Bachmann 4-8-4 Northern (HO) derails,...engine or track initiated?


B

beiland

Well-Known Member
a few seconds ago

Bachmann 4-8-4 Northern (HO) derails,...engine or track initiated?

I have 3 of the Santa Fe versions of these engines, and they all have the long-haul tenders. And to my knowledge they are all the latest versions of these locos, even thought they are no longer marketed. I'm betting they will all look super after a decent weathering job.
DSCF6415.jpg

I have experienced a particular problem recently while running one of them around the lower level of my layout,...a tender that derails its front truck,...not always but often enough to really bug me. And it all occurs at a particular spot. It has me wondering if its a problem with the track in that spot, or the loco in that spot??

The loco comes up the viaduct incline, then is directed off to the left by a large radius Peco 'Y' to proceed down the other incline of the viaduct.
DSCF6415.jpg

Up until recently all of the locos and trains I've run across this Y turnout and around the that bottom loop of my layout have run fine,...even the Bachmann Northern. But most recently I had detected a little clicking noise as the loco passed thru this spot. Then I began to experience a lot of derails by the front truck of that long-haul tender.

I need to determine what is the problem,...is it the track work OR the loco??
 
Track Work Considerations

That large radius Peco Y turnout should not inherently be the problem. It has plenty of radius to accept this Bachmann loco. Perhaps I should consider shimming its guard-rail flangeway,.. but I'm not yet convinced this is a problem in this case?

Another thought turned to the fact that this Y turnout was 'sort of located on 2 different planes',..one going up into the helix tracks, and the other going down to the viaduct decline. I'm not fully convinced that this is my problem as I tried to make things as level as I could thru this turnout itself. Now maybe those long 4-wheeled trucks on that tender don't see it that way?

Another thought turned to radius of the track diverging from the Y there, and if there was the slightest kink in that track joint there? I do believe there is some 'very slight' kink in that joint, but all the other trains ran thru it just fine, both forward and backward,...and numerous times.

I have decided to replace that first 1.5 feet of track leaving the Y turnout with a fixed section of 24" radius track to help with any discrepancies.
Locomotive-Tender Considerations
I began to look at the wiring that exist between the loco and the tender. Was that contributing to some sort of force on the front of the tender causing that front truck to derail?.....maybe a contributing factor that I need to look at more thoroughly? I did try unplugging this connection, but then I could not get power to to run the loco thru this trouble spot!

Is that long 4 wheel tender truck having trouble following these curves? I don't think it has a problem with the curves themselves, but just perhaps gets upset with any out-of-level situation?

I have come up with one other interesting factor. In most of my reading it has been suggested that this loco can negotiate 22" radius curves at the minimum,..so I was laboring under the idea that I did NOT have a radius near this minimum, but mine was greater? I turned the tender upside down and placed a 22" then a 24" piece of track onto the trucks. I noticed that the rear truck pivoted all way over to a point that its rear most wheel touched the coupler pocket when on those tight turns. If this was really the case, then perhaps this rear truck on the tender was reaching a point where it could no longer swing far enough,...and as a result was causing the front of the tender to bear off the track and resulting in the derailment of the the tender's front truck??
Currently I am investigating this idea further,...and I am going to file off the corners of those coupler pockets to try and limit this interference.
 
Brian, could be the way the wires are routed between engine and tender on that on particular engine. If the other two engines have three wires on one side of the drawbar pin, and it has two, that could be the culprit.
 
I'm only posting to ask questions and hopefully get some wheels turning (pun intended). Maybe some of the questions will lead to the answer you're looking for...

It sounds like the issue is isolated to the tender, not the tracks, simply because the issue does not exist on other equipment. To prove this theory, do you have any other stock that also as a 4-axle truck? How about 3-axle trucks? What's it like when they operate? Does this issue only occur when the engine/tender is running solo, or when it's pulling a heavy load or when it's pulling a light load?

To test the tender more, disconnect from the engine and fasten those wires tightly to the front of the tender to get them out of the way (a piece of tape, or simply tucking them into the ladder?). Now turn that tender around and pull it with the most reliable loco you have. If the issue persists, the problem most likely lies in the trucks. If the problem goes away, look into those wires (trying what @bnsf971 suggested is likely a good start point). It's also possible that pulling in reverse takes tension off of a particular wheel set or the truck is sitting differently on the tracks. How securely are the trucks fastened to the body of the tender? Is the tender heavy enough to keep the wheels pressed down when moving?

If the problem still exists after all of this, then revisit the track theory. IMHO, I think the tender is what should be focused on first. Good luck!
 
bklynman01 said:
, do you have any other stock that also as a 4-axle truck? How about 3-axle trucks?
Click to expand...
I tried another of this same engine/tender combo, and it did the same, derailed front tender. I then added some extra weight to the front of the tender and that did NOT do the job.

bklynman01 said:
What's it like when they operate? Does this issue only occur when the engine/tender is running solo, or when it's pulling a heavy load or when it's pulling a light load?
Click to expand...
Seemed to be a problem in both cases,...pulling a load of cars and not.
bklynman01 said:
To test the tender more, disconnect from the engine and fasten those wires tightly to the front of the tender to get them out of the way (a piece of tape, or simply tucking them into the ladder?). Now turn that tender around and pull it with the most reliable loco you have. If the issue persists, the problem most likely lies in the trucks. If the problem goes away, look into those wires (trying what @bnsf971 suggested is likely a good start point). It's also possible that pulling in reverse takes tension off of a particular wheel set or the truck is sitting differently on the tracks.
Click to expand...
Good idea that I forgot to test before I decided to pull up that section of tack curving off of the Y turnout. Now I may not be able to determine that potential cause.

bklynman01 said:
How securely are the trucks fastened to the body of the tender? Is the tender heavy enough to keep the wheels pressed down when moving?
Click to expand...
Yes I added lead weight to both ends of the tender to see if that would help...did not.
 
Question: When the tender(s) derail, are they picking the point of the frog? What Code is the turnout and how long since you bought it? What I'm thinking is that Peco Code 100 (and maybe some of the older Code 83) turnouts are actually OO ga, and the guard rail to the adjacent stock rail gap is a little wider than for HO. The solution, if the frog is being picked, is to add a .010" shim to the side of the guardrail that faces the stock rail, with maybe a little sticking above the top of the guard rail. I've only had this necessary on one turnout, but cementing a piece of .010" brass shim solved the problem completely.
 
This is where good back light and slow motion movement will show which axle lifts, and when. It may not even lift. Maybe the first axle simply moves over the points, hung up by friction on the drawbar, and of course that means the rest of the axles following are likely to at least jump one way or the other, into the gauge or out of it.

This can be due to:

a. low point tip;

b point not flush against the stock rail;

c. point tip not sharp enough (needle file and make a small beveled edge at the top corner);

d. point and opposite stock rail are not in gauge, but not necessarily just at the points (further toward the frog);

e. offending axle has been pressed wide or narrow in gauge. It only takes 0.3 mm to make a huge difference;

f. the turnout sags or is not on two planes with the three approaches to the frog;

g. the drawbar pin is too thick for the orifice in the drawbar and the result is a lifted tender front end when encountering dips or changes of elevation; and

h. approaches to the throwbar are not on the same plane. The rails are not at an even height transversely, or there's a hump or a dip just prior to the turnout;

One thing I learned with the larger steamers is that what happens at the derailment may not be due to anything at the point of derailment. It might be due to what is happening 6" rearward, at a last axle. Those long frames get horsed over in roll and in yaw by events in front of them and behind them, not just what is under them.
 
What Selector said a couple of posts up is a really good point. The root cause of the issue may not live in the area the derailment occurs.

beiland said:
this Y turnout was 'sort of located on 2 different planes',..
Click to expand...
While the turnout may be level enough to hold a puddle of water, the leading and trailing tracks are not. When the engine moves over the turnout, the tender is not on level ground. If the difference in levels is enough to caused the drawbar to put lift on the tender, the wheels will move "out of place" but not derail until the point/frog of the turnout.

Try loosening the screw on the engine that holds the draw bar to allow vertical slack. If this resolves the issue, the height difference could be the trouble.

I do not advise leaving the screw loose. This is simply a method to test a theory.
 
I've got some good news, I've got it working without derailments. Perhaps the negative news is I am not ABSOLUTELY sure of what the problems was,...because I was working on the two aspects at the same time.


First off I wanted to inspect that potential truck/wheel interference with the couple pocket. I took both a 22” & 24” piece of sectional track and placed it on the upside down tender trucks.


This 22” track section shows how close that rear wheel comes to the corner of the coupler pocket. (regrettably I had already started to trim the corners of that coupler pocket prior to taking some photos)
1643201022993.jpeg



This is the 24” track section,..
1643201059882.jpeg

I determined that I could trim some more from that coupler pocket, so I decided to do just that,...just in case.




I took out the section of track that followed the Y turnout, and laid it down with those two pieces of sectional track. Here is that comparison with the 2 sectional pieces on either side,..
1643201105501.jpeg

As you can see the track I had laid in there originally was closer to the 22” curve. That made me decided to place a fixed radius 24” curve at the exit to the Y turnout, plus eliminate any possible kink in that connection with the Y. Fortunately I was able to connect the other end of that 24” curve to the rest of that viaduct track.


Bottom line, I believe I have solved this particular problem for this zone,...and I am doubly glad that I selected 24” as the very minimum radius on any of my mainlines that might be carrying steam engines. And I am now convinced that 24” should be a minimum for running this Bachmann engine.
 
I thought I had this diverging viaduct track solved, but it turns out it is still giving me problems. I continued to have some minor clicks/unusual noises when that long steam engine passed over the area. Some of them are occurring at the joint in the tracks where the curve tends to go straight on the viaduct down track.


Naturally it is in a somewhat difficult spot to reach,..even for my tall height and long arms. I can't view that joint from above to see if i have any kinks of sorts,...I'm suspecting I do.

Late today I got in the mail 3 Kato chassis I plan on considering for my powered freight car. We all know how smooth the Kato mechanisms can be. Surprise!, 2 of them actually derailed their leading trucks when going over this questionable joint. I think the problem is that I have too short of a piece of flex track inserted here, and a unsoldered joint in the track there.

I spent the rest of the day working on this problem area,....not what I had in mind for the day, but necessary to get this right. I'll finish up my next experiment tomorrow.
 
I'm not certain exactly where you mean. You may be well advised to remove the whole section of track and the turnout, lay it flat and solder the joint. Check the track gage to be sure it isn't too tight or too loose at the joint. Then reinstall the whole thing and see what happens. I take it you checked to see if the guard rails aren't allowing the wheels to pick the frog?
 
Here is that spot(s) I've been working on to 'smooth' out my track curve. Its 46" in from the aisle, so you can image trying to get the tracks cut and aligned with NO KINKS while I try to reach that spot,....and see it for an exact fit when my cataract eye surgery of a few years ago adjusted things such that one eye sees distance , and the other sees close up.

1643466738468.jpeg

1643466180994.png



Previously I had a short piece of flex track connecting the fix 24" curve to the remainder of the viaduct track,...with the joint at the yellow arrow here,..
1643466954498.png


I've now made the new joint further down the line at the blue arrow.

Trying to get short pieces of flex track to maintain a nice sweeping turns without adjoining kinks can be problematic. So I resorted to taking a fixed radius piece of sectional track and cutting numerous slots in the plastic ties along its length on one side,...then bending it to my desired radius.,..
1643467418556.png


1643467757400.png

Now I have that nice smooth 24" curve leaving the Y turnout, transitioning into my custom curve, then the viaduct down track.

NOW I think I have finally solved my problem.
 
Last edited:
I certainly hope this solves the problem. Have you tried running your "problem" engines and rolling stock yet? Looks like that transition section should work. When I was planning my current layout, I made transition easements using flex track into the fixed Atlas and Shinohara curves. Best of luck. Stay well and safe!
 
Kind of surprised that not many others have added anything to these discussions concerning a what I believe was a substantial selling Bachmann engine(s)?

I am making another attempt to contact spookshow.
 
i have mine working fine, but I was looking to see if anyone could add some history of the evolution of the HO model of this loco,...similar to that N scale history.

Spookshow did end up answering my email, but said he knew nothing of HO,...only N
 
beiland said:
i have mine working fine, but I was looking to see if anyone could add some history of the evolution of the HO model of this loco,...similar to that N scale history.
Click to expand...
I know the earlier models had the old three pole pancake motor going through a gazillion gears down to the axles. The motors were unreliable in the extreme, second only to the axle gears, which would split and cause the side rods to go out of quarter if you looked at them funny. Electrical pickup was, to be charitable, not very good. Bachmann did try to alleviate that somewhat by adding pickups to the front and rear trucks, though it wasn't very successful. These did have the benefit of having such a sloppy mechanism they would go through 18" radius curves, and sometimes smaller, without issue. The early version was also sold through Lionel, with the same problems as the Bachmann-branded units. Bowser made a retrofit kit for these, consisting of an entire running frame with motor to place the Bachmann shell on. These field conversions were great runners.
Later models in their "Plus" line had an actual 5 pole can motor and large flywheel with a worm gear machined onto it, and better electrical pickup. They still had issues with split gears, and the "better" drive introduced the problem of being very stiff, requiring expansive curves and perfect trackwork to keep them from derailing.
The "new, new" version is DCC equipped, with gears made out of better plastic that doesn't split so often, though they are still incredibly fussy about trackwork.
 
You must log in or register to reply here.



Back
Top