Beware NCE and ESU Momentum idiosyncrasies

[pauliebanger]

Hi Everyone,

 

This is not a platform to knock either NCE or ESU, just a way to explain why your sound projects may begin to operate strangely in some circumstances.

 

Despite what I have written below, I would still recommend PowerCab to anyone starting out since it is technically the best in both operational/programming features and in ergonomics for this class of controller. It is remarkably inexpensive, too.

 

I've had an increasing number of people asking about sound projects which, for no apparent reason, suddenly begin to operate differently.

 

This can arise because of non-NMRA 'features' which each manufacturer has applied to their handling of inertia and momentum values, CV3 and CV4.

 

The anomalies may arise in sound project operation and consisting. If you experience difficulties, then it's worth checking if these issues are the cause of your problem.

 

I've copied my responses from another thread concerned with a ZIMO-specific question.

 

.........With one notable exception. Although the ZIMO RE Class 47 is not reliant on high values in CVs 3 and 4, there is an insidious button on the PowerCab which in seeking to provide a useful feature uses the wrong (ie, not NMRA) method to achieve it. The PowerCab (and ProCab) manual explains what it does, but many people don't read the manual (why should you - it says on the outside of the PowerCab box that it is so intuitive that you don't need to read the manual), and of those that do, many do not realise the possible consequences.

 

Please note, that unless you are trying to consist any other brand of decoder with an ESU decoder of any description, this will will not have any serious consequences for non-sound decoders.

 

The button I refer to is the one marked 'Momentum'. That's intuitive enough - it changes the momentum of the loco under control, and you can change momentum as often as you wish. However, what is not intuitive (or NMRA compliant) is that it does so by writing new values 'permanently' to your decoder. It does not, like most other systems which have a similar function, temporarilly add or subtract a figure from the 'base' value, but calculates a new value and over-writes the value on the decoder. This could have serious consequences for the way in which sound projects work.

 

The only way to undo this is to re-write the correct value subsequently, but if you do not realise that PoweCab has changed your CVs without telling you, then you may not see the need to perform this re-writing.

 

So, for sound decoders, I strongly recommend that you do not use the Momentum button on your PowerCab/ProCab. And with the RE 47 (indeed all my sound projects) on ZIMO, the light engine key already (temporarilly) changes the momentum and inertia settings, reverting back correctly when the key is disengaged.

 

and

 

That's why I called it insidious . Quite a few people who ask me for advice during my sound clinics have inadvertantly done the same thing.

 

It's not such a problem with current ZIMO projects because progress through the sound schedule is not as dependant upon momentum to operate correctly as, say, Loksound or CT Elektronik.

 

In addition to that dependancy on 'known' momentum values (which is a feature, not a fault) Loksound and Lokpilot decoders have an additional issue which is exacerbated by the NCE way of changing momentum settings.

 

There is an NMRA standard way of calculating momentum. ESU have, for undisclosed reasons, decided to use a different formula. This results in Loksound decoders requiring a larger value in CVs 3 and 4 than for all other brands to acheive the same level of momentum.

 

Two issues arise from this.

 

1 ) NCE PowerCab/PowerPro use the NMRA calculations to write new values to CV3 and 4 to any decoder. Result for Loksound decoders will be that momentum will be much reduced from the figures the sound project is anticipating for its control calculations, even at the highest setting on the PowerCab. The sound project may suddenly apear to operate differently.

 

2 ) Consisting. If you have spent a long time speed matching locos fitted with different brands of decoder fo use in consists, you want that relationship to remain. (I would anyway). In the majority of cases, NCE 'Momentum' button will have the same impact on all decoders in the consist, so although NCE may screw with your settings, at least they are all screwed in the same way! Not so if you have a Loksound or Lokpilot in a mixed decoder consist, for the reasons given above. Not only will speed matching be lost, but will be dramatically out of step.

 

This state of affairs has arisen because two manufacturers, NCE and ESU have gone their own way in the area of inertia and momentum settings, and each, when used togther, amplifies the unexpected results (deviation from the norm) provided by the other.

 

To be fair, both manufacturers include information on their momentum calculations in their respective operating manuals. But neither highlight the impact this will have for end users - even those who actually read the manuals.

 

 

This also highlights the importance of testing sound projects on a wide range of DCC controllers before release to the public. All my ZIMO sound projects are fully tested on DCC controllers from ZIMO (obviously!), ESU, Lenz/Roco, Digitrax, Gaugemaster, Hornby and ZTC (restricted F keys). Even then, very occasionally something may slip through.

 

Forewarned is forearmed.

 

Kind regards,

 

Paul

[Enterprisingwestern]

So therefore NCE and ESU are not NMRA compliant despite what they say.

A case for the trade descriptions act to come into play?

 

Mike.

[Lady_Ava_Hay]

So therefore NCE and ESU are not NMRA compliant despite what they say.

A case for the trade descriptions act to come into play?

 

Mike.

 

No not at all. NMRA compliance is at a very basic level and just details which CV's do what up to about CV100. It has no control over protocols involving either feedback or any additions to decoder fuctionality.

 

Sound decoders have no NMRA compliance in the way they play sound projects or react to commands from a commercial command station.

[faulcon1]

I inadvertently pressed the momentum button on my NCE Procab throttle and my ESU sound decoders lose the coasting feature put on by Howes. The only way I found to get the coasting feature back was to ask Howes for a complete list of all the CV settings which I then checked on the programming track.

With Howes ESU sound decoders the coasting feature is lost if you press the acceleration/deceleration function key. Press it again and it returns.  

[cravensdmufan]

Thanks very much for highlighting this problem.

 

Particularly grateful as I am about to purchase my first sound decoder and I use NCE Powercab. I'm always carelessly hitting "momentum" instead of "direction"! Will now have to devise a method of blanking off the "momentum" button. I'm thinking a slice of plastic piping glued around it? Crude, but it's about all I can think of at this stage.

[ColinK]

Cravensdmufan, Somewhere on RMweb there are instructions on how to disable the momentum function button on the handset. It must be easy as I did it on both minenwithout any problem.

[cravensdmufan]

Cravensdmufan, Somewhere on RMweb there are instructions on how to disable the momentum function button on the handset. It must be easy as I did it on both minenwithout any problem.

Excellent, thanks for that information ColinK - I'll try and find that right now.

 

Cheers.

 

Edit/update. Found the other thread, thanks again.

http://www.rmweb.co.uk/community/index.php?/topic/93361-nce-momentum-button/