# Surging Aristo Pacific



## BodsRailRoad (Jul 26, 2008)

I was running my second gen Aristo Craft Pacific yesterday and noticed that it was surging on the curves (would come to a curve and slow down, and at low throttle (40/128 NCE 10amp) almost come to complete stop) and also somewhat on the straights. The other engines I have run dont do this just the pacific it seems. I am pulling 5 heavyweights which makes it more pronounced, but it also does it when solo.
I have wired the tender for track pick-up per Gregs site and have tested that it is getting power from the engine and tender.

Any ideas?

Thanks, Ron


----------



## pimanjc (Jan 2, 2008)

The first thought that came to me was wheel bind on the flanges if you are going around a small radius/diameter curve. Aristo advertises a minimum curve diameter of 6.5ft with 40ft cars or minimum 8ft diameter with Heavyweights. 

JimC.


----------



## Ward H (Jan 5, 2008)

I run mine on 10ft curves and have the same problem when pulling 4 heavyweights. The heavyweights are quite a load to pull, especially through curves and the Pacific does not seem to be the strong puller that other locos are. I have not seen the problem when it runs light.


----------



## BodsRailRoad (Jul 26, 2008)

I dont use sectional track on my curves but I am sure that the dia is greater than 11' my layout is 15' wide and as you can see in the pics the curves is pretty large. 






Uploaded with ImageShack.us





http://www.mylargescale.com/Communi...ack.us/img191/4391/dsc01418a.jpg][/IMG][/URL]


----------



## lownote (Jan 3, 2008)

I'm going to guess it could be the BEMF setting in the decoder. What decoder is it?


----------



## BodsRailRoad (Jul 26, 2008)

Its the Aristo QSI plug and play one.

Do you think I should disable it? Or how would I go about correcting it?


----------



## BodsRailRoad (Jul 26, 2008)

Here is a quick Video of it in action, if you watch closly you'll see what I meen. Once the engine leaves the rail yard and rounds the first corner, the throttle is constant.

http://www.youtube.com/watch?v=586-ir0omKw


----------



## Michael Glavin (Jan 2, 2009)

You might want to confirm that all the driver/power pick-ups are actually picking up power. This engine is known to have issues with same. 

What power supply is in play? 

Michael


----------



## lownote (Jan 3, 2008)

You said you were using the NCE 10 amp system? So it's running on DCC? Then you must have a decoder in there somewhere. Is it a QSI decoder? With sound? 

Back EMF (or BEMF) is way of having the decoder sense the train's speed/load. I'm guessing that it has something to do with that. It might be that very small variations in physical resistance on the track (track gage, grade) are being translated into changes in motor speed. I had a Pacific that did this and I could never figure out why. I cut it down to an Atlantic, and the surging seems to have stopped. Whatever brand of decoder you are using will have a mechanism for modifying or changing the BEMF settings.


----------



## lownote (Jan 3, 2008)

OK, I see from the video that it's a QSI decoder. Same system I use. Do you have the QSI programmer? 

If not, do you now what the acceleration and deceleration settings are (cv3 and 4)?


----------



## Greg Elmassian (Jan 3, 2008)

Looking at the video, it seemed to have problems at the left end, but not the right end. 

Is that true? 

Turn off the BEMF as an experiment. 

Regards, Greg


----------



## BodsRailRoad (Jul 26, 2008)

Posted By lownote on 27 Jul 2010 03:37 AM 
OK, I see from the video that it's a QSI decoder. Same system I use. Do you have the QSI programmer? 

If not, do you now what the acceleration and deceleration settings are (cv3 and 4)? 
Yes its the QSI/Aristo plug and play board, yes I have the QSI programer. In fact my NCE set-up is the exact same as Gregs, right down to the modified 24v base station and regulated 10amp 27v power supply


----------



## BodsRailRoad (Jul 26, 2008)

Posted By Greg Elmassian on 27 Jul 2010 02:03 PM 
Looking at the video, it seemed to have problems at the left end, but not the right end. 

Is that true? 

Turn off the BEMF as an experiment. 

Regards, Greg 
It's pretty much the same on both ends, the left appears worse because it's magnified at slow speed and th pacific was just starting out on the first curve. Once the engine gets up to speed the effect is the same at both ends. I will upload the latest file from QSI this weekend, and turn off bemf and see what happens. It's sort of strange because my DASH-9 and E-8 dont do this and I'm sure that bemf is on if its defaulted to on since I have not turned it off.


----------



## lownote (Jan 3, 2008)

I would guess that the Pacific has more resistance moving through curves--three big wheels in a rigid block rather than three smaller wheels in a pivoting block. Add a significant load of heavyweights and the decoder is, I suspect, reading the resistance as load and varying speed. I had an aristo pacific that used to do that, and I could never figure out why. Then I cut it down to an atlantic--same decoder, same settings, same train behind it--and the surging stopped. I'm guessing it's because of the lessened rolling resistance in curves. I had a terrible problem recently with surging in consists, and disabling BEMF in one of the locos fixed it. I bet tweaking the bemf settings will fix it


----------



## BodsRailRoad (Jul 26, 2008)

Do anyone have BEMF settings for a pacific?


----------



## Torby (Jan 2, 2008)

First, check for a rod bind. Examine the wheels on each side closely. The spokes should be in exactly the same position. If they're not, you'll get a 1 or 2 per rev surge. It's not a hard repair, unless it's the front wheel. Then it's easiest to pull the drive block off and disassemble the running gear to get to that accursed screw. 

The wheels on 1 side should be 90 degrees ahead of the wheels on the other, but that's not very critical 'cause we're not using the cylinders to run the loco, but the wheels on the same size must be in the same position.


----------



## Greg Elmassian (Jan 3, 2008)

Check my site under the QSI section on the BEMF settings for Aristo locos. 

I don't put the link here, because I want you to read/look at the entire QSI section. 

Regards, Greg


----------



## BodsRailRoad (Jul 26, 2008)

Ok thanks guys, I will try out all suggestions on Friday and get back to you on results. 
Ron


----------



## Dan Pierce (Jan 2, 2008)

I would verify the quartering of all the wheels. Aristo locos have had one wheel slip on the tapered axle and this will cause an undue load on the motor. 

On a straight stretch this engine should have no problems with 5 cars.


----------



## lownote (Jan 3, 2008)

I'd be willing to bet it's not binding rods or quartering. I'd first try switching from "regulated throttle control" to "standard throttle control" and see if it goes away. Then I'd switch back to regulated and monkey with various BEMF settings to see what happens. For example, I suspect that setting the accel and decel. (cv 3 and 4) to the same place number would get rid or it.


----------



## BodsRailRoad (Jul 26, 2008)

Well I tried everything you guys mentioned and it appears that the drivers themselves are binding on the curves. On a straight track section I can pull 5 heavyweights at 5smph and it creeps butter smooth forward or reverse. I had it on rollers and checked quarter and rod binding both are perfect. I tried turning off the bemf and it still did it. It does it forward and reverse. Whats strange is I know for a fact that the curvse are at least 12 dia, my GG1 pulled 6 USA Aluminum streamliners through all the curves at a crawl with no issues what so ever. 
My Pacific really hates curves it seems. Is this a know issue? Has anyone had a similar experiance with their Pacific? 
All my other engines work perfectly from the Mallet, to the Mikado, from the Dash-9 to the E-8s, just my Pacific doesnt seem to like to turn.
On the bright side I am now very good using my Quantum programer and the CV manager








The new sound files from QSI really sound great btw.

Thanks, Ron


----------



## aceinspp (Jan 2, 2008)

Ron one thing to remember is the pacific uses larger drivers than Mikes or Mallets. There tends to be a slight bind when entering curves due to the center drivers having a flange rather than blind driver. So when you enter the curve what ever so slight of resistance occurs will slow these big drivers down. It is more noticable with loads than without loads. I have had the same problem for years on the early version of the Pacific running on just DC. Now that I'm using the system you are and have a newer Pacific the problem still exists in DCC it's the nature of the loco. Later RJD


----------



## BodsRailRoad (Jul 26, 2008)

Has anyone tried making the center driver a blind driver?


----------



## Michael Glavin (Jan 2, 2009)

Have you checked the wheel/axle gauge spacing (driver back to back dimension)? Machining the center driver "blind" would be pretty easy as I have machined early Pacific drivers several times. 

Michael


----------

