG_3568 (2) by Andy, on Flickr

After all that the lathe was running again, in this clip I'm starting the lathe with the clutch engaged.

<a href="https://www.youtube.com/watch?v=nWXI5nJKJnY" target="_blank">http://www.youtube.com/watch?v=nWXI5nJKJnY</a>

So the real problem was the centrifugal switch and it was a real palaver getting the motor out and back in again, I really hope I won't have to do that again so I hope it will still be ok after a few hours use. I will continue in my quest for another rubber mount. If I can't obtain a mount with 1/2" UNC threads I will substitute a mount with a 10mm stud. I hadn't realised that the holes for the mounts go right through the base so a 10mm stud could pass through the 1/2" UNC hole and I could use a slim M10 locknut in the space beneath the lathe to fasten the mount.

Thank you to all the people who have posted suggestions and encouragement to this mini saga. I want to get back to making engines.

Andy

[Jo]

 

Success ! Well done Andy 

Jo

[Admiral_dk]

Always nice to get our Tools back to working condition