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Author Topic: Coreless motors v open frame.  (Read 1443 times)

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Offline Old Crow

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Coreless motors v open frame.
« on: July 18, 2018, 12:21:10 am »
New to all this and currently using pre-owned locos. I'm thinking of buying a new loco - maybe Ivatt 2-6-0. Now I can see why, for accuracy, small motors would be desirable but how, honestly do they compare with old-style open frame in terms of power and reliability. Are they "better" or just different and downsized to fit?  I like locos to have pulling power and traction and the heavy weight of the old motor and a metal body seems to work for me. I've not tried a new loco (I'm happy with dc) so wondering. I've heard the new motors are better at slow running???

Offline dodger

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Re: Coreless motors v open frame.
« Reply #1 on: July 18, 2018, 06:25:33 am »
In my opinion there  is no contest in the regarding reliability. The older open frame motors only require regular servicing and replacement of wearing parts which can be carried out in a few minutes and will accept more abuse. Coreless motors require no servicing but require changing at regular  periods when they fail, that if you can obtain a spare.

For me open frame motors win hands down, I have several bought pre-used in the early nineties that are still running.

Dodger

Offline elmo

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Re: Coreless motors v open frame.
« Reply #2 on: July 18, 2018, 06:31:14 am »
Another vote for open frame motors here. I have stuff in oo and N that is donkeys years old and still working because I can repair and service them.
I also have a newer loco that had to wait over a year for the motor to be available.
In addition, these sealed motors to not seem to last that long whereas I have some early 1980's open frame well used locos still on their original components.
I know a shop that has a working display who utilises old locos because the new ones will only last a couple of months of daily service before they pack up needing a new motor.
Elmo

Offline Chris Morris

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Re: Coreless motors v open frame.
« Reply #3 on: July 18, 2018, 07:05:54 am »
It would be interesting to see how various locos compare for longevity. Iím happy with the coreless motors even though they donít run well with my feedback controller. Non of my coreless locos have done months of continuous running though. I may change my mind if I have problems. Probably my biggest concern is availability of spare motors; they should be easily available.

Is it clear which locos have coreless motors? We can be certain that all Dapol N gauge locos have traditional motors because we know that they were looking to find one for the Bullied Pacific. So far as I am aware the Farish Castle, Ivatt 2-6-0 and 64xx are coreless. Are there any others?

Offline PLD

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Re: Coreless motors v open frame.
« Reply #4 on: July 18, 2018, 07:54:14 am »
Iím happy with the coreless motors even though they donít run well with my feedback controller.
The instructions from Farish specifically state to NOT use feedback controllers...
(In doing so you have probably shortened the motor life and invalidated the warranty...  :thumbsdown:)

Offline ntpntpntp

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Re: Coreless motors v open frame.
« Reply #5 on: July 18, 2018, 08:53:56 am »
As others have said, old style traditional open frame motors - and also older can motors - at least have "user serviceable parts" eg. brushes and springs. I agree they can last for decades if not abused. I have locos made in the 60s and 70s still happily running on original motors and are still perfectly good enough for exhibition running.

Coreless motors are more efficient and draw less current, but as I understand it there are potential issues with them:

1) Because they don't have an iron cored armature they can't conduct away any heat build-up as well as a traditional motor. It is said that PWM controllers can induce such heat build up more readily than smooth DC.

2) Again because they don't have an iron armature, their Back-EMF response is different to a traditional motor. Hence if you use a feed-back controller it may not be tuned to the BEMF characteristics and may under- or over-compensate, resulting in jerky running.

3) They are often completely sealed with no option to replace brushes.

Of the points above, the heat build-up is probably more likely to cause reduction in motor life.

Remember that a feed-back controller is 99% likely to use PWM, but not all PWM controllers include feed-back circuitry.

Also remember that every DCC decoder I've ever heard of uses PWM for motor drive, and the majority seem to include feed-back although is it usually possible to switch it off.  Also with more comprehensively specified decoders the PWM frequency and feed-back response can be tuned to better suit the motor characteristics. Most decoders use higher frequency PWM than a classic PWM controller.

I still use KPC PWM/feed-back controllers I've had since the 80s, and find they give no trouble at all nor do I notice any heat build up in locos, though my typical operating pattern is to run each train in a sequence rather than leave things belting round and round for many circuits. I did modify the controllers a long time ago to allow the feed-back to be switched off, and yes some more recent locos behave better without the feed-back.  On balance I probably only use the feedback for 30% of the time, and that will be mostly with older models.
« Last Edit: July 18, 2018, 08:57:19 am by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "KŲnigshafen" exhibition layout!

Offline Chris Morris

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Re: Coreless motors v open frame.
« Reply #6 on: July 18, 2018, 09:22:30 am »
As others have said, old style traditional open frame motors - and also older can motors - at least have "user serviceable parts" eg. brushes and springs. I agree they can last for decades if not abused. I have locos made in the 60s and 70s still happily running on original motors and are still perfectly good enough for exhibition running.

Coreless motors are more efficient and draw less current, but as I understand it there are potential issues with them:

1) Because they don't have an iron cored armature they can't conduct away any heat build-up as well as a traditional motor. It is said that PWM controllers can induce such heat build up more readily than smooth DC.

2) Again because they don't have an iron armature, their Back-EMF response is different to a traditional motor. Hence if you use a feed-back controller it may not be tuned to the BEMF characteristics and may under- or over-compensate, resulting in jerky running.

3) They are often completely sealed with no option to replace brushes.

Of the points above, the heat build-up is probably more likely to cause reduction in motor life.

Remember that a feed-back controller is 99% likely to use PWM, but not all PWM controllers include feed-back circuitry.

Also remember that every DCC decoder I've ever heard of uses PWM for motor drive, and the majority seem to include feed-back although is it usually possible to switch it off.  Also with more comprehensively specified decoders the PWM frequency and feed-back response can be tuned to better suit the motor characteristics. Most decoders use higher frequency PWM than a classic PWM controller.

I still use KPC PWM/feed-back controllers I've had since the 80s, and find they give no trouble at all nor do I notice any heat build up in locos, though my typical operating pattern is to run each train in a sequence rather than leave things belting round and round for many circuits. I did modify the controllers a long time ago to allow the feed-back to be switched off, and yes some more recent locos behave better without the feed-back.  On balance I probably only use the feedback for 30% of the time, and that will be mostly with older models.

I also have a couple of non feedback controllers which I use with the coreless motor locos so I probably havenít either invalidated the warranty or shortened the motor life. My observation was merely that coreless motors donít run very well with feedback controllers.

Offline Dorsetmike

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Re: Coreless motors v open frame.
« Reply #7 on: July 18, 2018, 10:18:46 am »
I had an open frame motor on a Fleischmann tender drive burn out a couple of yeas ago I'd only had it since 1974,I have numerous other open frame motors still running of similar vintage. The only other burn out was a Minitrix class 27, that was due to using half wave power on an old H&M controller.
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Offline Bramshot

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Re: Coreless motors v open frame.
« Reply #8 on: July 18, 2018, 10:53:30 am »
No problems here with coreless, lovely and smooth running especially at low speeds(on dcc). Note that Zimo decoders do have a specific setting for coreless motors, others may, but they usually say Ďsuitableí for coreless motors. This also applies to the (Zimo) one supplied by Bachmann, though you will not find any instructions for it about using the coreless motor feature on locos with coreless motors. The relevant CVís are not listed in the tiny instruction card. Canít remember them now, will look it up again if anyoneís interested. I picked it up from the Zimo small decoders manual. Checked with Bach and they confirmed that the coreless setting should be used.
Regarding which are coreless, the Farish catalogue does say so for some. Those I know about are the Ivatt 2MT, N Class, Princess Coronation.
The open frame ones used by Dapol, in the A4ís at least (I have 5) are awful. They may be user serviceable but about half of them seeem to be very poorly balanced and rattle the tender on the tracks, making the most awful noise. This can be improved by fitting a better decoder that the DCC23, by the way.

Offline Railwaygun

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Re: Coreless motors v open frame.
« Reply #9 on: July 18, 2018, 11:55:04 am »
@Bramshot - can you add/copy your advice on Zimo / coreless settings to the DCC section please

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Offline trkilliman

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Re: Coreless motors v open frame.
« Reply #10 on: July 18, 2018, 12:39:28 pm »
I'm not technically minded so cannot comment accordingly.

I do have two of the latest Farish Princess Coronations and they run superbly, and incredibly slow when wanted.
I use a four track Morley controller.

Offline Old Crow

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Re: Coreless motors v open frame.
« Reply #11 on: July 18, 2018, 05:58:52 pm »
Wow! I hadn't expected to open such a can of worms. I had suspected that the new motors were smaller for scale purposes but didn't expect to hear they might have problems. On the one had if they were potentially so troubled you'd expect Bachmann to be handling a lot of returns. On the other, well I've often thought hi-tech can mean over-complex and unproven and with open frame, yes you can see issues and potentially fix them. I've some quite old stuff running fine and for my purposes, weight and traction are more important than pure scale.

Offline dodger

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Re: Coreless motors v open frame.
« Reply #12 on: July 18, 2018, 06:50:42 pm »
Its strange the Dapol can motors as fitted to their early locos, 2005 vintage seem OK but there are few spares available. As regards to the Bachmann motor I had 2 failures in the 4CEP in three years and I've had to replace all of the motors in the Class 101 & 108 DMU's.

Discussions about 5 years ago suggested they had a life of about 100 hours, not very good in the scope motor life.

Interesting that Dapol change back to open frame motors for some of their later models.

Its a real can of worms and will never be resolved?

Dodger

Offline Bramshot

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Re: Coreless motors v open frame.
« Reply #13 on: July 18, 2018, 08:09:18 pm »

The instructions from Farish specifically state to NOT use feedback controllers...
(In doing so you have probably shortened the motor life and invalidated the warranty...  :thumbsdown:)
Where is this stated?
I havenít seen any instructions regarding coreless motors from GF anywhere, so would be happy to see some.

Online longbow

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Re: Coreless motors v open frame.
« Reply #14 on: July 18, 2018, 10:17:48 pm »
Coreless perform much better than open frame motors and cost only a couple of dollars at trade prices, so in theory it would no great problem if they had to be replaced every few hundred hours rather than serviced.

Is there a source for official Farish replacement coreless motors and if not are there readily available alternatives out there on eBay? 

 

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