# Why the 1st car after your Loco might derail



## xrunner (Jul 29, 2011)

I've run into this 2 times already. The first car after the Loco derails, and I couldn't understand why. Now I do and I'd like to pass on the info.

The Loco coupler, at least on my Katos, is attached to the body. As such, the centerline of the coupler follows the centerline of the Loco body. Yes it can swing side to side a bit but the centerline of that + or - swing follows the centerline of the body. As the Loco goes into a turn the centerline follows the body and "pulls" the center of the +/- swing outwards.

Stay with me ...

On the cars it doesn't work that way. The centerline of the +/- swing of the coupler follows the truck (not the body), and so follows or points into the curve better. That's great for all the cars after the first one, but ...

What happens is that this geometry combo on the first car attached to the Loco causes a pull outwards by the coupler on the loco. Since the car wheelset has play in the tracks (it can twist side to side a bit) it causes the wheelset to twist in the track and the flanges dig into the outside rail.

Now the cause of the derails. If the two outside rails don't fit together very well the mis-alignment will catch the flanges of the first car and cause it to ride up a bit and derail. I've fixed this both times by filing the place where the two pieces of track meet and it fixed it. It wasn't much but this geometry seems very sensitive to this issue. I've had worse rail alignments elsewhere on straight track and it doesn't cause cars to derail. I know it's hard to see without pics but I'll try to draw up some perhaps.


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## Big Ed (Jun 16, 2009)

With my small N layout I have not encountered that problem?

Do you think weighing the first car some would help?


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## xrunner (Jul 29, 2011)

big ed said:


> With my small N layout I have not encountered that problem?
> 
> Do you think weighing the first car some would help?


Maybe. I tried that and it didn't help on one that did it. It's one of those very finicky little things that isn't easy to figure out and doesn't happen a lot. The way I first figured it out was to take the car and pull it around the corner with my finger while putting that outside "pull" on it like the Loco would. Sure enough, I felt the flange hit the place where the rails meet and it popped up a little bit. It also depends on the manufacturer of the wheels I think since some flanges are "sharper" than others. I really need to draw it up to make it clearer.


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## Big Ed (Jun 16, 2009)

Just find a car that works and leave it as the lead car.
Or did you try other cars too?


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## xrunner (Jul 29, 2011)

big ed said:


> Just find a car that works and leave it as the lead car.
> Or did you try other cars too?


Yea some other cars won't do it, true. But I don't want to be dependent on certain cars. I want to understand the problem it and fix it for all cars. I thought you already knew I was anal-retentive.


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## Big Ed (Jun 16, 2009)

xrunner said:


> I thought you already knew I was anal-retentive.


Yes, I read the Why aren't RR wheels painted thread.:laugh:
You need a hobby so you don't think so much.

Maybe take up painting?
Then you could paint a mountain backdrop on your wall in the layout room.




Just be sure to add a big beeeutifull BLUE LAKE.


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## JohnAP (May 4, 2011)

With a blue mountain lake! :laugh: Good explanation on the derailment though. This can also happen with the pilot wheels of staem locos, which are also very sensitive to track misalignments, and yes, curves greatly accentuate the problem.


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## gunrunnerjohn (Nov 10, 2010)

Some of Lionel's recent O-gauge entries, like the GenSet locomotives have fixed pilots. These also don't handle sharp curves at all well. I lust for one, but I can't consider it because I have O-31 and O-36 track.


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## powersteamguy1790 (Mar 26, 2012)

xrunner said:


> Now the cause of the derails. If the two outside rails don't fit together very well the mis-alignment will catch the flanges of the first car and cause it to ride up a bit and derail. I've fixed this both times by filing the place where the two pieces of track meet and it fixed it. It wasn't much but this geometry seems very sensitive to this issue. I've had worse rail alignments elsewhere on straight track and it doesn't cause cars to derail. I know it's hard to see without pics but I'll try to draw up some perhaps.



That's why track alignment is so important especially curved radii. All the track work should be tested and re-tested with all locomotives and rolling stock before the track is permanently adhered to the roadbed.

Very sharp radii will produce the same results with a body mounted coupler on a locomotive and a truck mounted coupler on the first car. 

This situation will also occur on the new MT heavy weight passenger cars if they are used on layouts with radii sharper than 12 3/4 inches. The body mounted couplers on the heavy weights will cause derailments.


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## xrunner (Jul 29, 2011)

big ed said:


> You need a hobby so you don't think so much.
> 
> Maybe take up painting?


No not painting. I need a hobby with all manner of little fidgety things that I have to tinker with to get going right. Don't worry I'll find one.



powersteamguy1790 said:


> That's why track alignment is so important especially curved radii. All the track work should be tested and re-tested with all locomotives and rolling stock before the track is permanently adhered to the roadbed.


^^^ good advice.

Yes indeed, I've learned that lesson by now. Run trains both directions and change up the car sequence so you flesh out the trouble makers. By today I'd thought I had done it enough but I was mistaken.


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## gunrunnerjohn (Nov 10, 2010)

I've sold about 1/2 a dozen locomotives just because they don't run well on my track and switch selection. They were supposed to, they just didn't.


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## xrunner (Jul 29, 2011)

gunrunnerjohn said:


> I've sold about 1/2 a dozen locomotives just because they don't run well on my track and switch selection. They were supposed to, they just didn't.


Hmmm ... What do you think the problem was? Something regarding the way you had curves set up or bad designing of the Locos? Did you futz around and try to "fix" them before returning?


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## gunrunnerjohn (Nov 10, 2010)

For the most part, it was simply a bad design, at least that was my analysis. The last one would short out the center track roller on curves, and there was no way to possibly fix it. However, that didn't stop Lionel from saying it was compatible with O-31 track! 

Another one was a GG-1, the leading truck would derail frequently with the obvious result. No amount of tweaking would make it better, so I finally sold it.


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## Blade3562 (Mar 13, 2012)

Just my 2 cents on this, what about larger lips on the wheels? Not a huge lip, but just slightly more, most of my cars are older and I have never seen this issue, even while backing up. The issue I experience is Kato loco to Kato loco in a left hand turn. The lead loco is stronger and ends up sliding uncoupled after entering the halfway point of the curve due to the awkward Kato coupler styling.

I'm a car guy and can't figure out a car analogy at the moment but drew pictures step by step lol


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## Xnats (Dec 5, 2010)

X are there certain types/ brands that are giving you trouble? I had a few MicroTrain cars that would derail at sporadic times. I solved that by removing all the un-coupler wires from the bottom of the couplers(the copper wire in the pic). They seemed to get pushed out of alignment in the tighter radius and would push onto the inside of the rails. None of my stuff has them anymore and it seemed to stop all problems. 








The only bad car I have is a Atlas tanker. The car in to light and the truck assembly does not track well. One of these days I put a set of BLMA trucks on and see what happens.


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## xrunner (Jul 29, 2011)

Xnats said:


> X are there certain types/ brands that are giving you trouble?


The last one was an Atlas car with Accumate couplers/truck.



> I had a few MicroTrain cars that would derail at sporadic times. I solved that by removing all the un-coupler wires from the bottom of the couplers(the copper wire in the pic). They seemed to get pushed out of alignment in the tighter radius and would push onto the inside of the rails. None of my stuff has them anymore and it seemed to stop all problems.


About the little wires - I don't like them for two reasons.

#1 Without the wires I can pull a car off the tracks straight up and it doesn't tangle with the other cars it's coupled to. With the wires on it tends to grab the other cars coupler. 

#2 I played around with a magnetic uncoupler and it didn't work very reliably so months ago I decided I didn't want that headache.

On Accumate couplers I pull the wire off.

But wait a minute - you can't completely remove the wire from a Micro Trains coupler because it's required to make it function properly. 



> If you aren't using magnetic uncouplers under your tracks, I don't , and you want your frieght cars to look more prototypical then cut off your dingers (trip pins.) For M.T. cut it flush to the botton of the coupler with a Xuron tool. For Accumates you can just wiggle and pull...they come right out (they are pressed into a hole in the bottom of the coupler.)
> 
> http://www.nscale.net/forums/archive/index.php/t-11346.html


What I did was to _reverse_ the wire - I remove it and put it in facing backwards. Another way I did it on the engine couplers was to cut it off and leave a small piece in the coupler to make it work right.


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## bwoogie (Mar 31, 2012)

Does the length of the car matter?


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## powersteamguy1790 (Mar 26, 2012)

bwoogie said:


> Does the length of the car matter?


The length of the car matters and its chance of derailment is solely dependent upon the curved radii of track you use. If you use radii under 11 inches the chances of a very long car derailing significantly increases.


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## Xnats (Dec 5, 2010)

Ok I made a major booboo. X you are correct with the MicroTrain couplers. It was the Altas and Katos that I removed the wires from because I was having problems with them spinning out of place. I just snipped the wires on the MT couplers so everything matched. I like just pulling cars straight up too, it makes things so much easier. Once you said it, I had to go pull everything out of my box and look at them  sorry about that.


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## Carl (Feb 19, 2012)

After I had checked my track, as well as every car.....everything has gone well. My problem was with the height of the coupler.


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## dualgauge (Apr 4, 2009)

I have had couplers that did not pivot freely would pull cars off the track.
Dan


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