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Ringfield Magnets.





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#1 beeman

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Posted 27 July 2010 - 09:38

Any member fitted a new modern Neodymium magnet to a ringfield drive, post 1976 type unit. How does the much stronger magnet behave?. I have been 'shopping' to see what a minimum run quantity of a suitable magnet might cost.I was surprised to see that Hornby virtually never offered these as a spare part according to the spares lists, and as such are virtually not available. I have recently been upgrading some of my locos from 3 to 5 pole, this does need a bearing change!!. but there is a marked difference in the slow speed performance, from getting 1 sec per driving wheel revolution [DCC steam locos], to between 5-8 secs/rev. I am putting this 5-8 variation down to the magnet strength. I have been quoted a price of around 5-6 euros [approx 5pounds ] for these but a minimum quantity of 50 would be necessary for a production run. I myself would want about 10 items so for me alone this would be somewhat costly . Are there any members who are in a similar position who would be interested in this idea, perhaps thro a dealer.I would think that the replacement magnet could be of a larger I/D, and better for fitting, [original size is 28x22x8 mm] as they are between 5-7 times stronger than the original versions fitted, many of them being a 'rubber' flexible type, and between my A4 Seagull, Un-rebuilt Patriot, and Black 5 finding 3 types of magnet but sized the same.I feel sure that there are many enthusiasts in my position, if your are please respond so a judgement can be made on the viability of this suggestion, and of course if you have any experience in updating. I have certainly found the armature changes worthwhile and satisfying. I have also asked a supplier to ask Hornby WHY can they not supply the 5 pole with an increased shaft diameter similar to the original, there must be money in it for them.!!!, and considering the thousands of locos still about that would benefit, perhaps Hornby feel this would cancel out some of their new sales and treat it as a none starter. Beeman

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#2 Horsetan

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Posted 27 July 2010 - 09:42

I would only ever need two, for my old twin-motored Hymek. I've been playing with the idea of converting the motors from 3-pole to 5-pole, but it's not a great priority.

#3 Simon G

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Posted 27 July 2010 - 16:57

Beeman, like you I have wondered about fitting neo magnets to some of my older Ringfield units and also discovered that they are not easy to find. There is a site - Superneomagnets (link below) - that appears to do Neo magnets for Hornby Dublo ringfields. What I am not sure about is whether the dimensions are the same as for Hornby ringfields. If they would fit, it might be a suitable source for them (please note that I have not been in touch with Superneomagnets and havent done any business with them, so this isnt a recommendation, just a suggestion).

http://www.superneomagnets.co.uk/

If the Hornby Dublo ones dont fit, I think that there is probably a market for a Hornby ringfield Neo magnet. There seem to be many old HSTs etc that are for sale advertised as running slowly - this is most likely due to the original magnets losing their strength over the years. I would certainly have a few if I could lay my hands on them. If there are currently no manufacturers at all for these, you might buy the whole production run and try to sell the excess on ebay etc. You might cover the costs doing it that way.
Simon

#4 beeman

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Posted 27 July 2010 - 21:19

Hi Simon further to your suggestion, I emailed the site you mentioned and respectfully asked about the dimensions of the ringfield magnets they supply for Dublo locos in an attempt to see if I could make them fit.. I got a RUDE reply telling me that they do not give out details on sizes and have supplied many replacements to date, which should suffice. My feelings toward this ignoramus is F*** U. I some times wonder why these PEOPLE are in business, c'est la vie.Further to your suggestion I have never used ebay,I would have thought that there were sufficient members in a similar position to myself to be be interested, perhaps early days for the post yet cheers. Beeman

#5 bertiedog

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Posted 27 July 2010 - 22:04

The Dublo Ringfields are quite different to the Tri-ang Hornby type use in the tender drive or diesels. The dimensions are different, and the field is across the faces, not as two poles on the ring.


The modern type magnet in neodymium would have to be specials, made to order. Hornby should have supplies of the Ringfield Magnets spares in the alnico type for replacement, or they can be re- magnetised, although few service shops have the equipment.

Stephen.

#6 beeman

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Posted 28 July 2010 - 08:52

Further to the comments by Bertidog, this item was posted to see if there were any like myself who would be interested in obtaining Neodymium magnets which could be obtained by a minimum production run. Hornby 'should' have stocks of these original items?, I believe they never sold these as a spare part item, as it appears if the spares lists are checked, unless purchasing the main chassis which I believe included the magnet. I have tried obtaining these through an agent/Hornby with no success. The only outlet listing these was Modelspares, if they actually had them ?, and of course the've 'gone'. Neodymium is 5-7 times stronger than the old type and I understand does not deteriorate with age. I am well aware there is a size difference' thats why I asked 'Superneomagnets' to advise, some help !!! Please correct me if wrong but in each motor type does not the armature revolve within the i/d of the magnet/field , hence ringfield, embodying the basic principles of small electric motors. If as you suggest,please advise how the Dublo armatures rotate if the magnets are polarised across the faces rather than their diameter. This suggestion appears to break the mould of electrical theory and practice. I regret being critical but confusion for other modellers is misleading when advice appears incorrect.
Beeman. Electrical/Mechanical.Eng.Retd.

#7 bertiedog

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Posted 28 July 2010 - 10:52

It is not across the faces,(sides) , but across the flats on the outside, resulting in two poles at 90o to the flats. The Hornby originals are thicker, and the hole smaller than the later pancake type. A lot of ring magnets have no flats, using marks to align the poles.
Both types have the same magnetic path, and the original Ringfield followed Lindsay patent, which with his skew slots gave a smooth transition between poles, as the poles are less distinct than say a horseshoe or twin magnet type. Hornby originals just copies the magnet, dropping the skew slot.

Stephen.

#8 bertiedog

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Posted 28 July 2010 - 11:17

One minor point to consider with neodymium magnets is that when fitted to older motor designs the current may remain high, the power efficiency goes up, but as the wattage in may be higher than modern designs the motor may heat up more under load. In practice the motor is more efficient, and a lower voltage balances it out.


The downside of neodymium magnets is that they have a remarkably low "Curie"point, the temperature at which the magnets fail.....and with some designs the wattage can warm the motor enough for the magnet to fail. In theory the temp is 320deg C, very hot!!, but in practice failure can occur at 170/200. I have seen one fail at about 110, just a bit above boiling water temperature.

The modern Hornby motor should not draw enough current to do this, but older original types might, and need re-winding with a smaller gauge wire to reduce the current. The thicker wire was to draw more current to work with the less efficient magnets, upping the power of the magnets still leaves the thicker wire, and with a high load lots of current and heat.

With the usual loads the motor draws less current for the power output, so it is only an overload that might cause concern.

If the magnets are specially commissioned make sure as high as possible Curie point is specified. I am told the problem ones are from some Chinese makers, who make the full specification magnets as well but also the production produces low curie versions which are sold in effect as second grade, perfectly all right as long as they are cold.

Stephen.
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#9 Simon G

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Posted 28 July 2010 - 16:18

Hi Simon further to your suggestion, I emailed the site you mentioned and respectfully asked about the dimensions of the ringfield magnets they supply for Dublo locos in an attempt to see if I could make them fit.. I got a RUDE reply telling me that they do not give out details on sizes and have supplied many replacements to date, which should suffice. My feelings toward this ignoramus is F*** U. I some times wonder why these PEOPLE are in business, c'est la vie.Further to your suggestion I have never used ebay,I would have thought that there were sufficient members in a similar position to myself to be be interested, perhaps early days for the post yet cheers. Beeman

Hi Beeman,
I can only apologise for their lack of courtesy - I wish that I had tried to contact them myself, so I wouldnt have then put the link on this site. I entirely agree with you about suppliers being rude - there is nothing to put you off them faster than that.
I have bought Neo magnets for older Triang X04 and powered bogie motors from elsewhere, so I will see if that supplier can help (before I put their details on here!)

#10 beeman

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Posted 28 July 2010 - 21:38

Interesting observations from Bertidog re replacement magnets. some temperatures he quotes are higher than Class H enamel wire, which is at best 200 C, so I would assume that the wire would 'burn out' around the same temperature anyway.I am surprised that it would be possible to get a motor to the 300+ temperature he mentions, if on DCC the 'chip' is set up correctly ,unless it failed to a short. I would assumed this should be recognised by the DCC system . I have found after converting some 30+ locos that in every case I have needed to drop CV5 values to reduce the top speed of the loco to an acceptable level. giving me a scale speed of around 70 mph max for express passenger locos. There are few layouts that can accept locos charging around at scale top speed due to the layout size/run length including mine. This then reduces the maximum current the chip feeds to the motor in relation to the top speed required. Also from my 'tech' days the back emf of the motor is a product of the rotation of the motor within the magnetic field trying to act as a generator. Logic says that if a stronger magnet is used this will be greater. If back emf did not exist the motor would rev ever higher until it destructed by centrifugal force. Back emf will restrict this until the motor settles at its 'slip speed', the difference between the input current and the back emf. Whilst composing this I see where Bertidog is coming from, that with the higher back emf it may require a higher input current to counter the stronger back emf, but at the same time the stronger magnet should be creating more attraction to the energised poles of the armature. It would seem this may be a 'try it and see' if it gets as far as obtaining suitable magnets. been interesting discussion so far, thanks to contributors.Beeman.

#11 hollywoodfoundry

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Posted 28 July 2010 - 22:52

I would thoroughly agree with Bertiedog regarding low curie point magnets. I have had several Mashima motor that have failed due to the motor getting too hot and the magnets losig their effectiveness. But the current does not necessarily rise, and there is no setting in a DCC chip that will prevent this as long as the current stays well within the 'stalled motor' capability of the decoder. In these cases, the current rose to 800mA and the motor was cooked, and the motor certainly never reached 300 degrees.

#12 bertiedog

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Posted 29 July 2010 - 11:05

The 300c plus curie point is quoted by makers and net sources including Wikipedia, I think though that it can be much lower dependant on the supplier, and the form of the magnet. In lab work the exact Curie point can be as high as 640c, but this is for total field loss.

Most suppliers are the Chinese and Japanese, and the quality varies a lot, maybe the compression moulding of the materials before firing varies, but I know as with LED lamps, the makers have few "failures", they just grade the output according to specification, the poorest going to "toy" magnet uses.

The magnets also suffer in the post production nickel or chrome plating, and this treatment also lowers the Curie point, where magnetism is lost. It is also not a sudden change, the increasing heat reduces the field, and in a motor would cause the current and the heat to rise as it fails.

It seems the main troubles come with the very thin rare earth magnets in enclosed can motors, they seem to fail at as low as 120c, so a run away failure must be occurring, with the current constant, and the heat increasing due to the failing magnetic field.

Trying to describe what happens to current/voltage/field inside what is a dynamic situation inside a motor is a bit beyond these postings.

Normally it is assumed for clarity that DC voltage and current works with DC motors, but I am sure you realise this is not what is going on, with alternating AC current, back emf, etc, driven by the coils.

There is a hidden effect adding to localise heating in the magnets and that is eddy currents within them, and in neodymium this is far higher than other magnets, and seems to quicken heating effects.

In the end I think it quite unlikely a big ring magnet would de-magnetise, it would be melting the plastic for a start, but it is possible, as Hollywood foundry experienced, to get the smaller motor types to loose the field.

Stephen.

#13 beeman

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Posted 23 August 2010 - 10:39

Here is the update for fitting a Neo magnet to the older Ringfields. Loco chosen was an older Hornby A4 Seagull, having a 'rubber' magnet fitted of nominally 28x22x8mm, the 'replacement I obtained in N42 was 27x23x6. In my previous post I suggested that while this was u/s to the original the power of the magnet would compensate. This proved correct. I fitted an outer liner of mild steel strip to centralise it within the diecast frame which also acts as an external keeper. This was also quite sufficient to locate it. On the bench the drive would rotate at 50mA when supplied from an old transistor controller, ammeter connected in motor armature lead.This loco was prior converted to DCC and at best I could only get 1 rev.in 1 sec of the driving wheels. I then fitted a 5 pole armature which gave an improvement to 4-5 secs for 1 rev., on fitting the new magnet this halved to 1 rev taking 9-10 secs. I have attempted to measure the current taken after fitting the Neo magnet. I do not have a 'rolling road so the following had to suffice. The ammeter connected in one motor lead, the loco was 'held' on the track physically, and the power applied, [ Dynamis/Bachman chip ], with the loco held so that the wheels were skidding on the track it was only when the traction tyres were skidding that the current went up to 300mA , obviously it would have increasedthe load to stall, but it was certainly under excess load, and certainly wont produce overheating,!!!!.Must admit I adjust cv5 to give maximum speed to approx scale 70mph. This project has contradicted the 'doubters' who commented on my proposals previously. The economic downside is it cost approaching 10 pounds, and on visiting a Toy & Train sale a week ago find drive units for sale at 10 pounds, these are advertised elsewhere around 20+, having brushes.springs.traction tyres.wheels,and should have a good magnet as they were fitted with a 5 pole armature. so perhaps next time I shall indulge if still available..Beeman.

#14 Horsetan

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Posted 27 August 2010 - 22:07

Interesting. Where did the N42 neo magnet come from again?

#15 beeman

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Posted 03 September 2010 - 09:50

Interesting. Where did the N42 neo magnet come from again?

Checkout 'PowerMagnetStore.com' if you purchase/fit please post your results for interest, Beeman

#16 Horsetan

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Posted 16 September 2010 - 14:54

Here is the update for fitting a Neo magnet to the older Ringfields. Loco chosen was an older Hornby A4 Seagull, having a 'rubber' magnet fitted of nominally 28x22x8mm, the 'replacement I obtained in N42 was 27x23x6. .....


Any chance of seeing the new magnet in-situ?

#17 Trev

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Posted 13 October 2010 - 22:54

Hi Beeman, I also have an A4 seagull and have been searching all over to find a suitable magnet. The loco runs smoothly on DCC, but has little power. Thanks for your post, I think I will have a go with the N42 magnet.

#18 Trev

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Posted 14 October 2010 - 10:25

Here is a reply I got from 'superneomagnets' when I asked them about a suitable one to my A4 seagull.
"Sorry, we do not do motor magnets for Hornby Tender Drive Loco's. Development tests have proved that the magnets are just too strong to allow motor rotation due to lack of turns on armature and lack of armature mass."

#19 k9-70

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Posted 24 October 2010 - 12:12

I fitted one of these "Super Neo Magnets" to my old Hornby Dublo EE Type 2 (Class 20).
It was a bad move. Nothing happened, the armature refused to turn, a lot of buzzing from the motor and then smoke appeared from the armature. The loco was removed from the track and the original weakish magnet was replaced and tested again.
Luckily the loco still worked after refitting the original magnet.

In my opinion, these magnets are just too strong for the older motors to work properly.

K9-70

#20 jipf1

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Posted 17 August 2011 - 16:57

I have just purchased a Neo Magnet from eBay specifcally designed for Hornby ringfield motors. I got it for my Intercity APT which had given up the ghost. The neo magent fit purfectly with out any alteration & it amazing how well the train runs now.

From what I saw in his ebay shop he does different magents for all different models.
http://www.ebay.co.u...=item588f604b6c

#21 beeman

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Posted 29 August 2011 - 09:03

Good to see a member has done this without any probs and a good satisfactory result obtained, as I suggested earlier it is IMPERATIVE that a new magnet is fitted perfectly in both axis otherwise uneven forces are applied to the armature which can unbalance and cause it not to run, It seems that obtaining a correct size magnet which jipf1 obtained is the way to go to eliminate any alignment which was necessary for me, purchasing a near fit one before the proper size fit was available. I would suggest it may be a problem if these magnets are fitted to a motor with very worn bearings, this could give uneven field on to the armature so causing probs.

#22 Borsini

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Posted 02 December 2012 - 11:53

Here is the update for fitting a Neo magnet to the older Ringfields. Loco chosen was an older Hornby A4 Seagull, having a 'rubber' magnet fitted of nominally 28x22x8mm, the 'replacement I obtained in N42 was 27x23x6. In my previous post I suggested that while this was u/s to the original the power of the magnet would compensate. This proved correct. I fitted an outer liner of mild steel strip to centralise it within the diecast frame which also acts as an external keeper. This was also quite sufficient to locate it. On the bench the drive would rotate at 50mA when supplied from an old transistor controller, ammeter connected in motor armature lead.This loco was prior converted to DCC and at best I could only get 1 rev.in 1 sec of the driving wheels. I then fitted a 5 pole armature which gave an improvement to 4-5 secs for 1 rev., on fitting the new magnet this halved to 1 rev taking 9-10 secs. I have attempted to measure the current taken after fitting the Neo magnet. I do not have a 'rolling road so the following had to suffice. The ammeter connected in one motor lead, the loco was 'held' on the track physically, and the power applied, [ Dynamis/Bachman chip ], with the loco held so that the wheels were skidding on the track it was only when the traction tyres were skidding that the current went up to 300mA , obviously it would have increasedthe load to stall, but it was certainly under excess load, and certainly wont produce overheating,!!!!.Must admit I adjust cv5 to give maximum speed to approx scale 70mph. This project has contradicted the 'doubters' who commented on my proposals previously. The economic downside is it cost approaching 10 pounds, and on visiting a Toy & Train sale a week ago find drive units for sale at 10 pounds, these are advertised elsewhere around 20+, having brushes.springs.traction tyres.wheels,and should have a good magnet as they were fitted with a 5 pole armature. so perhaps next time I shall indulge if still available..Beeman.



Hi Beeman, Restoring 8F 2-8-0 tender drive and City of Nottingham tender drive type 6 ringfields. Really interesting. I contacted power magnet store and, although they have Neo ring magnets easily physically adapted, the guy states they were all axially (face) polarized and not diametrically polarized. So, do you know summat I don't cos I'm hornswoggled? I believe one needs diamtetrically polarized magnets (as per originals) in order to be successful? I have found segmented magnets for sale as "sets" with diametrically polarized (North O/D ; South I/D & vice versa), bur, harder to adapt + I'm not sure what angle to cover for optimum performance (one can make them up to a full circle, each segment is approx 45 degs). MTrains (john@mtrains.co.uk) has diametrically polarized magnets for the old Dublo. Big one is very near! BUT I/D is 20 m.m., so, such a shame as Neo is almost impossible to machine I think. I got the superb beautifully constructed 5 pole armatures from Earlesmeade/Ebay. Shafts are sleeved with excellent brass bearings to create correct diameter. If you have time I would greatly appreciate your input /support. Regards Borsini.

#23 stewartingram

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Posted 02 December 2012 - 16:57

Why do you need to replace the magnet? Personally I have had hundreds of locos pass through my hands for repair, mainly of Triang/Hornby origin, with a lot of Hornby-Dublo, and a handful of others. (I speak from experience as a service engineer for a number of modelshops). In all that time, I could probably count on one hand the number of Triang or Hornby locos that needed attention to their magnets. Hornby-Dublo/Wrenn models though, I included a re-mag on every loco as a matter of course as so many had lost magnetism over time. How many of either type were user faults though, I don't know. A magnet should NEVER be removed from its magnetic circuit, as this will cause loss of magnetism.
Good luck to those that have introduced new types of 'super-magnets', I'm sure there are some that will find use for them, I'm not decrying that. But certainly with the Triang/Hornby range, I don't believe there is a need to replace magnets. If anyone does need a remag done, please contact me. (Note - not a sneaky advert for services, I still have the re-magnetiser, and will gladly re-mag for you at minimal cost, ie postage)

Stewart

#24 Borsini

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Posted 03 December 2012 - 10:57

Post 23. Hi Srewartingram, Thank you for the input. OK, is there a simple effective way to assess the stength of the originally fitted magnets on a Ringfield 6? I'm fitting a sound chip decoder and it is a lot of work. What I do not want to do is put everything back together and then find the motor does not perform very well cos magnet has lost strength. With expensive sound chips it is not desirable to assemble/disassemble too many times. I think Beeman has left RMWeb and gone to Model Rail Forum. Regards. Borsini

#25 stewartingram

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Posted 03 December 2012 - 14:47

My simple way is just measure the current taken by the motor. I have an in-line ammeter, which measures the current taken by the controller and the motor. In my case this is typically 1/4 amp; any loss of magnetism increases this noticeably.
I might add that 1) I use a homebuilt PWM dc controller, which uses current itself; 2) supply voltage to the controller is around 18-20v dc ( a tad higher than normal 12v); 3) the ammeter is not accurately calibrated, other than to show roughly 1A on fsd. All these factors mean that my meter indication is just that, an indication, which I aim for, any variation is therefore not normal.But the general idea of around 200-250mA on dc is about right. Any cheap multimeter is probably capable of reading that I suspect. If you have a known good motor, use that for a comparison.
If you need any assistance, please get back to me.

Stewart

Edited by stewartingram, 03 December 2012 - 14:47 .








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