Coreless Motors and DCC

 
  LaidlayM Chief Commissioner

Location: Research
So given discussion elsewhere, what decoder should I have driving my 1219 Portescap?  This was one of the first locos I put a decoder in as I didn't want the loco being put on DCC track accidentally without one.  It currently has a TCS M4.

I also have a Garratt with two 1624s in it that has no decoder/s currently, that might get two decoders to avoid all the wires going back and forth.

Mark

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  Aaron Minister for Railways

Location: University of Adelaide SA
So given discussion elsewhere, what decoder should I have driving my 1219 Portescap?  This was one of the first locos I put a decoder in as I didn't want the loco being put on DCC track accidentally without one.  It currently has a TCS M4.

I also have a Garratt with two 1624s in it that has no decoder/s currently, that might get two decoders to avoid all the wires going back and forth.

Mark
"LaidlayM"

Mark, the TCS decoder ought to be fine, you may have to disable BEMF (set CV 61 to 0) on a coreless motor, but you would probably have discovered this already if you were having a problem with it.

For sound, Loksound I know to be some of the best (or just THE best) coreless drivers on the market. Steer clear of QSI and Titan in particular at the moment, there seems to be some issue there, and QSI acknowledged that driving coreless motors is the most annoying headaches they have.
  Blackaddar Junior Train Controller

Location: Canberra, ACT
Hey Guys,

Sorry to air my ignorance, but what is the issue with coreless motor and DCC?

is there away to identify what a motor is from the exterior of the item?

-Black
  LaidlayM Chief Commissioner

Location: Research
Hey Guys,

Sorry to air my ignorance, but what is the issue with coreless motor and DCC?

is there away to identify what a motor is from the exterior of the item?

-Black
Blackaddar
Differences I know of are current consumption (lower), price (higher) and mounting (they don't like thrust).

Generally if the model is run of the mill it won't be coreless and it would normally proudly announce "coreless" on the box.

Mark
  merlin Chief Commissioner

Location: North East Adelaide
The main design feature with coreless motors, is they accelerate very, very fast (less mass to accelerate). not something we actually want as modelers! not to mention they surge horribly at low speed, for the same reason (less mass / intertia to smooth them out). They also require very, very good cooling as there is no core to act as a heatsink. again, not something you want inside a plastic loco body.

coreless motors also have very different back-EMF characteristics and generally hate low frequency PWM drive (they burn out) which is the opposite of what DCC controllers are designed for.

The really, really short answer is: if you want to use a coreless motor, stick to plan DC only. If you want to take the huge risks of coreless vs DCC (and risk burning the motor out and melting your plastic loco) then at the very least, turn back-EMF sensing off on your DCC controller. I'd also say add a flywheel, but then you're completely defeating the purpose of having a coreless motor to begin with Smile
  Kevin Martin Chief Train Controller

Location: Melbourne
The main design feature with coreless motors, is they accelerate very, very fast (less mass to accelerate). not something we actually want as modelers! not to mention they surge horribly at low speed, for the same reason (less mass / intertia to smooth them out). They also require very, very good cooling as there is no core to act as a heatsink. again, not something you want inside a plastic loco body.

coreless motors also have very different back-EMF characteristics and generally hate low frequency PWM drive (they burn out) which is the opposite of what DCC controllers are designed for.

The really, really short answer is: if you want to use a coreless motor, stick to plan DC only. If you want to take the huge risks of coreless vs DCC (and risk burning the motor out and melting your plastic loco) then at the very least, turn back-EMF sensing off on your DCC controller. I'd also say add a flywheel, but then you're completely defeating the purpose of having a coreless motor to begin with Smile
merlin
Must be a good reason why no one followed Portescap's idea. With the vastly superior mechs of the last 15 years or so, none have gone down the coreless motor path. Lots of skew wound motors with more than 3 armature segments instead and better gears.

Kevin Martin
  TheBlacksmith Chief Commissioner

Location: Ankh Morpork
Marklin are advertising the fitting of a core-less motor in their latest steam locomotive releases.

Core-less motors are very popular in servo applications and such because of their rapid response. But in these applications, the motors are very closely controlled and not generally subject to any forms of abuse, electrical or otherwise. There are a lot of them still made, but the better ones are fiendishly expensive, particularly if you buy the German ones through their local agents, often up to five times the cost of conventional iron-cored motors.

In my opinion, core-less motors are not well suited to model railway applications, as they have to be handled very carefully, and that is something that is not always possible in the model rail world.


Frankly, I think they are old hat, the modern emerging brushless multi-phase motor is much more exciting, much more rugged and better suited to our hobby, but unfortunately no-one is putting the dollars into designing ones suitable for model rail, all the best ones are intended for model aircraft.
  robertc Chief Train Controller

Most decoders offered these days have a high enough pulse rate to control a coreless motor without issue.

Coreless motors find favour particularly with those using battery powered/radio control models in gauges 0 and below. Their low current consumption is very handy when longer running times are desired from the available battery capacity.
Ditto the remarks re skew wound 5 (or more) pole motors.... hard to go past for regular model railway applications, smooth and robust.

Marklin have offered brushless motors for some years (C sinus and SDS).

Regards
Bob Comerford

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