NMRA vs 'Large Scale' Polarity Settings

[James Day]

Dear All,

Just idle thinking on a hot day:

I first came accross the NMRA polarity setting some years ago when we borrowed a Maerklin Maxi Train for use at a show. I need to insert a DC 'chip' to replace the AC one and the loco then responded to the controller the opposite way to the LGB and Playmobil stuff we were running. The only solution would have been changing the hard wiring which was not an option.

Next encounters were via my Large Scale Thomas and Percy in early 2010, which were of the first batches without switches - More hard wiring needed, but this time they were mine so i could go ahead. Now the TTE stuff comes with a switch, so no hard wiring is needed any more.

BUT....

How do LGB get on in America if Bachmann and presumably other makes are wired for the NMRA settings, but LGB lack this option? Or is it just Bachmann the sell locos wired the NMRA way? (I have no real knowledge of this at all).

I actually bought a new LGB loco last year and this had no polarity switch? So what do people do?

Finally, does anyone know what the NMRA standards are for in G Scale? Presumably they were introduced after the scale was 'invented' in 1968, so I am tempted to ask what is/was the point?

Idle curiouity you understand.....

James

 

[Dave500UK]

Haven't a clue what you are on about!
If one of my locos runs the other way, I just turn the knob the opposite way. Sorted, and involves no wiring mods.

Had a few locos running outside on Sunday for the first time since last year. Oiled the points, put loco on the rails turned the knob and off it went, Ran jiggly for a circuit or two then after that pretty good. Just had to trim a few plants back.

 

[James Day]

Haven't a clue what you are on about!
If one of my locos runs the other way, I just turn the knob the opposite way. Sorted, and involves no wiring mods.

Had a few locos running outside on Sunday for the first time since last year. Oiled the points, put loco on the rails turned the knob and off it went, Ran jiggly for a circuit or two then after that pretty good. Just had to trim a few plants back.

Dave,

A very neat, elegant and low tech solution that would work very well in just about all cases, EXCEPT where you are running several automatically, when it becomes an issue!

Just curious why the NMRA has differnet standards to Europe, that is all.

Idle curiousity!

James

PS it always satisfying to get your trains running and running well, especially if it has been a while since the last time!

 

[Melbournesparks]

Dave,

A very neat, elegant and low tech solution that would work very well in just about all cases, EXCEPT where you are running several automatically, when it becomes an issue!

Just curious why the NMRA has differnet standards to Europe, that is all.

Idle curiousity!

James

I suspect the answer is simply because there was two possible options, so inevitably we ended up with both!

A byproduct of using overhead power is that the direction of any piece of rollingstock is governed by the way it faces on the track. So if something goes the wrong way just pick it up and turn it around.

 

[PaulRhB]

The NMRA went their own way and it just happens several European manufacturers followed their standard.
There are people who moan about the newer plux18 sockets because they are a euro invention and aren't specified by NMRA
The Lenz DCC standard was adopted by NMRA and added to but it's not compulsory.

If you are DCC chipping locos you just need to reverse direction using cv29. Usual value is 0 = normal, so you just add 1 = reverse, to the default value of cv29. (You do occasionally find they are already set reverse so then you subtract 1 )

 

[ntpntpntp]

Not sure I'd agree that NMRA "went their own way". The root of the problem as I understand it is that LGB are the ones who "went their own way" with their analogue DC using the opposite rail polarity to the convention adopted by just about every other scale - including European HO, N etc..

The NMRA standards are meant to encompass all scales and it makes sense to specify polarity based on that used by the vast majority of model trains.

Bachmann, Aristo, USAT et al come along to G scale after LGB and, being american companies, naturally want to be seen to follow the established NMRA standards. In order to ease compatibility with LGB a polarity change switch is fitted to many models..

 

[PaulRhB]

I meant they didn't try to establish it in line with anyone in Europe it was just within the US

 

[James Day]

Not sure I'd agree that NMRA "went their own way". The root of the problem as I understand it is that LGB are the ones who "went their own way" with their analogue DC using the opposite rail polarity to the convention adopted by just about every other scale - including European HO, N etc..

The NMRA standards are meant to encompass all scales and it makes sense to specify polarity based on that used by the vast majority of model trains.

Bachmann, Aristo, USAT et al come along to G scale after LGB and, being american companies, naturally want to be seen to follow the established NMRA standards. In order to ease compatibility with LGB a polarity change switch is fitted to many models..

Nick,

Thanks for a very helpful and incisive posting indeed. I had not thought of that, but you are right LGB is indeed the other way round. I wonder why they did that?

Re MelbourneSparks comment.

Yes turning a loco around certainly works on Dublo 3-rail or other systems where the two running rails and bonded, but my overhead shares a common rail with the track powered trains for isolation etc, so sadly that is not an option for me!

Thanks to everyone else who replied as well.

James

 

[dunnyrail]

Have to say when chipping a Loco always test before the body work goes on. If it does not go the correct way I just reverse the Motor Wires. Used to do the same with analogue as well back in my old TT Days. And yes I do know that I can change the CV on DCC fitted beasties. Have in fact done that as well.
JonD