Large Scale Central

USA Trains SD70 and Truck Mount Coupler Issue

General Discussion
#1

I had a friend over and was showing my trains and for the first time I had repeated issues with the trailing cars uncoupling from the SD70. I didn’t have time to analyze the issue until today. At the time the problem was very repeatable. Today I was only able to repeat it once on one of the 3 SD70’s I own and only once over the # of times I tried. The good news is I got the problem on video.

As you can see in the video, the one time it has an issue the engine’s coupler lifts up the trailing car’s coupler causing the derailment.

On the day I had the problem, I had tried inserting a box car in between but it had the same issue going through the specific spot. I have only USA Trains couplers and cars. I have not converted any to body mount couplers.

I have a few options available.

  1. Fix the grade in this spot. Looking at it I could tweak the spot a bit and smooth the grade some.
  2. Install body mount couplers on my rolling stock. This would be time consuming and expensive. I would still use USAT couplers.

Any thoughts on other options or what my best option would be are much appreciated.

#2

you need to add the S to your http

It’s not the grade it’s the tight corner and the longer loco forcing the car sideways.

Reduce the curve, or modify the couplers for a wider swing.

#3

Nicolas Teeuwen said:

I had a friend over and was showing my trains and for the first time I had repeated issues with the trailing cars uncoupling from the SD70. I didn’t have time to analyze the issue until today. At the time the problem was very repeatable. Today I was only able to repeat it once on one of the 3 SD70’s I own and only once over the # of times I tried. The good news is I got the problem on video.

As you can see in the video, the one time it has an issue the engine’s coupler lifts up the trailing car’s coupler causing the derailment.

On the day I had the problem, I had tried inserting a box car in between but it had the same issue going through the specific spot. I have only USA Trains couplers and cars. I have not converted any to body mount couplers.

I have a few options available.

  1. Fix the grade in this spot. Looking at it I could tweak the spot a bit and smooth the grade some.
  2. Install body mount couplers on my rolling stock. This would be time consuming and expensive. I would still use USAT couplers.

Any thoughts on other options or what my best option would be are much appreciated.

#4

I don’t see how body mounted couplers could be the cure, I would think it would be worse.

#5

John Caughey said:

you need to add the S to your http

It’s not the grade it’s the tight corner and the longer loco forcing the car sideways.

Reduce the curve, or modify the couplers for a wider swing.

Added the S though so hopefully that fixed it though it was reposted to fix the issue.

I thought about that. My GP38’s which are shorter have never had an issue like this. I did have a similar issue on a grade with the engine going from a straight to a similar curve as well but was not able to reproduce that to get it on film. That would add up though to not enough swing on the coupler.

#6

I think both John and Joe are right and I will have to widen the range the coupler can move on the SD70’s if I want to eliminate the issue. Changing track configuration here is too difficult and I have had similar problem on another spot going from straight to 10’ diameter curves on a grade.

I sit possible just removing the springs from the SD70 coupler mechanism would be enough? It would reduce the resistance it has for swinging in each direction. It would also prevent it from recentering but a post I found for widening the swing on it already has me removing the springs.

#7

I’ve seen folks open the sides of the coupler box. Use a small square file that fits in the opening and thin the side walls.

I hope that helps.

#8

I have an Aristocraft RS-3. I also have R1 switches. The RS-3 has a tremendous amount of swing going through a tight switch and would always derail the car behind it. I cured the problem by making a long draw bar and mounting a Kadee coupler on it. Now it goes through all my switches without derailing the car behind it.

I also opened up the coupler notch in the end frame.

#9

Took apart one of the couplers for the SD70. Looks like I should be able to easily add some more space for it to swing without having to sacrifice the springs inside. I am glad I didn’t go with 8 foot diameter curves. It would have been nicer to go with more then 10 foot but that was the best compromise for my yard.

#10

Easement curves can make tighter curves more manageable. Think of in your car, you start straight and by turning the wheel more your turn gets tighter. That spiral from Tangent to Curve gets both cars in alignment faster.

Yeah I know, too hard to do now. Hey it’s how we learn…

#11

Here’s one idea:

https://elmassian.com/index.php?option=com_content&view=article&id=276&Itemid=308

And more about the SD70:

https://elmassian.com/index.php?option=com_content&view=article&id=343&Itemid=387

I do not think much of USAT couplers, they don’t always work smoothly for me, and I went to Kadees.

I can’t watch the video but if you are getting coupler misalignment, body mounts might make it worse… but normally truck mount couplers can be deflected by the pulling force and cause vertical force on the couplers. Also truck mount couplers will try to turn the truck creating extra drag.

Fix the grade transition as best as you can, and try a body mount coupler on that first car.

Greg

#12

Greg Elmassian said:

Here’s one idea:

https://elmassian.com/index.php?option=com_content&view=article&id=276&Itemid=308

And more about the SD70:

https://elmassian.com/index.php?option=com_content&view=article&id=343&Itemid=387

I do not think much of USAT couplers, they don’t always work smoothly for me, and I went to Kadees.

I can’t watch the video but if you are getting coupler misalignment, body mounts might make it worse… but normally truck mount couplers can be deflected by the pulling force and cause vertical force on the couplers. Also truck mount couplers will try to turn the truck creating extra drag.

Fix the grade transition as best as you can, and try a body mount coupler on that first car.

Greg

You say “I can’t watch the video”. Why is that. It now appears twice!

#13

Joe Zullo said:

Greg Elmassian said:

Here’s one idea:

https://elmassian.com/index.php?option=com_content&view=article&id=276&Itemid=308

And more about the SD70:

https://elmassian.com/index.php?option=com_content&view=article&id=343&Itemid=387

I do not think much of USAT couplers, they don’t always work smoothly for me, and I went to Kadees.

I can’t watch the video but if you are getting coupler misalignment, body mounts might make it worse… but normally truck mount couplers can be deflected by the pulling force and cause vertical force on the couplers. Also truck mount couplers will try to turn the truck creating extra drag.

Fix the grade transition as best as you can, and try a body mount coupler on that first car.

Greg

You say “I can’t watch the video”. Why is that. It now appears twice!

I grabbed the video off the blank first post! Saw it in wide screen format to boot.

OMG!!! I out teched Gregg!!!

It’s not a grade issue either… (edit; I didn’t see the grade from the close up)

#14

John Caughey said:

Easement curves can make tighter curves more manageable. Think of in your car, you start straight and by turning the wheel more your turn gets tighter. That spiral from Tangent to Curve gets both cars in alignment faster.

Yeah I know, too hard to do now. Hey it’s how we learn…

I had read about easement curves and even had explored the option a bit when I started. In hindsight it would have been a good idea. I went with preformed curves when I started and wasn’t a fan of cutting track. If I had to do it over I’d probably purchase 16’ diameter curves, cut the pieces and use them to ease into many of the 10’ diameter curves. The only place where I have an easement is where my 10’ eases into a small section of 9’ and this one problem area I showed in the video.

In the section of the video, the track goes from #6 switch to a 10’ diameter section and then half of a 14’ diameter section and then straight. I had one piece of 14’. So it eases into the curve in one direction not the other.

#15

I had looked through the articles, Greg, on your site and originally thought I would have to do the modifications for the coupler widening it as per the first page. I wasn’t a fan of having to remove the springs. Taking it apart again I realized though I can widen the range of the coupler, just not as much as the article presents and hopefully fix the problem. Then I will be able to leave the springs in place.

I think the grade puts extra twist on the situation. I have never had an issue on any of the level spots of my railroad… The two spots so far that have had the problem are both down hill grades. One that I wasn’t able to reproduce was a long straight section going to a 10’ diameter curve on down hill grade. The other was the one in the video going from a #6 switch turned out to a 10’ diameter curve.

I’ll try the coupler widening first on an engine and see if the problem goes away. Being intermittent it may take some time before I’ll know its fixed.

#16

I did not have the time or environment to watch the video at the time I posted… sorry, did not mean there was an issue with the post.

From watching the video, you have a (negative) vertical grade transition that raised the rear coupler on the loco. The tension kept the couplers engaged for quite a while. It also appeared that the coupler on the trailing car was kind of low initially.

I’d look at reducing the abruptness of the downward vertical grade transition where this happened.

Greg

#17

Vertical curves are worse than horizontal curves when it comes to uncoupling. It took me awhile to realize this.

#18

Yep, I had a very sharp “turnover” at the top of my main grade, and my E8 being very long would just lift it’s coupler and 45 cars would head back down the grade! The problem was 2 5’ lengths of “flex” and I replaced it with a number of sections of foot long that made it easier to make a smooth vertical curve… this was the top of a 3.5% grade.

Greg

#19

One thing is certain, vertical curves are easy to find. (https://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif)

Vertical curves are why Aristo designed their couplers the way they did, with a flange on the bottom of the knuckle that prevents vertical uncoupling.

#20

Yep, that is why so many people loved Aristo couplers. But there was a downside, when people wanted to change to another coupler, they often discovered all kinds of problems with their trackwork, or coupler mounting.

I considered going Aristo couplers, but at the time, there was inconsistency in them staying coupled on long trains (problem came and went like the UV resistance of the track ties), and there was no really consistent remote uncoupling… and the big uncoupling blade just looked ugly to me.

Greg