Model Railroading > Battle of the Geep Thirty Eights

I took my three current BN GP38 variants down to the club the other night to run a heavy local train. They were my new Rapido GP38 BN #2158, Athearn Genesis GP38-2 BN "Pacific Pride II" #2085, and Proto2000 GP38-2 BN #2336. The Rapido comes in a brighter green than my other BN models, especially my too dark P2K #2336 unit (really need to fade and weather that locomotive). The white lettering wasn't nearly as opaque on the Rapido as it was on the other models. The road number was also smaller. Individually all these locomotives run super smooth and quiet, although the Athearn model is a bit more noisy than the other two. But I encountered issues running them together. The ESU sound equipped Rapido and Tsunami 2 equipped Athearn really had a surging issue when running together even though I did speed match them before hand. The surging was really bad in the lower speed range where the Tsunami wants to outrun just about any other decoder brand. It wasn't much a issue in the middle and upper speed ranges where the two were best speed matched. I had a much smaller surging issue running the Rapido with my NCE non-sound P2K unit, and that issue went away after tweaking the speed on the P2K unit to exactly match the Rapido model. I've had similar issues with the Tsunami decoders not playing nice with other brands in the past, so will probably have to create a custom speed table for it in the future, a real Pita. Wish JMRI had some better tools for customizing the speed table.
Scenes are on the Caldwell Model RR Club layout in Caldwell, ID.

Ted Curphey
Ontario, OR



Edited 1 time(s). Last edit at 10/18/24 05:59 by funnelfan.

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Ran the Rapido with the Athearn until the surging got too frustrating, then swapped the Athearn for the P2K unit and ran the train up the mountain. The P2K is a very heavy puller.

Ted Curphey
Ontario, OR

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Last two for today.

Ted Curphey
Ontario, OR

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I was running my Genesis SP GP38-2 just yesterday and thinking that it might be my favorite loco. It looks great, with really good lighting and sounds fantastic. My unit also runs quiet and smoothly with a TCS KA2 installed. I can't imagine though, trying to pair it with and ESU equipped locomotive. I know some do with success. I'm a odd one in that I really like how the factory speed table is set up on the Tsunamis. I realize it might be a bit fast on the low end for many but with the way my throttle controls are arranged it works well for me in 28 speed step mode with momentum and independent braking set up. It allows me to control the speed by feathering the throttle and independent just like the real thing, which I know your very familiar with Ted in real life. I rarely get above speed step 7 if ever with my freight engines so it keeps the throttle very manageable like an eight notch throttle. 

I don't have a PK2 version, but I enjoy the GP60 which I imagine is probably identical mechanically. The Rapido straight 38 I have no need for but thought they look great also. 

Great photos of the various BN GP38 variants on the layout.  I have an Athearn Genesis BN GP39-2 put away that needs some running (someday).  They were common on trains on the Inside Gateway in the 80s.

Rich

TED..That BN2158 looks like  a little of car sporting....I bougnt  a WalterLivn Western box that is being handled by the BN2158...this car pulled to the left on curves due to lack of weight  in the car...I drilled many holes on the bottom of the body and used BB's are extra weight to put a stop on the sag, now this car can be postioned any place in a freight and moves running straight lke it should do..  This layout has interestinglooking switching to take place...

Ted,

A problem with Soundtrax decoders on a NCE system is the speed control on the lower steps can be jerky using the 28 step speed selection on the NCE throttle . Switch to the 128 speed step and the Soundtrax engines will run smoother. Another problem is Soundtrax has their back EMF setting CV 212 at the max at 255. Setting CV 212 to a 120-140 value smooths the engine performance. Most motors don’t need the back emf set to max . I speed match the Soundtrax decoders using the 128 step setting on the NCE throttle and run all DCC engines on 128 step .

Dave

Posted from iPhone

The club uses a Digitrax system, but I was using a TCS Wifi throttle so the consisting is handled by the throttle and not the system. It was using the 128 speed steps. I will have to try adjusting the Back EMF. I like the ESU system that automaticlly adjusts the BEMF by setting CV54=0, then pressing F1 and the locomotive will run forward a couple feet and automaticlly setup the BEMF based on the BEMF it measured.

Ted Curphey
Ontario, OR

Sounds like you can't run all three together. Too bad. Maybe standardizing on one decoder brand is the way to go?

CPR_4000 Wrote:
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> Sounds like you can't run all three together. Too
> bad. Maybe standardizing on one decoder brand is
> the way to go?

Is it the decoders only or motors, gears, and other mechanical & electrical issues that make speed matching so difficult among different brands? I’d really like to know which variables are the root cause of this problem.

Posted from iPhone

My suspicion here is also Back EMF.  I've experienced this same surging on multi-unit multi-manufacturer lashups, and I think the BackEMF function is mis-reading the resistance (weight resistance) of the other units and then changing the motor output to attempt to compensate.

I haven't taken the time to mess with turning this off... eventually I will though.

UPDATE; I did some planned upgrades on the Athearn Genesis #2085. I added a current keeper to the factory GN1000 Tsunami board, and replaced the speaker with a Scale Sound Systems speaker. So it's already sounding much better. I tweaked the BEMF and some other decoder options and it does seem to be running with the #2158 better. But I won't know for sure until I take it back to the club.I have a Athearn Genesis GP50 that will be getting the same treatment when parts arrive this week.

Ted Curphey
Ontario, OR