MTH 20-80003A BNSF GS-4 Daylight Stutters When Running Slow

Could be a million things ……you’ll have to start diagnosing the issue,……if the tach sensor looks to be ok, ( correct gap, etc. ) start looking at mechanical binding issues, traction tire hanging up on a brake arm, rods and valve gear colliding with things, ….lots of stuff to look at…..take the shell back off, and rotate flywheel by hand, noting any spots that bind. If you find a spot that binds, look for the obvious first, then move on to more complex diags ……..I’ve seen the cross head guides on GS’s squeezed in just enough from shipping & handling to rub a crank bolt and cause a drag every time it went by, …..that’s just one scenario…..you’ve got a little bit of investigation to do,…..if all seems fine, you might want an ASC to take a look at it,…

Pat

Thanks for your input Pat. I will take a look at the side rods and linkage more closely. From what I could tell just by a quick glance, everything seems fine.  I also didn't notice any binding going on either when I was turning the flywheel. 

PS2 5V board, maybe check the capacitors, ensure the battery is good.

2001 engine now 21 years old, while the engine is likely good mechanically, that may or may not be the electronics giving the death rattle here. I hope that is not the case but again one of those know what you have kind of situations. PS2 5V can have problems and failures at a higher rate than some other control boards.

https://ogrforum.com/...0#154730474415780680

Check for mechanical binding. Also check the gap between the tach sensor and flywheel. It should be 1mm or so, but nothing more than 2mm. It honestly looks more like a mechanical issue than an electronic one to me.

Smoke off I assume.  Check all the mechanical as stated especially the thrust bearing in the gear box.  G

I’d do what Pat says and check the brake shoes. I weather my steamers and always remove the brake shoes and do them separately. I reassembled one of my Legacy steamers and it ran much like yours. When you tighten the screws that hold them. They naturally want to turn in with the screw putting them a little out of position. I’d check out the 2 on the traction tires.

@GGG posted:

Smoke off I assume.  Check all the mechanical as stated especially the thrust bearing in the gear box.  G

Yup the smoke is turned off. I'll take a look at that and see if the bearing is out of whack.

@GGG posted:

Smoke off I assume.  Check all the mechanical as stated especially the thrust bearing in the gear box.  G

Yes!…I forgot about mentioning the thrust bearing in the gearbox, ….I have seen that too,….it literally punched through the bearing and knocked it apart,….little BB’s all clumped up in the grease…..😳

Pat

@TRAINMANTIM 

I agree that it is a mechanical issue - but it is common to both.  Have you serviced both engines prior to running them?  If so look at what you may have disturbed by accident while doing so. 

If not, then try a lub and grease job and see if the issue disappears. 

Get real close down at track level and very carefully look and listen for changes when the issue appears.   You may have a binding issue.   

Try both on your test track and try to figure out what is common to both that would cause this problem by using the technique above.

So I took some time at work today to look at my Dad's engine. Checked for anything that would cause the engine to bind. I did not find anything. When turning the flywheel by hand, all the side rods and visible drive train parts move smoothly. I know it doesn't seem so in the video because I took the gear box cover off to show that the worm gear and thrust bearing move fine. The brake shoes are not touching the drivers. I even loosened up the side screws a little so they weren't so tight. Also the tach sensor seems to be spaced properly to me (see photo of tach sensor). Yes there is a tach tape over the existing tach stripes on the flywheel. That was done a few years ago when this issue came up. Obviously the tach tape didn't solve the issue 100% but it make the engine stutter less violently. So with all that being said, I am about 90% ready to rule out a mechanical issue and say that it is an electronic issue. But I will continue to look just to be safe.

The second video shows the engine running conventionally. While running conventionally, the engine runs smooth which makes no sense. So with it running smoothly in conventional, I am thinking that it is a board issue. When I brought the engine to work to get looked at, the tech checked the boards and said "That one of the boards is bad and that's why the engine is doing what it's doing." After that I brought it home from work, I just let it sit because I didn't have a layout (still don't have one) so decided to not upgrade it at the time.  Fast forward to 6 or 8 months ago, I decided to figure out what the issue was so I could get it fixed with either a PS3 upgrade or whatever is causing the stutter. After seeing a 3rd one do the same thing, I am definitely thinking that the 5-volt board is bad. But I wanted to get your inputs first before I go in for a PS3 upgrade(s).

Do both of these engines have barely any run time on them?…..are they fairly fresh out of the box?……if you’re convinced the boards are toast, by all means have fun, ….but if these things have practically no run time, but back & forth on a test track, I’d run the snot out of them for a while on a layout before I go cussing a board out,….😉….if they ain’t been PM’ed ever, lube them up and let them eat for a while, and recheck to see if they smoothed out,….I’m not the electrical wizard, but I’ve only seen two kinds of PS2 5V boards,….good ones, or dead ones….just a suggestion,….

Pat

@harmonyards

My dad's engine has a lot of run time on it (at least a 1,000 scale miles). Not sure how much run time Uncle's has but if his AFT GS4 had less than 120 scale miles on the odometer then the BNSF has about the same. The repair tech at my work did re-lube my uncles engine so it's good in that regard. My dad's was re-lubed when the issue first appeared with it. But anyway I will pull out my uncle's engine tomorrow and run it for a while and see if it smooths out.

Reload the sound file … had the same engine do exactly what you are talking about… for some reason it had a corrupted file … I reloaded and engine runs smooth as silk and I still have it …

@vinndiesel posted:

Reload the sound file … had the same engine do exactly what you are talking about… for some reason it had a corrupted file … I reloaded and engine runs smooth as silk and I still have it …

I will try that out.

FWIW, doing the binding check for the gearbox with the cover off proves nothing.  I've seen a few of these gearboxes where the cover need a shim to avoid dragging on the worm.

I have great difficulty with three boards all failing in the same manner, that seems somewhat unlikely.  Also, if it runs smoothly at higher speeds, that screams out mechanical issues, at least to me.  I sure wouldn't suspect the board first in this case.

If your bandaid with the tach tape changed the running, have you considered swapping out the tach sensor board?  Also, check closely the gap, it should be between about .8mm and 1mm.  More or less gap will give you problems, and it doesn't take much.  Don't eyeball it, measure it.

@TRAINMANTIM posted:

...

The second video shows the engine running conventionally. While running conventionally, the engine runs smooth which makes no sense. So with it running smoothly in conventional, I am thinking that it is a board issue.

...

@TRAINMANTIM posted:

I will try that out.

Did you reload the soundset and try it out?

When you ran it conventionally, did you turn OFF speed control (Whistle-Bell-Bell)?  The default conventional mode USES THE TACH!  Speed control can be confusing because it is adding additional variables to the mix.  Much more informative in this situation to apply "raw" track voltage by turning turning OFF speed control.  This way you can see if the engine runs smoothly. It should also run at essentially the same speed in forward and reverse.  If it is still jerky with speed control OFF, or if it runs at materially different speeds with speed control OFF, then I'd look for mechanical issues.

Separately, you can operate DCS command mode at reduced track voltage - such as 12V rather than 18V.  The technical gobbly-gook gets pretty nerdy but a DCS command engine running 5 sMPH with 18V on the track is a different animal than a DCS conventional engine running at the same 5 sMPH with 10V (or whatever voltage) on the track.  It would be instructive to know if lowering the track voltage to, say, 12V (rather than 18V) when running in DCS command mode at 5 sMPH materially reduces the jerkiness.

From what I've read so far, my vote is with the "mechanical issue" as opposed to electrical.

Hi everyone,

I'd like to give an update to this problem I was having with this engine. Over the weekend I met up with Lou1985 and we took a look at the two BNSF GS-4's. We determined quickly that both engines were mechanically sound. So with mechanical and linkage binding being ruled out, we decided to try reloading the sound file. Once the sound file was reloaded in both engines, we tested each engine out and they both ran great. There was no stuttering at all under 10 SMPH.

Now that both engines are running well, I'd like to thank everyone that responded and offer their expertise. Big thanks goes out to Lou for offering to spend some time helping me out with these engines. I really appreciate it.

Sometimes it's the easy fix. Fortunately it was this time.