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Wiring an Atlas O GP-9 in Sequence

IM Industrial ModelsOGR Forum Member

Hey Gang! 

There has been a lot of talk about the poor slow speed performance of the earlier Atlas O engines. Ben Brown was kind enough to show me how to wire motors in sequence a few years ago and thought I would share the results. I was initially concerned with how it may effect the motors but after almost 4 years of heavy use they all run fine and this really solved the problem (to the point that I use an Atlas GP-9 in yard service). I run straight DC so I am not sure about how this would impact DCC- perhaps someone else here would comment? There are 2 very important points: first is the need to add extra weight to the engines for smooth performance (I use (2) 8oz fishing weights).  Second is that there are different wiring diagrams for Atlas engines. So the GP-9 is different than the GP-35 etc etc.

 Here is a step by step with diagram and movie:

1. Remove the shell

2. Remove the Atlas control board so you are left with 4 wires on each side. Blue and yellow motor wires and red and black truck wires

3. Solder connections

4. Add weight secure with hot glue gun. 

5. Install 9V battery powered lighting (I use 9v warm white LED's with a 470ohm 1/4 watt resistor) on a microswitch. 

6. Re-install shell 

 I will post the diagram for the Gp-35 and F-3 later today or tomorrow.....

D

Atlas GP-9 Wire in Sequence Diagram

 

 

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SundayShunterSundayShunterOGR Forum Member
Yes it's not a difficult procedure, it does reduce top speed as well although this is rarely an issue I imagine?! This also works with DCC too, so that an HO decoder can run a China-drive Atlas loco - although I have only done this at slow-to-moderate speeds, not having space to reach full speed on my layouts.
I call this wiring "in Series" rather than in 'sequence'. Not sure if that's a UK term but it's what we say over here.
For a single motor it is also possible to use a suitable resistor to tame it down on 12v DC operation & enhance slow speed running, again reducing top speed.
BT big trainOGR Forum Member

Off topic question, but I really would love to know where you got the roof top air tanks from? I need them for Central Vermont passenger gp9's equipped with steam generators. Are they scratchbuilt, and if so, how did you form the ends of the tanks. Also, what dimensions did you use for them.

 

Sorry for the interruption - now back to regular programming....

 

Thanks,

Jim 

jonnyspeedjonnyspeedOGR Forum Member

Hi Don,

 

You have to let me know if you ever want to thin out your B&O diesel roster

 

The "Series" modification is a good idea for DC and DCC alike. It will lower the theoretical top speed, but that usually isn't an issue for 2 railers. It will essential half the amperage draw which lends itself well to DCC as well. As was already mentioned, it allows for use of HO scale decoders in many instances.

 

Here is a quick diagram that I made that clears up some of the clutter. I think it is self-explanatory:

 

Series

Of course if you run DCC like I do the track power goes to the decoder inputs and the decoder outputs go to the positive of motor1 and negative of motor2 with a jumper between the motors like the diagram shows.

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Last edited by jonnyspeed
SundayShunterSundayShunterOGR Forum Member
Must admit I didn't look closely at the OP wiring diagram before posting, & no, it doesn't seem to make sense.
The red pickups of both trucks should go to one motor's blue wire; the black pickups to the other motor's blue wire, with the yellow linking the two motors, as shown - provided Atlas are consitent with their wiring colors!! Better to use the electrical + & - to follow the current path & make sure both motors turn the right way when wired together.
jonnyspeedjonnyspeedOGR Forum Member
Originally Posted by SundayShunter:
Must admit I didn't look closely at the OP wiring diagram before posting, & no, it doesn't seem to make sense.
The red pickups of both trucks should go to one motor's blue wire; the black pickups to the other motor's blue wire, with the yellow linking the two motors, as shown - provided Atlas are consitent with their wiring colors!! Better to use the electrical + & - to follow the current path & make sure both motors turn the right way when wired together.

It has been my experience that Atlas is not always consistent with their wire colors. Which is why I like to use the NMRA color code for DCC and just rewire everything. If you don't know what each color is doing then you might as well just have all black wires...

 

If I were running DC I would just use good old Red/Black.

Last edited by jonnyspeed
IM Industrial ModelsOGR Forum Member

Hey gang,

Atlas is not consistent with the motor wire colors. While they are always yellow and blue on some models they are in a different order. Its the same with the electrical pickups, on the GP35's they are both on the same side and this necessitates different wiring arrangement which I will post. I can only comment on what I know works. 

As far as the above arrangement not making sense to some of you, I really don't know what to say . The loco you see in the photo is wired that way and has 16oz of additional weight. It runs much better than it did out of the box. I will post the GP35 and F3 diagram when I get a minute . I am def not an electrical guy but I was able to make this mod to my Atlas engines and it has made a big difference. 

S SteinzeitOGR Forum Member

For those of you having difficulty understanding why red is connected to black on the Atlas GP:  It may help if you think of the power trucks as separate [ and interchangeable ] pre-wired assemblies;  when mounted in the locomotive one is of course 'backward' compared to the other.  This also explains why it is yellow to yellow rather than the blue-yellow-blue-yellow sequence one might have expected for wiring the motors in series.

 

Hope that helps !  SZ

V vonhammer87OGR Forum Member

Hi all, 

I also own an Atlas  O GP9 with the china drive. (Soo Line #2410), and although I think i understand this diagram, it would be helpful at least to me if I could see what the finished product looks like on the locomotive. I have also noticed (not sure if anyone else has reported this but it seems at least to me that the two motors are not in sync with each other and would this solve that problem?

railroad-guyrailroad-guyOGR Forum Member
vonhammer87 posted:

Hi all, 

I have also noticed (not sure if anyone else has reported this but it seems at least to me that the two motors are not in sync with each other and would this solve that problem?

I will make it worse because of the series wiring but you will only notice that on an incline.

See my article in  September / October 2013 The O Scale Resource

http://oscale.uberflip.com/i/1...ptember-october-2013

V vonhammer87OGR Forum Member
railroad-guy posted:

I will make it worse because of the series wiring but you will only notice that on an incline.

See my article in  September / October 2013 The O Scale Resource

http://oscale.uberflip.com/i/1...ptember-october-2013

I will do that. How much of grade would it take to get noticed? The club I run at has a max 2.5% grade one part of the layout and it's only a short run. The longest grade we have as 1.5%

Bill McBrideBill McBrideOGR Forum Member
vonhammer87 posted:

Hi all, 

I also own an Atlas  O GP9 with the china drive. (Soo Line #2410), and although I think i understand this diagram, it would be helpful at least to me if I could see what the finished product looks like on the locomotive. I have also noticed (not sure if anyone else has reported this but it seems at least to me that the two motors are not in sync with each other and would this solve that problem?

Like Don said, wiring seems to vary between different Atlas models. What I did to verify if I had the wiring correct, before blowing a DCC decoder, was to use an Athearn HO DC circuit board from an RTR SD40T-2 on DC and then with a decoder plugged into the board with an HO decoder. Of course, I had the wiring wrong the first time but there are only so many options for arranging the wires and eventually, like a monkey and a word processor, I produced "The Merchant of Venice."

Once set up with the correct wiring, I merely substituted an HO sound board (Loksound Select Direct) and I had sound and DCC. So far I have done this in an Atlas MP15DC, C424, GP15, and SD35.

Is the performance smooth? Well, on the MP15 - yes but it's not a "China" drive. On the others, I think so. I don't have jerking and stuttering anymore. I didn't in my DC tests and again none once I put an ESU decoder in.

 

 

HW Hot WaterOGR Forum Member
David Eisinger posted:

but Jerry Kimble of Atlas has assured us that the two vertical motor drive is superior to any single horizontal motor drive. so why is it necessary to rewire the motors?

Mr. Kimble has subsequently stated that Atlas has WAY TOO MUCH invested in the "China Drive" design to change now. Thus, it is no longer worth arguing about, as the facts stand for themselves.

gnnpnutgnnpnutOGR Forum Member
David Eisinger posted:

but Jerry Kimble of Atlas has assured us that the two vertical motor drive is superior to any single horizontal motor drive. so why is it necessary to rewire the motors?

Jerry Kimble needs to go talk to his HO and N counterparts to learn how to manufacture a quality drive.  I have several HO Atlas diesels, with the latest being their recently released ALCo S-2, with ESU LocSound.  SUPURB low speed performance, absolutely silky smooth starts. 

My three rail Atlas GP9s and F3s run like crap in comparison.  If I wasn't looking to sell them, I would have rewired them to series.  

Dan Dawdy of O Scale Resource documents how he converted his Atlas RS1s (two rail, but the procedure is the same).  

Here is a video of his RS-1 locomotives in operation:

 

Regards,

gnnpnut

F flangerOGR Forum Member
gnnpnut posted:
Dan Dawdy of O Scale Resource documents how he converted his Atlas RS1s (two rail, but the procedure is the same).  

Regards,

gnnpnut

 

I followed Dan's conversion of his RS-1 and with his email assistance applied the upgrade to my Atlas RS-1 including the Soundtraxx DCC decoder. This is now an excellent running/sounding locomotive. I highly recommend this improvement to anyone with an Atlas RS-1.

Bob

Last edited by flanger

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