Coreless Motors - Back EMF - Feedback Controllers - DCC

[maico]

On 13/04/2020 at 17:50, melmerby said:

Well if you do come up with the definitive list it will probably be enough for a book.

 

Coreless motors were originally developed for electronic kit that required fast response, which coreless motors with their lack or armature mass were ideal for.

I used to service X-Y plotters and these usually had Canon or Maxxon motors. Expensive but extremely high quality. Built like a Swiss watch!

I wish I had kept the surplus ones I used to have!

 

The current crop of coreless motors are as developed in China for cheap mass production, the lack of core makes them cheaper than a similar rated iron cored motor and more compact, ideal for cheap mass produced lightweight items, the side effect they are now starting to be used in model railways where the lack of rotary mass and light weight is not an advantage.

 

Oxford replaced the original 5 pole skew wound iron core motor in the Dean Goods with a 3 pole coreless design which IMHO is definitely inferior.

 

 

 

Don't you mean Maxon? Some Trix shunters use them https://www.maxongroup.com/maxon/view/content/product-overview

 

My Trix P10 dcc sound loco has a Portescap Athlonix motor which is a brush coreless design

 

https://www.portescap.com/products/brush-dc-motor/athlonix-high-power-density-brush-dc-motors

 

https://www.portescap.com/products/brush-dc-motor/brushed-dc-motor-basics

 

 

Edited April 18, 2020 by maico

[melmerby]

29 minutes ago, maico said:

 

Don't you mean Maxon? Some Trix shunters use them https://www.maxongroup.com/maxon/view/content/product-overview

 

My Trix P10 dcc sound loco has a Portescap Athlonix motor which is a brush coreless design

 

https://www.portescap.com/products/brush-dc-motor/athlonix-high-power-density-brush-dc-motors

 

https://www.portescap.com/products/brush-dc-motor/brushed-dc-motor-basics

 

 

 

Maxxon is the result of banana fingers on the keyboard

You won't find a brushless, coreless DC motor, they all need some sort of brushgear.

A pretty hefty flywheel there, which overcomes the disadvantage of lack of rotary mass of coreless designs in model railways.

 

[maico]

13 minutes ago, melmerby said:

 

You won't find a brushless, coreless DC motor, they all need some sort of brushgear.

A pretty hefty flywheel there, which overcomes the disadvantage of lack of rotary mass of coreless designs in model railways.

 

 

Er...so what's this, brushless slotted core design? https://www.portescap.com/products/brushless-dc-motor/bldc-motor-design

 

 

Edited April 18, 2020 by maico

[melmerby]

10 hours ago, maico said:

 

Er...so what's this, brushless slotted core design? https://www.portescap.com/products/brushless-dc-motor/bldc-motor-design

 

 

It's not a DC motor, whatever they try and tell you.

It's a type of AC motor with a power convertor to drive it from DC.

I hate the term Brushless DC as there is no such thing, it's misleading.

DC is a steady state, the only way it works with motors is by commutation, either using brushes or electrically.

On it's own DC won't make anything rotate.

Edited April 18, 2020 by melmerby

[maico]

Came across this article about a guy re-motoring with cheapish ($12 or so) used Maxon and Portescap brushed coreless motors. He seems to have some success looking at his videos

http://cs.trains.com/mrr/f/88/t/273297.aspx

 

Should probably mention the German company Faulhaber too as they make a large range of micro-motors. https://www.faulhaber.com/en/products/brushless-dc-motors/brushless-dc-servomotors/

 

Edited April 18, 2020 by maico

[RBAGE]

I'm still trawling for information to try and come up with a summary of the do's and don't's for coreless motors so you won't be surprised that I've made enquiries elsewhere.

I spoke to a friend who's used ECM feedback controllers with coreless motors for 30+ years with no ill effects. At my suggestion, yesterday he tried two different designs of ECM on an EM gauge J39 with RG4 1616 - sweet as a nut with both the Compspeed F and CA. The same loco has also run extensively on Retford (Modelex controllers) and recently had a spin on Buckingham Great Central. Buckingham station has the ECM Compspeed as its No. 1 controller and a hand-held AMR for the yard, while Grandborough Junction uses some ancient piece of history of indeterminate make. The loco was fine, whatever controller was used.

I'm not sure if this conflicts or correlates with information already discussed here. I need to pick the bones out of what we have and summarise everything. If there are disagreements, I'll raise specific questions to see if there are reasons.

 

If anyone has any thoughts on this information that I'm missing, please let me know.

 

If there are any other contributions that might be useful, please let me know. First hand experience of specific equipment is most valuable.

 

Thanks for your help.

 

Bob

[NIK]

Hi,

 

There may be two aspects to running coreless motors in model locos:

 

1) Motor damage.

2) Poor slow running.

 

With DCC aspect 1) can be addressed by selecting a DCC decoder that can output a high enough frequency drive to the motor.

 

2) Poor slow running on DCC - I don't have any practical experience of. If a motor outputs too much torque at low revs and the feedback system in the decoder is not correct then surging could happen.

Many DCC decoders have some adjustment of key feedback parameters and some brands have quite sophisticated adjustment.

 

Also DCC systems can respond differently to tiny interruptions in the track/wheel and wheel to pickup interfaces than DC controllers and locos. Coreless motors have less magnetic friction (cogging) so respond quicker to fast changes in the power being applied (such as pulses from DCC decoder motor drives). For the same reason they have more of a flywheel effect than iron cored DC motors so once they have been given a power impulse it takes longer for the motor/output gear to retard back to a lower speed.

 

Take care.

 

Nick

[Chuffer Davies]

4 hours ago, RBAGE said:

I'm still trawling for information to try and come up with a summary of the do's and don't's for coreless motors so you won't be surprised that I've made enquiries elsewhere.

I spoke to a friend who's used ECM feedback controllers with coreless motors for 30+ years with no ill effects. At my suggestion, yesterday he tried two different designs of ECM on an EM gauge J39 with RG4 1616 - sweet as a nut with both the Compspeed F and CA. The same loco has also run extensively on Retford (Modelex controllers) and recently had a spin on Buckingham Great Central. Buckingham station has the ECM Compspeed as its No. 1 controller and a hand-held AMR for the yard, while Grandborough Junction uses some ancient piece of history of indeterminate make. The loco was fine, whatever controller was used.

I'm not sure if this conflicts or correlates with information already discussed here. I need to pick the bones out of what we have and summarise everything. If there are disagreements, I'll raise specific questions to see if there are reasons.

 

If anyone has any thoughts on this information that I'm missing, please let me know.

 

If there are any other contributions that might be useful, please let me know. First hand experience of specific equipment is most valuable.

 

Thanks for your help.

 

Bob

Well I think I'm going to have to accept that the evidence does not appear to support my understanding with regards supposed incompatibilities between ECM controllers and coreless motors.  I looked up the specifications for Portescap motors in the EMGS manual and the spec actually recommends ECM controllers for Portescap motors so my apologies for any  misinformation I may have provided.  

Rechecking the Gaugemaster site the spec for the HH controller definitely warns against their use with coreless and 'N' gauge motors so that part of my previous entry remains correct.

 

We live and learn.

Frank 

[RBAGE]

I'm still going and from information gathered here and elsewhere, feedback controllers operate by PWM (pulse width modulation) or PTM (pulse time modulation).

Stop me if I'm getting too far into the long grass. And don't worry, I haven't seen a flash of inspirational light, I've just followed Chuffer Dave's path to the EMGS manual.

Anyhow, from other sources, the suggestion is that any problems experienced has been with PWM controllers. I'll accept that this is the experience of a small number of modellers and when I say small, it's a number approaching one, so it's not necessarily gospel. We need to be careful of much of the information circulating. However, following up on this lead, it would be interesting to know which feedback controllers are pulse width and which are pulse time. Does anyone have information on some or all or their example of feedback controller so that I can have a look to see if there is any correlation with perceived performance? Please.

 

Also, furthering the discussion about ECM controllers, there is a suggestion that panel mounted controllers appear to present no problems with coreless but hand helds do. Again, a limited sample size but does anyone have any experience? Can the same be said for other manufacturers of panel mounted and hand held controllers?

 

Finally, for this post at least, I have an observation that may be a question. Worth thinking about though.

From the mid-80s on, can motors and Portescaps were and in many cases still are the norm for finescale model locomotives. Feedback controllers work particularly well with can motors and many people found they also worked well with coreless motors. Not everyone used Pentrollers, and the like, so where did this idea that coreless motors are incompatible with feedback controllers come from? Was it based on hard evidence and observation or did someone just make it up? We know (because we've seen it with our own eyes) that some makes of feedback controller (such as KPC) don't seem to like coreless motors but on the same evidence we also know that many other designs such as ECM have no problem whatsoever.

 

Once again, any hard evidence will be pounced on and much appreciated.

 

Thanks,

 

Bob

 

 

[Beechnut]

I have two locos with Portescap motors, a 1219 plus one of the larger ones. All locos controlled using AMR handheld, no problems for the last 25 years.

 

Brendan

[RBAGE]

So, in a nutshell, would any members know any specific makes of controller past and present that feature Pulse Wave Modulation (PWM)? I'm told (by a highly regarded modeller with a distinguished career in electronics) this could well be the root cause of problems with coreless motors. He swears by Modelex controllers, by the way . . .

Other brands of controller are available.

 

 

[RBAGE]

7 minutes ago, Beechnut said:

I have two locos with Portescap motors, a 1219 plus one of the larger ones. All locos controlled using AMR handheld, no problems for the last 25 years.

 

Brendan

Thanks Brendan,

Valuable, first hand information. Smashing.

[CF MRC]

I have been using coreless motors for the last 40 years in 2mm scale, with no failures.  Mostly, over that time, they have been DC controlled by the special feedback controller ‘Pentroller’ made by Stewart Hine.  Latterly, we have used the equally effective ‘PICtroller’.   The low inertia and lack of magnetic locking means that locos fitted with coreless motors are ideal candidates for flywheels, giving the loco a good run on when power is turned off.  Our original motors were Portescap 1219s & 1212s, but more recently we have used Maxon motors which, size for size, are generally slower running and more powerful: the 8x16 motor with a 1:4 gearbox on the front is particularly useful.  Tramfabrik are also supplying excellent slow running and powerful motors.   Some of these mechanisms figure in an article in the latest MRJ #278. 
 

Tim

[Michael Edge]

3 hours ago, Beechnut said:

I have two locos with Portescap motors, a 1219 plus one of the larger ones. All locos controlled using AMR handheld, no problems for the last 25 years.

 

Brendan

That's more or less what I've been saying all through this - I've had no problem with the hundreds of Portescap motors of all kinds on any of the wide variety of controllers they have been run with. There's an awful lot of erudite theory above and not much practical experience - as usual.

[NIK]

38 minutes ago, Michael Edge said:

That's more or less what I've been saying all through this - I've had no problem with the hundreds of Portescap motors of all kinds on any of the wide variety of controllers they have been run with. There's an awful lot of erudite theory above and not much practical experience - as usual.

Hi,

 

The topic is about Coreless Motors on DCC so DC controller experience is not so relevant.

High frequency PWM drive is becoming very common in DCC but until recently in the UK coreless motors were restricted to non RTR locos so there wont be much practical experience of coreless with DCC.

 

Maybe there are not many instances of problems of coreless motors with DCC on UK locos because folks now buy a modern design of DCC decoder to go with their expensive RTR loco.

Maybe the first few UK locos with coreless motors were highlighted by the reviewers in model railway magazines so DCC users has some sort of guidance of what sort of DCC decoder to fit.

Now some magazines don't bother to mention if a newly released loco's motor is iron core or coreless.

 

Take care.

 

Nick

[d00m]

7 hours ago, RBAGE said:

I'm still going and from information gathered here and elsewhere, feedback controllers operate by PWM (pulse width modulation) or PTM (pulse time modulation).

Stop me if I'm getting too far into the long grass. And don't worry, I haven't seen a flash of inspirational light, I've just followed Chuffer Dave's path to the EMGS manual.

Anyhow, from other sources, the suggestion is that any problems experienced has been with PWM controllers. I'll accept that this is the experience of a small number of modellers and when I say small, it's a number approaching one, so it's not necessarily gospel. We need to be careful of much of the information circulating. However, following up on this lead, it would be interesting to know which feedback controllers are pulse width and which are pulse time. Does anyone have information on some or all or their example of feedback controller so that I can have a look to see if there is any correlation with perceived performance? Please.

 

Also, furthering the discussion about ECM controllers, there is a suggestion that panel mounted controllers appear to present no problems with coreless but hand helds do. Again, a limited sample size but does anyone have any experience? Can the same be said for other manufacturers of panel mounted and hand held controllers?

 

Finally, for this post at least, I have an observation that may be a question. Worth thinking about though.

From the mid-80s on, can motors and Portescaps were and in many cases still are the norm for finescale model locomotives. Feedback controllers work particularly well with can motors and many people found they also worked well with coreless motors. Not everyone used Pentrollers, and the like, so where did this idea that coreless motors are incompatible with feedback controllers come from? Was it based on hard evidence and observation or did someone just make it up? We know (because we've seen it with our own eyes) that some makes of feedback controller (such as KPC) don't seem to like coreless motors but on the same evidence we also know that many other designs such as ECM have no problem whatsoever.

 

Once again, any hard evidence will be pounced on and much appreciated.

 

Thanks,

 

Bob

 

 

 

I have been using ECM Composed controllers for over 30 years. In all that time only one unit died (I use 5), that was due to an extremely old Triang loco which drew too much current. Lots of visiting locos with all types of motors including coreless no problems at all. Just wish the company was still going - could do with two more. ( Don't want to go DCC - too many locos)!

[NIK]

5 minutes ago, d00m said:

 

I have been using ECM Composed controllers for over 30 years. In all that time only one unit died (I use 5), that was due to an extremely old Triang loco which drew too much current. Lots of visiting locos with all types of motors including coreless no problems at all. Just wish the company was still going - could do with two more. ( Don't want to go DCC - too many locos)!

Hi,

 

How relevant is this to the OP or to the topic involving DCC?.

 

I think you mean Compspeed but maybe your fingers weren't composed at the time.

 

Take care.

 

Nick

[RBAGE]

22 minutes ago, NIK said:

Hi,

 

How relevant is this to the OP or to the topic involving DCC?.

 

I think you mean Compspeed but maybe your fingers weren't composed at the time.

 

Take care.

 

Nick

The topic is about DC and DCC. My original post explained that I trial kit built locos (during the build) in DC until I'm satisfied of good running. Once I'm happy and when the build is complete, then I fit a decoder for DCC operation. If I'm getting poor operation from a coreless/feedback arrangement, I might never get to a finished model.

Mind you, the question of whether the issue is genuine is starting to rear its head, as 30 years of successful ECM operation might support.

Valuable information.

The topic is in a non-DCC section because it crosses over. In the first post I made a note that the same item was posted in DCC.

[AndyID]

5 hours ago, d00m said:

 

I have been using ECM Composed controllers for over 30 years. In all that time only one unit died (I use 5), that was due to an extremely old Triang loco which drew too much current. Lots of visiting locos with all types of motors including coreless no problems at all. Just wish the company was still going - could do with two more. ( Don't want to go DCC - too many locos)!

 

I'm not sure how the Compspeed worked (perhaps someone has details?) but there are two ways to compensate for speed variations due to load etc. Typically that's done by cutting power to the motor periodically and sampling the voltage produced while the motor acts as a generator (the EMF). Depending on the period (the time between samples) the motor may or may not tend to overheat.

 

The other way to do it is not to cut the power at all. The motor receives uninterrupted DC. The controller needs to have some idea about the motor's resistance and it uses that to calculate the motor's speed based on the current the motor is consuming. It compensates for an apparent drop in speed by raising the voltage if the current increases or lowers the voltage if the current decreases. The analog circuit to do that is not complicated.

 

It's possible the Compspeed uses the second method. If it does it won't harm any type of DC motor.

[Michael Edge]

9 hours ago, NIK said:

Hi,

 

The topic is about Coreless Motors on DCC so DC controller experience is not so relevant.

High frequency PWM drive is becoming very common in DCC but until recently in the UK coreless motors were restricted to non RTR locos so there wont be much practical experience of coreless with DCC.

 

Maybe there are not many instances of problems of coreless motors with DCC on UK locos because folks now buy a modern design of DCC decoder to go with their expensive RTR loco.

Maybe the first few UK locos with coreless motors were highlighted by the reviewers in model railway magazines so DCC users has some sort of guidance of what sort of DCC decoder to fit.

Now some magazines don't bother to mention if a newly released loco's motor is iron core or coreless.

 

Take care.

 

Nick

I was including DCC in this and there must be at least 150 locos running on DCC on the Carlisle layout with Portescap motors.

[NIK]

Hi,

 

It may have been deleted but I think the history of Pulsed DC controllers and their operation with coreless motors has been covered before as a topic on RMWeb.

 

Just out of interest the only RTR loco I have that came with a coreless motor is a DJ Models Class 71 OO Electric outline loco.

 

It draws 200ma light engine (without lights or sound), top speed of 55mph and can't pull the skin of a rice pudding.

 

I've bought a Faulhaber coreless motor to try as the motor for a kit built OO EMU and hopefully I will have better results.

 

Take care.

 

Nick

[melmerby]

1 hour ago, NIK said:

Hi,

 

Just out of interest the only RTR loco I have that came with a coreless motor is a DJ Models Class 71 OO Electric outline loco.

 

Nick

AFAIK the motor in the Hattons/DJM 48XX is also coreless, mine runs quite nicely now after it's intial roughness, however it is not expected to pull much of a load.

The later motor in the OxfordRail Dean Goods is coreless and like your Class 71 is totally gutless, it slows down noticeably on a gradient with a load that a Bachmann 57XX Pannier takes in it's stride.

If a motor has a completely cylindrical case, there is a good chance it is coreless as the magnet lies inside the rotating part, rather than outside.

 

N.B. I use modern DCC decoders, mainly Lenz, occassionally Zimo and they have high frequency BEMF control and are fine with coreless motors.

Edited April 20, 2020 by melmerby

[Michael Edge]

The locos on Carlisle have a wide variety of decoders, various Digitrax, TCS, Lenz and Zimo (the last mostly for sound fitting) - there have been no problems with the motors at all.

[St Enodoc]

On 14/04/2020 at 17:04, Michael Edge said:

the best running ones don't quite stop when the controller is turned right back - you have to switch it off as well.

Like my Lima King with a Q driver...

[melmerby]

On 14/04/2020 at 08:04, Michael Edge said:

 the only slight problem is that the best running ones don't quite stop when the controller is turned right back - you have to switch it off as well.

Which is unlikely to be connected to coreless motors as on their own they have little inertia and stop dead (almost) when the power is off)

A decent gearbox without a worm drive married to any motor with a flywheel will do that.

Edited April 20, 2020 by melmerby
keep missing out words! too long in lockdown.