MTL couplers and the "inchworm" (slinky) effect

Mark Truelove Jul 15, 2021

  1. CSX Robert

    CSX Robert TrainBoard Member

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    One thing I've done some experimenting with is replacing the spring with a picece of foam rubber (craft foam):
    20210720_105716.jpg

    Before anybody comments, yes, those wheels are nasty. I'll probably leave them like that while testing because wheels like that will magnify the slinky problem - if I can get no slinky with that then there definitely shouldn't be any with clean wheels.

    I haven't done enough testing yet to be able say if I think it's going to work, but it does show promise.
     
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  2. Shortround

    Shortround TrainBoard Member

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    I could use some help with HO coupling, haven't gotten involved to much with N, so I would like to hear how this works and how it's done.
    All trains have dirty wheels. Ha!
     
  3. locomcf

    locomcf TrainBoard Member

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    My observation is that the more free-rolling a car is, the more likely it is to exhibit the slinky effect. Consider the MTL retarding spring - its purpose is to make a car LESS free-rolling. If you want to enhance the slinky effect you should probably use the cleanest wheels you have, and possibly go for metal wheels.

    But I do like the idea of using a bit of foam instead of a spring.
     
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  4. Inkaneer

    Inkaneer TrainBoard Member

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    QUOTE="locomcf, post: 1188021, member: 8359"]My observation is that the more free-rolling a car is, the more likely it is to exhibit the slinky effect. Consider the MTL retarding spring - its purpose is to make a car LESS free-rolling. If you want to enhance the slinky effect you should probably use the cleanest wheels you have, and possibly go for metal wheels.[/QUOTE]

    +1
     
  5. CSX Robert

    CSX Robert TrainBoard Member

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    Do note that these are still free-rolling - slightly less than clean wheels, but not much. I'll admit I've never actually done any testing to directly compare them, but here's my theory on dirty wheels: With dirty wheels as the wheel rolls along it's resistance to rolling varies. When the resistance increases it puts more drag on the car causing the springs to compress slightly as the increased drag stretches the train. Then when the resistance decreases it allows the springs to expand and draw the train back together.
     
  6. acptulsa

    acptulsa TrainBoard Member

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    That's a great idea. Coil springs love to oscillate (ever ride in an Electra 225 without Dramamine?) but sponge rubber does not.
     
  7. Doug Gosha

    Doug Gosha TrainBoard Member

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    Of course, if the foam is too stiff, it will make it harder to couple without the car moving.

    Doug
     
  8. acptulsa

    acptulsa TrainBoard Member

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    And if it's way too stiff, you may decide your uncoupler magnet needs to eat its Wheaties, too. But it's worth a try.
     
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  9. JMaurer1

    JMaurer1 TrainBoard Member

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    After putting some thought to this isn't the problem the spring being too 'soft'? The T shank of the coupler needs to be able to move left and right and the springs keeps it centered but the soft spring allows the entire coupler to move backwards when slowing or going down a hill. Wouldn't a stiffer spring (much stiffer) keep the spring from moving backwards but still give enough for the coupler to move side to side. In fact, the only problem I can see with not having a spring but a plastic stop would be that the coupler won't want to center (which is its own problem). Thoughts?
     
  10. acptulsa

    acptulsa TrainBoard Member

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    It just depends on how you feel about coupling using Giant Hand action.

    Far be it from me to judge. I consider what someone does with his or her hands during coupling to be a personal matter. But if you don't want the two sides of the coupler to move relative to each other, there are solid plastic couplers that are both cheaper and better looking.
     
  11. CSX Robert

    CSX Robert TrainBoard Member

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    To me, the not centering would not be a problem, but the two halves of the coupler do need to move relative to one another and to automatically close. On a 1:1 railroad, someone has to go between each and every car on most trains and attach the break lines anyway and sometimes even align the couplers, so I'm not opposed to a little hands on work when coupling. What I do not like, however, is when I have to lift one coupler over the other, as you have to do with some of the one-piece couplers, and most of the one-piece couplers I have that do not require it do not stay coupled as well.
     
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  12. CSX Robert

    CSX Robert TrainBoard Member

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    I'm not too concerned about automatic uncoupling. If I had to choose bewteen automatic uncoupling and slinky or no automatic uncoupling and no slinky, I would choose the latter, in 1:1, someone has to go to each car and pull the pin anyway, but for someone who relies on automatic uncoupling, it's definitely something to keep in mind.
     
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  13. locomcf

    locomcf TrainBoard Member

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    Yes, me too. I don't use magnetic uncoupling at all, and as long as cars will couple when pushed together (by a loco), and can be uncoupled using a skewer, Rix Pick, or similar, I'm happy.
     
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  14. Inkaneer

    Inkaneer TrainBoard Member

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    Attended the Greenberg Train Show in Monroeville, PA. Great to see the shows coming back. Attendance was very good and probably would have been better had the weather not been so nice. At the show I paid particular attention to trains, including my own, to see if any exhibited the 'slinky' effect. I ran trains of 20-30 cars equipped with truck mounted MT couplers. Cars were weighted to NMRA recommendations or a little above. Trains were equipped with either a Bowser PRR caboose or the last car contained a "Firefly Fred" EOT. Result was no 'slinky'. Others who did experience the slinky were running cars with no added weight to them and were all under the NMRA weight recommendations, The cars equipped with the MT couplers were easier to roll than the stock Bowser caboose or the "Firefly Fred" equipped car. The caboose did not have any weight added to it. The conclusion drawn was that the added weight plus the increased rolling resistance of the caboose or the EOT equipped car cancelled out the spring action. Also noticed was that the lighter cars were more prone to derailments and unwanted uncouplings.
     
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  15. Mark Truelove

    Mark Truelove New Member

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    I just wanted to add back some details since my original post.

    As I mentioned, I'm running an Inglenook puzzle layout (small, simple) that is all about switching. I have eight boxcars on the layout that have all been NMRA weighted. They're mostly 50-foot so that works out to 1.1 oz each. I can't run a train on this layout so considerations like the caboose or a tensioned last car don't apply.

    I mentioned earlier that I was going to try the velcro-on-the-axle approach I'd seen someone mention. That did provide some great results. However, the amount of drag, although I don't know how to measure it, is significant. My switcher now struggles to move a full line of five cars from one end of the layout to the other.

    I also don't think the method used to add the drag matters so much. I did notice that as I was adding velcro (thinner to thicker, skinnier to wider strips used, etc.), the slinky did not stop immediately, i.e. it took a certain amount of drag applied before the cars actually became stable.

    Probably a longer running train would benefit from end-drag only so the drag wouldn't add up like this scenario. But for this case and the sake of the experiment, I was able to get this puzzle running without a hitch using the velcro method.

    Thanks for everyone's ideas!
     
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  16. BarstowRick

    BarstowRick TrainBoard Supporter

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    Someone out there had to know this was coming. Don't let BarstowRick read this. He'll be all over it.

    Allow me to declare my position here. MTL's are my first choice and have always been highly regarded by this modeler.

    The slinky effect. When I first tuned in here to see what's up? I read the title and thought, Oh shasam or a replacement word for poopoo... here we go again. It's true! Did I say that?

    The Slinky Effect can be a problem at times. Especially on a 40 car train running downhill. That's when the Inchworm can be seen with a caboose or last car with a EOTD okay Fred. I've seen that happen on the tail end of my trains. Harrumph!

    To fix that. I'll run older wheelsets / trucks that have more drag then MTL's. Run on the last car or caboose. Which goes against everything I'm trying to accomplish here. I love the smooth, minimal drag of MTL's I can pull more train cars behind fewer locomotives / motors.

    I keep wondering on your switching layout why this is a problem? Oh I read what you had to say about it. What you described is an exaggerated Slack.

    I sit by the railroad tracks watching crews switch trains and the Slack is phenomenal. I keep wondering at what point they are going to pull a coupler loose? Break a pin or bust a coupler. Considerably more movement in the coupler pocket and the coupler itself then I first thought.

    Now the boys and girls in the math department will tell you there is a big difference between the Slack on the Railroad and what you see on you layout. After all in N Scale, you'd think it wouldn't be noticeable.

    Well, I wish you the best. Seems no matter what knuckle coupler I use in N scale I see the same problem.

    Lot's of luck and I hope you find a reasonable solution without destroying the positive affect of MTL's, top of the line knuckle couplers.
     
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  17. acptulsa

    acptulsa TrainBoard Member

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    Yeah, I'm having trouble picturing the slinky effect happening with an eight car switching movement too. And adding friction to cars will only cause the springs in the couplers to compress more, giving them farther to rebound. Sixty cars will definitely compress those little springs. But four? Continuous running and grades can cause those springs to rebound. But a switching movement?

    Whatever you saw, you found a cure that works for you, and I'm happy for you. But don't be too adamant it was slinkyitis. Be open to the possibility that's a misdiagnosis. Dr. Barstow may just have his finger on it. When it comes to slacking, I wouldn't dream of questioning his expertise.

    Oh, wait... :censored:
     
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  18. CSX Robert

    CSX Robert TrainBoard Member

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    Yes, it's pretty well know that increased drag will reduce or eliminate slinky, but if you want to run very long trains and be able to have any car you want on the end without changing out trucks or wheels, increased drag is not a good option.
     
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  19. CSX Robert

    CSX Robert TrainBoard Member

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    Slinky is not exagerated slack action. I've seen plenty of slack action when crews are switching cars, but I've never once seen the cars springing back and forth like they do with slinky action.

    The only knucle couplers I get slinky action with (at least any appreciable amount) are Micro-Trains. Accumates, McHenrys, and E-Z Mates do not have any noticeable slinky action.
     
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  20. Doug Gosha

    Doug Gosha TrainBoard Member

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    Of course, none of the others work as well as MT's. either.

    Doug
     
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