Dublo Ringfield motor question.

[Wolseley]

My Ringfield motored Castle has begun misbehaving.  At times it can move off very slowly when starting and when this happens it either either stops (a push will restart it) or it picks up speed after it has travelled 6 feet or so.  This can happen either in forward or reverse, but is more likely to happen in the forward direction.  Then it will happily travel around for a few minutes (sorry to be vague, but it is very variable) then begins to slow down again and, unless it picks up speed, which it sometimes does,  it stops dead.  When it is behaving itself, it draws about .45amp, but when it shudders to a stop, the ammeter needle hits the stop, as if there is a short circuit.  I was just testing it at full speed, rather than a more normal speed, to see if it made any difference, both in forward and reverse and noticed that, just before it stopped, which it did after eight circuits of my 8'x4' layout, there was a shower of sparks from the condenser.

 

I have never had this happen before.  Can someone please explain what is happening here and how to fix it?

[Nearholmer]

Things to look at:

 

- end-float of armature, is it just a fraction, not excessive?

 

- magnet, does it have good, strong, field (test by seeing how firmly it tugs at a screwdriver tip dangled gently against it)?

 

- brushes, have they worn down to “nothing”, thereby leaving only intermittent contact with the commutator?

 

- commutator, is it in good condition, without deep scoring or excessive build-up of crud between segments?

 

- armature windings, are the connections to the commutator good (I wonder from the symptoms of one might be detached)?

 

If all that is good, and the chassis rolls freely with the armature out, I might begin to suspect an invisible winding fault, open circuit or short-circuited turns, which sometimes shows itself as visible heat damage on the surface of the windings, but sometimes not.

 

Report findings.

[Wolseley]

Thanks for the response.  As it's almost 10pm here and there's a fair bit of dismantling involved, I might leave this for tomorrow night.  At this point I can say that it is definitely not the magnet, as I replaced the original one a few months ago with a neo-magnet when I bought the loco, as the original magnet was so weak that the it barely moved when power was applied.  I think I replaced the brushes, but I'll have to take them out to check (wouldn't be the first time I've thought I have done something and I haven't).

 

I have a horrible feeling that the most likely culprit will be the armature windings, but I'll have a look into it and report back.

[Gordon A]

When did you last lubricate with a light oil?

[locomad2]

From 50 odd years of experience locomotives purchased by me and constantly used, oiled, cleaned have performed the best and continued to do so, perhaps not mess about with much. As yet not had to remag any of these, still under .50 amps, ampmeter in series is permanent feature and about only instrument needed.

 

Buying 2nd hand bit like buying cars, it's the previous owners who cause the problems from "systemically wrecked" to just not looked after, plus the low mileage rust and gummed up engines.

 

Think everyone has covered the usually suspects, but don't forget the extra wiring the  condenser and choke and wires connecting them, some are over 50 years old and probably decay to some extent. I actually find running without them seems to cause all kinds of problems apart from radio inference. Another problem shorts with the body, again over the years most metal bodies fitted with insulation tape inside

 

Often I check out this little book might be old but very useful 

[Il Grifone]

A shower of sparks from the condenser suggests this component is faulty. Try disconnecting it from the brush. A replacement should be 470pF, but the motor should run OK without it.

Short circuit windings usually cause clouds of (terminal) smoke and faulty brushgear usually results in erratic running by going intermittently open circuit.

Too much oil in the wrong place can cause problems but again usually cause smoke.

Edited March 25, 2021 by Il Grifone

[mossdp]

Quite common on Hornby Dublo Castles are the armature windings shorting out a bit or a lot as they warm up and expand slightly causing the loco to slow down or stop and the current to increase. However, you mentioned a shower of sparks. Are you sure the condenser is not very nearly touching both sides of the motor so shorting out when subject to vibration or warming slightly or that it is not faulty itself causing a short circuit under certain conditions.

[dcordingley]

I think another potential problem with these motors is carbon dust from cheap replacement brushes clogging the magnet and causing intermittent short circuits. I have cured a couple of my ringfields of the problems described above by dismantling them, cleaning out the dust, and fitting new brushes. One thing to watch for are the tiny ball bearings which lodge in the top and bottom bearings. These can easily go missing during the maintenance process, with the result that you get rough running.  

 

David 

[sagaguy]

Check the carbon brushes,some early ringfields had one carbon brush and one copper carbon brush.Over the years,these can get oil soaked and give you the problem you have here.Remove the brushes,remove the end cap with bearing and clean the commutator and end cap with a cotton bud soaked in IPA.Clean the brush tubes and fit a new pair of carbon brushes,discard the old ones.How do i know this?,you can probably guess.

 

                             Ray.

[DCB]

I have five H/D or Wrenn Castle Ring Field motors and  they are addicted to sluggish starts. Usually a quick clean of the commutator and brushes, a clean out of the plastic residue inside of the magnet and trimming the smeared plastic from the armature, quick oiling of the armature bearings and adjusting the end float they are back to speed. The older 1/2" motor Castles just seem to go on and on.

I wouldn't run one without a capacitor, they stop the arcing across the brushes which makes the commutator dirty, wears the brushes etc.

Sometimes the ball bearing in the end of the armature bearings goes missing and the motor wil run very badly without it.

However I wouldn't use a super neo ring field magnet on one, too strong, I would guess yours has worn its bearings due to excessive magnet strength and the armature or some of the windings are hitting the magnet.   Its quite normal for the windings to get hot and melt the plastic  which smears onto the inside of the magnet but there is a limit to how much material can be lost before the windings start to flail around  hit the magnet lose their insulation and produce sparks.    It's a good motor the ring field but its a kids toy, designed for 2 coaches at scale 150 mph.  It's fine for 8 coaches run at a scale 60 mph but run slowly with a heavy load it will overheat.  My 08 burned out within 20 minutes of being taken from the box brand new 40 years ago. I resodered the armature and fitted Romford 60:1 gears and does about 30 flat out and its been rouble free since.  Likewise my 56XX has a Ringfield Castle chassis with 40:1 gears and runs very happily at a scale 30.  Its not easy but the Ringfield is much happier revving well than running slowly when hauling a decent load.

 

[sagaguy]

Two things,ringfield magnets rarely lose magnetism.The diesel shunter armature  burnt out quite regularly because of lack of ventilation to the armature and Meccano used a plastic or nylon insulating material under the windings,i do have a copy of the original Meccano drawing.Ring field armatures do seem to have a habit of burning out,this is normally caused by over oiling.

 

                         Ray.

[stewartingram]

I disagree about the ringfield magnets losing magnetism. I did loco servicing for many years, for a number of local shops. I did numerous re-mags (and still do some occasionally) on H/D locos, most of which were ringfields. I had many more Triang-Hornby locos pass through for service, than did H/D, but the number of T-H remags was small in comparison.

 

Stewart

[locomad2]

As happen to Davidcboard class 08 is vulnerable to burn out, happened to my father in mid 60's while the locomotive was still under guarantee. Fortunately Meccano had an excellent repair service and factory repair was done, have a letter somewhere. Warned only to use it for shunting and be careful spent 25 years as a shunter just moving 4 coaches out of the way so leading engine could be turned.

 

Careful management using ampmeter it's still used as a shutter and a excellent chassis, and haulier, so much so its having a new body fitted cause I like the "wasp" end, still under construction plastic cutting turning into a longer job, but getting there

 

 

BTW the modern Hornby chassis & motor has failed purchased as a non runner, motor burnt out  just not worth repairing, can't pull anything worthwhile anyhow

 

 

[Wolseley]

Well, this has been a very interesting collection of responses, containing much information that needs to be noted for future reference.  Thank you everyone.

 

I removed the body and ran the locomotive for a couple of circuits and found that, not only was the problem getting worse, but it was starting to get rather noisy.  Now I don't mind dismantling other Dublo motors to service them, but I would much rather leave Ringfields alone, so I started off by looking at possible problem areas that did not require the motor to be pulled apart.

 

The first thing I checked was whether or not the brushes were worn and it turned out that my memory wasn't playing tricks on me - I had renewed them.  Then I checked the end float of the armature, as Nearholmer had suggested.  Initially it looked in order but, as I was about to look elsewhere, I noticed something amiss - sure there was no excessive end float, but the shaft was at a slight angle and, with a bit of a prod from a screwdriver, it would move slightly from side to side.  What had happened was the grub screw securing the adjustable bearing housing assembly was not tightened down properly, and the assembly (it is the earlier one that is screwed in from the front of the motor housing) must have become looser with use, and the armature shaft had come out of the bearing hole (or whatever you call the bit in the housing it fits into) and was moving slightly up und down sideways as well.  I put everything back in its right place, tightened up the grub screw and was pleasantly surprised when it started and ran as it should - and ran a bit more quetly than it had been.  Problem solved.....

 

Now I don't know the history of this loco, and it was in a rather parlous state when I bought it (it was a "non-runner" with missing paintwork and bent cab roof and was said to be only suitable for spares) but I suspect a previous owner must have been mucking about with it, as the adjustable bearing housing assembly is one part I definitely didn't touch when I was servicing the motor and chassis a few months ago.

 

Anyway, after all that talk about my Ringfield Castle, here it is (I hesitate to call this one "she" as I renamed it Isambard Kingdom Brunel):