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Discussion Starter · #1 ·
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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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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Discussion Starter · #3 ·
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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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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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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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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Also, if your reversing unit is acting silly, try reversing the throttle.
 

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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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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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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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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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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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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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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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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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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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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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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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