The slinky effect has already been discussed to death here. Dead horse comes to mind. For you newbies it is what rails (1:1 foot scale railroad employees) call "Slack". It's as realistic a railroad action as you could ask for. Each engineer knows better then to take the slack out of a train or a set of cars... quickly. That will cause coupler damage and possibly break a pin or two. Requireing crew members to go walk it out and replace the damaged coupler. Some model rails who know little of the action and how to take out a train or bring a train in get all excited about the "Slinky" effect. All the couplers ever built, irregardless of scale have a certain amount of "Slack". Slam your train to a halt and you will see the slack cushioning the cars. Pull hard on a start up and you will see the caboose react like it's on the end of a whip. There's nothing wrong with this "Slinky" effect. It's actually slack handed down from the real railroad world. "Slinky Effect" how demeaning. It's "Slack" according to American Railroad Lingo. Now don't be giving me no flack about the slack. Have fun!
Hopefully my response will be flack-free.... That said, the amount of "slack" introduced by a slinky MT coupler is far beyond anything prototypical, as are many of the grades on model layouts that induce the effect. My layout is totally flat and 100% of the cars are MT equipped. I have no slinky effects. However, back in the day when I upgraded rapido equipped engines (Atlas/Kato GP30s, GP35s, SD35s, etc.) to MT 1015's, I would routinely be irritated by the slinky pistoning going on among my motive power at constant speed on level track. This I considered to be unprototypical and just plain irritating (not really irritating like a bad boss or reality TV, just more of a minor annoyance). When Atlas started installing Accumates at the factory on their motive power, I found this to be a vast improvement. Also, it should be pointed out that the screw mounted Accumates on Atlas engines are both explosion proof (due to the screw) and don't induce the wide spacing as on the Accumate equpped trucks.
To me the 'slinky effect' is more annoying when you are switching with a few cars than the prototypical slack like effect of it on a long train where you can put springs in the trucks to stop the caboose slinking back and forth. Back to the topic, who would be willing to pay a bit extra if Athearn, Atlas, etc. used MTL couplers instead of Accumate, we often want things but cringe at the thought of paying for them. The Accumates don't worry me personally because I don't feel as bad about snipping them off to body mount Z scale 903's.
