# G scale power Requirements



## chrisb (Jan 3, 2008)

Engine in question is a Bachmann 2 Truck Shay
Track length is under 100 feet. When looking at the specs for a transformer
what would a person want? 0-? VDC and ? amps? Thanks


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## jimtyp (Jan 2, 2008)

Chris, The length of the track actually has nothing to do with your power needs, just what the loco draws. So it depends on the loco itself, how many cars you are pulling and how steep a grade you may have. 

I would think you would want at least 5 amp, and at least 18 volts. But if you want to get something that will handle multiple locos in the future you might want to go with 10 amps. No need to go over 24 volts as some Bachmann locos, not sure if the the 2 truck Shay is one of them, can only handle 21 volts max.


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## chrisb (Jan 3, 2008)

Thanks. What brought this up is a friend of mine just bought an Aristo reversing unit. He was having trouble getting it to work. 
We got the diodes correct for bachmann polarity but he was using a little HO toy transformer. Wonder if this could be part of the problem? I plan to take my MRC trans for over to check it out.


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## krs (Feb 29, 2008)

I agree with jimtyp's assessment but I would go for a 24 volt transformer.
Not sure why Bachmann engines would only be able to handle 21 volts since 24 volt max. is the de facto Large Scale standard and has been for years.


You can always reduce the voltage to the track with the trottle, but you can't increase it beyond the maximum the transformer is able to provide. Some engines will just not run at a prototypical scale peed with only 18 volts (and others of course run much too fast).

With an H0 transformer you have two problems - one is that the maximum H0 track voltage is defined as 12 volts and H0 transformers typically provide only that or 14 volts maximum - the other is that the current requirement of H0 engines is a lot less than for Large Scale. And if you draw more current than the H0 transformer can provide, the voltage sags and you get even less than the 12 volts which in itself is not sufficient.


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## NavyTech (Aug 2, 2008)

I have a local train hobby shop telling me that G scale loco's motors are only 12vdc..... I have an Aristo Craft Pacific that is 18 years old. The motor is unmarked. Is he telling me the truth? 

I ran it on 12 vdc and it does not seem to go as fast as it could but I am afraid of blowing the motor if I run it over voltage. 

I am making my own power supply and got a fixed 29vdc at the moment I am just waiting to get a PWM to hook to it that should bring me to variable 24vdc


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## lownote (Jan 3, 2008)

I ran an old style pacific on up to 24 volts regularly, had no problems. I used to run all my locos--which include LGB 4 wheeler's that are close to 20 years old--using a 24 volt 10 amp power supply with an aristo 10 amp throttle. Voltage gives you some idea of the speed, but amperage is more important if you are running a lot of locos at once or pulling very heavy trains


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## Torby (Jan 2, 2008)

Also, if your reversing unit is acting silly, try reversing the throttle.


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## jimtyp (Jan 2, 2008)

NavyTech, 12v is the standard for HO. The NMRA says 18v for G. But some go higher, my LGB and Accucraft can both go to 24v.


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## NavyTech (Aug 2, 2008)

Thanks for the confirmation on voltages. We really need to get some knowledgeable G scalars out here in eastern Canada


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## krs (Feb 29, 2008)

Posted By jimtyp on 10/15/2008 9:36 AM
NavyTech, 12v is the standard for HO. The NMRA says 18v for G. But some go higher, my LGB and Accucraft can both go to 24v.







Where do you find the maximum voltage for G Scale on NMRA?
All I see is standard S-9 and it only talks about 12 volts. It doesn't address the maximum of 8 volts for Z scale either.

As far as I'm concerned, all G Scale equipment should be able to handle 24 volts DC - the NMRA DCC spec calls for a track voltage of 22 volts DCC maximum, that means you could have at least 20 volts to the loco motor, perhaps a bit more.

So to me an 18 volt DC Max NMRA spec for G Scale makes no sense if the NMRA DCC voltage spec is allowed to exceed that.


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## Dan Pierce (Jan 2, 2008)

I find that the newer engines with electronics (esp LGB with MTS) need 24 volts from the power source and the controllers place 21 to 22 volts output to the engines. 
The Non-electronic engines max out at 18 volts (Bachmann especially) and some are 12 volts (Older Accucraft and the whismscal Disney engine). 

My outdoor supply is 24 volts, and I readjusted my 13 amp Elite to 24 volt output. Arsito shipped this unit at 22.5 volts. 

PS, Aristo's newest Everest I believe is spec'd at 24 volt output. 

Thye older Ultima was a 16 to 21 volt unit depending on the load.


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## jimtyp (Jan 2, 2008)

krs, regarding voltages, I was responding to the post by NavyTech where someone told him G scale motors were rated at 12v, just letting him know that is bogus info. 

As far as DCC goes, my NCE system came set at 16v. My trains ran so slow I was ready to give up on DCC until I found out that there was a pot adjustment. I set it as high as I could and now get about 22v. 

The following is a quote from the document below "NMRA recommends 12V for N-scale, 14.25V for TT, HO, S, O-scale & 18V for G-scale" 

Source:  Wiring


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## aceinspp (Jan 2, 2008)

Jimtyp I also have the NCE system did the same thing but you loose some of the voltage once it gets to the track. Mine ended up at 19 volts to track. My older Pacific runs just fine with these voltages. Later RJD


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## jimtyp (Jan 2, 2008)

RJD, that is my understanding also, that the output drops to the track, and I suspect even less than the track voltage may actually get to the motor as the decoder may take some? My NCE has plenty of juice now for me with the pot set high, but if anyone wants more I believe NCE will make an adjustment for a small fee that will get it to 24v (or very close) output to the track. I think Greg E. had that done for his system to run his modern diesels at prototypical speeds?


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## Guest (Oct 17, 2008)

Posted By Dan Pierce on 10/16/2008 5:05 AM
I find that the newer engines with electronics (esp LGB with MTS) need 24 volts from the power source and the controllers place 21 to 22 volts output to the engines. 
The Non-electronic engines max out at 18 volts (Bachmann especially) and some are 12 volts (Older Accucraft and the whismscal Disney engine). 

My outdoor supply is 24 volts, and I readjusted my 13 amp Elite to 24 volt output. Arsito shipped this unit at 22.5 volts. 

PS, Aristo's newest Everest I believe is spec'd at 24 volt output. 

Thye older Ultima was a 16 to 21 volt unit depending on the load. 






i also have 2 elites and a bridgewerk 25amp tdr but i was going to sell the elites cause they didnt put out 24volts. i would like to keep them as spares, the bridgewerks will do most of the work.i have read here lately there is a way to ajust the voltage on the elites? Dan can you tell me how you did it and do you have a photo?








Thanks Nick...


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## krs (Feb 29, 2008)

Posted By jimtyp on 10/16/2008 9:38 AM

The following is a quote from the document below "NMRA recommends 12V for N-scale, 14.25V for TT, HO, S, O-scale & 18V for G-scale" 

Source:  Wiring 


Hi Jimtyp -

I was going to ask you for a link to this wiring source since I couldn't find it in the NMRA standards and RP's, but when I used the 'quote' feature in this forum it turns out that the word wiring was the link already.
When that text is quoted, 'Wiring' is underlined to show it's a link - in the original post it's not underlined. If I look real close, in the original post, I can see now that the word 'Wiring' is in dark blue (which I assume indicated a link), but that colour is so close to the black of the rest of the text that it's not noticeable.

I really wish mls wouldn't be using alpha software to run this forum - it just wastes so much time and the bottom line is that people just don't post.

As to the presentation you linked to - it desperately needs an update. It's more than five years old and a lot of things have happened in DCC. Not only are there things missing in the presentation but some items are no longer correct.


As to this NMRA recommendation - I still don't know where it is in the current NMRA specs, but I do remember the 14.25 volt number for H0.

That is based on the maximum specified voltage of 12 volts DC for H0 plus the expexted drop through the DCC decoder. 


What you want to achieve with DCC is the same maximum voltage at the motor leads of the engine as you would have if you were running DC. So for H0 that makes sense.

I'm not sure where the 18 volts for G-scale comes from. For the last ten years at least, G-scale DC power packs had a maximum voltage of typically 24 volts with the odd one at 22 volts, so the DCC voltage for G-scale should have been defined at 26 volts to get 24 volts to the motor.

For some reason which nobody has ever been able to explain to me, NMRA specifies the maximum DCC voltage to the track at 22 volts which in turn only allows up to 20 volts to the motor which is not enough for some engines.


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## jimtyp (Jan 2, 2008)

krs, yes, it is an old document but it's one of the better references I've found. It also is mostly geared towards smaller scales. If you have a link to a better document, especially G, maybe you could post it in the DCC forum? 

I didn't want to get too much into DCC as this was a topic posted by Chris about DC, and I originally posted to let NavyTech know that 12v DC for G is bad info. Maybe we could pick this up in the DCC forum? I'll start a topic there.


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## Dan Pierce (Jan 2, 2008)

Nick, it was very easy to adjust my elite. 
Look inside and you will see a small potentiometer. 
I used a digital meter and adjusted this clockwise to go to 24 volts. 
I did use a plastic adjustment tool as there are dangerous voltages inside these units. 

A hair dressers stick can be reshaped to do this.


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## Greg Elmassian (Jan 3, 2008)

Knut, unfortunately, the NMRA has been pretty clueless about G scale, look at how they specified a different standard DC polarity, after the manufacturers had been using one for years. It's clear they did not take history into consideration, just mandated something they figured makes sense. 

Regards, Greg


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## Guest (Oct 18, 2008)

Thanks Dan, i will give it a go this weekend..
Nick...


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## Trains West (Oct 4, 2008)

the NMRA stanard for power is the same as it is in every other scale and the same as they have always used ........

LGB was doing the opposite and was told by the nmra to change to the us stanard ...... lgb declined 

so do you feel that the NMRA should have bowed to LGB?


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## krs (Feb 29, 2008)

Posted By Trains West on 10/19/2008 1:06 AM

LGB was doing the opposite and was told by the nmra to change to the us stanard ...... lgb declined 

so do you feel that the NMRA should have bowed to LGB?




Not "bowed" to LGB but made the right decision and that is to create the standard to match existing poroduct unless there is a valid technical reason not to.

There was no "US" standard for IIm scale (or more broadly G scale now) when LGB was introduced, NMRA added that to their documentation much later.

I'm not sure who is steering the ship at NMRA nowadays, but if you look at this ongoing mess with the NMRA Large Scale scale and gauge definitions - NMRA has now gone overboard in the opposite direction by trying to accommodate every Large Scale variation that's out there along with a few that are not. They withdrew their first "standardization" attempt and are now at it again.


What the point of having a standard (for track polarity for instance) if none the manufactures follow it (well Bachmann gives you a switch sometimes)?

I sat on the standards committee for a number of global telecommunication standards - the implementation by existing product of the "standards item" discussed was always a major consideration and unless there were valid technical reasons for changing (or different manufacturers had implemented it differently), the implementation used in the existing product was chosen.


As far as I know, the selection of DC track polarity in model railroading is arbitrary - there is no technical benefit to chose right rail + for forward over right rail - for forward; not like an automotive power system for instance where a positive ground is actually better technically, but even there the standard now is negative ground simply because that's what manufacturers chose before a standard was created.


Sorry - longer post than intended.


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## Rayman4449 (Jan 2, 2008)

Wow, I'm surprised to hear the NMRA standard is 18v for G. Every engine I own except for the Bachmann engines were 24v. This includes USA Trains, Aristocraft and MTH. Because you may likely need 24v in the future make sure you get on that can output that. I like the Bridgewerks line.


Raymond


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## krs (Feb 29, 2008)

Posted By Rayman4449 on 10/19/2008 9:25 AM
Wow, I'm surprised to hear the NMRA standard is 18v for G. Every engine I own except for the Bachmann engines were 24v. This includes USA Trains, Aristocraft and MTH. Because you may likely need 24v in the future make sure you get on that can output that. I like the Bridgewerks line.


Raymond



I don't think the *DC standard* in NMRA is even 18 volts, but I can't really find a maximum DC voltage specification in the NMRA documentation itself.
18 volts seems to be the recommended NMRA *DCC voltage, *that would make the voltage at the motor of the engine about 16 volts.


Turns out the European NEM 630 standard which defines the nominal maximum DC voltage for the various scales does show 16 volts for scales using a gauge of 32mm or larger.

So unless I see something to the contrary in NMRA, I would conclude that the "Official Standard" for G scale is 16 volts DC.


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## yardtrain (Feb 18, 2008)

MTH has this warning for their 1 Gauge Trains



"Use 22 volts maximum track voltage when operating a MTH locomotive equipped with Proto-Sound, Loco-Sound, or Proto-Sound 2.0 "


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## Rayman4449 (Jan 2, 2008)

I have confirmed with Jeff Strank, VP of Service and he checked with his staff to make very sure, 24v is safe to run DCS equipped engines. I asked because some of the power supplies they listed as approved listed 24v max. 


Raymond


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## krs (Feb 29, 2008)

Posted By Rayman4449 on 10/19/2008 10:54 AM
I have confirmed with Jeff Strank, VP of Service and he checked with his staff to make very sure, 24v is safe to run DCS equipped engines. I asked because some of the power supplies they listed as approved listed 24v max. 


Raymond




If you are using Bridgewerks supplies you need to be careful.
At least some of those put out a much higher voltage than 24 volts at low current since they are not regulated - at least that was the case with their older units, don't know if Bridgewerks has fixed that problem.


Knut


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## Rayman4449 (Jan 2, 2008)

I agree you do need to be careful and it depends on what type you are using. 

With:

- Throttle type power supplies: many usually do put out over 24v so you have to watch your max throttle voltage put. That's why bridgewerks has an adjustable throttle stop on theirs so you can set the max out. It's also why I added aftermarket digital voltmeters on my throttle PSs.
- Regulated power supplies are usually set so there isn't an issue but I added digital voltmeters on that as well. Bridgewerks has both 18v and 24 versions but they are actually the same and the output voltage is adjustable via a potentiometer in the PS. 

Now on the sole Bridgewerks Mag15 unregulated power brick, those things put out 35+ volts DC even under load! (you may hear that under load they drop to 24v, well I can tell you that is not true, You may also hear that well if you have high home input voltage that is what's causing the 35+ voltage output. I can tell you that is not true either or at the very least misleading.) I have a warning posted on my website under the DCS Tips page warning people to NOT use this power supply unless they are using it to power an unpowered Bridgewerks throttle contoller to regulate the voltage. Anyone reading this who uses the Mag 15 by itself, needs to stop and check the output voltage before continuing!!!!


Raymond


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## Greg Elmassian (Jan 3, 2008)

Thanks for the info Raymond, I have seen lots of posts about the high voltage output. Indeed if the output of the Bridgewerks was radically affected by the AC input voltage, that would be a very poor design. 

Many people want the "best", but do not realize on a system that uses fixed track voltage, a REGULATED supply is very important, especially if you are running at the upper limits of the max track voltage. 

The Bridgewerks was not intended to be a precision power supply, in the normal sense, it is a high power throttle, with variable output. Simply putting a mechanical stop on a throttle lever does NOT make it a regulated supply. 

In DCC (which has to be similar to your DCS in this respect) if you are running at a nominal 24 volts (Max NMRA) with an unregulated supply, the voltage when lightly loaded is most likely higher than the maximum. 

There is a reason regulated supplies exist. 

Regards, Greg


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## Rayman4449 (Jan 2, 2008)

Anytime and I agree. I have found that in practice, their throttle type supplies do stay within a fairly reasonable voltage range so as not to really be too much worry. (at least from what I've seen) With DCS I've found I get slightly better track signal with the throttle type over the fully regulated which is why I may eventually go back to the throttle type... but having a fully regulated PS is a nice thing to have 'turn on and forget'.... never have to worry about what the voltage levels are. 

With the case of the Mag 15, most don't realize and are told from the get go that they put out safe voltage levels, so they trust it and just plug and go. I've heard at least three instances of these things putting out crazy voltage levels. But I think again that they were really intended and thus designed to not be used all by themselves but instead mated to power their unpowered throttle powersupplies. In which case there is probably a reason why he designed it that way to put out such a high voltage. From what Dave said the output voltage levels do drop as the load gets higher so that is probably why lightly loaded they put out 35+ volts. And from what I've seen with stronger track signal on the throttle type power supplies, I've come to the conclusion (either right or wrong) that the unregulated supplies probably put out cleaner power with less 'noise'. (whatever that 'noise' is) That may also be why he designed an unregulated supply to go with the unpowered throttles. 

Don't really know for sure, all my theory based on my observation, but it sure sounds good. 

As usual, good points get driven out from all the discussion. I guess it does take a village... ; )


Raymond


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